SOILS FEETILIZEES, 723 



It is sbowu that sulphuric, uitric, liydroclaloric. and hydrofluoric acids de- 

 compose kaoliu and, therefore, can not have contributed to its formation. 

 Sulphuric and hydrochloric acids in the presence of little water form sulphates 

 and chlorids. With large quantities of water and siliceous rocks they form 

 almost pure silicic acid. 



Tourmalin, fluorspar, topaz, and turquoise have nothing to do with the for- 

 mation of kaolin, even though they are formed in unkaolinized rocks; fluorspar 

 and boron are, therefore, not kaolinizing agents. Neither is hydrogen sulphid 

 such an agent. 



All analyses point to the fact that cold water containing carbonic acid is the 

 principal kaolin-forming agent. 



Determination of the outer soil surface, E. A. Mitscheblich, F. Scheeffee, 

 and R. Floess (Lamhv. Jalirh., J,0 (1911), No. 5, pp. 6^5-659, flg. i).— The 

 authors report the results of studies of the hygroscopicity or outer surface area 

 of a number of different soils as determined by Mitscherlich's method, pre- 

 viously described (E. S. R., 24, p. 419). 



Although the authors admit that drying the soil produces colloidal changes, 

 they believe that the esttiblishment of vapor tension equilibrium by exposing 

 the soil to 10 per cent sulphuric acid eliminates such colloidal changes or so 

 reduces them as to render them negligible. 



The biological stimulation of natural humus, T. Remy and G. Rosing 

 (CenthJ. Balct. [etc.], 2. AM., 30 (1911), No. 16-18, pp. 8J,9-38h' a^s. m Jour. 

 Chem. Soc. [London], 100 (1911), No. 586, II, p. 7J8).— This article reports 

 a series of experiments which were undertaken to determine why the addition 

 of soil to a mannite nutrient solution causes such a great development in the 

 growth and nitrogen-fixing power of Azotobacter cfiroococcum. 



The results, in agreement with those of Krzeminiewski, showed that the 

 crude humus acid extracted from soil has an extraordinary influence in pro- 

 moting the development and nitrogen-fixing power of A. chroococcum. It was 

 found, however, that this effect was not due to the humus acids as such, but 

 to the iron which the crude acids contained. Humus acids free from iron pro- 

 duced no such effect as the crude substances, whereas the addition of iron com- 

 pounds alone to the mannite solution resulted in normal growth of Azotobacter 

 and increased nitrogen fixation. One of the most effective forms of iron was 

 found to be an alkaline solution of iron hydroxid in cane sugar. Iron silicate 

 was also effective for this purpose. 



Examination of soils for org-anic constituents, especially dihydroxystearic 

 acid, O. ScHREiNER and E. C. Lathrop ( U. 8. Dept. Agr., Bur. Soils Bui. SO, pp. 

 33, pis. 2). — "This investigation is a partial survey of the nature of soil 

 organic matter in the soils of the United States. Soils from 18 different States, 

 extending from Maine to Oregon and southward to Texas, of widely different 

 origin, topography, texture, climate, drainage, and cropping, varying from 

 soils of the highest productivity to soils incapable of producing profitable crops, 

 were examined for definite organic soil constituents. 



" To facilitate this examination, the numerous individual methods for the 

 separation of these compounds have been so coordinated as to form a single 

 comprehensive procedure of analysis. 



" In the soils so examined, pentosans, pentose sugars, histidin. cytosin, 

 xanthin, hypoxanthin, and dihydroxystearic acid were quite frequently en- 

 countered and the results indicate that these substances will be found to be 

 widely distributed. 



"Argenin, agroceric acid, lignoceric acid, a-monohydroxystearic acid, agros- 

 terol, phytosterol, and hentriacontane were only occasionally found, but no 

 general statement as to their limited occurrence can be made. 



