SOILS FERTILIZERS. 815 



shaken up with solutions of sodium chlorid, potassium nitrate, and sodium 

 acetate is not due to double decomposition in which insoluble humic acids are 

 involved but to adsorption of the base of the salt. 



Acid was set free by similar reactions when solutions of the salts named 

 were shaken up with kaolin. 



" That the acid is not adsorbed by the soil and kaolin and liberated again 

 when treated with a salt solution was shown by treating samples of soil and 

 kaolin with sulphuric acid, washing out the acid, and treating with itotassium 

 nitrate solution. Although a soluble acid was set free in the potassium nitrate 

 solution, no evidence of the presence of the sulphate radical could be found. 

 This showed that there had been no adsorption of the acid. 



" To show that the base of the salt is actually adsorbed by the soil and kaolin, 

 samples of these substances were treated with dilute hydrochloric acid, and then 

 with a barium chlorid solution, the amount of acid that was set free in the 

 solution being determinetl. The soil and kaolin after being thoroughly washed 

 were treated again with hydrochloric acid and the amount of barium recovered 

 by this process determined. It was found that the barium recovered in the 

 ease of the soil corresponded to 95 per cent of the acid liberated in the barium 

 chlorid solution and to 89 per cent in the case of the kaolin. The soil was found 

 after this second treatment with hydrochloric acid to have regained all its 

 original capacity for liberating an acid from a salt solution. 



" Finally it was found that a soil which had been boiled for six or seven 

 hours with concentrated sulphuric acid to remove the organic matter, after 

 being washed to remove the soluble acid, had the power of setting free almost 

 exactly the .same quantity of acid from a salt solution as a sample of the 

 same soil which had been treated with twentieth-normal or fortieth-normal 

 acid and in which all the organic matter was present. This would indicate 

 that acid soils of the sort investigated (sandy loams) owe their acidity not to 

 organic matter but to inorganic matter, probably to hydrated silicates." 



The nonexistence of magnesium carbonate in humid soils, W. H. MacIn- 

 TiRE, L. G. Willis, and J. I. Hardy {Tennessee Sta. Bui. 101 (1914), pp. 151- 

 202, figs. .'t). — This is a full account of investigations more briefly noted else- 

 where (E. S. R., 31, p. 25). 



In basket and pot experiments magnesium carbonate equivalent to applica- 

 tions of 8 tons per acre of calcium carbonate in excess of the lime requirement, 

 as shown by the Yeitch method, was entirely decomposed after contact, without 

 leaching, with fallow soils of three distinct types for a period of one year. 

 Similar experiments under field conditions showed that magnesium carbonate 

 equivalent to 28,180 lbs. of calcium carbonate per acre (2,000,000 lbs.) of soil 

 had been entirely decomposed at the end of 8 weeks without leaching, while in 

 soils treated with equivalent amounts of precipitated calcium carbonate the 

 carbonate was still plainly discernible. 



It was foimd in laboratory exi)eriments that sand, both coarse and fine, 

 clay, silt, opal, kaolin, kaolinite, bauxite, hornblend, rutile, soapstone, serpen- 

 tine, and aluminum silicate, as well as the three different types of soils ex- 

 perimented with, decomposed precipitated magnesium carbonate and dolomite, 

 with evolution of carbon dioxid, by moist contact at room temperatures both 

 with and without the presence of precipitated calcium carbonate. Pure alka- 

 line silicon dioxid, hydrated and dehydrated, decomposed precipitated calcium 

 and magnesium carbonates and dolomite at room temperatures. The magnesia 

 of precipitated magnesium carbonate also showed a strong afiinity for alkaline 

 titanium oxid at room temperatures. In all cases the magnesium compounds 

 showed a greater affinity for the substances named and underwent more rapid 

 decomposition than did the calcium compounds. The great affinity of mag- 



