and phloretine, C15H1405, which on cooling separates in colourless plates. Phloretine is a salt of phloretic acid and phloroglucin (§ 1000), and is decomposed into these on evaporation with solution of potassic hydrate. When the dry alkaline mass is extracted with alcohol, potassic phloretate dissolves, whilst potassium phloroglucin remains behind. Phloretic acid crystallises in long colourless prisms, melting at 128°130°; it is readily soluble in alcohol, ether, or hot water, and gives a green colour with ferric chloride. It forms normal and basic salts, and is converted into paraoxy-benzoic and acetic acids on fusion with potassic hydrate, and into phlorol (§ 1018) and carbonic anhydride on distillation with lime. 1084. Phenyl lactic acids, C6H5.C2H3(OH).CO.OH. Two isomeric acids of this formula are known. 1. Phenyl lactic acid, probably ẞ-phenyl-a-hydroxy-propionic acid, C6H5.CH.CH(OH).CO.OH, is obtained by the action of sodium. amalgam on phenyl-chlor-lactic acid (CH5.CHCI.CH(OH).CO.OH, obtained by action of hypochlorous acid on cinnamic acid) or phenyl brom-lactic acid. It crystallises in pointed needles readily soluble in cold, still more so in hot water, melts at 93°-94°, and decomposes at 180° into water and cinnamic acid. Concentrated halogen hydroacids convert it into phenyl halogen propionic acids. 2. Tropic acid, which, from its decompositions and its connection with atropic acid, is probably a-phenyl-3-hydroxy-propionic acid: C&HS.CH.CH2.OH is formed by heating atropic acid and concentrated hydrochloric acid at 180° for several hours. It dissolves in 49 parts of water at 14.5°, is more readily dissolved in alcohol and ether; it crystallises in prisms and melts at 117°. By long heating with hydrochloric acid it loses water and is converted into atropic and isatropic acids. Higher Homologues. 1085. The isomeric phenols thymol and carvacrol (§ 1023) are converted by the action of carbonic anhydride and sodium into two isomeric acids of the formula: thymotic and carvacrotic acids, both giving intensely blue colorations with ferric chloride. Thymotic acid crystallises in fine needles; it melts at 120°, cannot be sublimed unchanged, and is difficultly soluble in water. Heated with phosphoric anhydride, it yields an ethereal anhydride, thymotide, CH12O2, which is crystalline and melts at 187°. Carvacrotic acid forms flat needles, melting at 133°-134°. Dihydroxy-Acids of the Formula CnH2n-9(OH)2.CO.OH. 1086. Orsellinic acid, C6H2(CH3)(OH)2.CO.OH, is obtained from lecanoric acid or erythrine by boiling for a short time with baryta or lime water. It crystallises in colourless prisms of both acid and T T caffeic acid and umbellic acid. They are probably both represented by the formula CH3(OH)2.C2H,.CO.OH. Hydrocaffeic acid is obtained by the action of sodium amalgam on caffeic acid, C,H,O,. It forms colourless rhombic prisms, readily soluble in cold water. It yields amorphous salts, which decompose on exposure to air from oxidation, whose solutions reduce ammoniacal solutions of copper and silver and give a dark cherry-red colour with ferric chloride. From its connection with caffeic acid it would appear to have the formula (HO), :C6H3.CH2.CH2.CO.OH. On fusion with potassic hydrate it yields pyrocatechin, Umbellic acid, which yields resorcin on fusion with potassic hydrate, is obtained by the action of sodium amalgam on an alkaline solution of umbelliferone, C,H6O3. It forms colourless granular crystals, melting below 125° and difficultly soluble in cold water. Its salts also oxidise on exposure to air, and reduce alkaline silver and copper solutions. It 1089. Tyrosine, C,H11NO3, doubtless belongs to the disubstitution products of monobasic aromatic acids of the formula C,H1002. has not yet been prepared synthetically, but has only been obtained, together with leucine (§ 750), aspartic acid (§ 863), and glutamic acid (§ 866, 3), as a decomposition product of different albuminoids, equally whether the decomposition has been effected by fusing alkalies, by acids, or as in putrefaction by the action of ferment-like bodies. This last method of formation explains its occurrence in the animal organism. It is best obtained in large quantity by boiling horn shavings with a mixture of 2 parts sulphuric acid and 8 parts water for twelve hours, the water evaporated being replaced; the liquid is then rendered alkaline by milk of lime, the filtrate evaporated to a small volume and over-saturated with acetic acid. On long standing tyrosine separates, whilst leucine, &c., remain in solution. It is purified by hot water, and then forms bunches of fine silky needles, soluble in 150 parts of boiling water and 1,900 parts of cold water, scarcely soluble in alcohol, insoluble in ether. It can be recognised by the red colour obtained when its solution is heated with mercuric nitrate and nitrous acid, and by the violet coloration on heating with sulphuric acid, neutralising with baric carbonate, and adding ferric chloride. 11 9 Tyrosine dissolves readily in mineral acids, forming saline compounds, e.g. C,H,,NO3. HCl, crystallising in needles; it also dissolves in ammonia solution and caustic alkalies. With baryta water it gives prisms of barium tyrosine, C,H,BaNO3,2H,O. By mixing tyrosine solutions with argentic nitrate two compounds (C,H10AgNO3, which is crystalline, and C,H,Ag2NO,, a precipitate) are obtained according to the concentration and quantity of the silver solution. Tyrosine behaves similarly to the glycines. By fusion with potassic hydrate it yields ammonia and the potassic salts of paraoxybenzoic and acetic acids; by the action of chlorine and bromine it gives chloranil and bromanil (§ 1005). From this tyrosine is probably a para compound of the formula NH2.C6H4.C2H3(OH).CO.OH, or HO.CH.C2H3(NH2).CO.OH. Excess of dilute nitric acid converts tyrosine into brownish yellow crystals of nitro-tyrosine nitrate, C9H10(NO2)NO,,HNO3, from whose aqueous solution ammonia precipitates sulphur-yellow needles of nitro-tyrosine, CH10(NO2)NO3. On heating with nitric acid dinitrotyrosine, CH(NO) NO3, is formed, crystallising in golden yellow plates; it does not yield salts with acids. Concentrated sulphuric acid converts tyrosine into several sulphonic acids, e.g. CH10(SO..OH)NO3, whose haric salts are coloured violet by ferric chloride. 1089a. Aldehyde Acids.-But few of these bodies are known at present. They are prepared by boiling the oxybenzoic acids with sodic hydrate, water, and chloroform. Salicylic acid thus treated gives rise to two aldehydo-salicylic acids: [CO.OH a-CH OH [CHO (1:2:3) forms slender needles, which can be sublimed; its solution is coloured red by ferric chloride. BCH.CO.OH он (1:2:5) forms slender needles, melts at 249°, and can be sublimed, and gives a cherry-red colour with ferric chloride. CH,, prepared from paraoxy-benzoic acid, crystal- lises in prisms, melts at 243°-244°, is sublimable, and gives a brick-red colour with ferric chloride. Aldehyde-vanillic acid, or aklehylo-methyl-protocatechuic acid, 221-2222, and gives a violet colour with ferric chloride. Opianic acid, aldekydo-dimethyl protocatechuic acid: is described under the opium derivatives (§ 1265). |