448 NITRIC ACID. 



3. PROPERTIES. 



(a.) Its sp. gr. is usually 1.5 or 1.55 ; it has been obtained as high 

 as 1.62, by Proust ;f supposed to be in its pure state an acid gas of 

 sp. gr. 2440, air being 1000 ; this acid gas with water forms the 

 common acid; that having the sp. gr. 1.55, contains nearly 86 per 

 cent, of acid, and 14 water. 



Table of the strength of nitric acid, from Thomson's First Prin- 

 ciples, Vol. I, p. 114. 



Equiv. of acid. Equiy. of water. Acid in 100. Sp. Gr. 



1 - - 1 - - 85.714 - - 1.5500 



1 2 - 75.000 - - 1.4855 



1 - 3 - 66.668 - - 1.4546 



1 - - 4 - - 60.000 - - 1.4237 

 1 - 5 - 54.545 - - 1.3928 



1 - - 6 - 50.000 - - 1.3692 



1 - 7 - 46.260 - - 1.3456 



1 8 - 42.857 - - 1.3220 



1 - 9 - 40.000 - - 1.3032 



1 - - 10 - - 37.500 - - 1.2844 

 1 - - 11 - - 35.294 - - 1.2656 

 1 - - 12 - - 32.574 - - 1.2495 

 1 - - 13 - - 31.579 - - 1.2334 

 1 - - 14 - - 30.000 - - 1.2173 

 1 - - 15 - - 28.571 - - 1.2012 

 (b.) Hydro-nitric acid, as it is called, is a pale colorless fluid, like 

 water, with a pungent odor, and it emits smoke in the air. 

 (c.) It has all the acid properties in perfection. 

 (d.) Highly corrosive, and turns the skin yellow, 

 (e.) Boils at 248, and is distilled without change ; but this boil- 

 ing point belongs to acid of the sp. gr. 1.42, containing acid .60 and 

 water 40. 



acid,* we obtain the strongest nitric acid, with sp. gr. 1.55. When the proportion of 

 sulphuric acid is doubled, the retort is not so liable to be broken, but the nitric acid, 

 obtaining a larger supply of water from the sulphuric acid, is of course weaker. 

 When 12| parts sulphuric acid are mixed with 12| parts of pure anhydrous nitre, the 

 whole of the nitric acid is obtained, but of the sp. gr. 1.4855, and its composition is 1 

 equivalent acid and 2 water. In the London Pharmacopeia, equal parts of nitre and 

 sulphuric acid are ordered ; this contributes to the formation of a bi-sulphate of pot- 

 ash, which is said to be necessary to the entire decomposition of the nitre, and af- 

 fords two proportions of water, which are required to condense the whole of the 

 nitric acid. The Edinburgh Pharmacopeia and the manufacturers use three fourths 

 or four fifths of sulphuric acid, and these proportions are the best. 



* It is well, before using it, to heat the sulphuric acid nearly to its boiling point, 

 to expel the water it may have imbibed. 



t Gay-Lussac says, (Ann. de Chim. et de Phys. Vol. I, p. 396,) that 1.510, at 18 

 centigrade, is the heaviest that had then, (1816,) been obtained. 



