22 Farmyard Manure. 



6. i Ib. of prepared gas-lime was treated with 20 ounces of 

 distilled water. The clear liquid filtered from the insoluble 

 matter was yellow-coloured, and smelt similar to the solution of 

 M'Dougall's powder. It possessed a stronger alkaline reaction 

 than the solution of M'Dougall's powder. 



By mixing 8 ounces of liquid manure with 4 ounces of this 

 solution of gas-lime a considerable deposit was produced, the 

 liquid became much clearer and brighter, and lost all disagreeable 

 smell. 



7. 6 ounces of liquid manure were mixed with 20 grains of 

 M'Dougall's disinfecting powder. 



The colour of the liquid became lighter, ammonia was liberated, 

 and the peculiar disagreeable odour of liquid manure completely 

 removed after some time. 



8. 6 ounces of liquid manure were mixed with 20 grains of 

 M'Dougall's powder, previously saturated with sulphurous acid. 



The colour of the liquid remained unaltered, and the smell 

 remained as bad as before the addition of the powder. 



If the deodorizing effects of the disinfecting powder were due 

 to the sulphite of magnesia contained in it, the deodorizing effect 

 of the powder when saturated with sulphurous acid, it is plain, 

 should have become more marked ; but the contrary was the 

 case. Indeed, by neutralizing the free alkaline constituents in 

 the powder its deodorizing power was destroyed. 



9. It is but fair to state that Mr. M'Dougall recommends the 

 addition of a soluble phosphate to liquids containing much free 

 ammonia. He mentions liquid manure and sewage as two liquids 

 which do not contain sufficient phosphoric acid in a soluble 

 form to unite with all the ammonia contained in these liquids 

 and the magnesia of the disinfecting powder. Following his 

 advice, I added to liquid manure phosphate of soda, in various 

 proportions, and used small and large doses of the disinfecting 

 powder. In every instance M'Dougall's powder failed to fix the 

 ammonia in liquid manure, notwithstanding the presence of 

 abundance of soluble phosphates. 



It thus appears from these various experiments : 



1. That M'Dougall's powder is unfit to fix any ammonia in 

 dung. 



2. That its deodorizing effects are not due to the sulphite of 

 magnesia or sulphite of lime, but to the alkaline constituents 

 which it contains. 



3 That, instead of fixing ammonia, it liberates, like all alka- 

 line matters, ammonia from its combinations. 



It is well known, however, that animal excrementitious 

 matters, when deodorized by lime, after some time give off again 



