72 



CHEMISTRY. 



solutions of potassium hydrate and ferrous sulphate before 

 collecting it in a receiver. 



82. Properties of Laughing-Gas. The nitrous oxide gas is 

 as colorless and transparent as air, and has a sweetish taste. 

 A lighted taper burns almost as brightly in it as in oxygen, 

 and if there be but a spark on the wick, on introducing it 

 into a jar of this gas it lights up instantly. When breathed, 

 it occasions no irritation in the lungs, but produces a sin- 

 gular excitement, a delicious intoxication, which lasts but 

 two or three minutes. Individuals under the influence of 

 it act variously. Some dance, some laugh, some declaim, 

 some fight, etc. The excitement is very commonly of a 

 pleasant kind, and hence this gas is called in common lan- 

 guage laughing-gas. It also possesses the property of 

 causing insensibility to pain, and is now much used by den- 

 tists. 



83. Nitric Oxide. This is a colorless gas which has just 

 twice as much oxygen in it as the nitres oxide. It can be 

 obtained from nitric acid and copper in the apparatus rep- 

 resented in Fig. 15. 

 Bits of copper and 

 nitric acid, some- 

 what diluted, are in- 

 troduced into a flask. 

 The gas passes out 

 through the tube, 

 and may be collect- 

 ed in the usual way 

 in jars in the pneu- 

 matic cistern. The 

 first gas that passes 

 over will be orange- 

 colored, and we must 



not begin to collect till the gas is colorless. The object of 



