Farmyard Manure. 13 



salt, which is not volatile at the ordinary temperature, it is evi- 

 dent that the foetid smell of putrefying matters has much less to 

 do with ammonia than is generally believed. 



The following experiment is decisive in this respect. A 

 couple of ounces of genuine Peruvian guano were completely 

 drenched with dilute sulphuric acid. Any free ammonia in the 

 guano by the addition of acid must therefore have been instantly 

 converted into sulphate of ammonia. The characteristic smell 

 of the guano, however, was not removed nor even weakened by 

 the acid. The guano moistened with acid was next dried in a 

 water-bath for five or six hours, and during all that time gave off 

 the strong peculiar smell which characterises genuine Peruvian 

 guano. When dry it still smelt strongly, though weaker than 

 when wet ; but moistened again with a little water the smell again 

 became as strong as before. In order to make quite certain that 

 no ammonia would remain in a free state, I employed a great 

 excess of acid, in consequence of which the guano, after drying 

 up with acid, tasted as acid as any of the most concentrated 

 samples of superphosphate. 



I may further mention that I dried guano for days at a tempe- 

 rature of boiling water without being able to remove its peculiar 

 smell. 



Whilst speaking of guano it may interest some of my readers 

 to learn that genuine Peruvian guano contains a very small 

 quantity of volatile carbonate of ammonia. 



There are many people who run wild with the idea that every- 

 thing that smells strongly must contain free ammonia. Hence it 

 is not surprising that salt, gypsum, acids, and various other sub- 

 stances should have been suggested to be mixed with guano for 

 the purpose of fixing the ammonia, as it is said, in guano. 



It is not my purpose to enter here into a discussion of the 

 merits of salt or gypsum as fixers of ammonia, but I cannot 

 help observing that both salt and gypsum are ill adapted for 

 fixing any free ammonia in putrefying organic matters. I do 

 not mean to speak disparagingly of the mixing of salt or gypsum 

 with guano, for I believe this to be attended with very great 

 benefit. The good effected by mixing guano with salt, how- 

 ever, I feel assured is not due to the salt fixing the ammonia in 

 guano, as generally believed by practical men, and transcribed 

 from one text-book on agricultural chemistry to the other ; for 

 in the first place salt is incapable of fixing any free ammonia in 

 guano, and in the second place the amount of free ammonia in 

 genuine Peruvian guano is so inconsiderable, that salt, even 

 supposing it to fix ammonia, finds very little free ammonia in 

 Peruvian guano upon which to exercise its supposed power of 

 fixing ammonia. 



