THE BOOK OF THE LANTERN. 31 



adopted on a commercial scale, depends upon the action of 

 cobalt on bleaching powder (Calcic hypochlorite). The 

 lime must be in the form of a concentrated solution, and 

 this is best brought about by mixing, say, one pound of 

 bleaching powder, which is commonly called chloride of 

 lime, with a quart of water. Stir this mixture and allow 

 it to remain for an hour. Now decant the clear liquid, 

 and pour it upon a fresh pound of lime stir as before, 

 and strain the product through a calico or flannel bag. 

 Place the liquid in a large bottle, to the cork of which 

 a tube is fitted. Now drop into the liquid, taking the 

 cork out for the time being, a small quantity (say 2 ounces) 

 of a strong solution of cobaltic peroxide, when oxygen gas 

 will be quickly evolved, and will come off through the 

 replaced tube. The evolution of gas is increased by 

 warmth. The same cobalt can be used again and again, as 

 it does not undergo any permanent change. It seems to 

 act merely as a conveyer of oxygen, taking it from the 

 lime, passing it to a higher state of oxidation, and then 

 giving it up again ; any solution of cobalt will answer the 

 purpose. When the gas ceases to come, the residue in the 

 bottle should be diluted with water, and, after having been 

 allowed to rest for some time, the cobalt will settle at the 

 bottom of the vessel. This can then be washed, kept in a 

 moist state, and used over again as often as required. 



But the more general method of preparing the gas is by 

 means of the decomposition of potassic chlorate, and 

 that method I shall now, therefore, describe in detail. 



The lime-light has, in certain quarters, earned the cha- 

 racter of being dangerous, not so much from accidents 



