sm 



ON DEAD LIME. 



Lime that will a violent and long continued fire, limestone may be converted 



nOTsfack* 1 int ° a kind ° f lime that doeS n0t heat with vvater 5 and does 

 not slack ; and this has been called dead lime. This state 

 of lime does not appear to be iecognized by all chemists, 

 since it is not mentioned in elementary treatises on chemistry : 

 some however think, that clay combined with lime may give 

 it the property of hardening by great heat, and thus cause 

 it to lose those of heating and slacking with water, giving 

 rise to dead lime. Perhaps 1 may remove the uncertainties, 

 and reconcile the different opinions, to which this substance 

 has given rise. 



May be owing Four cases may be supposed, to each of which lime may 

 pass to this state. 



to alumine, J. When it contains a great deal of clay, and is heated 



so strongly as to become very hard. In this state it will not 

 effervesce with acids, because all the carbonic aeidis expelled. 



si j ex 2. If it contain silex, and be heated strongly after the 



complete expulsion of the carbonic acid, it will not effervesce 

 with acids. 



too hasty and 3. In the third case, lime being heated at once very vio- 



strong afire, lently, forms a'mass perfectly similar to dead lime. It passes 

 into a semifluid state, the possibility of which I have shown 

 in the Berlin Journal, and it requires to be heated gradually, 

 to expel the carbonic acid of large pieces in particular. 

 When the kiln is emptied, there will remain pieces half- 

 fused, that will neither heat nor slack with AYater, but effer- 

 vesce with acids : these are carbonate of lime, fused or 

 hardened by the fire. 



or fire too long 4. Lastly on calcining carbonate of lime in a fire conti- 



continued. nued long after the expulsion of the carbonic acid, a true 

 dead lime is formed, which neither heats with water, nor 

 effervesces with acids. All the circumstances of its forma- 

 tion are not yet well known. 



Dead Lime I saw some years ago this kind of lime formed by the cal- 



*h n* °y ster< cination of chalk and of oyster-shells ; but not being satis- 

 fied, that they contained neither silex uor alumine, I ascribed 

 to these earths the peculiar properties of the lime obtained. 

 Lately the same phenomena occurred to me, and as I was 

 very certain, that the oyster-shells employed Contained no 

 earth but lime, no phosphate of lime, and no salt soluble in 



water, 



