292 HOW CROPS FEED. 



gault, In his investigations on the assimilability of free 

 nitrogen, found in various vegetation-experiments, in 

 which crushed seeds were nsed as fertilizers, that nitrogen 

 was lost "by assuming some gaseous f )rm. This loss prob- 

 ably took place to some slight extent as ammonia, but 

 chiefly as free nitrogen. Lawes, Gilbert, and Pugh, found 

 in thirteen out of fifteen trials, including the exj^eriments 

 just referred to, that a loss of free nitrogen took place, 

 ranging from 2 to 40 per cent of the total quantity con- 

 tained originally in the vegetable matters submitted to 

 decomposition. In six: experiments the loss was 12 to 13 

 per cent. In the two cases where no loss of nitrogen oc- 

 curred, nothing in the circumstances of decay was discov- 

 erable to which such exceptional results could be at- 

 tributed. Other experiments (Phil. Trans. 1861, II., p. 

 509) demonstrated that in absence of oxygen no nitrogen 

 was evolved in tlie free state. 



c. Nitric acid is not formed from the nitrogen of or- 

 ganic bodies in rapid or putrefactive deca}', but only in 

 slow oxidation or eremecausis of humified matters. 

 Pelouze found no nitrates in the liquor of dung heaps. 

 Lawes, Gilbert, and Pugh, {loc. c«Y.). found no nitric acid 

 when the seed-grains decayed in ordinary air, nor Avas it 

 produced when ozonized air was passed over moist bean- 

 meal, either alone or mixed with burned soil or with 

 slaked lime, the exjjeriments lasting several months. It 

 thus appears that the carbon and hydrogen of organic 

 matters have such an affinity for oxygen as to prevent the 

 nitrogen from acquiring it in the quicker stages of decay. 

 More than this, as Pelouze has shown [Comptes Rendus, 

 XLIV., p. 118), putrefying matters rob nitric acid of its 

 oxygen and convert it into ammonia. "We have already 

 remarked that putrefaction and fermentation are reducing 

 processes, and until they have run their course and the 

 organic matters have passed into the comparatively stable 

 forms of humus, their nitrogen appears to be incapable of 



