CHAPTER XVIII 



SALT 



Properties of Salt. We shall now investigate common or 

 table salt, and the various products which we can obtain from 

 it. At the outset salt itself should be carefully examined, 

 and a table prepared of its characteristic properties. It will 

 be thus found to be a white soluble powder, which forms 

 crystals in the form of small cubes, containing no water of 

 crystallisation. It does not suffer any apparent change un- 

 less heated very strongly, when it can be fused or melted. 

 If a little be placed in the non-luminous flame of a Bunsen 

 burner the flame becomes coloured bright golden-yellow. 



EXPT. 277. Place a little salt in a test-tube, and add some 

 strong sulphuric acid ; warm slightly. Observe that a gas is 

 evolved which possesses a powerful pungent odour, and forms 

 white fumes in the air. 



We must now endeavour to collect and examine this ' ' salt 

 gas." 



Salt Gas. EXPT. 278. Fit up a glass flask for the prepara- 

 tion of this gas from the above materials, and collect it as 

 shown in the diagram (Fig. 128). When fumes form at the top 

 of the jar in which the gas is being collected, the jar may be 

 regarded as full. Fill two jars, and keep them closed until 

 required by pieces of greased glass. 



(1) Insert a lighted taper and observe that the gas does 

 not burn, neither does it support combustion. 



(2) Open under water, and observe that the water rushes 

 up and completely fills the jar. (Probably owing to the 



