Proceedings of the Farmers' Club. 4G1 



the coal is brought. For tins reason an analysis of any particular 

 sample can serve only as an approximate indication of the average com- 

 position of gas lime, but this is enough to enable general rules to be 

 laid down sufficiently accurate for practical purposes. 



AVhen the lime in the racks has become so surcharged with sulphur- 

 ous impurities from the gas that it can absorb no more it is taken out. 

 This stage is ascertained by thrusting down into the box through a 

 hole in the top a piece of moistened paper impregnated with acetate 

 of lead. If the paper turns brown it is a sign that the lime has failed 

 to abstract all the sulphur, and must be replaced by new material. 



When taken from the racks the lime is found caked in greenish yellow 

 masses, very porous and having a peculiar odor. According to an 

 analysis made some years ago by Prof. Johnston, of lime from the 

 gasworks of Edinburgh, the material when first taken from the racks 

 contained about sixty-nine per cent of carbonate of lime ; of caustic 

 hydrate of lime, i. e. of quick lime combined with a certain propor- 

 tion of water, about two and one half per cent ; of sulphate of lime or 

 gypsum seven and one-third per cent ; sulphite and hyposulphite of 

 lime two and one-fourth per cent ; and of free sulphur upward of one 

 per cent, the balance being made up of other substances of little 

 account one way or the other. Now, of these materials embracing 

 nearly the whole of the gas lime, the carbonate when applied to the 

 soil would serve the same purpose as ordinary air slaked lime. The 

 The hydrate was of common water slaked, and the sulphate that of 

 gypsum or plaster. None of these could, in themselves, produce the 

 injurious effi^cts ascribed in many instances to the use of gas hme and 

 the sulphite and hyposulphite must, therefore, be charged with the 

 damage. Both of these substances are very soluble in water. When 

 gas lime is applied to young and tender vegetation, the rain washes 

 the sulphite and hyposulphite into the ground in such quantity 

 that their action destroys the vitality of the plants, and while remain- 

 ing unneutralized the soil will deteriorate its productive powers. 

 Prof. Johnston also analyzed samples of the same material 

 after exposure to the weather for a considerable time and 

 found that the free sulphur, sulphites and hyposulphites had 

 disappeared while the proportion of the sulphate or gypsum had 

 quadrupled. This result occurs from the gradual oxydation of 

 the three substances iirst named, their consequent formation of 

 an additional proportion of sulphuric acid and the combination of 

 the latter with lime to form a sulphate. This change is apparently 



