110 DIVERS : CONSTITUTION OF NITRIC PEROXIDE. X 11. - Cons tit u t iorL of Nitric Pel-oxide. By EDWARD DIVERS. IN a paper now appearing (this vol., p. 78), Haga has demonstrated that Fremy’s sulphaxilate is an oxime-peroxide and a trivalent nitrogen compound. If Hantzsch and Semple’s suggestion is accepted (Ber., 1895, 28, 2744; compare Piloty and Schwerin, Ber., 1901, 34, 1884 and 2354), that Fremy’s salt is also a sulphonated nitric peroxide, it follows that the constitution of nitric peroxide is a t last determined, being that of nitrosyl peroxide. Hantxsch and Semple must be right, for, after Haga’s researches, a sulphazilate as a peroxylaminesulphonate cannot be supposed to be other than a sulphonated nitric peroxide. It only remains, therefore, to show that nitric peroxide is a true peroxide in its chemical relations.It is formed from nitric oxide and oxygen, just as sodium peroxide is formed from sodium and oxygen, Nitrous acid cannot, indeed, be shown to pass simply into it and back again, as a hpdroxylamine-DIVERS : CONSTITUTION OF NITRIC PEBOXIDE. 111 disulphonate (sulphonated nitrous acid) changes into a peroxylamine- sulphonate, but that is only on account of its own instability and that oE nitrous acid. Its interaction with organic oximes, in which it converts these substances into peroxides and becomes hydrogenised into nitrous acid (Scholl), is in accordance with its nature as a true peroxide. Similarly, it converts a hy droxylamined is ulphonat e into a perox y lamines ulphonate Nitrosyl peroxide and a peroxylaminesulphonate both interact with water in essentially the same way, the apparent difference being due t o the limits imposed by the sulphonation in the case of the latter substance.The former yields half its nitrogen as nitric acid and half as nitrous acid, whilst the latter yields half its nitrogen as a mixed anhydrosulphate (hydroxylaminetrisulphonate) and the other half as nitrous acid and sulphonated nitrous acid (hydroxylaminedisulphonate) : 2N20, + 2H,O = ZHNO, + 2HN0,; 2N20z(S03K), + H,O = 2(S03K)2N*O*S03K + [HO*NO + HO*N(SO3K>,]. It would seem, therefore, that, wholly on the evidence afforded by Haga’s work, it can now be confidently asserted that llinitric peroxide is nitrosyl peroxide and a compound of exclusively trivalent nitrogen. The constitution of mao-nitric peroxide, in regard to these two points, remains to be considered, but can hardly be very different.Hantzsch and Semple have suggested (Zoc. cit.) that the bluish- violet dissolved form of a peroxylaminesulphonste corresponds with mono-nitric peroxide, and its crystalline form with di-nitric peroxide. Since then, Piloty and Schwerin (Zoc. cit.) have expressed the belief that porphyrexide, which has the colour of mono-nitric peroxide, may also be a derivative of this peroxide, because it contains the group :NO singly, as shown by the formula (C,HgN,):NO. Its molecular weight, however, has been only indirectly ascertained, that is, by cryoscopic determinations of those of its nitrate and its chloro- derivatives. That its molecular weight is not double as great is a re- markable fact,, for, in its chemical behaviour, and especially in its re- versible relation with porphyrexine, (C,HgN3):NOH, porphyrexide seems to belong to the class of oxime-peroxides Piloty and Schwerin do not indeed recognise this, and have instead come to the conclusion that the nitrogen of the group :NO in porphyrexide and in mono-nitric peroxide must be quadrivalent.I n the light of Haga’s experimental results, this view of the matter has become untenable, since por- phyrexide and the peroxylaminesulphonates appear to belong to the same class of nitroxy-compounds, as Piloty and Schwerin themselvea have pointed out. I n the few cases in which it has been possible to determine (Hags).112 DIVERS : COKSTITUTION OF NITRIC PEROXIDE.cryoscopically the molecular weight of a glyoxiine-peroxide, this has been found to include :NO twice. This result may be owing to the glyoxime constitution of these peroxides, but, even SO, there is still no peroxide, except mono-nitric peroxide, and possibly porphyrexide, the molecular weight of which is such that it contains the group :NO only onc0. The cccurrence of many nitroso-zompounds in a colour- less, solid form, and in a bluish-violet liquid form, does not lend much assistance in deciding the molecular weights of the two forms of a peroxylaminesulphonate, since they contain not :NO but *NO. But it must not be left out of sight that Piloty (who thinks otherwise, and has been followed by Schmidt, Bamberger, and others) has succeeded in showing that the white form of these compounds contains the group *NO twice, and that the deeply-coloured modification contains i t only once.But here the latter is the form which must be treated as the chemically active one, whilst the double weight found for the white form has t o be left uninterpreted chemically, as, for example, in the case of the formula (C,H,,NO), for nitroso-octane, I n the paper by Hantzsch and Semple (Zoc. cit.), there occurs, but in a foot-note only and without comment or explanation, the punctuated formula O*N:(SO,K),; whether this is to be regarded a8 a printer’s error for O:N:(SO,K), is uncertain, but if it is not, it indicates some recognition by these chemists of the presence of univalent oxygen, However this may be, the possibility of the nitrogen being quadria valent being inadmissible, the only solution of the matter seems to be to consider that both mono-nitric peroxide and porphyrexide are com- pounds of univalent oxygen, although still peroxides.The fact t h a t a molecular quantity, such as that formulated by HO, NO,, (SO,K),NO, or (C,H,N,)NO, is never met with singly in chemical interactions mili- tates against the acceptance of this explanation. Piloty and Schmerin, in discussing the quadrivalency of nitrogen, conceal this fact by stating that porphyrexide is produced from porphyrexine by the action of half an atom of oxygen, It is much more correct to hold with Haga that the molecule of peroxylaminesulphonate, and therefore also of mono- nitric peroxide and of porphyrexide, is not leas than that represented by [NO(SO,K),],, (NO,),, or (C,H,ON,),, as the case may be, if by molecule is meant the smallest chemically active weight of a substance.But still the fact remains that, when measured by comparison of their physical properties, the molecular weights of porphyrexide and red nitric peroxide are expressed by half the above formulae, and that probably the bluish-violet form of a peroxylaminesulphonate has also a molecular weight, which, when physically considered, should be expressed by the formula NO(SO,K),. These weights, only physically determined, have no chemical significance, and should be distinguished from their doubles, the truly chemical molecular weights. But, asSOLUBILITY CURVES OF THE HYDRATES OF NICKEL SULPHATE. 113 pseudo-chemical molecules, they must be represented as containing a univalent atom of oxygen. It is, after all, not so difficult to admit that oxygen may be univalent in a peroxide. I n fact, a true peroxide may be defined and differentiated from other oxides, as being a compound in which some or all of the oxygen is exerting on the rest of the compound only half its usual valency. Or, conversely, a peroxide may be defined as a compound containing oxygen which is either actually univalent or exterior and quasi-univalent. Apart from the unfamiliar nature of the conception of actually univalent oxygen, it seems natural enough to find a normal molecule of nitric peroxide dissociate a t a gentle heat into two identical but simpler ones, in consequence of the linked oxygen atoms becoming parted and losing valency. On the other hand, the assumption that nitrogen is quadrivalent does not accord with the result actually obtained, when by cooling nitric peroxide it is found that the valency of the nitrogen decreases instead of increas- ing, 2 0 : K :O becoming O:N*O*O*N:O.