CHANGES IN INORGANIC CONSTITUENTS 359 



some base, usually calcium carbonate, resulting in the formation of 

 calcium sulphate. Thus: 



S02+0+H20 = H2S04 

 H2S04+CaC03 = CaSOi+HaOJfCOa 



We owe much of our knowledge concerning the sulphur bacteria to 

 Winogradski. This investigator showed that in places where hydrogen 

 sulphide is generated in considerable quantities sulphur bacteria grow 

 vigorously and accumulate granules of sulphur within their cells. 

 When the cells containing sulphur granules are removed to suitable 

 media, in which no hydrogen sulphide is present, the sulphur seems 

 to be gradually ojddized and disappears and the bacteria finally die of 

 starvation. Thanks to the sulphur bacteria, the higher plants are 

 enabled to utilize again the sulphur once locked up in plant and ani- 

 mal tissues, and liberated thence by decay bacteria. The circulation 

 of sulphur is thus made possible and the cycle is completed when the 

 sulphates are again used by plants to build protein compounds. It 

 may also be noted in this connection that " Thiobacillus denitrificans," 

 described by Beyerinck, may also oxidize elementary sulphur. In 

 this case, however, the oxygen is derived from nitrates instead of the 

 atmosphere. Thus: 



6KNO3 + SS + 2CaC03 = 3K2SO4 + 2CaS04 + 2CO2 + 3N2 



SuLPHOPiCATiON. — Lint has found that under optimum temperature 

 and moisture conditions, sulphur applied at the rate of 600 pounds 

 per acre was almost completely oxidized within ten weeks. Boullanger 

 and Dugardin in explaining the fertilizing action of sulphur on the 

 basis of its effect on the supply of available nitrogen found that am- 

 monification was increased by small amounts of sulphur, nitrogen- 

 fixation was not affected and nitrification was depressed. It has been 

 pointed out by Kossovitch, Brioux and Puerbet that the mechanism 

 of sulphur fertilization is very complex and that the oxidation of free 

 sulphur occurs entirely by bacterial and not by chemical means. 

 Brown and Kellogg have recently advanced evidence to prove that 

 soils have a definite sulphofying power which is determinable in the 

 laboratory by a newly devised method. They claim that the process 

 of sulphofication is mainly brought about by bacterial action, but 



