101 



into the flask the exit tube may also be filled with water. When this 

 has been accomplished the apparatus is tested for leaks by closing the 

 stop-coek and opening the pineh-cock. Should there be a leak, water 

 will siphon out. No water should remain in the bulb of the funnel. 



When the apparatus is tight an accurately measured volume (15 to 

 20 cc) of concentrated hydrochloric acid (dilute acid can be used with 

 magnesium I is put into the separating funnel; the exit tube is put into 

 the second flask which has previously had its sides dampened with water. 

 About one half of the acid is now allowed to flow into the tube con- 

 taining the zinc. A rapid evolution of hydrogen occurs which drives 



water over into the second flask. When the action slows down more 

 acid is run in. care being taken that at the end the surface of the acid 

 is just at the stop-cock. When all the metal has dissolved (it may take 

 one-half hour) the surfaces of the liquids in the two flasks are brought 

 to a level by raising or lowering one of them, and while level the pinch- 

 cock on the exit tube is closed. The stopper is now withdrawn from 

 the generating flask and the temperature of the water in it is taken. 

 Also the reading of the barometer is noted. The volume of the water 

 in the receiving flask is carefully measured and from its volume the 

 volume of the acid used is deducted. The remainder is the volume of 

 hydrogen produced during the action. This is corrected to standard 

 conditions, and from the corrected volume and the weight of zinc used 



