152 SCIENTIFIC AMUSEMENTS. 



Evolution of Gases from Liquids in consequence of 

 Chemical Action. 



In the preceding experiments we have had several illustrations 

 of the production of gases of different kinds during the solution 

 of solids; thus hydrogen gas is set free when zinc dissolves in 

 hydrochloric acid (Expts. 10, 104, &c) ; sulphuretted hydrogen, 

 when sulphide of iron is acted upon by the same acid (Expts. 13, 

 145, &c.) ; nitric oxide, when copper is dissolved in diluted nitric 

 acid (Expt. 116); sulphur dioxide, when copper is heated with 

 strong sulphuric acid (Expt. 117) ; carbon dioxide, when chalk is 

 treated with diluted hydrochloric acid (Expt. 99). In similar 

 fashion gases are frequently evolved by chemical actions taking 

 place between liquids of various kinds ; sometimes the action takes 

 place in the cold, sometimes the application of more or less heat 

 is requisite. An example of this class of action is afforded by 

 Expt. 143, where the action of hydrochloric acid upon solution of 

 carbonate of soda gives rise to the evolution of carbonic acid gas ; 

 the production of effervescence on dissolving "lemon kali," &c., in 

 water (Expt. 73), is really due to exactly the same kind of action ; 

 the water dissolves the carbonate of soda present in the powder, 

 and the tartaric acid is also dissolved by the water, so that the 

 acid solution thus formed acts on the solution of the carbonate 

 of soda just as the hydrochloric acid does. 



Expt. 160. To generate Ammonia Vapours from Solutions. 

 Place in a test-tube a teaspoonful of a strong solution of chloride 

 of ammonium or sulphate of ammonium, add as much solution of 

 caustic soda, and heat the whole; when tolerably hot you will 

 find that a strong smell of ammonia is perceptible at the mouth of 

 the test-tube. Hold over the mouth of the tube a piece of litmus 

 test-paper (Expt. 142) that has been reddened by dipping in a 

 tumblerful of water to which one drop of hydrochloric acid has 

 been added ; the escaping ammoniacal vapours will turn the red 

 paper blue. 



Expt. 161. To generate Sulphur Dioxide by mixing two 

 Liquids. Add a teaspoonful of diluted hydrochloric acid to as 

 much of a strong solution of sodium sulphite ; a strong smell of 

 burning brimstone will then be noticed, owing to the evolution of 

 sulphur dioxide on account of the chemical action taking place. 

 If sodium hyposulphite be used instead of sodium sulphite, the 

 liquid will gradually become milky, and develop the smell of 

 burning brimstone, the milkiness being due to the precipitation of 

 particles of solid sulphur. 



Expt. 162. To produce Chlorine Gas by mixing two Liquids. 



