GLADSTONE ON THE PYROPHOSPHORIC AMIDES. VIII.-On the P~rophosphom'cAmicles. By J. H. GLADSTONE, Ph.D. F.R.S. INfermer communications" I have described three acid bodies wl-liclz ma3 be viewed as pyrophosphoric acid in which one two * Quart. Journal Chem. SOC. 1-01. 111 pp. 135 and 353. Do. do. , xmr p 225. Do. do. , XIX,pp. 1 and 290. GLADSTONE ON THE PYROPHOSPHORIC AMIDES. or three semi-molecules of ainidogen have displaced an equal number of molecules of hydroxyl. Their composition and their rela,tion to the original acid may be thus exhibited :-Pyrophosphoric acid .. .. P,H,O Pyrophosphamic acid .. * * P,(NH,)H,O6 Pyroplioaphodiamic acid .. . . P2(NH,),H205 Pyroyhosphotriamic acid .. P,(NH,),HO The basic hydrogen of these acids decreases as the amidogen increases but irk the case of the last one half the hydrogen combined with the nitrogen msy alsa be replaced by certain metals.Since these papers were written I liave come across some additional f'dcts and liave fwinecl a inore precise conception of the rational formule of these bodies. I propose to narrate these facts first and then to develop the inore complete theory. Pyrop7~osplitcmic AcitZ.-Tliis acid had hitherto been formed only by the breaking down of the higher amide under the influence of a metallic salt and heat. There is also another series of bodies-the tetraphospliamides-wllich yield it by decomposition; and in some cases I have found that a solution containing free pyrodinmic acid gnve indications of its presence after standing for some weeks at the ordinary temperature.The following experiments led me at' first to believe that it might be produced syntlietically hit tliere is no coiiclusiva proof that the compounds are not a peculiiir series of double ammonium salts. I. 0rdiii:xi-y pyrophosphoric acid was saturated with ammonia and to this solution hydri3,te of b;triurn was added iiot in excess. A precipitate was obtained which wlieii well washed aid dried gave the inclicatioiis of a pyrophosphamate ; that is when heated per se it tinned black and gave off ammonia and a peculiar sublimate. When excess of hydrate of barium was dried notliing but the pyrophosphntc wm obtained. 11. Similar experiinents w~\reretried with acetate of lead arid f'erric chloride instead of hydrate of barium and with like results.111. The insoluble modification of ferric pyrophosphate was prepared in the presencc of it quantity of chloride of ammonium. The well-xvvasliccl precipitate gave the ordinary indications of GLADSTONE ON THE PYROPHOSPHORIC AMIDES. the pyrophosphamate. In one experiment 0.427 grm. of the salt thus produced was decomposed by boiling with hydrochloric acid and gave 0.200 grm. of ammonio-chloride of platinum which is equal to 2-93 per cent. of nitrogen. Had the -whole precipitate been the pyrophosphamate the ni trogeii would have been 5.65 per cent. or nearly double that found. IV. 0.355 grm. of ferric pyrophospliate was dissolved in ammonia and reprecipitated by dilute sulphuric acid.The salt thus obtained was well washed and decomposed by hydrochloric acid when it gave 0.234 grm. of ammonio-platinum salt equi- valent to 4.13 per cent. of nitrogen. V. This experiiiient was repeated with copper instead of iron salt and with a similar result. VI. The converse of these last experiments was tried. 0.333 grm. of ferric pyrophosphate (soluble modification) was dis- solved in dilute sulphuric acid and reprecipitated by ammonia of course not in excess. The well-washed precipitate gave 0.170 grm. of ammonio-platinum salt equivalent to 3-14 per cent. of nitrogen. That the azotized ferric compound contained in these pre- cipitates is not the ordinary pyrophosphamate is shown by the followirig properties :-It is soluble in excess of either pyro- phosphate of sodium or ferric chloride; it is decomposed by cold dilute sulphuric acid; and moreover it is somewhat soluble in pure water.But while these properties distinguish it from the insoluble ferric pyrophosphamate previously known t>hey are rather suggestive of the idea that it inay be a soluble modification analogous to the soluble ferric pyrophosphate. An attempt was made to convert it into the ordinary salt by boiling its solution in very dilute sulphuric acid but without success. Ferric pyrophosphamate formed in the cold by the double decomposition of pyrophosphamate of potassium aid ferric chloride was found to be identical in properties with the ordinary salt. The action of heat upon this ferric compound is similar to its action on the pyrophosphamate but even the production of water and of the white sublimate must be taken as evidence with considerable reserve ; at any rate these substances are formed when the compound of pyrophosphoric acid and am-monia is heated per se.For analysis it would of course be necesfiary t-o prepare this GLADSTONE ON THE PYROPHOSPHORIC AMIDES. compound free from pyrophosphate or any other salt. The fact that it is somewhat soluble in water but not in a solution of cliloride of ammonium was taken advantage of for this purpose. An aqueous solution was in fact precipitated by the addition of the concentrated chloride and the white flocculent compound was quickly xvdied wit,h as little water as possible.Of what remained on the filter 0-390grm. decomposed by hydro-chloric acid gave 0.334 grin. of ainmoiiio-chloride of platinum which is equivalent to 3-35 per cent. of nitrogen. This agrees nearly with tlie amount contained in ferric pyrophosphamate viz. 5.65 per cent. but no ultimate analysis can decide between the formula P,(NH,)Fe,O,,H,O and a possible double ammo- nium salt of the composition P,(NH,)Fe,O,. Pyrop7~o~pllodiarnic Acid-I formerly published a character- istic test of this acid founded on tlie fact that when a solution containing it is rendered strongly acid and is heated with a few drops of a ferric salt the flocculent white pyrophosphamate makes its appearance. Precaution8 were given so as to avoid mis- taking for pyropliosphodiamic acid two others which I have since called tetraphosphoric compounds.With my further knowledge of .these amides I still think that tlie process may be looked upon as furnishing a characteristic test but a chemist inex- perienced in these compounds might easily be misled by the formation of the insoluble ferric pyrophosphate whicli so closely resembles the pyrophosphamate. Hence it will be generally desirable if not necegsary to dry a portion of’ the precipitate and examine which conipouiid it is by heating it per se in a test tube when the pyrophosplinte simply fuses and the pyrophospliarnate does iiot fuse but turns black at first and gives off ammonix and a little white volatile salt. This sublimate is very soluble in water riot so in alcohol its aqueous solution contains amnioiiia and some acid that gives a brown-black precipitate with nitrate of silver like phos- phorous acid.It may also be borne in mind that the pyrophos-pliamate will separate from a solution so acid as to prevent the formation of the insoluble pyrophosphate. A large excess of acid will also nearly if not antireiy prevent the formation of the compound resulting from pyrophosphorio acid and am-monia in juxta-positim. So there is little fear of error from this source. Still as the !!roof that this acid may be prepared by the GLADSTONE ON THE PYROPHOSPHORIC AMIDES. eleven methods noted in my paper rests mainly on the evidence of this test I thought it well to repent the principal expe- riments examining whether it was the pyrophogphamate that was really produced.I have found it to be so in all cases and I have no reason to doubt that in each instance it had been formed by the decomposition of pyrophosphodiamic acid. Pyr.o~Jio,~pJ~otra~~~ic Acid.-The method formerly given for preparing this body was not a productive one and the acid was apt to be contaminated with another compound unless great attention was paid to t'he temperature. The following is a far more productive and a Fetter process :-Saturate oxy-chloride of phosphorus with dry ammonia gas without regard to the rise of temperature; heat the resulting mass at about 220°C.; add water to it ; and boil for aboilt a minute. This will convert the whole of the insoluble portion into pyrophos-photriamic acid with very little loss from the production of other phosphoric compounds.This acid has also been met with among the products of de- composition of one of the tetraphosphoric amides t,hat remain to be described at some future time. Its formation along with other compounds when pentachloride of phosphorus is tlirowii into the strongest aqueous ammonia has been already noted. YheoreticaI Constitution. In my last communicatioii to this Societ,y,* I suggested as the rational formula of pyrophosphoric acid -P,(HO),O -or at greater length (Ho)20) 0;-and I expressed iny con-P(HO),O victiori that when this acid is pi-oduced by the mutual action of water and oxychloride of phosphorus the two atoms of hydro- gen in the molecnle of water art attacked simultaneously by two moleciilcs of the chloride and tlie water type is preserved in the new phosphorus compound.A similar explanation will hold good in the formation of these amides from oxychloride of phosphorus ammonia and water. When the oxychloride is exposed to a current of the alkaline gas at a low temperature it absorbs two equivalents giving doubtless the first amide thus :-PC1,O + 2NH = NH,C1 + P(NH,)Cl,O. * Journ. Chem. SOC.,vol. XX p. 435. GLADSTOYE OX THE PYROPHOSPHORIC AMIDES. 6'3 When the oxychloride is dropped into the strongest aqueous solution of ammonia it seems probable that the first action is the same. In both cases the production of the second pi-ro- phosphoric amide by the. action of water (or alkaline hydrate) may be well explained on the assumption that the two atoms of hydrogen (or ammonium) are attacked simultaneously by the chloride.The reaction must be expressed on paper in two successive stages though they probably take place together in reality :-or P2(NH2),H,0, pyrophosphodiamic acid. These forrnuh are precisely analogons to those by which the formation of pyrophosphoric acid was soirglit to be explained. But the above is not the oiily rtmiclated oxychloride from which the pyro-diamic acid may be produced. Oxychloricle of phosphorus combines with 4 equivalents of ammoilia gas giving rise doubtless to a second amide thus :-PC1,0+4NH3 = 2iYH,C1 + P(NH,),ClO When this is treated with water it is oiily necessary to suppose that the action is precisely similar to that given above the two rJtages being probably simultaneous and the resctioii being favoured in this instaaxe by the affinity of the resulting acid and alkali for one another.2P(NH2),C10 + 0 = 2HC1 + P(NH2)20}0 P(NH,),O It will be perceived tlmt hliis pyro-diamic acid is the synl- GLADSTONE ON THE PYROPHOSPHORIC AMIDES. metTical one and that the unsymmetrical pyro-amic and pyro- triamic acids are not to be produced by this kind of reaction. This acid is also formed hrectly by the mutual action of ammonia and phosphoric anhydride. Nothing can be simpler. But P,O is probably also constructed on the water-ty,pe and in that case we shall have- or P2(NH2)2H205, pyroplzosphodiamic acid.The unsymmetrical pyro-amic acid is produced by breaking down t8he symmetiical pyrophosphodiamic acid. P(NH,) (MO)0 P(MO)(MO)O 1o or P,(NH,)M,O, a pyroplzosplmmate. The unsymmetrical pyro-triamic acid is produced from an amidated oxychloride of unknown composition or by the break- ing down of tetraphosphoric compounds. As these have not yet been described I will content myself with writing down the formula of this acid in a manner analogous to its con- geners :-Pyrophosphotriamic acid ;[g;;[;;jg)}0. It is easy to understand how a substance of this cornposition when boiled for a long time with -water or heated with sul-phuric acid parts with one of its nitrogen constituents and becomes the symmetrical pyrophosphodiamic acid.