coMrnrxns OK NITROGKN AVJTII IIYDIH^JKN AND OXYGEN 259 



of giving salts with acids ; for example, with hydrochloric acid, 

 NH 3 (OH)C1 which is a substance corresponding with sal-ammoniac, 

 in which one atom of hydrogen is replaced by hydroxyl. (2) The other 

 extreme case of substitution given by ammonium hydroxide, NH 4 (OH), 

 is \\lit-n the whole of the hydrogen of the ammonium is replaced by 

 oxygen ; and as ammonium contains 4 atoms of hydrogen, the highest 

 oxygen compound should be NO 2 (OH), or NHO 3 , as we find to be 

 really the case, because NHO ; , is nitric acid, or the highest degree 

 of the oxidation of nitrogen. 26 If instead of the two extreme aspects 

 of substitution we take an intermediate one, then we obtain one 

 of the intermediate oxygen compounds of nitrogen. For instance, 

 N(OH) 3 is orthonitrous acid, 27 with which corresponds nitrous acid, 

 NO(OH), or NHO 2 , equal to N(OH) 3 - H 2 O, and nitrous anhydride 

 N 2 O 3 = 2N(OH) 3 - 3H 2 O. Thus nitrogen gives a series of oxygen 



tion, like ammonia, precipitates basic hydrates, and it deoxidises the oxides of copper, 

 silver, and other metals. Hydroxylamine is obtained, in a great number of cases, for 

 instance, by the action of tin on dilute nitric acid, and also by the action of zinc on ethyl 

 nitrate and dilute hydrochloric acid, &c. The relation between hydroxylamine, 

 N 1 1 ,(OH), and nitrous acid, NO(OH), which is so clear in the sense of the law of substi- 

 tutions, becomes a reality in those cases when reducing agents act on salts of nitrous 

 acid. Thus Raschig (1888) proposed the following method for the preparation of the 

 hydroxylamine sulphate. A mixture of strong solutions of potassium nitrite, KNO 2 , and 

 hydroxide, KHO, in molecular proportions, is prepared and cooled. An excess of sul- 

 phurous anhydride is then passed into the mixture, and the solution boiled for a long 

 time. A mixture of the sulphates of potassium and hydroxylamine is thus obtained : 

 KNO 2 + KHO + 2SO 2 + 2H 2 O = NH 2 (OH),H 2 SO4 + K 2 SO4. The salts may be separated 

 from each other by crystallisation. 



With respect to substances intermediate between NH 3 and the oxides of nitrogen, we 

 must turn our attention to hyponitrous acid, NHO, and amidogen, which are mentioned 

 in Note 67. 



- t; Nitric acid corresponds with the anhydride N 2 O 5 , which will afterwards be described, 

 but which must be regarded as the highest saline oxide of nitrogen, just as Na 2 O (and the 

 hydroxide NaHO) in the case of sodium, although sodium forms a peroxide possessing the 

 property of parting with its oxygen with the same ease as hydrogen peroxide, if not on 

 heating, at all events in reactions for instance, with acids. So also nitric acid has its 

 corresponding peroxide, which may be called pernitric acid. Its composition is not well 

 known probably NHO.j so that its corresponding anhydride would be N 2 O7. It is 

 formed by the action of a silent discharge on a mixture of nitrogen and oxygen, so that 

 a portion of its oxygen is in a state similar to that in ozone. The instability of this sub- 

 stance (obtained by Hautefeuille, Chappuis, and Berthelot), which easily splits up with 

 the formation of nitric peroxide, and its resemblance to persulphuric acid, which we shall 

 afterwards describe, will permit our passing over the consideration of the little that is 

 further known concerning it. 



27 Phosphorus, as we shall afterwards find, gives the hydride PH 3 , corresponding 

 with ammonia, NH 3 , and forms phosphorous acid, PH 3 O 3 , which is analogous to nitrous 

 arid, just as phosphoric acid is to nitric acid ; but phosphoric (or, better, orthophosphoric) 

 acid, PH 3 O.j, is able to lose water and give pyro- and meta-phosphoric acids. The latter 

 is equal to the ortho-acid minus water = PHO 3 , and therefore nitric acid, NHO 3 , is really 

 meta-nitric acid. So also nitrous acid, HNOo, is meta-nitrous (anhydrous) acid, and then 

 the ortho-acid is NH 3 O 3 = N(OH) 3 . 



s2 



