116 



CHANGES IN FAEM-YABD MANUEE 



CO(NH 2 ), 



Urea. 



H 2 = NH 4 .O.CO.NH 2 



Ammonium carbamate. 



resulting in the formation of ammonium carbamate, has been de- 

 tected. At least five or six different bacteria, some micrococci, some 

 bacilli, and even some moulds have been shown to have the power of 

 bringing about this change. 



(e) Sulphuretted hydrogen fermentation. A large number of dif- 

 ferent bacteria have been shown to have the power, under certain 

 conditions which are not exactly known, of producing sulphuretted 

 hydrogen by their action upon albumin. 



(f) Cellulose fermentation. Cellulose, which forms the larger 

 portion of the tissues of straw and other vegetable matter is, under the 

 influences of an organism known as Bacillus amylobacter and other 

 bacteria, converted eventually into carbon dioxide, CO 2 , and methane, 

 CH 4 , though many intermediate products, e.g., acetic acid, CH 3 .COOH, 

 free hydrogen and perhaps, butyric acid, C 3 H 7 .COOH, have been de- 

 tected. The process is anaerobic and the bacteria producing it have 

 been detected in the intestines of cattle. 



(g) Other carbohydrates, chiefly starch, various sugars and gums, 

 occur in dung and readily undergo change by the influence of many 

 bacteria, some aerobic, some anaerobic. Carbon dioxide, water, lactic 

 acid, CH 3 .CH.OH.COOH, butyric acid, CH 3 .CR,.CH 2 .COOH, and 

 sometimes free hydrogen are formed. 



A study of the gases evolved during fermentation of manure was 

 made by Schloesing in 1892. l He found that, in presence of air, the 

 temperature of a manure heap is raised by the action of aerobic 

 organisms until purely chemical oxidation sets in and this may go on 

 until the temperature is so high that destruction of the organisms is 

 effected. No combustible gases are produced. By allowing the fer- 

 mentation to proceed in a current of nitrogen or other indifferent gas, 

 the anaerobic bacteria only are active and carbon dioxide and marsh 

 gas are chiefly produced. 



The details of one experiment may be of interest. 124*4 grammes 

 of fresh manure were allowed to ferment in an atmosphere of carbon 

 dioxide for two months ; in this period, nearly 9 litres of gas were 

 evolved, the maximum rate of evolution being 16-3, cc. per hour (on 

 the sixth day). The gas contained 15*8 cc. of hydrogen, 4217*5 cc. 

 of carbon dioxide, and 4577*4 cc. of marsh gas (equal to 4'72 grammes 

 of carbon, 6'033 grammes of oxygen, and 0'819 gramme of hydrogen). 



The loss suffered by the manure is shown by the following table, 

 which gives the amounts, in grammes, of the various constituents in 

 the dried manure, before and after the experiment : 



x Ann. Agron. 18, 5; Jour. Chem. Soc., 1892, Abstracts, 1123. 



