HEW JfOBK BTAT1 MUSEUM 



Afore than 1^ of magnesia makes the lime short, and 25# to 



ra tlie stone unfit for burning; " never* 

 theless, Buch is burned in the southeastern part of New 



3 orl 



silica, it i> maintained, gives the lime hydraulic proper- 

 tit-. 



tsch also states that limestone of 95# purity yields 59# 

 burnt lime with ilcium oxid; of 90^ purity, gives G0^ burnt 



lime with 80^ CaO; - tie gives 65.50 with 72# CaO, and 



•ne givea 700 with 64^ CaO. 



Slaking. Lime in its normal condition and when dry is totally 

 unaffected by carbonic acid gas but when heated takes it up 

 rather quickly. The addition of water to lime can be done in a 

 variety of ways according to the degree of slaking that is to be 

 brought about. If a lump of quicklime is immersed in water 

 for an instant it saturates itself at once, and this absorption is 



iompanied by the evolution of heat and a swelling and bursting 

 of the lime, which finally falls to a fine powder, the hydrate of 

 the lime, Ca (OIi) 2 . The chemical action which has taken place 

 is expressed by the formula Ca() + IL,():=Ca(OII) 2 . 



This method of hydration is considered to be better than pour- 

 the water on the lime. 



The hydrate of lime thus obtained is a fine, white powder of a 

 Bpecific gravity of 2.1. Its water of hydration is pretty firmly 

 combined and is only driven off by reheating to redness. 



Fat. limes slake very fast and produce more heat than lean 

 ones, ami lime will slake even in the air by the absorption of 

 moisture, so that, if not used immediately, it should be protected 

 from the atmosphere as much as possible. 



Lime may also be slaked by putting the lumps in water for a 

 few minute-, then withdrawing and packing away to allow the 

 linn- i" change to powder. The common method usually em- 

 ployed in building operations is to mix the lime with water in a 

 box. I"" much Water makes it thin and injures its cohesive 



Btrength. If only a part of the water required is added at first 



