18 Dr John Davy on the Slaking of Qvicklime, 



I shall now relate one or two other results which are 

 rather favourable to this conclusion, and at the same time 

 show how unstable is the union (if it be admitted) with the 

 smaller proportion of water. 



8. To 39-5 grs. of quicklime added gradually 4 grs. 

 of water. A little heat was produced, but a bearable one. 

 Now plunged the mass into cold water, moving it rapidly 

 for about a minute ; it remained cool. Transferred it now 

 to the balance ; it had gained 8 grs. In a few seconds action 

 took place, and the hydrate was formed. This experiment 

 has been more than once repeated with the same result. 



9. Instead of mere water a mixture of about equal parts 

 of water and sulphuric ether was poured on a piece of 

 quicklime. The immediate effect was the cooling of the 

 little mass by the evaporation of the ether. For many 

 minutes there was a retardation of action, and when it 

 began it went on slowly, the evaporation probably inter- 

 fering, and preventing rapidity of combination. 



10. If, instead of cooling the quicklime, its temperature 

 be at all raised, so much the more rapidly is the hydrate 

 formed on the addition of water. Thus, on pouring a few 

 drops of water on a small piece of quicklime fresh from 

 the fire, allowed to cool, so that its warmth was hardly to 

 be felt, no sooner did the water touch it than the union 

 took place with explosive violence, driving the little frag- 

 ments to the distance of several feet. 



There are other results which I have obtained of like 

 significance. 



11. If aqua ammoniae, or a strong solution of common 

 salt, or of chloride of calcium — compounds having an afii- 

 nity for water, and not readily parting with it — be added to 

 quicklime, the formation of the hydrate is more or less re- 

 tarded, but is nowise prevented, and when it takes place 

 it is sudden, with the usual phenomena as to evolution of 

 heat, &c. 



12. A similar retardation is witnessed when quicklime 

 in inass is X3ut into a solution of the carbonate or sesquicar- 

 bonate of ammonia, or of the carbonate or bicarbonate of 

 potash ; but when action commences it is rapid, the hydrate 

 of lime being formed, with the usual production of heat. 



