286 Domestic Science 



the mouth of the tube with the thumb and bring it, 

 mouth downwards, near a flame. Remove the thumb 

 and place the open end of the tube close to the flame. 

 Should a squeaky explosion be heard, collect another 

 sample and again test in the same manner. When the 

 gas burns quietly, a number of gas- jars may be filled 

 for use in the performance of the following tests. 



The acid is a solution of a compound of hydrogen 

 with another element, chlorine, and the zinc is able 

 to displace the hydrogen from combination, forming 

 a compound with the chlorine called zinc chloride. 

 The action may be represented thus : 

 Zinc + hydrogen chloride = zinc chloride + hydrogen. 



The zinc chloride remains in solution in the liquid 

 at the bottom of the flask, and the hydrogen, being 

 only slightly soluble in water, is obtained in the free 

 state. 



Exercise for Student. 



Devise and carry out a method of obtaining a specimen of zinc 

 chloride in the solid state from the solution in the flask. 



Show that the gas in the jars corresponds in 

 properties to that collected in Experiment 130 by 

 repeating the tests there suggested. The extreme 

 lightness of the gas may be emphasised by filling 

 a balloon with it. 



EXPERIMENT 133. The flask in Fig. 94 contains 

 zinc and the acid may be poured as before down the 

 thistle funnel. T is a drying-tube containing small 

 lumps of calcium chloride to prevent the moisture 

 which always escapes with the gas from entering the 

 light collodion balloon B. This balloon should not 

 be attached until all the air has been displaced from the 

 flask by hydrogen by allowing the action of the acid 



