AGRICULTURAL CHEMISTRY. 107 



from a pipette till the fumes have au alkaline reaction, and after boiling for a 

 little longer it is left to settle and the precipitate transferred to a weighed filter, 

 dried, and weighed. 



Determinations are furthermore made of the humus content of the sample, 

 calcium carbonate and sulphate, iron sulphid, sodium chlorid, and hygroscopic 

 moisture. 



According to the results obtained by this method of analysis, the clays are 

 referred to one of the following classes : Very stiff clays — fine clay with more 

 than 50 per cent hydrochloric-acid-soluble clay and less than 25 per cent coarser 

 portions (Silt, sand, and grit) ; stiffer medium clays — fine clay with 3.3 to 50 per 

 cent hydrochloric-acid-sohible clay, 20 to 40 per cent coarser portions, and rela- 

 tively low content of coarse clay; lighter medium clays— fine clay with 16 to 

 33 per cent hydrochloric-acid-soluble clay and 40 to 70 per cent coarser portions 

 (silt mostly below 50 per cent) ; silty clays — fine clay with less than 16 per cent 

 hydrochloric-acid-soluble clay and more than 50 per cent silt ; sandy clays, with 

 low content of fine clay and hydrochloric-acid-soluble clay and high content of 

 sand (and grit) with high silt content; and " mjun " clays, with more than 50 

 per cent coarse clay (or coarse clay and fine silt content). 



The colorimetric determination of nitrates in soil solutions containing 

 organic matter, W. A. Syme (Xorth Carolina Sta. Rpt. 1908, pp. 6.'/, 65). — In 

 the method proposed, potassium permanganate is added to the hot soil solution, 

 containing a slight excess of sulphuric acid. The solution is filtered, made 

 alkaline with sodium carbonate, and evaporated to dryness on water bath. The 

 residue is treated with water, filtered, and diluted to its original volume, and 

 nitrates determined in the usual way with phenoldisulphonic acid and ammonia. 



Tests are reported which indicate that no nitrate was formed by the action 

 of the permanganate on the organic matter. 



The colorimetric determination of nitrates in soil solutions containing 

 organic matter, W. A. Syme {Jour. Indus, and Engin. Chem., 1 {1909), No. 3, 

 pp. ISS, 189; abs. in Science, n. 'ser., 29 {1909), No. 7S8, p. 307; Analyst, 3// 

 {1909), No. 398, p. 2.'fl). — Noted above from another source. 



A new method for the determination of soil acidity, R. Albert {Ztschr. 

 Angew. Chem., 22 {1909), No. 12, i)p. 533-587; ahs. in Chem. ZentU., 1909, I, 

 No. 16, pp. 1350, 1351; Analyst, 3Jt {1909), No. 398, pp. 228, 229).— In the method 

 proposed the soil to be tested is suspended in water with a known amount of 

 caustic alkaline earth (magnesia, lime, or baryta) and an excess of neutral 

 ammonium salt (chlorid or sulphate), and the solution is boiled until all of 

 the ammonia set free by the caustic alkaline earth is driven off. The ammonia 

 is measured by collection in standard sulphuric acid and titration in the usual 

 way. The dift'erence between the amount of ammonia thus formed and that 

 shown by direct action of the alkaline earth on the ammonium salt solution is 

 taken as a means of calculating the amount of the base combining with the 

 soil acids and thus affording a measure of the latter. For use with magnesia 

 the author recommends ammonium sulphate, with lime and baryta ammonium 

 chlorid. On the whole the baryta ammonium chlorid coml)inatiou seems prefer- 

 able to any other used. The method as a rule gives somewhat higher results 

 than that of Tacke. 



A study of the methods for the determination of iron and alumina in 

 phosphate rock, W. C. Dumas {Chem. Engin., 9 {1909), No. J,, pp. 107-113).— 

 A compari-sou of the more important methods which have been proposed for 

 this purpose is reported, and the sources of error in the different methods are 

 pointed out. The conclusion reached is that the Glaser alcohol method is the 

 best for iron and aluminum in the hands of the inexperienced. It was found 

 also that "a combination of the (ilaser alcohol and acetate methods gives 

 732— No. 2—09 2 



