SOILS — FEETILIZEKS. 321 



of the acid soluble nitrogen in the soil studied was made up of acid amids, 

 monoamino, and diamiuo acids. 



In order to ascertain the proportion of diamino and monoamino acids the soil 

 extracts were examined as follows : " The soil extract containing amino acids, 

 upon examination of the optical activity, is made up to a definite Tolume, say, 

 to 60 cc, for which the nitrogen in 15 cc. is determined by the Kjeldahl method 

 to ascertain the total nitrogen present in the sample, 15 cc. are titrated in the 

 ordinary way to determine the acidity of the substance, and 2 iwrtions of 15 

 cc. each are titrated with formaldehyde to find the increase of acidity due to 

 the reaction with formaldehyde. These 3 operations furnish all the data 

 which are necessary for the calculation of the percentage of diamino or mono- 

 amino acids present in the substance under examination." 



The results of this study showed that the larger part of the phosphotungstic 

 acid precipitate represented diamino nitrogen, the smaller part belonging to 

 classes other than diamino acids. In the case of the filtrate from the phos- 

 photungstic acid precipitate " it was found that from 68.02 to 85.98 per cent of 

 that filtrate represent in fact monoamino nitrogen, the rest (from 31.98 to 

 14.02 per cent) consisting of nitrogenous compounds other than monoamino 

 acids." 



The " availability " of phosphoric acid in the soil, H. J. Vipond (Agr. Jour. 

 Union So. Africa, 2 (1911), No. 5, pp. 602-611).— The author attempts to classify 

 Transvaal soils on the basis of a comparison of " the ratio of ' total ' to ' avail- 

 able ' phosphoric acid with the ratio of the iron oxid and alumina to the lime 

 and one-half of the magnesia." 



This method applied to about 250 samples of soils indicated a decrease in 

 availability of phosphoric acid with an increase of the ratio of iron oxid and 

 alumina to lime and half the magnesia up to 1 : 40, but practically none be- 

 yond. Of the soils examined 22.8 per cent showed an " iron-lime " ratio of less 

 than 1:30. 



The general conclusion reached was " that a fair amount of lime in the soil 

 insures a fair availability of the phosiihoric acid. On the other hand, many 

 soils with a poor ratio of lixue to iron oxid show a high ratio of availability of 

 the phosphoric acid. Soils rich in humus almost invariably contain a good deal 

 of available phosphoric acid whether rich in lime or not — there is no doubt, 

 therefore, that the phosphates of the humus are dissolved to a considerable ex- 

 tent by 1 per cent citric acid. Sandy soils, which usually contain low percent- 

 ages of iron oxid, alumina, lime, and phosphoric acid, with nevertheless a high 

 ratio of iron to lime, show as a rule a better ratio of availability of phosphoric 

 acid. This does not mean that the actual amount of available phosphoric acid 

 is greater in the sandy soils." 



Influence of the acid content of green plants on the utilization of insoluble 

 phosphates, G. Corso (Staz. Sper. Agr. Ital., U (1911), No. 5-6. pp. 309-316; 

 abs. in Chem. ZentbL, 1911, II, No. 12, pp. 895, 896). — From pot experiments 

 with plants of different botanical families on soils containing a high percentage 

 of insoluble phosphoric acid, the author concludes that the solvent power of 

 plants for citrate-insoluble phosphoric acid varies with different families of 

 plants. The higher the acid content of the plants the greater the utilization of 

 the insoluble phosphoric acid. 



Investigations on the decomposition of the carbon compounds of different 

 organic substances in the soil, especially under the influence of lime, O. Lem- 

 MERMANN ET AL. (Laudw. Johrh., 41 (1911), No. 2, pp. 217-256; abs. in Chem. 

 ZentbL, 1911, II, No. 25, pp. 1880, 1881).— The decomposition of the organic 

 compounds in soils was studied by examinations of the air drawn through glass 



