Anatjfsis of Scientific Books. 409 



** On Slaking. — Quick-lime, thrown into a proper quantity or 

 water, splits with noise, produces a bubbling, liberates hot and 

 slightly caustic vapours, and at last forms a thick paste. One 

 part of common lime, thus slaked, is expanded into 3.1 parts of 

 paste. If a sufficient quantity of water has not been added in 

 the first instance to the lime, it is necessary to wait till it is 

 cold before more be given. If a second portion be poured on 

 whilst the lime is hot from the effect of the first insufficient 

 quantity, then the lime does not divide well, but remains gra- 

 nular. This process is called ordinary slakingf or the first 

 process. 



** Quick-lime plunged into water for a few seconds, and with- 

 drawn before it begins to split, then hisses, splits, and bursts 

 apart with noise, and falls into powder. This powder, when 

 cold, does not heat by the addition of more water. One part of 

 lime thus slaked, expands into 1.5, or 1.7 parts by measure. 

 This is called slaking by immersion j or the second process. 



" If quick-lime be exposed to the air it falls to powder, one 

 part increasing in volume to 1.75, or even to 2.55. This is 

 called spontaneous slaking y or the third process." — p. 16. 



" Hydrates of Lime. — Limeslaked in these three ways was made 

 into masses with water ; these were dried in the sun, and then 

 their resistance or tenacity, and their hardness, ascertained ; and 

 the result was, that for all kinds of lime the resistance and the 

 hardness was in proportion to the expansion in bulk by the 

 process of slaking, t. e., the process which divided the lime 

 most completely, gave a hydrate of the greatest strength."— 

 p. 25. 



" Effects of Slaking on the Hydraulic Mortars. — It appears 

 from experiments on the hydraulic mortars made from common 

 lime, intermediate or meagre lime, and lime slightly hydrau- 

 lic, that the three modes of slaking, arranged according to 

 the order of their superiority, arc the third, the second, and the 

 first; but that for highly hydraulic lime, the order becomes 

 reversed. If common lime be considered as the commence- 

 ment of the scale, and we pass from that through the various 

 shades of difierence to the hydraulic lime which is most meagre, 

 Vol. X. ^ E 



