NITROGEN, BINOXIDE OF 



421 



tho volume of the hydrogen added, it will show that no combustible gas was present, 

 and that, therefore, the original gas consisted of pure nitrogen. 



Compounds of Nitrogen with Oxygen. The following table contains the composition 

 and principal physical properties of the oxides of nitrogen : 



Table of the Composition and Physical Properties of the Oxides of Nitrogen. 



In the above table .the densities of the vapours of nitrous and nitric acids are given 

 as obtained by calculation on the hypothesis that they could exist at 60 and 30 inches 

 without condensation ; that is to say, as the numbers would come out in a determi- 

 nation of the vapour-density by the method by M. Dumas. 



Special Affinities of Nitrogen. In the same manner that ordinary metallic substances 

 absorb oxygen with avidity from the atmosphere, especially at more or less elevated 

 temperatures, so other elementary bodies combine with nitrogen to form the nitrides. 

 Messrs. Wohler and Sainte-Claire Deville have carefully investigated this subject, and 

 with great success. When a mixture of titanic acid and charcoal is heated in a char- 

 coal tray (contained in a charcoal tube) to a temperature sufficient to fuse platinum, 

 and a current of dry nitrogen is sent over the mixture, the gas is absorbed with such 

 rapidity that, no matter how rapid the current, none escapes from the tube. 



Boron also possesses great tendency to combine with nitrogen at high temperatures. 

 Amorphous boron heated in a current of ammonia becomes incandescent ; the nitrogen 

 is absorbed, and the hydrogen escapes, and may be inflamed at the exit of the appa- 

 ratus. A mixture of boracic acid and charcoal, if ignited in a current of nitrogen, 

 yields the white infusible nitride of boron, first described by Mr. Balmain under the 

 name of ^Ethogen, but subsequently more accurately investigated by M. Wohler. 



Silicon also combines with nitrogen under favourable circumstances. These facts, 

 coupled with the old experiment made by the French chemists on the nitride of po- 

 tassium, and the action of ammonia at a red heat upon iron, show that nitrogen is 

 far from being the inert substance generally supposed. C. G. W. 



NITROGEN, BIN-OXIDE OP; Nitrogen dioxide, or Nitric oxide (Deutoxide 

 d azote, Fr. ; Stickstoffoxyd, Ger.), NO 2 (N 2 O 2 ), is a gaseous body which may be 

 obtained by pouring upon copper or mercury, in a retort, nitric acid of moderate 

 strength. The nitrous gas comes over in abundance without the aid of heat, and 

 may be received over water freed from air, or over mercury, in the pneumatic 

 trough. It is elastic and colourless; what taste and smell it possesses are unknown, 

 because the moment it is exposed to the mouth or nostrils, it absorbs atmospherical 

 oxygen, and becomes nitrous or nitric acid. Its specific gravity is 1-0393, or 1-04 ; 

 whence 100 cubic inches weigh 36 - 66 gr. Water condenses not more than ,^th of 

 its volume of this gas. It extinguishes animal life, and tho flame of many com- 

 bustibles; but of phosphorus, well kindled, it brightens the flame in a remarkable 

 degree. A mixture of nitric acid and bisulphide of carbon burns with a flame of 

 high actinic power, and may be used in photography. Nitric oxide consists of 

 47 parts of nitrogen gas, and 53 of oxygen gas, by weight ; and of equal parts in 

 bulk, without any condensation. The constitution of this gas, and the play of affinities 

 which it exercises in the formation of sulphuric acid, are deeply interesting to the 

 chemiecil manufacturer. 



The Hyponitrous Acid (Salpetngcs'dure, Ger.), like the preceding compound, deserves 

 notice here, on account of the part it plays in the conversion of sulphurous into sulphuric 



