452 DEUTOXIDE OF NITROGEN. 



7. MISCELLANEOUS In the arts, copperas calcined to redness, is 

 mixed in equal quantities with dried and purified nitre ; the distilla- 

 lation is performed in an earthen retort or an iron pot with an earth- 

 en head, and a very strong fuming acid is thus obtained, called aqua 

 fords. If the materials have not been before heated, they will afford 

 water and a diluted acid which fumes very little ; it is called single 

 aqua fortis. The sulphate of potassa is separated by solution, and 

 the oxide of iron is sold for polishing metals ; it is called colcothar. 

 On the continent of Europe, they use clays, boles and other earths 

 containing silex ; the affinity exerted by these earths, towards the al- 

 kali of the nitre decomposes the latter at a red heat. As crude nitre 

 is employed, the acid which is called spirit of nitre, is contaminated 

 with muriatic acid. 



The French distil the nitric acid in large cast iron cylinders, but 

 when iron is used, more of the nitric acid is decomposed, and there 

 is of course more nitrous acid produced. 



The corrosive fumes of nitrous acid are carefully avoided in the 

 manufactories; they sometimes cause the workmen to spit blood. 

 The double aqua fortis is half as strong as pure nitric acid ; and sin- 

 gle aqua fortis being half as strong as double, is of course one fourth 

 the strength of the strongest acid. Nitric acid is distinguished by 

 its ready action on copper and mercury ; by forming nitre with potash, 

 and nitro-muriatic acid with muriatic acid, and thus becoming capa- 

 ble of dissolving gold,* by bleaching a very dilute solution of indigo, 

 if in the proportion of 7 |oj or turning it yellow if ^^, when a few 

 drops of sulphuric acid are added ; also by the scintillation which it 

 produces when dropped upon ignited charcoal. For economical 

 purposes, 100 good nitre, 60 strong sulphuric acid, and 20 of water, 

 form a good proportion. 



Dr. Ore states, as the result of his own experiments, that if the 

 respective terms of dilution of nitric acid with water, be taken as an 

 arithmetical, the densities will be in a geometrical series. f 



In its concentrated state, it is a deadly poison, corroding and de- 

 stroying the animal organs. 



NITRIC OXIDE GAS NITROUS GAS OR DEUTOXIDE OF NITROGEN. 



1. REMARKS. In the strictness of logical arrangement, this oxide 

 should be described after the protoxide or exhilirating gas, and both 

 of them before nitric acid, but as it is obtained by the decomposition 

 of the latter, its history will probably be most intelligible if intro- 

 duced here. 



* But muriatic acid produces a similar iluid with the chlorates and bromates. 

 t Diet, 2d Ed. p. 57. 



