CHAPTER XXV. 

 HYDROGEN. 



DURING the study of the properties of acids, it was found that when 

 certain metals acted on dilute sulphuric and hydrochloric acids an 

 inflammable gas was produced. For a reason which will presently 

 appear, this gas is called hydrogen. 



75. PREPARATION AND PROPERTIES OF HYDROGEN. 



i. Preparation of hydrogen. Select a flask and fit it up as is shown in 

 Fig. 101. Be very careful that the stopper and the tubes respectively fit 

 very closely. Into the flask put enough granulated zinc to cover the bottom. 



FIG. 101. Zinc turns hydrogen out of dilute sulphuric acid. 



Pour some water upon the zinc. Arrange the delivery tube in the trough 

 as when making oxygen. Pour a little sulphuric acid down the thistle- 

 headed acid funnel, and be quite sure that the end of the funnel dips beneath 

 the liquid in the flask. Do not collect jars of the gas until you are sure 

 pure hydrogen is being given off, which you can find out in this way. Fill 

 a test-tube with water and invert it over the end of the delivery tube. When 

 it is full of gas, still holding it upside down, take it to a flame (which should 

 not be near the flask in use ; notice that there is a slight explosion. Continue 

 this until the hydrogen burns quietly down the test-tube. When this 



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