Silicate, soluble drying

The monohydrate of the metasilicate, LiaSiC HjO, is obtained as an almost insoluble, white, granular precipitate by the interaction at 80° to 90° C. of a solution of sodium metasilicate and the equivalent amount of lithium chloride in presence of normal lithium hydroxide. It is also produced by dissolving silicic acid dried below 100° C. in twice the theoretical proportion of twice-normal lithium hydroxide at the ordinary temperature, and subsequently heating the solution to 80° C. A readily soluble modification has also been prepared.1... 

You can find sodium silicate in the colorful Magic Rocks seen in gift shops at museums. The dry form is mixed with salts of various metals. When you drop them in water, the sodium is replaced by the metal. The resulting metallic silicate is not soluble in water, and it takes on a color characteristic of the metal (e.g., copper is blue). The metallic silicate is also a gel, so it expands and grows into colorful stalagmites in the water. 

Drying and remoistening air-dry soils greatly lowers their ability to oxidize Cr (Bartlett and James, 1980). Since Cr3+ has a similar ionic radius (0.64 x 10 10 m) to Mg (0.65 x 10 10 m) and trivalent Fe (0.65 x 10 ° m), it is possible that Cr3+ could readily substitute for Mg in silicates and for Fe3+ in iron oxides. This explains the high proportion of Cr found in the residual fraction in the native arid soil. On the other hand, humic acids have a high affinity for Cr (III) (Adriano, 1986). Thus, present results show that when soluble Cr was added to soils, Cr3+ was initially and immediately bound to the organic matter fraction. Due to its slow conversion into the reducible oxide and residual fractions, Cr in the amended soils departed and remained removed from the quasi-equilibrium. However, Cr approached the quasiequilibrium with time. 

The most common route for the s5mthesis of magnesium silicate is via a precipitation reaction between a soluble metal silicate (e.g., sodium orthosilicate, sodium metasilicate, or potassium silicate) and a soluble magnesium salt (e.g., magnesium sulfate, nitrate, or chloride). The aqueous suspension of the precipitate is filtered and the collected solid is washed and dried (Fig. 7.2) [6,7]. 

---