18 Farmyard Manure. 



the same liquid ; a strong smell of sulphuretted hydrogen re- 

 mained, and no deposit whatever of sulphur was produced. 



The solution of the disinfecting powder in water had a distinct 

 alkaline reaction, and contained, as ascertained by direct experi- 

 ment, in addition to sulphite of lime and sulphite of magnesia, 

 some quick lime. 



Lime-water, i.e. a solution of quick lime in water, I find pos- 

 sesses the property of removing sulphuretted hydrogen from its 

 solutions to a larger extent than a solution of M'Dougall's 

 powder ; whilst a solution of pure sulphite of lime and magnesia 

 apparently does not possess the power of removing sulphuretted 

 hydrogen from its solution. At any rate, even a concentrated 

 solution of sulphite of lime or sulphite of magnesia, added in 

 large excess to a solution of sulphuretted hydrogen, produces no 

 deposit of sulphur, and has no immediate effect upon this gas. 



Having proved experimentally that it is not the sulphite of 

 lime or magnesia in M'Dougall's disinfecting powder, but in all 

 probability the free-lime contained in it, which instantly removes 

 sulphuretted hydrogen from its solutions in water, I will next 

 describe some experiments which I have made in conjunction 

 with Mr. Coleman, our farm-manager, with a view of testing the 

 disinfecting properties of this powder. 



The fact that refuse gas-lime contains sulphurous acid in com- 

 bination with lime, as well as free lime, induced me to compare 

 the effects of M'Dougall's powder with dried and finely pow- 

 dered gas-lime, to which a small quantity of gas-tar was added. 

 By incorporating some gas-tar with the refuse lime of gas-works, 

 previously dried and powdered, a product is obtained which 

 smells very similar to M'Dougall's powder, and resembles the 

 latter closely in its general appearance; and also so far in com- 

 position, as it contains likewise sulphite of lime, free lime, and 

 carbolic acid. The proportion of caustic lime in this pre- 

 pared gas-lime, however, was much more considerable than in 

 M'Dougall's powder, which no doubt accounts for the fact that 

 this sample of prepared gas-lime greatly excelled the newly- 

 invented powder in deodorizing properties. 



It appeared to me also desirable to mix slaked lime with a 

 little gas-tar, and to try this mixture simultaneously with the two 

 other powders in the stable. 



With these three powders the following experiments were 

 made : 



1st Set of Experiments. 



Three loose boxes were cleared out and respectively sprinkled 

 with M'Dougall's powder, prepared gas-lime and tar, and with 

 slaked lime and tar. 



