48 DE. THOMAS STEERY HUNT ON THE 



that they must be referred to christianite," ^ which is but another name for phillipsite. 

 "We have here, as iu the case of palagonite, and in ordinary zeolitic rocks, the breaking-up 

 of a basic igneous silicate into an acidic crystalline aluminous silicate of lime and alkalies, 

 and a more basic insoluble residue, rich in iron-oxyd ; a portion of which, as is well known, 

 separates from these red clays in the form of concretions, often with oxyd of manganese. 



§ 96. We have next to examine the conditions imder which zeolites, feldspars and 

 related silicates have been artificially produced in the chemist's laboratory. "When, accord- 

 ing to Berzelivis, three parts of silica and two of alumina are fused with fifteen parts or 

 more of potassic carbonate, and the cooled and pulverized mass is exhausted with water, 

 there remains a double silicate, which has the composition of a potash-anorthite, with the 

 ratios, 1:3:4, corresponding to potash 28.68, alumina 32.04, and silica 39.31 ; the excess 

 of silica being dissolved as an alkaline silicate.'"* The analogous soda-compound may be 

 produced in like manner. A similar silicate, according to Ammou, is obtained when 

 recently precipitated alumina is added to a moderately concentrated and boiling solution 

 of caustic soda, mixed with silicate of soda. The alumina is at first completely dissolved, 

 but a white jjulverulent precipitate soon separates, which is a hydrous silicate of soda and 

 alumina, having for the fixed bases the same ratio as before, 1 : 3 : 4 ; corresponding to 

 anorthite and to thoiusonite..*^ 



§ 9V. C. J. Way, in his studies on the absorption of bases by soils, prepared artificial 

 aluminous silicates by dissolving alumina iu soda-ley, and adding thereto a solution of 

 silicate of soda containing not more than one equivalent of silica to one of alkali (R : Si = 

 1 : 3,) to which any convenient excess of soda might be added. A precipitate was thus 

 obtained, which, when washed and dried at 100' C, was a white pulverulent silicate 

 of alumina and soda, holding twelve hundredths of water, and having almost exactly 

 the oxygen ratios, 1 : 3 : 6 : 2 ; being a true soda-mesolite. This artificial silicate, when 

 digested with lime-water, or with any neutral salt of lime, exchanged its soda for 

 lime. It was difficult thus to separate the whole of the soda, but iu some cases the replace- 

 ment was almost complete, and a scolecite was formed. Either of these compounds, when 

 digested with sulphate or nitrate of potassium, was converted into a potash-mesolite. 

 With a solution of a magnesian salt, these compounds gave a magnesian double silicate, 

 which was not particularly examined."' Berzelius again, by adding a solution of silica 

 to one of alumina in potash, in proportions which are not indicated, found the mixture to 

 solidify in a few minutes to an opaque jelly, in consequence of the separation of a silicate 

 of alumina and potash having the oxygen-ratios, 1:3:8, which are those of analcite.*^ 

 Farther investigations are required to make known the precise conditions for the produc- 

 tion of these different silicates, which give for their fixed elements the ratios respect- 

 ively of thomsonite, mesolite and analcite. The most basic of these, according to Berzeliixs, 

 is formed in the presence of an excess of a soda-silicate. 



§ 98. Henri Ste. Claire Deville, by mingling solutions of silicate of potash and alumi- 

 nate of soda, in such proportions as gave for the oxygen-ratios, al : Si ^ 3 : 6, obtained a 



^ Lecture, in Nature, June 5, 1884, p. 133, 



"' Cited in Gmelin's Handbook, iiij 431. 



*^ Jahresbericlit der Chemie, 1862, p. 128. 



^ Way, On the Power of Soils to absorb Manures, Trans. Royal Soc. Agriculture, 1852, xiii, 123-143. 



*' Cited in Gmelin's Handbook, iii, 439. 



