CHEMICAL PARADOXES. 



and as the liquid produced is a powerful cor- 

 rosive, care should be taken to make the ex- 

 periment in a suitable place. In the case of 

 strong sulphuric acid, if a drop or small quan- 

 tity of water be poured upon it, the water is so 

 suddenly and violently heated as to be rapidly 



vaporised in an explosion 

 which may scatter some 

 of the corrosive acid. 

 It is, therefore, advisable 

 to begin making this 

 mixture by pouring the 

 sulphuric acid gently into 

 the water, not vice versa. 

 More commonly seen 

 is the heat produced by 

 letting quicklime unite 

 with water. This opera- 

 tion is often so carried 

 out in building work as 

 to produce actual boiling 

 of the water, and the 



method has lately been made use of for the 

 heating of food where no fuel or pans are avail- 

 able for the purpose. The prepared soup or 

 other food is sealed as usual in the inner tin 

 vessel, A, of Fig. 44. This is surrounded by 

 another compartment, B C, which contains 

 quicklime, also hermetically sealed. 



When hot food is wanted, the outer vessel 

 is unsealed, and water poured upon the lime. 



206 



FIG. 44,-TRAVELLER'S FOOD- 

 TIN HEATED BY LIME AND 

 WATER. 



