LIME AND CALCIUM. 277 



C 2. If a current of chlorine gas be made to pass Atomic 



n T i J weight of 



through a quantity or lime heated to redness, calcium. 

 this alkaline earth is decomposed, oxygen gas is 

 disengaged, and chloride of calcium is formed. 

 Sir H. Davy, to whom we are indebted for this 

 experiment, ascertained that for every half vo- 

 lume of oxygen gas extricated, a whole volume 

 of chlorine gas was absorbed. Now, these two 

 being equivalent, respectively, to one atom, it is 

 obvious that lime must be a compound of one 

 atom oxygen and one atom calcium. Conse- 

 quently, the atomic weight of calcium is 2%5. 



3. Muriate of lime may be easily crystallized, 

 by placing a concentrated solution of it under 

 the exhausted receiver of an air pump, over a 

 flat glass vessel containing a quantity of concen- 

 trated sulphuric acid. The crystals are large 

 transparent four or six-sided prisms, usually 

 striated longitudinally. They are composed of 



1 atom muriatic acid 

 1 atom lime . 

 6 atoms water 



14-875 



When this muriate is cautiously exposed to a 

 heat gradually raised to redness, it may be fused 

 and converted into chloride of calcium with 

 scarcely any loss of chlorine or muriatic acid. 

 In that case it loses 7 atoms of water, 14*875 



grains of the crystallized muriate being by this 



s 3 



