ABSTRACTS OF REPORTS OP FOREIGN INVESTIGATIONS. 



The formation and oxidation of nitrites during nitrification, S. 

 Winogradsky [Cdiiipt. icnd.. 113 [I'^Hl), pp. 6.v-.''^-'; (ib-s. in Jour. Clum. 

 ^S()(■., /.yy/, p. 1515). — 111 coiitiiiuatioii of iuvestigatious on iiitriticatioii 

 (see Experiment Station Record, vol. ii, p. 7.")1) the author made use of 

 wsoil.s from different parts of the world. From these soils cultures were 

 made in solutions containing: ammonium sulphate and other mineral 

 salts togetlier with iiiaijiicsium carbonate. In every case nitiitication 

 (commenced with the formation of nitrites. But when successive cul 

 tiires were made the results were not parallel. With all the European 

 soils the formation of nitrites proceeded slowly and with diminishing 

 activity, ceasing alt(»gctlicr after a number of generations. With otlier 

 soils the rate of oxidation was not only maintained, but could be 

 increased by successive additions of ammonium salts to the solution. 

 This was especially true of certain soils from Africa and South 

 America. The formation of the nitrites was in general iiuu-h more 

 rapid than their oxidation. 



Several ditlerent kinds of microbes were observed in the cultures, 

 esi)ecially in those in which nitrates had been formed. One jnedomi- 

 nant form closely resembled the nitrous microbe previously discovered. 

 Several of the forms analogous to the nitromonad were isolated and 

 found to retain tlieir power of oxidizing ammonia, Imt to soon lose tliat 

 ()f oxidizing nitrates. Negative results were obtained in attempts to 

 isolate the nitric organism from Tunis soil by gelatin culture, but the 

 metliod ])ieviously employed by the author in isolating the nitrous 

 microbe was m(»re successfully used. A solution of nitrites was sown 

 with Quito soil, and when the oxidation had become regular a little 

 dro]) of the culture was sown in gelatinous silica. Colonies of two 

 dilferent organisms api)eared, one of which proved to be the nitric 

 microbe. It has tlie form of a minute, irregular, angular rod, and bears 

 no resemblance to the nitrous organisms found in the same soil. Sown 

 in the solutions of nitrites, it changes them rapidly into nitrates but 

 has no effect on ammonia. (Organisms with a similar function were 

 observed in soils from Java and Zurich, These probably belong to a 

 different genus from the nitrous organisms, each species having its 

 habitat in a particular soil. 

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