COMPOUNDS OF NJTK'ocl-N WITH BYDROGEN AND OXYGEN 281 



has n strong tendency to give only the higher types of nitrogen com- 

 pounds, which we see in nitric acid, HNO ;5 or NO 2 (OH), in nitric an- 

 hydride, N 2 O:s or (NO 2 )._,O, and in ammonium chloride, NH 4 C1. If X 

 stand for an atom of hydrogen, or its equivalents, chlorine, hydroxyl, Arc., 

 and if O, which is, according to the law of substitution, equivalent to 

 H 2 , be indicated by X 2 , then the three above-named compounds of 

 nitrogen should be considered as compounds of the type or form NX 5 . 

 For example, in nitric acid X 5 =O 2 + (OH), where O 2 =X 4 , and 

 OH=X ; whilst nitric oxide is a compound of the form NX 2 . Hence 

 this lower form, as is true of lower forms in general, strives by combina- 

 tion to attain to the higher forms proper to the compounds of a given 

 element. NX 2 passes consecutively into NX 3 - namely, into N 2 O 3 and 

 NHO 2 , NX 4 (for instance NO 2 ) and NX 5 . 



As the decomposition of nitric oxide begins at temperatures above 

 600, many substances burn in it ; for instance, ignited phosphorus con- 

 tinues to burn in nitric oxide, but sulphur and charcoal are extinguished 

 in it. This is due to the fact that the heat evolved in the combustion of 

 these two substances is insufficient for the entire decomposition of the 

 nitric oxide, whilst the heat developed by burning phosphorus suffices 

 to produce this decomposition. That this is the true explanation of 

 the behaviour of nitric oxide in these cases is proved by the fact that 

 charcoal when very strongly ignited will burn in the gas. 62 



The compounds of nitrogen with oxygen which we have so far con- 

 sidered may all be prepared from nitric oxide, and may themselves be 

 converted into it. Thus nitric oxide stands in intimate connection 

 with them.' 53 The passage of nitric oxide into the higher degrees of 



62 A mixture of nitric oxide and hydrogen is inflammable. If a mixture of both 

 gases be passed over spongy platinum, the nitrogen and hydrogen even combine, forming 

 ammonia. A mixture of nitric oxide with many combustible vapours and gases is very in- 

 flammable. A very characteristic flame is obtained in burning a mixture of nitric oxide 

 and the vapour of the combustible carbon bisulphide, CS.,. The latter substance is very 

 volatile, so that it is sufficient to pass the nitric oxide through a layer of the carbon bisul- 

 phide (for instance, in a Woulfe's bottle) in order that the gas escaping should contain a 

 considerable amount of the vapours of this substance. This mixture continues to burn 

 when set light to, and the flame emits a large quantity of the so-called ultra-violet rays, 

 which are capable of bringing about chemical combinations and decompositions, and 

 therefore the flame may be employed in photography in the absence of sufficient day- 

 light (magnesium and electric light have the same property). A mixture of nitric 

 <>xi<lt> with many gases (for instance, ammonia) explodes in a eudiometer. 



63 The oxides of nitrogen do not proceed directly from oxygen and nitrogen by contact 

 alone, naturally because their formation is accompanied by the absorption of a large 

 quantity of heat, namely (see Note 29), about 21500 heat units are absorbed when 16 parts 

 of oxygen and 14 parts of nitrogen combine, consequently the decomposition of nitric oxide 

 into oxygen and nitrogen is accompanied by the evolution of this amount of heat; and 

 therefore with nitric oxide, as with all explosive substances and mixtures, the reaction 

 once started is able to proceed by itself. In fact, Berthelot remarked the decomposition 

 of nitric oxide in the explosion of fulminate of mercury. This decomposition does not take 



