NITROGEN AND ITS OXIDES. 73 



the funnel is to enable us to add more nitric acid as the ac- 

 tion moderates. 



Copper. Nitric acid. Nitrate of copper. Nitric oxide. Water. 

 3Cu + 8HNO 3 = 3(Cu(NO 3 ) 2 ) + 2NO + 4H 3 O 

 Though this gas is colorless, the moment that it is ex- 

 posed to the air it is changed into orange fumes. This is 

 very prettily shown if a jarful of this gas be raised out of 

 the water in the pneumatic trough. The air, entering the 

 jar, diffuses an orange-red color in every part of it. The 

 explanation is this : The oxygen of the air unites with the 

 nitric oxide, converting it into a mixture of nitrous anhy- 

 dride and mtric peroxide, 3(NO) + O 2 =N 2 O 3 +NO 2 . You 

 can now understand why the first gas that rises in the flask 

 is colored. There is some air in the flask, and when the 

 gas begins to rise-it takes the oxygen from this air, and be- 

 comes nitrous anhydride. When this is driven off the ni- 

 tric oxide will come along pure. 



In making these experiments you must be very careful 

 not to breathe the reddish fumes of nitrous anhydride mixed 

 with nitric peroxide, for they irritate the lungs. Indeed, 

 they smell so horribly we think you will not need to be 

 warned. 



84. Explanation of a Former Experiment. You will see 

 that in the above process the same materials are used as in 

 the experiment given in 73. Nitric oxide was formed in 

 that experiment, as well as in this process, and yet reddish 

 fumes arose from the copper and the acid. The nitric ox- 

 ide at once united with the oxygen of the air, and so was 

 changed into nitrous anhydride and nitric peroxide, as ex- 

 plained in 83. In the process for obtaining the nitric oxide 

 we prevent this change, as you see, by shutting out the air. 



85. Air and Nitric Oxide Contrasted. The two great in- 

 gredients of air are those which compose nitric oxide. And 

 yet how entirely opposite these two substances are in their 



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