Chemical Chanrjes in the Fermentation of Duiitf. 339 
please to bear in mind that tliis exactly represents the state of 
things in a manure heap lohicJi abounds in nascent hydrorjcn, and 
therefore what happens in the instance of which we can follow 
the change will certainly happen in any other instance in which 
the same conditions are fulfilled.* 
* Tlie formation of much phosphuretted hydrogen, and consequent loss during the 
fermentation of manure, is stated in the text rather as what analogy showed must 
he than as what was ahsolddij known. Up to tlie time of writing that, I had never 
met with a satisfactory statement on the subject, and had never made what 
appeared a perfectly trustworthy experiment. The difficulty of detecting the 
presence of phosphuretted hydrogen arose from the fact of sulpliuretted hydrogen 
being generated at the same time. By taking advantage of the dilFerent solu- 
bility of the two gases in water, I have been able to ascertain the copious evolution 
of phosphuretted liydrogen before the disturbing influence of sulphuretted hydrogen 
came into play. It is known that water dissolves three times its bulk of sul- 
phuretted hydrogen (Gay Lussac and Thenai-d), hut only an eighth of its bulk of 
phosphuretted hydrogen. The former gas is therefore twenty-four times more 
soluble than the latter. 
The large weed heap mention»d p. 33.3 contained much water, and afforded a 
favourable opportunity for experiment. The test employed. for phosphuretted 
hydrogen was ammonia-nitrate of silver ; and where this was affected almost 
instantly, acetate of lead showed no free sulphuretted hydrogen for days. By 
adding an acid to the fluid, however, the latter gas could be detected at any 
time. 
The same result was obtained with another weed-heap subsequently, and with 
several other parcels of decaying vegetable matter. 
Barley gives up a large portion of its nitrogen during the process of malting. 
The steep-water removes much, and the rootlets (cums) much more. This, there- 
fore, was selected as the least nitrogenized form of grain, with a view to investi- 
gate the products of its decomposition. It was mashed as for brewing, a portion 
of the fluid poured off and the rest left to decompose with the grains. Here, 
while phosphuretted hydrogen was given oil in considerable quantity ammonia and 
sulphuretted hydrogen were retained in solution, and the usual tests could detect 
neither in the state of gas. 
One of our best toxicologists informs me that he has seldom failed to find this 
gas given off by human bodies which have been disinterred for the purpose of 
chemical investigation in cases of suspected poisoning. Are we not, then, justified 
in concluding that while the British farmer is hiring ships to bring him phos- 
phorus from another hemisphere, he is literally wasting at home much of what he 
thus expensively imports? Countless thousands of manure-heaps, and still more 
countless ' middens ' and ' ash-pits,' in the three kingdoms, are sending forth 
their phosphorus as a volatile gas, which the winds bear away to distant oceans to 
advantage races of men who will inhabit lands as yet unformed, whereas by 
better management nearly or quite the whole of this may be retained at home. 
Mr. Noad found 57'18 grs. of nitrates, and 2G"5G grs. of sulphates per gallon 
iu the water of the well of Highgate churchyard, evidently formed from the 
' Mr. Noad's figures are — grs. 
Nitrate of lime 40-12 
Nitrate of magnesia 17'06 
Sulphate of potash 17'()4 
Sulphate of soda 9"52 
Chloride of sodium 9'63 
Chloride of calcium 5-91 
Silica -90 
lOO'lS grs. per gallon. 
