194 
Peruvian Guano. 
been received which ascribes to salt this power. The explana- 
tion of this mistaken notion no doubt lies in the fact that salt is 
an excellent antiseptic, and consequently prevents the further 
decomposition of nitrogenous organic matters, and with it the 
further formation of ammonia, but it does not fix any existing 
free ammonia. Free ammonia in a substance soon escapes, and 
since, by the use of salt, further decomposition is effectually 
stopped, and the pungent smell which accompanies it is no 
longer perceptible, it is easy to conceive how salt should have 
received credit for being a fixer of ammonia. 
In proof of the supposed value of common salt as a fixer of 
ammonia the following experiments of M. Barral, editor of the 
" Journal d'Agriculture Pratique," .are quoted : — M. Banal 
took samples of guano ; the one he kept pure, the other he mixed 
with an equal weight of common salt. The sample of pure guano 
was found on analysis to contain 12*56 per cent, of nitrogen ; the 
sample mixed with salt contained 6'23 per cent., or as nearby as 
possible half the quantity of nitrogen. Equal weights of the two 
samples were exposed to heat for three hours in the same stove, 
in a current of air, maintained at 212° Fahr. They were spread 
out so as to have the same thickness, and occupy an equal sur- 
face, and they had been equally pulverised. At the end of three 
hours, on examining the two samples, the pure guano had lost 
5*1 per cent, of its nitrogen, while the mixture had lost only 1'9" 
per cent. 
This experiment, which appeared to be in favour of the 
preservative power of salt, was repeated under another form. 
Equal weights of the pure and the mixed guano were left in the 
open air, in plates, during fifteen days. At the end of that time 
the amount of nitrogen was determined in each sample, and it 
was found that the pure guano had lost 11 "6 per cent, of its ni- 
trogen, while that mixed with salt had lost only 5 per cent. In- 
dependent of the influence of salt in these experiments is the 
important fact that in this case upwards of one -tenth of the 
nitrogen was lost in the course of fifteen days. It will be 
observed that the guano here used contained only 12 - 56 per 
cent, of nitrogen, that is, a quantity much smaller than occurs in 
genuine sound Peruvian guano. It appears to me, therefore, 
likely that the guano was not of the best description, but probably 
a sample in an actual state of decomposition. Such samples 
yield ammonia constantly as a product of decomposition of the 
nitrogenous matters, and the addition of salt had not the effect of 
fixing any free ammonia, but by checking decomposition, it pre- 
vented the further formation and loss of ammonia. The correct- 
ness of this view appears clearly from the following experiments,, 
which I made in the hope of confirming M. Barral's observations. 
