Dr John Davy on tlie Slaking of Quicklime. 19 



But if the lime be reduced to the state of a very fine 

 powder, and mixed (using trituration) with a strong solu- 

 tion of either, a carbonate of lime is formed with a very 

 slight elevation of temperature — that small degree refer- 

 rible, I believe, to the portion of hydrate at the same time 

 produced. 



On the supposition that two of lime can unite with one 

 proportion of water, the instability of the compound is no 

 more than might be expected. There are many analogous 

 examples, such as the sesquicarbonate of ammonia, the 

 neutral carbonate of this alkali, and the bicarbonate of 

 potash and soda. A priori, we cannot predicate the chemi- 

 cal relation of one body to another ; it may be conjectured, 

 but it can only be determined by experiment. It might 

 be supposed, that because carbonic acid is expelled from 

 lime by a bright red heat, that it would not combine with 

 this acid at a dull red heat. Yet tliis I find is the case. 



Considering the high temperature produced in the act of 

 union of water and lime, and the quantity of steam that 

 may be generated, the idea could hardly fail to occur, that 

 the formation of the hydrate may be applied to some useful 

 purpose, such as the blasting of rocks ; and if successful, 

 might be especially useful in collieries as a substitute for 

 gunpowder, which has so often occasioned, by the igniting 

 of gas, terrible accidents with loss of life. 



The few trials I have instituted, with a view to this 

 application, have not answered my expectations. I shall 

 mention one or two of the latest I have made. Recently I 

 had a boring made in a block of sandstone, about 15 inches 

 deep and 2 inches in diameter. It was filled with small 

 pieces of quicklime ; water was poured in, which, it was in- 

 ferred, found its way to the bottom in sufficient quantity,, 

 and the hole was then firmly closed by a plug of wood. 

 No rending of the rock was produced ; yet the hydrate was 

 formed. It must be concluded that the elastic expansive 

 force exerted was not superior to the resistance, and that 

 all the steam was condensed. A second experiment was 

 made, substituting for the boring in rock a strong earthen- 

 ware jar, capable of holding about a quart. It was simi- 

 larly charged and tightly corked ; the cork bound down 



