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THE SOLUTION OF SOIL MINERALS IN DILUTE ACIDS

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Science  15 Jun 1945:
Vol. 101, Issue 2633, pp. 619-621
DOI: 10.1126/science.101.2633.619-a

Abstract

Montmorillonite goes readily into solution in slightly acid water. In strong acids only bases, in pure water only free silica is removed.

In the range from 0.02 to 0.5 per cent. acid, both bases and silica go into solution and recombine as an aluminosilicate sol and as highly soluble salts.

The sol recovered by evaporation, washing and drying is an amorphous colloid near pyrophyllite in composition, Al2O3·mSiO2·nH2O, with m averaging 4.1 (3.9 to 4.5) and n about 1.5. The slight variation in m is unrelated to either sol, acid or clay concentration.

A general characteristic relation between the amount of sol formed and the amounts of clay, acid and water used has been found for montmorillonite clays. This relation differs in two essential properties from that previously deduced for halloysite-allophane solutions. The variation with temperature of the constants of these equations remains to be investigated.