342 
Chemical Changes in the Fermentation of Dung. 
black bj the separation of sulphuret of lead. (Liebig.) Ber- 
zeliiis proved that urine contains unoxidized sulphur, for after 
acidulating with hydrochloric acid and precipitating with 
chloride of barium and then decanting the clear supernatant liquid 
there still remained in solution a combination of sulphur. Upon 
evaporating to dryness and incinerating the residuum sulphate 
of baryta was found. 
Whoever has experienced the hoiTible smell of sulphuretted 
hydrogen given off by a large heap of fermenting broccoli or cab- 
bage-leaves will be quite ready to think that a very large part of 
the sulphur contained in the brassica tribe at least is unoxidized, 
and in the process of decomposition unites Avitli hydrogen and 
becomes volatile in preference to taking oxygen and remaining 
fixed. I have several times had an opportunity of testing this 
upon a neighbouring farm where vegetables were largely grown. 
From 20 to 30 cartloads of refuse broccoli-leaves was no uncom- 
mon accumulation in the spring, and the odour given off would 
have convinced the most sceptical of the position here taken 
without any attempt at chemical investigation. I once noticed 
the same phenomenon in an open field of broccoli belonging 
to the same farmer. The crop was planted about 18 inches 
asunder and most of the lower leaves fell off and decayed where 
they fell. The smell was so offensive as to be a general sub- 
ject of complaint, and several persons attempted to obtain a miti- 
gation of the nuisance through the authorities.' 
Putrefying nightsoil is well known to give off a large part of 
its sulphur as sulphuretted hydrogen, and hydrosulphate of am- 
monia (vide Liebig, Agricultural Chemistry, p. 186), and that 
the same thing occurs to every manure-heap may be proved by 
any one who will take the pains to collect and condense the 
fumes which arise and to analyse the product so obtained. I 
believe that all the unoxidized sulphur takes hgdrogea in prefer- 
ence to oxygen in a mamire heap, but am far from supposing that 
the loss of sulphur from the formation and volatilization of sul- 
phuretted hydrogen is limited to that; fori believe that sulphates 
are constantly decomposed by the agency of hydrogen which 
combines with their oxygen to form water and then with their 
sulphur as sulphuretted hydrogen. That this is quite possible 
any farmer may easily satisfy himself. 
" When a sohition of gypsum in water is mixed with a decoction of sawdust 
or a-iiy other orgrmic matter capable of putrefaction and preserved in well 
closed vessels it is found after some time that the solution contains no more 
sulphuric acid but in its place carbonic acid and free sulphuretted hydrogen, 
between which the lime of the gypsum is shared. In stagnant water con- 
taining suli)hates in solution crystallized pyrites is observed on the decaying 
roots," — Liebig, p. 289. 
