792 XANTHINE, OR XANTHIC OXIDE. Guanidine is homologous with methyluramine (Є,H,N). It is possibly, as Hofmann supposes, a triammonia formed from 3 atoms of ammonia, in which 4 atoms of hydrogen have been displaced by 1 of carbon iv,H,,N,, or carbotriammonia. By heating chloropicrin in sealed tubes with an alcoholic solution of ammonia for some days to the temperature of boiling water, Hofmann succeeded in obtaining guanidine hydrochlorate, mixed with ammonium nitrite and hydrochlorate, whilst gaseous nitrogen is liberated from the decomposition of the ammonium nitrite: Chloropicrin. = CHỌN,HCl + 2 HẠNHC1 + HẠNNG Among the products of the oxidation of guanine is xanthine in small quantity, the formation of which is best observed when guanine is treated with nitrous acid; the relation of the two bodies may be represented by the following equation: 5 41 4 (1612) Xanthine, or Xanthic Oxide (Є.H ̧N12), was discovered by Marcet as the principal constituent of a very rare variety of urinary calculus. Göbel has since found it in some oriental bezoars extracted from the intestines of certain ruminating animals. The concretions which contain xanthine are of a pale brown colour; they have a polished surface, and a lamellar fracture. These calculi are readily soluble in a solution of potash; and on neutralizing the alkaline solution with an acid, xanthine is precipitated in the form of a white powder, which is insoluble in water, alcohol, and ether. It acquires a waxy lustre on friction with a hard body. The caustic alkalies, particularly ammonia, dissolve it freely. Hydrochloric acid dissolves it very sparingly, but it is soluble in nitric acid without effervescence: the solution, when evaporated, leaves a lemon-coloured residue (hence the name xanthine, from Eavlòs yellow). This residue does not become red by the action of ammonia. When distilled, xanthic oxide yields hydrocyanic acid and ammonium carbonate, but no urea. It contains one atom of oxygen less than normal uric acid. Stædeler found xanthine diffused pretty extensively through different organs of the body, such as the liver, spleen, and pancreas, as well as the brain and muscular tissue. It may be separated from other bodies with which it is associated, by the insolubility of the compound with mercuric oxide, which is formed on adding mercuric acetate to a solution of xanthine; it also gives a precipitate with basic acetate of lead. (1613) Hypoxanthine (Є,H,N ̧) contains one atom of oxygen less than the preceding compound. It was found by Scherer in the liquid contained in the substance of the spleen both of man and of the cow. Hypoxanthine has also been found in the thyroid and thymus glands; and it appears to be identical with the base obtained from muscular tissue by Strecker, and called by him sarcine. Hypoxanthine is a white powder, which is nearly insoluble in water, but soluble in a dilute solution of potash, as well as in dilute hydrochloric acid; this acid may indeed be made use of in order to separate the base from xanthine. It is attacked by nitric acid with evolution of gas, yielding xanthine, and leaving a bright yellow crystalline residue. Strecker (Liebig's Annal. cxviii. 151) has lately pointed out the close relations which exist between several of the bases which have been just described; and experiments made by Rheineck (Lieb. Annal. cxxxi. 121) have shown that uric acid, when reduced by a very dilute amalgam of sodium, yields both xanthine and hypoxanthine : Guanine is regarded by Strecker as a cyanuretted compound triatomic base analogous to cyaniline and to cyanocodeia :— If kreatine be the hydrated ammonium base corresponding to kreatinine, we should have the following series : The formula of xanthine would also allow of its being considered as forming one of a series homologous with theobromine 794 BASES HOMOLOGOUS WITH GLYCOCINE. But direct experiments have shown that caffeine is a methylderivative of theobromine (1408), and these two bodies stand in a relation similar to that of ethylia to diethylia; whilst as yet the experiments on the conversion of xanthine into theobromine have been unsuccessful; for xanthine when treated with methyl iodide yields a new methylated base metameric with theo bromine, but not identical with it. The constitution of these bases may possibly be thus represented (Strecker) :— 2 xanthine, kreatine, and kreatinine containing glycolyl (Є ̧H ̧Ð)”, the radicle of glycolic acid, while theobromine and caffeine contain lactyl (EH)", the radicle of lactic acid. 3 (1614) Bases homologous with Glycocine.-The three bases, glycocine, alanine, and leucine, are homologous bodies, and when submitted to the action of nitrous acid, they are decomposed according to the following formula, and furnish acids which are also homologous with each other. ЄH2n+1NO2+ HNO2 = HЄ„H2-103 + N2+ H2O. 2n-1 The relation of these bases and acids to each other may be thus represented : The azotised bodies contained in this series possess but very feeble basic power, although they form crystallized compounds with the acids. There can be little doubt that they are the representatives of a class of compounds co-extensive with the volatile fatty acids, and probably the missing terms of the series might be obtained by processes similar to those which furnish alanine and leucine, viz., by acting upon a mixture of hydrocyanic acid with the corresponding aldehyd-ammonia, by means of hydrochloric acid. Glycocine, alanine, and leucine are isomeric with the amides of glycolic, lactic, and leucic acids; but they are not the amides themselves: glycolamide and lactamide may be obtained by acting upon the glycolic and lactic ethers with an alcoholic GLYCOCINE, OR GLYCOCOLL. 795 solution of ammonia, but they differ in properties from glycocine and alanine. Indeed, the true amides are all decomposed into salts of ammonium when boiled with dilute acids, whereas the compounds of the glycocine series may be boiled with dilute acids for hours without decomposition. These bases when submitted to dry distillation yield carbonic anhydride, and methylia, ethylia, and amylia respectively; for example : (1615) Glycocine, or Glycocoll (Є,H,NO,, or C,H,NO=75).— This substance is one of the products of the decomposition of gelatin when boiled with dilute sulphuric acid, and hence the name glycocoll, from yλukus, sweet, kóλλa, glue; after removing the acid by means of baric carbonate, the glycocine may be procured in crystals on evaporating the solution. It may also be obtained by heating gelatin with a solution of potash or of soda. But it is most easily obtained in a state of purity by boiling hippuric acid for half an hour, with hydrochloric acid (1442); as the liquid cools, benzoic acid is separated in abundance, and glycocine remains in combination with hydrochloric acid :— Hippuric acid. 3 Glycocine hydrochlor. Benzoic acid. 2) HЄH ̧ч ̧ + HCl + H2→ = €2H ̧ч„HCl + H¤‚Í ̧Є On the addition of absolute alcohol, after the solution has been concentrated by evaporation and supersaturated with ammonia, pure glycocine is deposited in minute crystals. Glycocine may likewise be obtained from glycocholic acid, one of the resinous acids of the bile (1693), when it is decomposed by ebullition with. hydrochloric acid. Perkin and Duppa have also obtained glycocine (Q. J. Chem. Soc., xi. 31) by acting upon an alcoholic solution of ammonia with bromacetic acid, exposing the mixture to heat in a sealed tube; the reaction is represented as follows: Glycocine, in fact, bears the same relation to acetic acid that amido-benzoic does to benzoic acid, and it may therefore be viewed as amido-acetic acid :— Pure glycocine has a sweet taste, which is less intense than that of cane-sugar: it is soluble in about 400 parts of cold water, and is less soluble in rectified alcohol; it is insoluble in absolute alcohol and in ether. Glycocine crystallizes readily by spontaneous evaporation of its aqueous solution. It is not susceptible of the alcoholic fermentation. Its solution has the power of reddening litmus feebly. It throws down metallic mercury from a solution of mercurous nitrate. Glycocine has a strong tendency to combine with the acids, with some of which, such as the sulphuric and hydrochloric, it combines in 2 or 3 different proportions, without, however, neutralizing them; many of these compounds, such as the nitrate (Є,H.NO,,HNO3), crystallize readily; the sulphate, the oxalate, and the hydrochlorate may also be obtained in crystals. A large number of the metallic oxides also combine with glycocine, displacing an equivalent of water from it, and forming with it soluble compounds, which may be obtained in crystals; this is the case with the oxides of zinc, copper, lead, barium, and silver. These compounds may be obtained by heating the hydrated oxides of the metals with a solution of glycocine. When glycocine is boiled with cupric acetate, acetic acid is expelled, and a compound of glycocine with cupric oxide is obtained in solution. If glycocine be heated with a strong solution of potash it gives a fleeting, beautiful fiery-red colour, ammonia is expelled, and oxalic and hydrocyanic acids are formed in the solution. Indeed, few substances enter so readily into combination as glycocine. In addition to its compounds with acids and with bases, it unites with many salts, and forms bodies which crystallize with great regularity and brilliancy. If a mixture of glycocine with sulphuric acid and peroxide of manganese or peroxide of lead be submitted to distillation, a brisk effervescence occurs, owing to the escape of carbonic anhydride, and pure hydrocyanic acid distils over :- ¤ ̧н ̧Ñ→2 + →2 = €0, + 2 H2O + HEN. 2 When nitrous acid is transmitted through an aqueous solution of glycocine, mutual decomposition occurs, nitrogen is disengaged, and on agitating the mixture with ether, decanting the ethereal liquid after it has risen to the surface, and submitting it to evaporation, glycolic acid (1308) is left in the form of a syrup, which is freely soluble in alcohol :— |