NITROGEN. 177 



Such action is called dcf (if/ration. Other oxidizing substances act 

 like nitrates. 



4. When a few drops of a solution of 0.1 gramme of diphenylamine 

 in ;")() c.c. of 10 per cent, sulphuric acid are added to a very dilute 

 solution of a nitrate, and then some concentrated sulphuric acid is 

 carefully poured down the side of the test-tube, a deep blue color is 

 produced at the line of contact. 



A similar reaction is also produced by hypochlorites, chlorates, 

 chromium trioxide, ferric salts, and similar oxidizing agents. 



When the test is made with a similar solution of pyrogallic acid 

 instead of the diphenylamine solution, a deep brown color is 

 produced. 



The tests with diphenylamine and pyrogallic acid show 1 part of nitric 

 acid in three and ten million parts of water respectively, and are used chiefly 

 to detect traces of nitric acid in drinking-water. As sulphuric acid may con- 

 tain nitric acid, the tests should also be made with the sulphuric acid alone in 

 order to prove its purity. 



Tests 1 and 2 are sufficient to identify nitric acid or its salts. Nitrites also 

 respond to these tests, but they give red fumes by merely adding a dilute acid, 

 thus differing from nitrates. 



Poisonous properties; antidotes. Strong nitric acid is a corrosive, 

 violent poison. It first stains the tissues with which it comes in contact a 

 bright-yellow color, and then corrodes them. 



As an antidote in cases of poisoning by nitric acid a solution of sodium car- 

 bonate, or a mixture of magnesia and water, milk of lime, or other alkalies 

 well diluted may be administered with the view of neutralizing the acid. 



QUESTIONS. State the physical and chemical properties of nitrogen. Men- 

 tion the principal constituents of atmospheric air and the quantity in which 

 they are present. By what processes can the four chief constituents of atmo- 

 spheric air be determined? Mention some decompositions by which ammonia 

 is generated. Explain the process of making ammonia water. State the 

 physical and chemical properties of ammonia gas and ammonia water. How 

 is nitrogen monoxide obtained, and what are its properties? Describe the 

 process for making nitric acid, and give symbols for decomposition. How 

 does nitric acid act on animal matter, and what are its properties generally? 

 Give tests and antidote for nitric acid. 

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