56 CHEMICAL FERTILIZERS 



TABLE 9. 

 COMPOSITION OF GAS LIME (DRIED AT 100 C.) (Voelcker). 



Water of combination and a little organic matter . . 7-24 



Oxides of iron and alumina, with traces oi phosphoric acid 2-49 



Sulphate of lime (gypsum) .. .. .. .. 4-64 



Sulphite of lime .. .. .. .. .. .. 15*19 



Carbonate of lime . . . . . . . . . . . . 49*40 



Caustic lime . . . . . . . . . . . . . . 18*23 



Magnesia and alkalies . . . . . . . . . . 2* 53 



Insoluble siliceous matter . . . . . . . . . . 0-28 



lOO'OO 



The chief results of applying gas lime to land consist in 

 the beneficial effects produced on the land by the calcium 

 carbonate contained ; as with other forms of calcium oxide 

 or carbonate, heavy land is rendered easier to cultivate. 

 There is nearly always a little nitrogen present in gas lime. 

 Where a soil is at all alkaline, the sulphate of lime will 

 be useful. Gas lime is also a means of killing off various pests, 

 such as wire worms, and destroying matted, useless growths 

 of grass of little feeding value. Inferior matted grass on 

 pasture can be removed by substantial dressings of gas lime, 

 as it burns up and destroys much of the rank herbage ; 

 although for the next few months the pasture is worthless, 

 it subsequently recovers, and in a few years becomes fine 

 pasture of good feeding value. Other methods of effecting 

 this result are fully described in "Plant Products " (pp. 6, 

 63, 95). Gas lime is now produced in such relatively small 

 quantities, owing to the introduction of other methods of 

 purification, that the subject of gas lime is of far less 

 importance than it was in former days. 



Acetylene Gas By-product. When calcium carbide is 

 treated with water in the production of acetylene, a residue 

 is left which contains about 50 or 60 % of pure lime. 

 The lime is in the form of calcium hydrate with an excess 

 of water. Traces of undecomposed carbide, phosphide, 

 sulphide and silicide continue to evolve traces of odorous 

 and poisonous gases, but the amount of these impurities is 

 of no practical importance in agriculture. Prudence suggests 

 that an application of such a residue should be early so that 



