The chemical problems growing out of studies of sedimentary rocks must, even more than other problems, be viewed from many angles. Each such problem is likely to lead to several highly specialized studies in restricted chemical fields. The mere statement of any one of these special problems will often require an extended study of its general chemical, geological, and biological setting. Because of the special nature of these chemical problems, no general outline for their study needs presentation here, but it may be worth while to present some viewpoints from which the problems may be seen.
From the standpoint of physical chemistry many of the problems of sedimentary rocks are especially difficult, because the solutions concerned may be very dilute and very complex; the solid phases are often ill-defined physically, or are stable at temperatures so little above the ordinary that heat to speed up reactions can not be effectively . . .