Abstract
The hydrous sodium silicate kenyaite can be synthesized from aqueous suspensions containing SiO2 and NaOH with SiO2/NaOH ratios ranging from 5 to 20 and H2O/NaOH ratios from 50 to 500 at 100-150°C. This phase can also be prepared from concentrated or diluted water glass solutions above 120°C. At 100°C magadiite generally precipitates as the first reaction product and then alters to kenyaite. The stable end product is quartz. This leads to the suggestion of the transformation: magadiite → kenyaite → quartz in agreement with field observations of Eugster (1969).
Formation of kenyaite at 100°C requires several months. The reaction times are much decreased at higher temperatures but under these conditions quartz forms rapidly. Synthetic kenyaites form spherical aggregates of well-developed plates.
Kenyaite gives intracrystalline reactions like other layer silicates. The intracrystalline reactivity reveals some differences between the different samples which are not detected by other methods. The reactivity mainly depends on the time of synthesis and is less influenced by the composition of the starting mixture. Through exchange of protons for the interlayer sodium ions, kenyaite is transformed into a crystalline silicic acid.
