3. THE MILIEU

The limits of the milieu for a certain organism strictly pertain to a certain stage in its development. The milieu for a larva and for an imago may be different. Still, we might consider an integration of the boundaries for a certain stage, as long as that stage requires a constant milieu. Geobiologically this is an organism distinct from another developmental stage. Potential milieu is limited by the faculties of the organism itself. These faculties, these properties, may never be ascertained completely. Dr. B. Hubert, for example, found a fungus (Oospora) growing on a solution (8 %) of vanadium chloride.¹ It seems improbable that the faculty to withstand this chemical is known of many other organisms. Temperature, pH, radiation and pressure range should be equally investigated, and the influence of every known chemical. It seems clear therefore that the boundaries of the potential milieu are the widest. The picture we obtain of the organism in the laboratory, the laboratory milieu, shows a much more modest extension of the boundaries. We may encounter a certain insect only in certain localities, the area total of the environmental factors at those localities we call the natural milieu. But the possibilities of the organism in question may be limited. It may be (as in the case of Opuntia, rabbits, wild cats etc.),² that there are large tracts of this earth equally suitable. If we take those into account, we widen the milieu limits again to the terrestrial milieu. The accompanying graph (Fig. 3.1) illustrates the idea.

In this book we shall, as far as possible, carefully designate which type of milieu is meant. If for a number of organisms, the laboratory milieu is known, the simultaneous occurrence of these organisms in nature often gives a sufficient description of the milieu, even without subsequent chemical analysis!

In the Figure 3.2, A, B, C and D represent milieu boundaries of four distinct organisms, it is clear that the “common denominator” (P) only gives a close description of the milieu. Inversely, by knowing the properties of a certain milieu, we may predict the occurrence of certain organisms.

In the next figure (Fig. 3.3) a biocoenosis of the solar salt works is given, the milieu factors salinity, acidity and temperature being considered. The boundaries of a number of organisms are given:³

A = Artemia salina, a phyllopod Crustacaea.

D = Dunaliellaviridi, a polyblepharid, green flagellate.

L = Lochmiopsis sibirica, a filamentous, green alga.

B = Purple sulphurim spirullaria.

N.B.Dunianella viridis occurs over the entire area.

The above examples are taken from hydrobiology. Oceanic biology and limnology, have a great advantage of dealing with homogeneous milieu or rather (as in stratified waters) with a different number of homogeneous milieus. Nearly all of our considerations pertain to these and similar environments, as the soil and the rock are highly heterogeneous and therefore difficult to characterise.

The laboratory milieu, when sufficiently characterised, enables us often to other specific organisms from an arbitrarily inoculum (garden soil, ditch mud, dust etc.). The milieu has a selective action. If we assume (Section 1) microbes to be omnipresent,⁴ the definite question put by the composition of a well defined milieu will call for a definite answer in the form of the appearance of the vegetated (non-latent) stage of the organism resonating with this syndrome of milieu conditions. Various examples may be given. We must not forget however the laboratory milieu cannot enlighten as completely on the process of an organism. The potential milieu is perhaps not even known to the organism itself, in as much as conditions have never been varied enough to test its width.

Radiation has several important properties as a milieu factor. In the first place it is absorbed by all molecules and changed in heat. This means that the average molecular velocity is increased. Further it may import some of its energy to substances raising the energy potential of these substances. In both cases useful work may be performed in the first case (heat movement) water evaporates which may be condensed at higher elevations, where it can be used to drive a turbine. In the second case out of carbon dioxide and water, sugar may be found which kinetic energy has been changed into potential energy (quantum h V, in which V = frequency; h = Planck constant = 6.1 × 10^-47).

[Baas Becking inserted Fig. 3.4.]

Nearly all the radiation we receive comes from the sun. This is an incandescent body of ±6500 °C, according to the wavelength of the most intense radiation at 5500 Å (Rayleigh’s law T = cλ⁴).

[Baas Becking further inserted Table 3.1 which compares the intensity of light during day and night.]

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Milankovicz⁵

Here measurements with the Amalux,⁶ as used at Leyden, and the solar meter are given. a. Zuyderzee 1935.⁷b. Somme 1937 and as many of the records I took in Australia. The effect of time of day, cloudiness etc.

[Baas Becking inserted Fig. 3.5.]

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Evaporation in the Australian desert may amount to 30 ml/day, corresponding to an evaporation of 3.0 × 580 = 1,740 calories/cm² day, or taken, as 14 hours sunshine the solar constant, 2 cal/cm² minute, would be 100 % utilised! Usually this is not the case, however. In moderate latitudes we attain values ranging from 0.3 to 1.2 ml/day. Still to our surprise in a natural wet country like Holland evaporation seems to exceed precipitation (830 to 750 ml/yr.). Only our high soil-water level saves us from drought!

[Baas Becking left this section blank.]

[The following notes and references are written in ink and therefore probably entered into the manuscript before Baas Becking was in the Utrecht Kriegswehrmachtgefängnis [German army prison in wartime] in July and August 1944.]

Not only that we have for vital processes a temperature minimum, optimum and maximum (v. Sachs),¹⁵ but also in below optimal ranges especially biological reactions are usually highly influenced by temperature. There exist several excellent treatises on this matter. An older by Kanitz (1919) and a comparatively recent treatment by Bělehrádek (1938).¹⁶ Usually an enormous anecdotal mass of data is brought together, but this would only come to confirm us about so. We restrict ourselves to the statement of a few generalities, pertinent to the concept of temperature as a factor of the external milieu.

Chemical and biological processes both, it was known to Berthelot,¹⁷ are influenced by temperature such that any 10 °C increase in temperature will double or triple the rate of the process. Van ‘t Hoff and Svante Arrhenius have given an empirical expression connecting the intensity of a process (reaction “velocity” with temperature) as;

or, at temperature T₁ and T₂;

The constant μ/2 is sometimes called the temperature characteristic and is thought to have the dimension of energy (W. Crozier). Unfortunately, the constant is not so very characteristic. Crozier (1924) has tried to find regularity in the μ of different biological reactions.¹⁸ All in vain. In physiological reactions the Q₁₀, which is I_t+10/I_t = 2-3, decreases with increasing temperature.

According to Guldberg and Waage the reaction velocity should be proportional to the number of impacts, such as:¹⁹

• a. Activation. This is proportional to the average velocity of the molecules. It should be proportional to the absolute temperature. This would yield, between 10 and 20 °C a Q₁₀ = 1.03 - 1.04! So, we often think that a certain group of molecules are activated by temperature (extend this?).

• b. New analysis, of Ohm’s law I = E/R speaks about chemical intensity as a quotient of chemical potential and chemical resistance. Now, the potential is apparently not much influenced by temperature, but the resistance, the internal friction, the viscosity might be! Belehradek.

On several physical processes, temperature has little influence. One of the best known is diffusion, both of gases under liquid or of solute in the solvent, the Q₁₀ being 1.14. It has become a habit in physiology to ascribe processes with a low Q₁₀ frequently to diffusion processes (see Section 4.1.6). Surface tension is another property, fast as density, refractive under that, varies but little with changing temperature.

These are almost never influenced by temperature, beyond the effect expected from thermal agitation of the molecules in the milieu (Q₁₀ = 1.04). There are, of course several weak processes. In the first place those connected with photosynthesis, further those connected with light perception, then the formation of argesterol by ultraviolet, and the introduction of auxin to lumination. The production of light by bacteria is a chemical process and has a high temperature coefficient.

a. Measurement of Brownian movement (Baas Becking, Pekarek). Micro method, based on equation of Einstein Smoluchovski; Baas Becking, Bakhuyzen and Hotelling (1925).²¹

[𝛥² = mean squared displacement; R = universal gas constant; T = temperature; 𝜇 = viscosity; 𝜌 = radius particle; N = Avogadro constant; 𝜏 = time interval]

b. Stokes’ law (Heilbrunn, Seifriz, Naber). Falling starter granules, in cell, moving iron particle in magnetic field, falling sphere, or ascending air bubble.²²

[F_d = Frictional force; 𝘳 = radius of spherical object; v = flow velocity relative to the object; 𝜇 = viscosity]

c. Poiseuille’s law (Oswald)²³

[V = volume of the liquid; r = radius of vessel; t = time; p = change of pressure; 𝜇 = viscosity; l = length of vessel.]

Therefore yield from same tube of two liquids 𝜇₁ and 𝜇₂, 𝜇₁: 𝜇₂ = t₂ : t₁ at constant temperature.

d. Couette method. Two concentric cylinders rotating one inside the other. Seems to be most satisfactory method although the falling bullet, under an angle of 80° is a close second. In the definitive section, topic should be extended.

For influence of temperature on viscosity of water and of brine, see Geobiology (1934, v. Leeuwen and Baas Becking).²⁴ [Baas Becking inserted Fig. 3.6 that also contained a table in which the viscosity of water as function of temperature was illustrated.]

Now Belehradek (1930)²⁵ called attention to the fact that, when dissolving substances in water, such as sugar, on mixing it with glycol, we may obtain temperature coefficients of any desired magnitude. Now viscosity is shearing force and had nothing whatsoever to do with chemical reaction. Still, it yields this very high Q₁₀. Belehradek looked for an explanation of the high temperature sensitivity of vital processes in the variable viscosity of the colloidal protoplasm.

Da Costa d’Andrade (1934) has succeeded to prove, from thermodynamic considerations the expression:²⁶

in which A and C are constants [and T = absolute temperature and 𝜇 = dynamic viscosity]. For 𝜇₁/𝜇₂ we obtain:

and we see that this is the inverse of the Arrhenius expression. If a Nernst analogue:

applies and E is only a little influenced by temperature, one would account for I = f(T) becomes R, and the chemical resistance is highly influenced by T.

Generally only if temperature be a limiting factor we may see the temperature effect (see also Section 5.4).

Hille Ris Lambers (1922) has shown that there exists a linear relation between temperature and velocity of protoplasmic steaming in Nitella.²⁷ Botteltier (1935) working with oat seedlings (coleoptiles) found no temperature influence below 17 °C.²⁸ Above that temperature the curve was linear. Baas Becking, Hotelling and van Sande Bakhuyzen have shown, by means of the measurement of particles in Brownian movement in Spyrogyra protoplasm, that micro currents exist and that their velocity is also a factor of temperature.²⁹

Here v.d. Honert (1928) has done the classical work with the alga Hormidium.³⁰

1. Diffusion of CO₂ (Q₁₀ = 1.17).

2. Photochemical process (Q₁₀ = 1.04).

3. Chemical or dark process (Q₁₀ = 2-3).

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(A. von Kaleczinsky).³¹

As brines have a lower specific heat than pure water, and as their vapour pressure, and consequently their evaporation intensity is less. They tend to heat up much more than freshwater. Temperature of 38 °C were observed by the author in Portugal in a saturated brine. In Bean Lake (Medve Lake) in Hungary, a layer of freshwater floating on the brine blankets it to such an extent that the brine heats up to more than 75 °C. The establishment of a bathing beach according to v. Kaleczinsky, distributed the phenomenon. Still, it might be feasible, as he suggested, to use some such an arrangement for the accumulation of solar energy.

(This really belongs under brines in Section 3.13.5).

[Baas Becking left this section blank.]

Apart from radiation and temperature the physical milieu has been very imperfectly studied. While aware of the fact that there is more between heaven and earth than is dreamt of in physiology, all sorts of physical causes have been ascribed to as many effects. Still, the result has been meagre. Promising would be the investigation of material or even (suspensions) and of high pressures (supposing that piezochemistry of aqueous systems were further developed).³² Of the other physical factors, cosmic radiation, atmospheric electricity and the like, it seems best to relegate these to a box in which we stored our magic waste and our terrestrial rags.

Water has a very low coefficient of compressibility although its space lattice (tridymite below 4 °C, quartdymite above 4 °C) does not exhibit the cases of closest packing. Pressure therefore, will but little change the aqueous phase of the living cell. Biological effects of pressure are mainly related to gases which, following the law of Henry decrease or increase their solubility in water proportional to the pressure. (Mountain sickness, diver’s sickness, caisson disease). The law of Dubois-Reymond states that the rate of change in the intensity of a stimulus determines the intensity of the reaction.³³ This is also the case with pressure, where according to Henry’s law, the solubility of gases is a function of the pressure and pressure changes may therefore, cause gases to escape from cells and thereby damage them (study on deep sea organisms). Shelford (Ecology) mentions a man’s death from various species of flies after a sudden barometric depression previous to a storm.

In the tropics a well known mode of fishing is by means of dynamite detonation under water. Quite large fishes are stunned, or even die by the material waves originated. Supersonic waves, originated by piezo quartz leave, when of sufficient amplitude, a lethal effect upon protozoa. Their disintegration may be observed immediately after application.

Other electromagnetic waves. The effect of ultraviolet is well known. Infrared (haute frequency) so often changes into heat, as water has intense absorption on the Infrared. Radium’s deleterious effects of X-rays on cells is well known. Sublethal dose may in induce mutations. It has been claimed that ultra-shortwave radio may have a lethal effect on membranes.

(W. Pfeffer,³⁴ A. Stoppel,³⁵ A. Dezovica [?], T. Kleinhoonte,³⁶ F. Blackman).³⁷

The periodic movement of leaves (as Canavaliaensiformis) from the periodic movement of leaf-inhabiting animals has raised the question behind this rhythm. Apparently not closely connected to a diurnal rhythm, might not be dictated by variations in atmosphere electricity, the gradient of which (± 100 volt/metre) may be easily measured by mean of an electroscope. The outcome of the very controversial matter has not led to a satisfactory general conclusion (Expand!)

Well known are the investigations of Muller on mutation rates of Drosophila.³⁸ It seemed that the rate was less in deep mine pits where the Geiger counter registered a much lower increase of cosmic radiation then at the surface of the earth. It is also claimed (Bohr) that effects have been obtained on sea urchin eggs.

This should be augmented by all sorts of biological material, such as ground frog larvae, but especially spear frogs. It should be ultraviolet and have a profound effect on the number of cell divisions of a detector organism.⁴⁰ Unfortunately, a careful statistical investigation of the bacterial plate method of detection has shown that we have to relegate this theory to the realm of the “Wünschträume” (see further monograph of Rahn).⁴¹

“Eau, - - - tu es la vie”, de St. Exupéry, Terre des Hommes.

[Baas Becking inserted Table 3.3 in which the properties of water were summarised.]

Water is a most unusual substance. While a substance like methane, M.W. = 16 or a substance like NH₃, M.W. = 17, have melting points far below zero (-70 to -80 °C) water, with its small molecular M.W. = 18, is a liquid at average terrestrial temperature. In nearly all of its physical properties it shows the same extreme character, its dielectric constant, its ionisation, its dipole character, its specific heat. We should not be amazed to find authors like the Rev. Whewell, who in his Bridgewater Treatises wrote paeans on this topic in order to show that this substance, the regulator of temperature and the regulator of life upon this planet, is placed here by special providence to enable us to enjoy the earth.⁴² A little more modesty allows us to see that life, as we know it, is counterpart of the water and the question whether water is here because of life or life is here because of water seems theological rather than scientific. We shall revert to this problem in Section 3 and in Section 5.

MP and BP, vapour kinetics. The whole range between zero and 100 °C is available for life. In this range most physical and chemical properties change gradually. MP and BP are influenced by dissolved substances, according to rules given by van ‘t Hoff. The rather high vapour pressure makes for effective use of absorbed radiation.

Spring and fall mixing of freshwater masses (Fig. 3.7). Pure water has an optimal density at 3.98 °C. Freshwater of this temperature is therefore the heaviest, and it will mix if the depth of a natural body of water be great, the deepest layer (hypolimnion) shall have this temperature. Later we shall revert to this phenomenon, when natural waters are described. In seawater (3.5 % salts), the temperature of maximal density is below zero and even below the freezing point of seawater, so that this factor cannot play a role in the vertical mixing. As in ocean water also salinity exerts its influence, vertical as well as horizontal currents may be predicted, salinity and temperature, being known, from the so called Bjerkness-theorem.⁴³ Discussion of which would lead us too far.

Water has usually a high absorption in the infrared, with distant bands (plate after Ellis). Aschkinass (1895) has determined the absorption coefficients for various wavelengths.⁴⁴ The absorption decreases towards the blue end of the spectrum, the “blueness” of water is due to this fact and also connected with light dispersion (Rayleigh phenomenon), which is the cause of the blueness of the sea. Water is fairly transparent to ultraviolet rays.⁴⁵ The opacity for these wavelengths in seawater is caused, according to Hulburt, by the magnesium salts present.⁴⁶

𝜇 = 0.01 poises at room temperature, with a temperature coefficient of 1.4. Winter and summer viscosity are, therefore quite different, a fact which has an important bearing upon the flotation power of plankton (Woltereck, Kizaki, Daphnia).⁴⁷ The temperature coefficient increases with the amount and the nature of dissolved substances (Baas Becking, v. Leeuwen, Belehradek).⁴⁸ A solution of 1 N cane sugar has already very high aqueous effluent. Spurious thermophily may result. The bearing of this phenomenon on temperature effects is discussed elsewhere, Correns (1939, p. 119).⁴⁹

(2 ergs/cm², an extreme value again). This surface tension is lowered by traces of dissolved substances, especially by lipophilic substances. Czapek has based his theory of permeability on the fact that many permeating substances are able to lower the surface tension of water.⁵⁰ Substances, which lower the surface tension, accumulate at interfaces, and so the lipophilic outer layer of liquid protoplasm may be accounted for. After diatom epidemics the surface tension of the ocean may be lowered and foam formation much favoured. After spring and autumn blooms of diatoms the phenomenon may be regularly observed.

𝜀 = 81 is by far the highest known, followed by liquid ammonia with 𝜀 = 67. Keller has elaborated a theory of vital staining,⁵¹ which takes into account changes in the value of the constant. According to the law of Lorentz-Lorenz the constant is related to the refractive angle which in water has a very low value 𝜀p²⁵ = 1.334, only deuterium oxide being lower as a liquid.

Water has a very high heat of fusion (80 cal) and a remarkably high heat of evaporation (580 cal at room temperature). This last value is the cause of the heat regulation due, on this planet, to water evaporation. The high specific heat, which does not fit Dulong and Petit’s rule,⁵² makes water an ideal heat accumulator, that accumulates and thermostats in one the 2/9 of the earth’s surface which are covered with water, actually guards against overheating and too rapid cooling. Apart from volcanic action the highest temperature on record in aqueous milieu is [ca. 35 °C] (Persian Gulf) on land 84.6 °C in the African desert. The author measured 31 °C in the Pacific near Corinto Nicaragua July 1928,⁵³ and 62 °C on a black sand of Verlaten Eiland, near Krakatou, Sunda Strait, October 1939.

Water shows an enormous cohesion, probably due to the semi-crystalline lattice in which its impermeable molecules group themselves and also their tendency to form chains (see Section 3.5.3). A capillary water column of several hundred metres still will not break. The theory of Atkins of the water movement in woods, the so called cohesion theory, makes use of these uninterrupted “water fibres”, which evaporate at the top and are replenished from below.⁵⁴ The cohesion process also accounts for the ease with which water, with only a little colloid (0.2 % agar) will form a solid substance.

The impermeability is very low, although the lattice structure does not represent closest packing.

Water reacts with several metals, forming the molecule of hydrogen:

The chemical reaction of both inorganic and organic compounds seem often to be excluded in sufficiently water-free systems. With carbides it forms acetylene:

It is able to saponify ester: ⁵⁵

An enormous range of substances, polar and non-polar, are soluble in water. Many molecules orient themselves in water (spreading). Water is also a universal catalyst.

The ionic product of water Kn is, at room temperature 7 × 10^-14 (Kohlrausch), influenced by the temperature. The hydrogen ion H⁺ is nowadays conceived as hydrated $OH3+$⁠. Neutral point exists when

and is called pH. pH at neutral point is therefore 7.0. The oxygen ion O^2-,as supposed by Nernst, may exist although the second dissociation constant of water will be exceedingly small.

Deuterium, M.W. = 2, was discovered in 1935 by Urey.⁵⁶ D₂O is a liquid very much like water, showing even anomalous expansion and maximum density at 3.5 °C. It solidifies at +3 °C, it boils at 101 °C, its refractive index is, for a liquid, is exceedingly low N_d¹⁵ = 1.29. D₂O was originally prepared from the liquid in a long used electrolytic bath, it was, therefore, originally contaminated with nickel. D₂O is present 1:5000 in natural waters. It does not accumulate in desert waters as Prof. P. Cohen had the kindness to analyse the brine of Searles Lake, Nevada⁵⁷ which, however, showed no increase! Physiological processes seem on the whole, retarded in D₂O, although the effect is often slight. More important is the use of D₂O in the Harvey technique of marked atoms to establish the role of water in physiological processes.⁵⁸ This technique has contributed much to elucidate the fact that the quintessence of metabolisation might well be the reaction

It has been said metaphorically that hydrogen is the fuel of living things. To the author this dictum is more than a metaphor.

Bernal and Fowler (1933) have shown that ice, at a too low temperature, and water below the point of maximum density, has a lattice structure much like tridymite (SiO₂).⁵⁹ Above 4 °C, up to ±200 °C, the lattice structure is closer, like quartzite, while the crystalline structure is reached between 200 °C and the critical point at 314 °C. There is evidence of chain formation (Fig. 3.8), but not so far as to warrant older assumptions of Armstrong (1908) according to which there should exist a tri-di-and mono- hybrid, the former in ice, the latter in steam.⁶⁰ Water is, of course, a dipole μ = 18 × 10^-18. The distances in the lattice are 2.9 × 10^-8A, 1.4 × 10^-8 Å, and the valency angle 104-106°.

Barnes, father and son,⁶¹ and Vouk have claimed that water which has been recently obtained from ice has other properties then water obtained from steam.⁶² The former exerts a beneficial effect upon organisms. The latter shows a deleterious influence. Repetition of their experiments with the algae Spirogira, and careful viscosity measurements of water of known previous history have convinced me that there is such effect. Vouk and recently Radermacher claim that water, autoclaved at a high temperature (“fervorised water”) has a beneficial effect, as compared to “non-fervorised” water.⁶³ Boezeman has repeated the experiments in my laboratory with positive results. I am unable to account for the curious phenomenon, which is not due to trace elements, having made use of quartz throughout.

The heat of formation of water, from the elements, amounts to 56,500 calories. The heat of formation from the ions is 28,000 cal. This is also the heat of neutralisation, when a base is titrated by an acid

or

According to the values given by L. Pauling for heat of formation of organic radicals the heat of formation of an organic compound does not change if its H and the number of its H and O atoms be increased or decreased in a ratio 2:1 as in H₂O (see Plate 3.1).⁶⁵ From this plate it may be seen which processes require energy, and by which energy is liberated.

See also Figure 6.5, Figure 6.6 and Table 6.2.

Complete combustion of an organic compound

yields for the respiratory quotient RQ = a/x. Now:

From this it follows, that addition, or subtraction of H₂O + a molecules will not change the RQ of the compound. From the rule found for the heat of formation of organic compounds we may derive directly H × RQ = heat = 120,000 cal/at c (see Plate 3.2). In incomplete combustion or in more complex reactions the relation, however, does not hold.

[The transcript of the notes in the plate reads as follows:]

The degree of reduction of a CHO compound may be expressed as

RQ × 𝛥H = 120 kcal

30 R = 𝛥H

𝛥H = heat of combustion

RQ = respiratory quotient

𝛥H is a multiple of the OH dissociation energy which is 56,000/2 = 18,000 cal.

The whole 𝛥H is dependent upon water!

The impact of the water molecules in thermal agitation may cause small objects (ϕ < 10ρ) to perform irregular, microscopically observable, motions (Brownian movement). Here the average deviation square of such a particle in time 𝜏,

In which 𝛥² = mean squared displacement; R = universal gas constant; T = temperature; 𝜇 = viscosity of the milieu; 𝜌 = radius particle; N = Avogadro constant; 𝜏 = time interval.

By means of this equation the author, with v.d. Sande Bakhuyzen, and later Pekarek, have shown that protoplasm, in certain instances, behaves almost like a dilute aqueous solution. See also Section 3.3.6.⁶⁶

It has been shown by Beyer [?] that the water content of the clothes moth and of the wax moth is entirely derived from metabolic water, that is water derived from dehydrogenation and oxidation of organic substances, e.g., when sugar is metabolised.

It is safe to assume that there are many organisms, which provide themselves with water in this way, for example the petroleum fly Psilopa petrolei (Thorpe, 1930).⁶⁸ Furthermore it seems safe to infer that part of the water present in every organism may be considered as metabolic water.

We recall an old experiment of Wieland a good model of catabolism;⁶⁹ the oxidation of CO – CO₂ in aqueous solution + Al catalyst.

We find:

We find a hydration, a hydrogen generation and a hydrogen acceptance, the latter usually as the formation of water. As such we suggest conceive the last act of metabolism, is acceptance of metabolic hydrogen by oxygen. Inversely, we might consider photosynthesis as a photolysis of water; the hydrogen evolved being accepted by carbon dioxide to form organic compound: photolysis and formation of water lie at the base of all metabolism (heat of formation from the elements 56,500 calories).

Osmotic phenomena may generate pressures of several hundreds of atmospheres, due to the one sided impact of dissolved particles delivered upon a membrane, the amount of energy liberated doing swelling of colloids, however, is such that the swelling pressure is measured by thousands of atmospheres! (colloid pressure, Energia, Graham).⁷⁰ As shall be argued later more extensively, all water intake by living things is regulated by one or both effects. The author, in a lecture for the Nat. Academy at San Francisco in 1929 has developed a picture of both pressures (Fig. 3.9).⁷¹

Gortner has in the last decennia developed the concept of bound water which is, essentially similar to that depicted under swelling pressure.⁷³ It is not, or is only partially, available for osmotic and chemical action. It may be determined by the expected and observed expansion at freezing of solutions, expected and observed contraction at the fusion of solutions, action on cobalt salts or measurement of freezing parts or of vapour pressures. In plant cells the amount of bound water shows a relation to drought and to frost resistance (Newton, Scarth and co-writers).⁷⁴ By measuring the volume of a plant vacuole in solutions of varying hypertonicity the deviation of the Boyle’s law PV = CT measures the bound water as a van der Waals correction P (V-b) = CT. This may be the only reliable way to measure bound water, which, according to some authors, is in no way different from free water.

This description of the properties of water is far from complete. Moreover, the advancement of science adds new data almost every year. We did not speak of the role of water in electrochemistry, in colloid chemistry. We did not mention the various forms of ice. Raman spectra and X-ray data were also omitted. Still the picture given will suffice to show the extraordinary, and complicated nature of this most marvellous of terrestrial substances. If any substance on earth is the counter mould, the resonator, the very core of life, it is water. Paramount not only as a biological substance, but also as the central compound of chemistry, and one of the most important factors in geology, it is the veritable carrier of things geobiological and geochemical. Few, if any substances (perhaps apart from liquid ammonia) could, at any place in the cosmos, fulfil a comparable role.

The gases that are dissolved in water may be roughly divided into two groups, which differ greatly as to their solubility. The first group, comprising carbon dioxide, ammonia and hydrogen sulphide, react with the water and are, consequently more soluble in water, while the other group, represented by oxygen, nitrogen, hydrogen do not associate themselves chemically with the water. Both groups are, however, subject to Henry’s law: the amount of the gas dissolved is proportional to the pressure of that gas, equilibria however, are very slow to establish themselves. Supersaturation with oxygen of 300 % may scarcely occur, while it takes 24 hours mechanical shaking to bring water into equilibrium with a gas as CO₂. The swiftness with which equilibria are established has an important bearing on hydrobiology, as a water may show something of its history by the composition of its gases.

[Baas Becking inserted Fig. 3.10, ratio of carbonic acid and bicarbonate and carbonate as a function of the various acidity levels.]⁷⁵

Part of CO₂ dissolved on water from [H₂CO₃] (see also Section 4.3.2). This H₂CO₃ is dissociated

and

In order to find the proportions of bicarbonate, carbonate and carbonic acid [follows formulae as in Geobiologie, 1934]. When we set the total amount of carbonic acid as equal to 100, it can be deduced that:

Sedimentation, photosynthesis, respiration, changes in pH influence the concentrations remarkably. Changes in the CO₂ and its dissociation are treated in this book in Section 4.6, Photosynthons. Of course, CO₂ is, apart from its geochemical importance, the most important nonorganic biological compound.

[NH₃], it forms immediately the highly oxidised base NH₄OH. In nature NH₃ is found in volcanic exhalations and around places where protein or urea is decomposed. Pasteur has discovered the Urobacilli and the Micrococci,⁷⁶ organisms able to decompose urea according to

In natural water the content is low, especially when the water is aerated. Nitrobacter oxidises $NH4+$ to $NO2−$ (see Section 4.7, Chemosyntonts).

The author [Baas Becking], and van Niel (1932) and Pop (1936) have called attention to the fact that this highly soluble gas shows great similarity to CO₂ as the substances show two dissociation stages k₁ being [9.6] × 10^-8 and k₂ [1.3] × 10^-13 [mol.L^-1],⁷⁷ sulphydryl SH^- (= the univalent radical SH is the sulphur analogue of hydroxyl and constitutes the thiol group) and sulphite S^2- on being formed respectively.⁷⁸ Van Niel showed that undissociated H₂S is probably toxic to purple sulphur bacteria, while Pop had a similar experience with unicellular green algae. With increasing acidity, the toxic effect mounts rapidly although H₂S is quickly oxidised by oxygen. The lack of an equilibrium condition makes it possible to find oxygen and hydrogen sulphide in same sample. H₂S originates chiefly from sulphate reduction and certainly not from the “pacification of protein”, as even various authors (Correns, 1939) claim.⁷⁹ See also Section 7.8.8, Sulphur cycle.

In industrial smoke much SO₂ is usually present, if not removed by Cottrell apparatus or by previous washing. It is quite soluble in water, where it forms sulphurous acid HSO₃.⁸⁰ It seems to exert a fatal action on the photosynthetic apparatus of green cells, and forms probably a rather stable compound with chlorophyll, even in low concentrations. In higher concentrations it causes actual burning or bleaching. In the neighbourhood of volcanoes SO₂ is very commonly occurring. On the remarkable occurrence of sulphatic plants (von Faber, 1925).⁸¹ Highly susceptible, at the other hand, are pines and oaks, strawberries and beets. They are veritable test organisms for industrial smelter damage.

Generated by volcanoes. Von Wolzogen Kühr pointed out one interesting way of H₂ generation by metallic iron such as water pipes.⁸² This iron would form, with the surrounding soil solution as electric element, where the iron would yield electrons to react with hydrogen ions, forming atomic hydrogen according to:

Hydrogen is further set free in a great many osmotic bacterial reactions. It easily enters the cycle again, being accepted by a great many organisms, especially the hydrogen organisms, Hydrogenomonas ruhlandii:

e being used to reduce etc.⁸³

Methane occurs in volcanic exhalations but its chief source is the anaerobic cellular fermentation, by which enormous amounts of illuminating gas disappear in the atmosphere (consequently the flatus of ruminants contains large quantities of methane, methane formed in sheep at 40 litre/day!), “source-gas” = biogas of the farmer in N. Holland. At Groningen city waste is used to make gas. It is probably mostly decarboxylation of fatty acid, however Lieske (1929) showed that CO may be reduced anaerobically to CH₄!⁸⁴ The CH₄ may be oxidised by autotrophs to CO₂, or anaerobically transfer H (Gailey). CO originates probably from HCOH and occurs in the bladders of the giant brown seaweed Nereocystis lütkeana (5 %) (Hoagland, 1915).⁸⁵

It is misleading to express O₂ as cc/L or mg/L, as this is a function of temperature. Much better is % saturation! Probably originated by photosynthesis action from water. With H₂ and CO₂, the most important biological gas. Accepted by specific enzymes (yellow enzyme of Warburg, red haemo and Ca oxide),⁸⁶ it reacts with the hydrogen as the substrate. Water may become easily saturated in mg/L up to 300 % (the same is true of CaCO₃, also 300 %, see Wattenberg, 1938, Meteor).⁸⁷

79 % of atmosphere. Enters into the cycle only through 3 bacteria and bluegreens, (molybdenum catalyst) to form NH₃. Equilibrium with water slowly obtained. It may be used to determine origin of natural water, using solubility as a function of temperature. Nitrogen is also formed by nitrate reduction, which is active even in highly saturated brines. In seawater it shows less activity, especially in the aerated surface water.

Biogene of biological origin. Ripening of fruits (Molisch, F. Denny). Technically prepared from alcohol by means of phosphine acid, PH₃. Molisch discovered (1937) the effect of the emanation of ripe apples upon the growth of tomatoes.⁸⁸ Denny (1924) recognised acetylene as active (6 parts per 10⁶) in bleaching celery, ripening of bananas (citrus fruit).⁸⁹ Nicolai and Baas Becking (1935) found that it could ferment tobacco.⁹⁰ Gouwentak (1941) proved that it could break dormancy in buds.⁹¹

See further Section 7.2, Ergones on enzymes. In Plate 3.3 on graphical chemistry, the position of the gas is shown to be unique. [Ethylene is represented as “i”.]

[Baas Becking (1959) described the equilateral triangular plot with compounds C – 4H - 2O in more detail:]

In order to represent changes in composition of organic matter (simplifying the processes to changes in C, H, and O) we may represent the relations in a triangular diagram (Baas Becking, 1947b) if the corners represent C, 4H, and 2O respectively. The point representing CO₂ will be halfway on the C–2O line, while CH₄ and H₂O occupy analogous positions on the other sides. It is easy to show that all substances with a reduction level of O will be situated on the line H₂O - CO₂, all substances with a reduction level 8 on the line H₂O - CH, while the line C - H₂O (“carbo – hydrate”) shows the reduction level 4.

A bundle of lines passing through H₂O represent (de)hydrations, a bundle through 4H represent (de)hydrogenations, while the bundle through CO₂ represent (de)carboxylations and that through 2O (de)oxygenations.

In the atmosphere up to 17.28 g/litre, has great effect upon thermal properties of atmosphere, upon wind formation and radiation, blanketing. [Baas Becking referred to table ‘Composition of Atmosphere at various levels’ according to Humphreys (1926) in Critical Tables I (p. 393).]⁹²

Water vapour may be absorbed by various organisms. Enters and leaves every leaf. See further Section 5.10.4.

It is a remarkable fact that the organisms occurring in the black mud, in hot springs and those in strong brines should show many points in common. It may be that the dictating factor here is the oxygen, or rather the absence of oxygen. The solubility of the gas in weak brines (saturated NaCl) is only 1/9 of that in freshwater while at high temperatures the solubility is also reduced materially. On the black mud the oxygen tension is practically zero. (For functions of oxygen see Section 5.10.12). The work of E. Reuter however tends to show that at least for higher plants, a diminution of the oxygen pressure to 1/9 does not materially return the vital functions.⁹⁵ This finding is corroborated by the data obtained with lower forms, when the oxygen starts to be limiting factor at very low pressures. Phylogenetically we need not wonder at this, if we adhere to the theory of V.M. Goldschmidt concerning the photosynthetic origin of the atmosphere oxygen. Extreme anaerobic we might only expect in the most recent forms, the so called “higher” plants and animals.

The chief causes of acidity and alkalinity in the natural milieu are the carbonic acid, the sulphuric and hydrochloric acids, and their dissociation and reduction products, organic acids play a subordinate role.

The equation developed in Section 3.6.2 may be extended by the concept of excess base.⁹⁶ If we write:

[B] represents the excess base as its order of magnitude is usually much higher than [H⁺] we may write the equation (Johnston):⁹⁷

Continuing Johnston’s equation with those derived in Section 3.6.2 (Michaelis),⁹⁸ we get:

in which k_w = dissociation [constant] of water [= 1.0 × 10^-14], or as 1/2k₁k₂ is very small

For B = 0 and for CO₂ = 10^-4, pH = 5.8. Titrating the water with 0.01 HCl with methyl orange or methyl acid to endpoint ±pH 5 gives B. For seawater this is 25 × 10^-3. Borates may influence the result slightly.

Wattenberg and Timmerman (1936) have investigated the condition of CO₂ in seawater, especially in relation to lime deposition. Increase in [H⁺] will cause CaCO₃ (K_CaCO3 ∼10^-8) to dissolve and inversely.

Increase of temperature changes K₂ more than K₁, hence an increase in $CO32−$ pressure causes an increase in solubility, and increase in [H⁺]. Pure NaCl increased the solubility of CaCO₃, which is counteracted in seawater by other ions. Taken all in all the influences tend to counteract one another, so that the solubility of CaCO₃ in seawater is the same as that in freshwater (±30 × concentration of CO₃ in air).

See further Section 3.5.2, Swelling pressure, Section 6.6.5, Lime deposition and Section 7.8.8, Sulphur cycle. The original paper by Wattenberg and Timmerman, Ann. Hydrog. Berlin 64 (1936), p. 23, should be consulted.⁹⁹

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[Baas Becking inserted Fig. 3.11.]

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We shall only give a brief summary of those elements that directly concern living matter and enter into dealings with living matter. We shall conclude the so called minimum elements; they are dealt with in Section 5.8, Minimum Elements. Of these “primary” biogenic elements we name fourteen, all of low atomic number (1-28), six of them metals. According to several authors, this number is too high, we should exclude Na, Al and Si, it is even claimed that certain organisms may develop without calcium, however, experiments in this direction being extremely difficult, it is better to reserve judgment in this case. Most of the mineralogical and geochemical information has been taken from Clarke’s (1916) well known work.

Bioelements: H, C, N, O, S, P, Cl, Na, K, Cu, Mg, Fe, Al, Si.

22 % of the lithosphere, 10.67 % of hydrosphere, overige [Dutch word for ‘other’] 0.95 %. In all rocks, either as included moisture, or as hydroxyl. With carbon the most important element in organic substances, where it functions as the universal fuel substance. Frequent in a native state in rocks, in volcanic exhalations, and formed by the reduction of organic matter or the ionisation of metallic iron.

19 % of the lithosphere, 0.002 % of the hydrosphere, average 0.18 %. Characteristic of all organic compounds, native as graphite (laminar lattice) and diamond (tetragonal lattice) or as coal (amorphous). Carbon dioxide 0.03 % of atmosphere air. Natural gas, petroleum and paraffin are essentially hydrocarbons. Carbonic acid is in natural waters, enormous sedimentary rock masses of calx [= lime] to aragonite CaCO₃ or dolomite to CaMg(CO₃)₂, siderite FeCO₃. In magmatic silicates only as cancrinite Al₃Na₄HCSi₃O₁₅. Methane CH₄ in volcanic exhalations is found by cellulose fermentation. See further Section 7.8.6, Carbon cycle.

Nitrogen is practically confined to the atmosphere (79 %), only 0.03 % of the known terrestrial matter. Of primary importance in organic matter, especially in proteins. Nitrogen is also a constituent of the important class of compounds known as porphins (chlorophyll, haemoglobin, enzymes). Volcanic water contains ammoniac compounds, electric storms may form some nitric acid, but all the rest is biogenic including the nitrate beds, as in Chile. Several microbes are able to reduce atmospheric nitrogen. Microbes and green plants are able to reduce nitrate to ammonia. See further Section 7.8.7, Nitrogen cycle.

47.33 % lithosphere, 85.79 % hydrosphere, average 50.02 %. According to Goldschmidt the earth crust is a “crystalline oxygen lattice with other elements interspersed”; oxysphere (Goldschmidt, see p. 36). The most abundant of elements, forming more than one half of the terrestrial elements. In the free state it constitutes about one fifth of the atmosphere, and in water it is “the chief element of the ocean” (Clarke, 1916, p. 18). All the important rocks contain ±50 % oxygen. The atmospheric oxygen probably is derived from the photosynthetic activity of green plants (Kelvin, Goldschmidt), which is the analysis of water into its elements. Rocks do not contain oxygen carriers such as haemoglobin and haemocyanin. See further Section 5.10.11, Oxido-reductions, oxygen.

0.12 % of lithosphere, 0.09 % of hydrosphere, average 0.11 %. Native (e.g., Girgenti, Sicily, W. Texas, Java), as sulphides, especially those of iron FeS (hydrotroilite), and FeS₂ (pyrite, marcasite and meinicovite). In the ocean as sulphate mainly, further gypsum CaSO₄.2aq and anhydrite CaSO₄. Sulphides and sulphate in volcanic deposits, and further formed by microbial reduction of sulphates. In igneous rocks as hauynite Al₃Na₃SSi₃O₁₆ [= Na₃Ca(Si₃Al₃)O₁₂(SO₄₎] and nosean Al₃Na₅SS₁₃O₁₆ [= Na₈Al₆Si₆O₂₄(SO₄)·(H₂O)]. Abundant in olia, petroleum, alky sulphides, also in coal. A primary biological element, particularly important in the amino acids cysteine, cystine and methionin, and as such an integral element in hair and horn. This reduced form of sulphur is made by green plants from sulphates, which are the only form of sulphur that the plant can use. Further in the plant as thiocyanate (mustard oil C₃H₃-CNS) as sulphide (mercaptane e.g., C₄H₉SH in Lysichiton). In the animal body in chondria paired sulphates. See further Section 7.8.8, Sulphur cycle. In sulphur bacteria rhombic sulphur and formation of sulphuric acid.

0.0011 % of known terrestrial matter. In meteoric rock as phosphine PH₃, otherwise always as phosphate. Chief minerals are the apatites Ca₅(PO₄) F and Ca₅(PO₄)Cl (magmatic) other minerals all of biological origin as P is important part of many crustacean shells (Lingula, 91 %) and of bone. From such phosphates are derived phosphoric increments of a deep sea, containing up to 24 % P₂O₅, the blue vivianite from our marshes Fe₃P₂O₈.8H₂O, the several species of guano phosphate etc. Living matter is probably unable to reduce the phosphate to phosphine. Phosphate occurs in living matter chiefly in the lecitinoids and in the nucleic acids. Absorption by green plants as H₂PO₄- ion.

2.46 % of the lithosphere, 1.14 % hydrogen, average 2.36 %. In magmatic rock in many feldspar such as albite NaAlSi₃O₈, nephelines such as aplite NaAlSiO₄, pyroxenes such as aegirine NaFeSi₂O₆. Abundant in rock salt, halite NaCl, further as a playa deposit trona Na₂CO₃.NaHCO₃.2H₂O, soda nitre in Chilian caliche. In nearly all natural waters, accumulated in the ocean as chloride dispersed in the atmosphere (cyclic salt). Probably necessary for animals and certain plants, Antagonist calcium.

2.46 % of the lithosphere, 0.04 % of hydrosphere, average 2.28 %. In magmatic rock chiefly in feldspar such as orthoclase KAlSi₃O₈, mica’s such as muscovite Al₃KH₂Si₃O₁₂ and leucite KAlSi₂O₄. Nearly all terrestrial water contains it, which is early exchanged by zeolite action. Saline beds near Stanford, Mülhausen and from Searles Lake, California. Kelp is an abandoned source. Accumulated also by higher plants. The most important vital metal, exchanged activity by cell and environment, chiefly as K₂HPO₄.

3.47 % of the lithosphere, 0.05 % hydrosphere, average 3.22 %. As sulphide in meteorites, in magmatic rock anorthite CaAl₂Si₂O₈, garnet Ca₃Al₂Si₃O₁₂, further epidote, amphibole pyroxenes and scapolite. Fluorspar CaF₂ and apatite Ca(PO₄)₃. As carbonate e.g., in calcite, aragonite and dolomite. As sulphate in gypsum and anhydrite. A very important biogenic metal and closely connected with cyclic biological phenomena. In bones, teeth and carapaces, in a great many plants preponderantly as lime.

0.06 % of lithosphere, 2.07 % of hydrosphere, average 0.20 %. In magmatic minerals such as sodalite Al₃Na₄Si₃O₁₂Cl and the scapolites. Further in halite, from oceanic deposits and the K salt carnallite KClMgCl₂.6H₂O. Free Cl₂ and hydrochloric acid in volcanic emanations. In the atmosphere oceanic NaCl. FeCl₃ in meteorites. The chief cause of the acidity of sphagnum bogs (Baas Becking and Nicolai, 1934; Thompson et al., 1927).¹⁰⁰ Necessary for animals, in known 0.6-0.9 % NaCl. Free chlorine (?) in the stomach of mammals. Cl^- ion is physiologically rather inert. See sodium.

4.5 % of the lithosphere, average 4.18 %. Next to aluminium the most abundant metal; native iron, however, is rare. In practically all rocks, particularly in amphiboles, pyroxenes, olivines and micas. In seawater as FeF₃, oxide magnetite Fe₃O₄ and haematite Fe₂O₃ and FeO. As hydroxides (partly bacterial in formation) limonite 2Fe₂O₃.3H₂O, further tungite, goethite, xanthosidentite and chimentite. Glauconite, possibly coprolite of echinoderms, FeKSi₂O₃.aq., as sulphides FeS hydrotroilite, FeS₂ pyrite and marcasite, FeCO₃ siderite besides a great many silicates, phosphates etc.

Functions as very important biological metal is coupled to its variable valency. Integral part of many enzymes and red blood pigment, in porphines. At high pH is soluble enough to cause agricultural troubles (citrus, peas, chloriosis). At low pH so soluble that soils may become depleted (podsol). Tropical weathering of soil causes red earth later to be found.¹⁰¹

In geosphere [?] 7.3 % Fe₂O₃ (Clarke, 1916), oceanic seawater 1.9-9.6 %, rivers <1 mg/L, ocean 1-10 𝛾/L [10^-6 g/L].

Water in equation P_O2 = 0.206. For P_O2 = 1.7 × 10^-29 (dissociation water vapour at 17 °C) we get more iron in solution.

[Baas Becking inserted Figs 3.12 and 3.13.]

See also Cooper (1935, 1937): Some conditions governing the solubility of iron, Proc Roy SocLondon B, 124, p. 299 (1937); Iron in the sea and in marine plankton. Proc Roy SocLondon 118, p. 419 (1935).¹⁰² [See Fig. 3.14.]

High acidity and low pO₂ make iron more soluble. The articles of Cooper should be consulted in the original. In seawater the iron is present as practically undissociated FeF₃. The older literature mentions ferrates, most probably these compounds do not exist. In the considerations of Cooper, no mention is made of ferrites and ferrates, compounds in which iron is present in anionic form, such as in the above example, Al is soluble at higher alkalinities as aluminate. Cations may be taken in by exchange while anions require much respiration energy. Still, if the anion is mobile, not only plasmatical, out of the acid vacuole, the ferrite would automatically give off natrium of iron. It seems that no consideration of an element is complete without taking into account all of its possible modes of occurrence. The question requires further investigation.

[Baas Becking inserted Fig. 3.14, drawn after Correns (1939, Abbildung 45, p. 202).]

27.74 % of the lithosphere, average 25.80 %. Oceans, in all rocks, except coastal water. Varieties of quartz, very common. In all natural waters, deposited as sinter from volcanic water. Solubility as given in Correns (1939, p. 129).¹⁰³ See Figure 3.15. Al silicates found between pH 4-5 and >pH 11. Necessary for many organisms as functional element. “Carrier” element of soil.

7.85 % of the lithosphere, average 7.30 %, the most abundant of metals. With the exception of the fluoride, it always occurs in the oxidised state. In all rock, except sandstones, silicates, but also as Al₂O₃ corundum, as Al(OH)₃ bauxite (tropical weathering of silicate rock) and AlF₃ cryolite. Although not primarily necessary, it is present in the ash of most organisms, notably in higher plants (Lycopodiacea, Symplicos). Its solubility is very low at pH 5-9, after a fashion, this solubility is antagonistic to that of SiO₂.¹⁰⁴ At very low pH aluminium dissolves and yields very acid solutions (alum lakes).¹⁰⁵

2.24 % of lithosphere 0.14 % hydrosphere, average 2.28 %. In pyroxenes, amphiboles and olivine, serpentinite H₄Mg₃Si₂O₉. From enstatite CaMg₃Si₄O₁₂, talc is derived; H₂Mg₃Si₄O₁₂. Further, in sedimentary rock as dolomite CaMg(CO₃)₂ and magnesite MgCO₃. Brucite is derived from talc and serpentinite, Mg(OH)₂. The abundant metal is never found native. Very important in seawater, dolomitisation of organisms is secondary to lime formation. In green plants an integral part of the chlorophyll, also present in certain enzymes, as an ion it shows affinity to alkali metal ions.

[Baas Becking inserted Fig. 3.16 and Table 3.4.]

G. Harmsen (diss.), Aerobe cellulose aantasting [Aerobic cellulose affects] (in press).¹⁰⁶

[Baas Becking inserted Fig. 3.17.]

We shall start with the primary anabolite, glucose. This is, as a solid, at least a heterocyclic compound, the ring formed from 5 C atoms and one oxygen. The compound originates from perhaps six superimposed chlorophyll matrices, by transference of hydrogen from water to carbon dioxide. It may be that ascorbic acid is either an intermediary or that it plays a role as catalyser. 𝛽 Glucose is the central substance of biochemistry after J. Mark.¹⁰⁷ It is the starting point for the formation of organic acids (Kluyver), of fats (Haehn and Kintoff, 1923 and 1924), of protein (Knoop, Oesterlin, Chibnall),¹⁰⁸ and of the great number of other classes of substances. 𝛽 Glucose may be broken down by all, or nearly all organisms (see Section 7.1, The Concept of Symbiosis and Antagonism). It is rarely present in the outer milieu, as it is such a universal food.

Cellulose, pectine, chitine, lignine are present in the outer milieu. Cellulose is found from β glucose by dehydration, one water molecule disappearing between two sugar molecules. It forms long chains. Pectine is the methylester of pectic acid, chiefly galacturonic acid, together with cellulose and hemicellulose. Chitine is a chain glucose where, in every glucose molecule, one amino group is present instead of an OH. The molecule is moreover acetylated. Lignine is already aromatic shows the graphite lattice. It contains aldehydes and methoxy groups. All these polymeric substances have to be hydrolysed by means of enzymes before they may enter into metabolism. This seems to be particularly hard in the case of chitin, which is found, as such, even in certain Trilobites. Benecke (1905) described a Bacillus chitinovorus which is, however, only able to attack chitin if other organic food is offered as well.¹⁰⁹ Other polymers may be named, sufficient to state that in the majority of cases they represent in the milieu. In summary: energy yielding food.

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In the section on metabiosis or succedaneous symbiosis (see Section 7.6, Heterosymbiosis, succedaneous (Metabiosis)).

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[Baas Becking inserted Fig. 3.18.]

Mitscherlich.¹¹⁰

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Rock decomposition is partly mechanical, partly chemical. Chemical decomposition is by water and carbon dioxide, yielding a solution of SiO₂, alkali carbonates, alkali phosphates, lime, and siderite of which some oxidises to magnetite or haematite, pyroxenes and amphiboles go into solution most readily, then follow the plagioclase, feldspars, then orthoclase and mica, while muscovite is the most resistant of all (Clarke, 1916). The matrices may crumble and a “sieving” action of wind and water may set in, sorting the material as to size. As end products of the decomposition we get soils, with, as extremes, sand, laterite, kaolinite, bauxite. Table 3.5 taken from the classical work of Müller (1877), showing % of rock dissolved and % of undissolved mineral (seven weeks digestion in carbonated water).¹¹²

[Baas Becking inserted Fig. 3.19, recalculated from Clarke (1916, p. 490).]

In clay we find only kaolinite Al₂O₃₂SiO₂.2H₂O, but also, and even more frequently, montmorillonite Al₂O₃ 4SiO₂.2 H₂O, also containing Mg and Ca. Montmorillonite is able to swell. Halloysite is Al₂O₃ 2SiO₂.4H₂O. These minerals are found in clay, they are found from feldspars, quartz, mica. Furthermore, we find the biogenic admixtures such as lime, silica and organic substances. Further, in the sediment there are found secondary minerals such as FeS, FeS₂, glauconite. Due to the small pore volume of the clay (the air place has to be considered more fully), biological influences may be much greater here (anaerobiosis) than in sand. The weathered clay minerals are capable of base exchange; they may exchange $NH4+$ in the outer solution for another cation:

3.4 % K₂O exchanged in montmorillonite! However, humus has even a higher exchange capacity!

Taking sand and silt as one, we may represent by a three component diagram the types of soil that interest us (Fig. 3.20). The components are

• 1) sand/silt,

• 2) lime and

• 3) humus.

At the same time the diagram gives roughly the pH of these soils (id est the pH of the soil solution), an important fact, in as much as most plants are sensitive to pH and the optimum range for many agricultural plants have been carefully determined (Goedewaagen).¹¹³ From a pH of 3.5 in peat (see Section 2.4.8, Table 2.12) we range to a pH 9 in the pure lime. Good agricultural land contains the three components but still ranges in pH from 5.5-8. Studies “Kalkzustand”.

A humus percentage and a mechanical analysis might, therefore, in principle, characterise a soil. On acid soils we get inevitably, a leaching out of the mineral matter, especially of the metals. The soil podsolises,¹¹⁴ and usually the humus substance dissolved forms again a layer of hardpan, spoiling the physical structure. The ideal agricultural soil should have a high humus content and a pH a little below 6. It is represented by * in the diagram (chemogram; Fig. 3.20) (included here from table of Goedewaagen for pH and agricultural crops). Here below are given typical plant communities for the different types of soil (Russell).¹¹⁵ Humus is the cause of the CO₂ production of soils (Hesselink van Suchtelen),¹¹⁶ alkali soils (black alkali) contain NaHCO₃ and Na₂ CO₃.

In Figure 3.20, the laterite soils and the clay are not mentioned. Of course, the symbol SiO₂ has to represent bauxite, montmorillonite, kaolinite, laterite and quartz. These minerals however, do not influence actual acidity as much as the humus, which is an active generator of H⁺ ions by exchange, as demonstrated in Section 6.3.4 of this book.

Humus. (Waksman, Naumann, Russell) Humus is a complex of plant and animal remains, partly mineralised, carbonised and caramelised, together with a living flora and fauna, consisting of bacteria, fungi, algae, protozoa, nematods, insects and crustacean, and their recretions, excretions and secretions and this complex is superimposed upon a mineral matrix. The organic and mineral matrix are both partly or fully saturated with capillary and colloidal waters. This complex, it stands to reason cannot be initiated by chemical or physical treatment of simple substances, as has often been attempted. From the data of geochemistry (Clarke, 1916) where several analyses of rock decomposition are given, it is known that with this decomposition the organic contents increase. It has often been assumed that the “metabolism” of the humus is so intense in tropical climates, that no accumulation occurs. Dr. Hardon, however found 5 % organic substance in a yellow Java lawn (oral communication).¹¹⁷ It is true that in the tropics leaf mould does not accumulate with the same intensity as in moderate climates, except where the pH is sufficiently low (the so called Borneo padango, for instance). Before the times of Justus von Liebig, it was assumed that plants needed this humus for their development. Liebig is the author of the mineral theory which, in a general form, still expresses the consensus of opinion. The virtue of stable manure or of “night soil” (China) was ascribed solely to the improvement of the soil structure and of the minerals contributed by the manure. A commercial fertiliser (guano excepted) used in enormous quantities, expresses the universal belief in the mineral theory. However, there are valid reasons to doubt the rigorous validity of this hypothesis in view of the fact, expressed at so many places in this essay, that plants are hardly ever dependent on other organisms. That nutrilites, or ergones, organic substances active in small or very small concentrations, might be as necessary for plant life as the mineral minimum elements! The manufacture of compost by biological means and with the use of a great many components might therefore yield an organic substrate immensely rich in ergones. Now it appears that excrements are particularly rich in ergones. The humus theory may be said to be revived. The mineral theory has been necessary to emphasise the fundamental facts of plant physiology. But the “ideal” plant, the organism totally independent of the organic environment, unfortunately rarely exists. “In principle”, plants are mineral feeders, synthesising their own organic matrix, but in practice they need more organic, than in organic minimum substances, the majority of which are, however, still unknown.

For our purpose a rough classification into clay, silt and sand, suffices, and a characterisation in a simple triangle is all that is needed. Of course, the transitions between the three concepts are gradual, and therefore Figure 3.21, as used by Correns (1939), is to be preferred.

A clay, due to the fine nature of its particles, but also due to the open laminar structure of its components, will have little air space. Aeration is difficult, which is important for many plants. Tobacco roots require, for instance, a highly aerated soil (Van der Wey, 1932), while there are other plants (rice, willow, water lily) which may live in almost anaerobic conditions.¹¹⁸ Clay induces anaerobiosis. Sulphate reduction sets in lastly.

Correns (1939) has made use of a method which shows the composition of a certain soil quite clearly (Fig. 3.22). If one plots particle size on the abscissa, frequency (summated) on the ordinate, a soil which shows an even distribution of all fractions may be represented by a straight line. If there is a preponderance of a certain range of particle sizes, it will show as a “humus” in the curve. In this way, by integrating, we evade errors due to class size.

Soil in relation to water (see Russell and Russell, 1912),¹¹⁹ requires special treatment. Here the water holding capacity depends not only upon the size and shape of the interstice, but also upon the swelling of the soil colloids. It is important to note that montmorillonite is highly swellable. A soil may hold water still in dispersed condition (the soil particles being continuous) while mechanical shaking will cause the phase to revert (thixotrophy). This is particularly striking in sea sand (drifting sand).

The composition of the air in soil is variable. Roughly the CO₂ contents goes in parallel with the humus percentage. In the original rock very curious gases occur, as Table 3.6, taken from Clarke (1916, p. 272), shows. [The composition of soil is summarised in Table 3.7.]

If the soil is well aerated, Azotobacter may function as a nitrogen fixing agent. In anaerobic soils Closteridium is active (see Section 6.4.2.a). Oxygen is, of course, variable. Hydrogen may be generated by cellulose fermentation and other fermentations. Hydrogen sulphide by sulphate reduction (or, as a secondary factor by “putrefaction of proteins”). It may be highly toxic to plants. Free ammonia only occurs in highly basic soils on the further composition of the soil solution. A soil without microbes, it should be stated, is a dead soil. The role of the organisms in the soil is still very imperfectly known. The contribution of ergones seems to be one of the chief acts (see Section 7.2, Ergones).

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[Baas Becking inserted Table 3.8, taken from Clarke (1916).]

16 mg/L HNO₃, 4 mg/L NH₃ (Caracas, Venezuela), rain contributes up to 75 kg/Ha in salts. An analysis of rainwater from Wyster, Drenthe is given below. See Figure 3.23.

[Baas Becking inserted Fig. 3.24, a triangular plot of 15 waters of unusual composition].

See Figure 5.14 and Figure 6.3, Section 6.4.3.

See also Section 6.4.3, Changes in the hydrosphere and Section 5.7.6, Natural waters again.

[Baas Becking inserted Fig. 3.25, copied from Geobiologie, 1934; Fig. X.1 in Baas Becking, 2016.]

Nowhere on this planet one meets with conditions so stable as in the ocean, says L. Henderson.¹²¹

[Baas Becking inserted Fig. 3.26.]

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[Baas Becking inserted Fig. 3.27.]

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