Alloxantin + 6 Aq.) is formed on adding together solutions of equivalent proportions of alloxan and dialuric acid, and could seem to be a compound of those substances. It may also be !ormed by the action of several reducing agents on alloxan. It occurs in small colourless rhomboidal prisms, slightly soluble in cold water, rather more so in boiling water ; oxidising agents reconvert it into dloxan. Boiled with hydrochloric acid it yields white, pulverulent, xllituric acid and dilituric acid, which has not been fully 3xamined. The dimethyl derivative of alloxantin is identical with =alio add. [CAPPErxr.] Alloxanic Acid may be considered as alloxan plus two 3quivalents of water. It is a product of the action of bases upon alloxan, and may be isolated on treating an alloxanate with a stronger acid. By evaporation it is obtained as a semi-crystalline mass, of unstable character. Its aqueous solution, by ebullition and evapora tion to near dryness, splits up into leucoturic acid which dissolves on rediluting with water, and a white, insoluble, slightly acid powder termed diftuan. Some of the allaxanates crystalline readily.
Mycomdic Acid (HO,C,H,N,0,, Aq.), or formed when a solution of alloxan in ammonia is boiled and cooled slowly.
Mesosalic Acid (2H0, Where solutions of alloxanates are boiled for some time, they break up into urea and mesoxalic acid :— Mesoxalic acid may be isolated from the baryta salt by sulphuric acid or from the lead salt by sulphuretted hydrogen. It is very soluble in water, but may be obtained in crystals. The silver salt is decomposed when heated, brisk effervescence of carbonic acid and carbonic oxide occurring.
Parabanic Add may be obtained in flat colourless prisms on evaporating the nitric acid with mother liquor of alloxan. It is permanent itself, but forms unstable compounds with bases. The parabanate of ammonia, for example, decomposes during evaporation the ammonia salt of oxaluric acid being formed. The latter occurs in brilliant crystals, and is interesting from the fact that dumb-bell crystals of oxaluric acid—at first mistaken for oxalate of lime—are sometimes met with in urinary deposits.
Phenyl-osaluramide or exaluranilide, is a white crystal line powder.
Thionuric Acid (2H0, 2S0,). Solutions of alloxan, sulphite of ammonia, and ammonia, combine together when boiled, thionurate of ammonia crystallising out on cooling in brilliant leaflets. The lead salt decomposed by sulphide of hydrogen furnishes an acicular mass of thionuric acid.
rrarsi/ murexan or dialuramide. When a hot saturated solution of thionurate of ammonia is treated with hydro chloric acid in excess, the mixture is converted into a semifluid mass.
The uramil thus obtained is in the form of plumose acicular crystals, which are permanent in the air, and become of a pink colour when heated ; they are insoluble in cold and but slightly soluble in boiling water. The alkalies dissolve uramil, and acids precipitate it from them unchanged. The solutions in ammonia and potash become of a purple colour by exposure to the air, and deposit green acicular crystals of a brilliant metallic• lustre. If the potash solution be boiled, ammonia is evolved and aratadie add is formed; dilute acids produce similar decompositiou. It is soluble in concentrated sulphuric acid, and is precipitated from it by water ; by concentrated nitric acid it is resolved into alloxan, with the evolution of hyponitrous acid, and the formation of nitrate of ammonia.
Nurexid purpurate of ammonia of Dr. Prout. This substance may be obtained by several processes. The least °pesos° is probably that of dissolving uric acid in dilute nitric acid, evaporating the solution till it assumes a reddish colour ; after the liquor has cooled to Fahr., add excess of ammonia ; then dilute it with half its volume of boiling water, and allow it to cool. Care must be taken not to employ too much or too little nitric acid. Whilst ammonia continues to give a red precipitate, when added to small portions, the nitric acid is insufficient. If, on the contrary, ammonia produces a glairy yellow precipitate, murexide cannot be obtained without passing a current of hydrosulphuric acid into the liquor.
Murexide crystallises in short four-sided prisms, which exhibit a green metallic reflection. They are garnet-red by transmitted light. It is very little soluble in cold water, and gives it a magnificent purplish red colour. It dissolves readily in water at 158°, and crystallises from the solution unaltered. It is insoluble in alcohol and in ether. It is insoluble also in solution of carbonate of ammonia, but dissolves in a solution of potash, producing a superb indigo-blue colour, which disappears by heat, with the evolution of ammonia, Purpurate of Pato/L.—According to Fritzche, this is best obtained by decomposing a boiling solution of purpurate of ammonia by moans of excess of nitrate of potash. This purpurate consists of very small reddish-brown crystal.; it may however be obtained in large crystal., which have the colour and lustre of the ammoniacal salt. It is difficultly soluble in water, and much less so in saline solutions, and hence the advantage of using excess of nitro in preparing it. It appears to be a neutral salt.