Poicer of Soils to absorh Manure. 



129 



was to produce artificially, and without the aid of heat, salts of the 

 same composition as felspar and albite. This was done by add- 

 ing to a solution of alum a solution of silicate of soda ; a gelatinous 

 precipitate was produced, which, when washed and dried, was 

 found to contain soda, and to be not silicate of alumina, but a com- 

 pound of this latter silicate with silicate of soda. This substance, 

 therefore, resembles albite, which has been before mentioned as a 

 double silicate of alumina and soda. 



The experiment was made as in the other cases of digesting 

 this salt in solution of muriate of ammonia; the excess of the 

 latter salt being washed av/ay by successive quantities of distilled 

 water, the precipitate was dried and examined for ammonia, which 

 it was found to contain in very considerable quantity. 



I may shortly state here, that with these double silicates of 

 alumina and other bases the greater part, if not all, the phenomena 

 of absorption of manures are connected ; and, without detaining the 

 reader with further accounts of the steps of the inquiry, I shall 

 proceed to describe these salts, the method of forming them, 

 and the changes which they undergo under different circum- 

 stances. 



It is just possible that these compounds, which I believe to 

 have a very important relation to the growth of plants, may at 

 some future time be manufactured at a sufficiently low cost to 

 make them available as manure ; and this must be my apology for 

 describing the mode of making them with the greatest advantage, 

 which would otherwise be quite unnecessary. 



The first step is the production of the silicate of soda. When 

 carbonate of soda is fused, at a high temperature, with sand or 

 powdered iiint, a glass is obtained, which is more or less soluble 

 according to the proportion of soda employed. The greater the 

 proportion of alkali the more soluble is the silicate produced. 

 The formation of silicate of soda in this way is, however, very, 

 troublesome and costly, on account of the high temperature neces- 

 sary, and the consequent destruction of the furnaces. A more 

 easy and economical method of obtaining an alkaline silicate is., 

 that pursued by ^Messrs. Ransome and Parsons, of Ipswich, in the 

 manufacture of their patent artificial stone. A solution of caustic 

 soda is heated in contact with unbroken flints in large high- 

 pressure boilers ; the temperature becomes very high, and under 

 its influence the flints in a few hours soften and melt away, the 

 result being a strong solution of silicate of soda. 



From silicate of soda formed by either of these methods the 

 different double silicates may be prodiuced. 



Double Silicate of Alumina and Soda. — This compound is 

 formed whenever soluble silicate of soda is added to a solution of 

 a salt of alumina, but the relative proportions of the ingredients 



VOL. XIII. K 



