urine, to which some sulphuric or hydrochloric acid had been added, acetic acid and benzoic acid were evolved, the latter of which was deposited in crystals in the neck of the retort. Liebig, in repeating these experiments, found that after neutralization of the acetic acid so obtained by the addition of oxyde of lead, there was formed in the fluid a considerable amount of a white precipitate, which consisted of pure benzoate of lead. The presence of benzoic acid in putrefied urine could, moreover, be proved by concentrating the urine, adding some sulphuric acid, and letting it stand for several days, after the lapse of which benzoic acid was found to have formed in brown glistening scales. No urine which was subjected to this test by Liebig during a period of three months was found to be void of this acid. There could be no doubt that benzoic acid was not contained as such in the fresh urine, inasmuch as it had been proved to certainty by the experiments of Ure and Keller, that crystallized benzoic acid is transformed in the body into hippuric acid, and appears in the urine as hippurate of soda. As it was furthermore known that the hippuric acid in the urine of graminivorous animals is decomposed during the putrefaction of this urine, and that benzoic acid is one of the products of that decomposition, it was to be supposed with certainty that the benzoic acid discovered in the putrefied urine of man had the same origin, and in the fresh urine was present in the form of hippuric acid. On a closer examination, Liebig found this to be the fact. All urine of individuals taking mixed food was found to contain hippuric acid in about equal proportions with uric acid. Occurrence and Methods of obtaining it pure. 3 Hippuric acid is a regular ingredient of the urine of man1 and the graminivorous animals-the horse, (from which it derives its name) horned cattle, camels,2 and elephants. It is found in guano, as hippurate of ammonia, and has been observed in the excreta of a tortoise (Testudo Græca), and in the excreta of the larvæ of butterflies, and of butterflies themselves. It has been found in the blood of calves and oxen by Verdeil and Dollfus.5 It is absent from the urine of Liebig, 'Ann. d. Pharm.,' xxxvii, p. 82. 2 Schwarz, ibid., liv, p. 31. 3 Marchand, N. Journ. d. Pharm.,' vii, p. 134. T. Davy, Edinb. New Philos. Journ.,' xlv, p. 17. 5 Ann. d. Chem. und Pharm.,' Ixxiv, p. 215; also Lehmann's Physiolog. Che mistry,' Cavend. Soc. Edit., vol. ii, p. 212. animals exclusively carnivorous. It may, however, be made to appear in their urine by giving them, with their food, hippuric acid, or any substance capable of forming it. Schwarz1 had given to a dog some hippuric acid, it made its reappearance in the urine. Buchheim found that when free hippuric acid, hippurate of soda, or acid hippurate of ammonia were taken, a quantity of hippuric acid was obtained from the urine, which was so large that scarcely any acid could have been lost in its passage through the organism. The amount of hippuric acid in the urine may be considerably increased by the ingestion with the food of benzoic or cinnamic acids, or essential oil of bitter almonds. Any amount up to 10 grammes of benzoic acid, whether taken as such, or in combination with bases, soda, ammonia, magnesia, iron, will in the course of a few hours or over night, appear in the urine as hippuric acid. The hippuric acid in each case corresponds in quantity to that of the benzoic aeid taken (Buchheim). Dr. Garrods obtained, however, only 15 to 29 grains of hippuric acid, after having taken from 20 to 30 grains of benzoic acid. Marchand4 obtained 392 grains of hippuric acid from the urine after having taken 300 grains of benzoic acid. The consumption of a large amount of fruit, such as apples (Pettenkofer) or plums (Prune Claude, Prunus domestica chlorocarpa, Duchek), will cause a considerable quantity of hippuric acid to appear in the urine. Duchek examined the greengage, and found benzoic acid in it, but not in sufficient quantity to account for the whole of the hippuric acid found in the urine after the use of a certain quantity of that fruit. He accordingly is of opinion that the greengage might contain some other compound of benzoyle capable of being transformed into hippuric acid. Duchek did not find hippuric acid to be a constant constituent of human urine. Hoefle could never find it in his urine. Pathologically an increased amount of hippuric acid is met with in the acid urine of fever-patients (Lehmann), in the urine of diabetic patients (Lehmann's7 and Hünefeld's observations both confirmed by Duchek). In one instance hippuric acid was observed in the scales from ichthyosis 3 Philos. Magaz,' xx, p. 501. 4 'Journ. of Pract. Chem.,' xxxv, p. 309. 54 Prager Vierteljahrschrift,' 1854, vol. iii, p. 25. See also the Lancet,' July 26, 1856, p. 114. 6. Chemie und Microscop am Krankenbette.' 7 Journ. d. Pract. Chem.,' vi, p. 112. Ibid., viii, p 552. urine, to which some sulphuric or hydrochloric acid had been added, acetic acid and benzoic acid were evolved, the latter of which was deposited in crystals in the neck of the retort. Liebig, in repeating these experiments, found that after neutralization of the acetic acid so obtained by the addition of oxyde of lead, there was formed in the fluid a considerable amount of a white precipitate, which consisted of pure benzoate of lead. The presence of benzoic acid in putrefied urine could, moreover, be proved by concentrating the urine, adding some sulphuric acid, and letting it stand for several days, after the lapse of which benzoic acid was found to have formed in brown glistening scales. No urine which was subjected to this test by Liebig during a period of three months was found to be void of this acid. There could be no doubt that benzoic acid was not contained as such in the fresh urine, inasmuch as it had been proved to certainty by the experiments of Ure and Keller, that crystallized benzoic acid is transformed in the body into hippuric acid, and appears in the urine as hippurate of soda. As it was furthermore known that the hippuric acid in the urine of graminivorous animals is decomposed during the putrefaction of this urine, and that benzoic acid is one of the products of that decomposition, it was to be supposed with certainty that the benzoic acid discovered in the putrefied urine of man had the same origin, and in the fresh urine was present in the form of hippuric acid. On a closer examination, Liebig found this to be the fact. All urine of individuals taking mixed food was found to contain hippuric acid in about equal proportions with uric acid. Occurrence and Methods of obtaining it pure. Hippuric acid is a regular ingredient of the urine of man1 and the graminivorous animals-the horse, (from which it derives its name) horned cattle, camels, and elephants. It is found in guano, as hippurate of ammonia, and has been observed in the excreta of a tortoise (Testudo Græca), and in the excreta of the larvae of butterflies, and of butterflies themselves. It has been found in the blood of calves and oxen by Verdeil and Dollfus. It is absent from the urine of 4 T. Davy, Edinb. New Philos. Journ.,' xlv, p. 17. 5 Ann. d. Chem. und Pharm.,' lxxiv, p. 215; also Lehmann's Physiolog. Chemistry,' Cavend. Soc. Edit., vol. ii, p. 212. animals exclusively carnivorous. It may, however, be made to appear in their urine by giving them, with their food, hippuric acid, or any substance capable of forming it. When Schwarz1 had given to a dog some hippuric acid, it made its reappearance in the urine. Buchheim found that when free hippuric acid, hippurate of soda, or acid hippurate of ammonia were taken, a quantity of hippuric acid was obtained from the urine, which was so large that scarcely any acid could have been lost in its passage through the organism. The amount of hippuric acid in the urine may be considerably increased by the ingestion with the food of benzoic or cinnamic acids, or essential oil of bitter almonds. Any amount up to 10 grammes of benzoic acid, whether taken as such, or in combination with bases, soda, ammonia, magnesia, iron, will in the course of a few hours or over night, appear in the urine as hippuric acid. The hippuric acid in each case corresponds in quantity to that of the benzoic acid taken (Buchheim). Dr. Garrods obtained, however, only 15 to 29 grains of hippuric acid, after having taken from 20 to 30 grains of benzoic acid. Marchand obtained 39.2 grains of hippuric acid from the urine after having taken 300 grains of benzoic acid. The consumption of a large amount of fruit, such as apples (Pettenkofer) or plums (Prune Claude, Prunus domestica chlorocarpa, Duchek), will cause a considerable quantity of hippuric acid to appear in the urine. Ducheks examined the greengage, and found benzoic acid in it, but not in sufficient quantity to account for the whole of the hippuric acid found in the urine after the use of a certain quantity of that fruit. He accordingly is of opinion that the greengage might contain some other compound of benzoyle capable of being transformed into hippuric acid. Duchek did not find hippuric acid to be a constant constituent of human urine. Hoefle could never find it in his urine. Pathologically an increased amount of hippuric acid is met with in the acid urine of fever-patients (Lehmann), in the urine of diabetic patients (Lehmann's and Hünefeld's observations both confirmed by Duchek). In one instance hippuric acid was observed in the scales from ichthyosis 1 Loc. cit., p. 32. 2 Archiv für Physiol. Heilk.,' 1857, vol. i, p. 122. Philos. Magaz,' xx, p. 501. Journ. of Pract. Chem.,' xxxv, p. 309. Prager Vierteljahrschrift,' 1854, vol. iii, p. 25. See also the 'Lancet,' July 26, 1856, p. 114. 144 a milk-white crystalline mass. By dry distillation it yields a red oil, which has the odour of the Tonka bean (" the pride and flower of the snuff-box"), ammonia, and benzoic acid (the latter two, perhaps, in part as benzoate of ammonia) and a large residue of charcoal. Sometimes the acid before charring evolves a cyanogen compound, having the odour of hydrocyanic acid. If the temperature during dry distillation be not raised above 482° F. (250° C.), benzoic acid is obtained, slightly reddened, a trace of hydrocyanic acid, and benzonitrile is collected in the receiver. Hippuric acid is soluble in warm nitric acid, and hot hydrochloric acid, and from both solutions crystallizes on cooling; but when boiled for some time in either of these solutions it undergoes a decomposition, by which benzoic acid crystallizes out of the solution on cooling. Combined with the nitric acid there remains glycine, or glycocoll, or sugar of gelatine. This decomposition may also be produced by sulphuric and oxalic acids, and by boiling with caustic soda or potash. From this mode of decomposition Dessaignes concluded that hippuric acid was a combination of benzoic acid and glycine, and that by the artificial combination of these two bodies hippuric acid might be produced. He succeeded in producing hippuric acid by exposing a combination of glycine with oxyde of zinc to the influence of chlorine-benzoyle. Under the influence of a ferment, in the presence of an alkali, hippuric acid undergoes the same decomposition into benzoic acid and glycocoll. The disintegration of hippuric acid in putrefying urine is thus satisfactorily explained. Hippuric acid is the amide of a new acid, benzoglycolic acid, which is free from nitrogen, and has the composition CHO. It is formed when hippuric acid is acted on by hyponitrous acid, and is obtained by conducting a current of oxyde of nitrogen through a solution of hippuric acid in nitric acid. C18H2NO+NO, C12H2O+2N + HO. 6 Hippuric acid. 3 18 8 8 Benzoglycolic acid. Benzoglycolic acid crystallizes from the solution in colourless prisms, which are easily soluble in alcohol and ether, but sparingly soluble in water. It forms neutral salts with one equivalent of base, which are mostly crystallizable. The limesalt, CaO, CH,O,, crystallizes in colourless needles, and has a tendency to form oversaturated solutions. 18 Buchner, Ann. d. Chem. und Pharm.' Ixxviii, p. 203. 2 Socoloff and Strecker, Ann. d. Chem. und Pharm.,' lxxx, p. 17. |