3C8 ANALYSIS OF SOILS. 



The analyses were conducted through two operations. The fire) was precisely that by 

 which we obtained the results already stated. The silicates, alumina and iron, lime and 

 rnesia, wi • ally obtained bj the usual methods. To secure exactness, the double 

 filters were always well washed, dried, burnl and weighed. We then tested for phosphates, 

 by redissolving the alumina and iron in chlorohydric acid : the soluble silcx was separated 

 by filters, and, if in a decidedly appreciable quantity, it was weighed. The solution being 

 freed from silica, was exactlj neutralized by caustic ammonia, and the phosphates, if any 

 existed, were thrown down by a solution of acetate of potash. Sometimes the phosphate 

 of alumina and phosphate of the peroxide of iron did not immediately appear, but, in the 

 course of five or six hours, it would become perceptible, and in twenty-four hours it 

 subsided. In some cases its presence would be sensible, but its quantity so small that it 

 did not appear of sufficient importance to filter and weigh. The iron and alumina were 

 not separated. 



Having subjected the alumina and iron to the above test for phosphates, we then took 

 up the farther examination of the silicates obtained in the first operation. This was, in 

 the firsi place, fused in a platina crucible, with three times its weight of carbonate of soda. 

 The fused mass was then dissolved out by boiling water acidulated with hydrochloric acid, 

 evaporated to dryness, and then redissolved : when it was subjected to the same course of 

 treatment, for alumina, iron, lime, magnesia, potash and soda. 



By this treatment, we supposed the capability of the soil would be determined. The 

 advantages of this double process consist in obtaining first the elements which are more 

 immediately available to the crops ; and, in the second process, we learn the amount of 

 the elements which are more securely locked up by the silica for future use. Both ope- 

 rations give the capabilities of the soil. In the second operation, phosphates are never 

 obtained, but lime, alumina, iron and Bome magnesia usually ; and in a few instances, 

 where the soil contained much matter from the primary rocks, a greater amount of lime 

 was obtained than by the first operation : the amount of magnesia is much less also. The 

 phosphates of the soil which have been derived in the last place from animal or vegetable 

 origin, may be expected to be easily dissolved ; and it is quite doubtful whether any exists 

 in any soil, which may not be dissolved and obtained by the first operation. They pro- 

 bably exist in line particles in the soil as phosphate of lime and alumina, and, if so, are 

 almost as soluble as the phosphates contained in bones. The phosphates, then, so far 

 as they exist, are always soluble, and never locked up in combination with an acid, such 

 as will not yield to the action of the weak organic acids, which are formed in the soils by 

 peculiar changes that take place in woody fibre and other vegetable products. 



The process by which soluble silica was obtained, we deem highly important. We 

 believe we do not err when we state that silica is an element ecmally important in vegeta- 

 tion with the phosphates, or the potash and alkaline earths. It is a mistaken notion, if it 

 exists, that fertility is due to any one element; that a good crop of corn can be raised, 

 provided the phosphates, or any other one of the necessary elements, are in sufficient 



