214 EXPERIMENT STATION RECORD. [Vol.43 



tention is called to the fact, however, that there is no standard of p\irity for 

 such substances by comparison with which their degree of purity can be ac- 

 curately indicated. For this reason an apparent purification process may in 

 reality serve to concentrate certain impurities. 



On the other liand it is brought out that hurain acids obtained in different 

 ways and of different ages and biological history show so much similarity with 

 reference to their composition, chemical constants, and their important chem- 

 ical properties that there is no doubt such acids are substances of fixed con- 

 stituents and properties, which ^re contaminated witli different foreign sub- 

 stances consisting of humus acids, peat acids, soil acids, and the like. To a 

 certain extent it Is concluded with Berzelius, Hoppe-Seyler, Berthelot, and 

 others that humus and humus acids are related to certain substances in the 

 soil. While in this connection the author apparently is not much impressed 

 with theories of adsorption, adsorption complexes, and adsorption decomposi- 

 tion, he considers it evident that humus bodies and humin acids occur In dif- 

 ferent dispersoid divisions. This physical condition is considered to be of strik- 

 ing importance for certain appearances, but in other reactions the inherent 

 purely chemical properties play the most important part. In this connection 

 he gives a rather extensive basic study of the laws of chemical mass action, 

 hydrolysis, and disassociation appearances, together with a rather exhaustive 

 discussion from the chemical standpoint. 



A list of 386 references to literature bearing on the subject is included. 



Nitrate production in field soils in Illinois, A. L. Whiting and W. R. 

 ScHOONovER (Illinois Sta. Bui. 225 {1920), pp. 21-63). — Four years' studies are 

 reported which were undertaken in order to measure systematically the amount 

 and rate of nitrate production in certain surface soils of Illinois, principally 

 with respect to the influence exerted by seasonal changes, soil treatment, differ- 

 ent crops, and rainfall. 



It was found that the most important factor in increasing nitrate production 

 is soil treatment. Raw rock phosphate was an important factor in increasing 

 the amount of nitrate produced, and in good rotations the effect of rock phos- 

 phate was much greater than in poor rotations. The complete treatment with 

 organic matter, phosphate, and limestone furnished the largest amount of 

 nitrates, and at an earlier period than organic matter and limestone or organic 

 matter alone. 



It was further found that the nitrogen of red clover or of sweet clover 

 plowed under in April or May furnished nitrate for the succeeding crop. Stable 

 manure was efficient in nitrate production, especially when used with phosphate 

 and limestone, but when applied alone it did not approach the rate and amount 

 of production exhibited by the green sweet clover or green red clover. Active 

 organic matter greatly increased the amount of nitrate in brown silt loam. 

 Crop rotations in which legumes were used as green manure, and in which 

 the crop sequence was such as not to have two crops in succession that are 

 heavy feeders on nitrogen, were superior for nitrate production to rotations in 

 which these points were ignored. With corn and soy beans, the maximum 

 nitrate production occurred in most cases in June. On land in wheat and oats 

 the largest production was found in May. 



The most active period of production and accumulation of nitrates was dur- 

 ing late spring and early summer. A second active period occurred frequently 

 in the autumn, which is considered the second approach to optimum. Little 

 nitrate production occurred in summer unless the weather was cool and there 

 was a supply of available moisture. No evidence of nitrate production was 



