C2H5O.CH2.CO.O.C2H5, at 155°. The latter, on saponification with alkalies, yields alkaline ethyl glycollates. Isoamyl glycollic acid boils at 235°. 714a. In addition to the above bodies, which correspond to the mixed ethers, the simple ether anhydride of glycollic acid-diglycollic acid-O(CH2.CO.OH)2, is also known, and is isomeric with the first ethereal anhydride. It is obtained, together with glycollic acid, by boiling chlor-acetic acid with bases, the yield being especially rich on employment of milk of lime: CH2Cl CH,–0–CH, 21 + 2CaO = CaCl2 + H2O + co.o.ca.o.co CO.OH The difficultly soluble calcic salt separates from the solution in crystals, leaving calcic glycollate in solution, and may be decomposed by oxalic or sulphuric acids. Diglycollic acid is also obtained by oxidation of diethylene alcohol with nitric acid. It forms large transparent rhombic crystals, which dissolve readily in water and alcohol and melt at 148°. It is a dibasic acid, yielding acid and normal salts: As an ether diglycollic acid is not decomposed by boiling with excess of alkali; excess of phosphoric chloride converts it into chloracetic chloride : HO.CO.CH.O.CH.CO.OH + 3PC1, 3POCl3 + 2HCl By heating ethylic chlor-acetate with dried sodic carbonate diglycollic ethyl-ether is obtained: 2CICH2.CO.O.C2H5 + Na2CO3 = 2NaCl + CO2 +O(CH,.CO.O.C,H,), as a colourless oil, heavier than water, which boils at 240° and yields salts of diglycollic acid on saponification. The acid anhydride of glycollic acid, HO.CH.CO.O.CO.CH.OH, has not yet been prepared. Sulphur Derivatives of Glycolic Acid. 715. Thio-glycolic Acid.-Of the possible isomeric thio-glycollic acids, CH2(SH)CO.OH and CH2(OH).CO.SH, only the first, mercapto-glycollic acid, has been prepared by heating potassic chlor-acetate with potassic sulph-hydrate: CI.CH.CO.OK+ HSK = KCl + HS.CH.CO.OK. It is best separated by treatment of the amorphous difficultly soluble lead salt with hydric sulphide, and is then obtained on evaporation of the aqueous solution as a nearly solid, yellow, deliquescent mass, of strongly acid reaction. The ethylic salt, HS.CH.CO.O.C2H5, is readily prepared by boil ing the acid with alcohol and some hydrochloric acid. It behaves as a true mercaptan, e.g. yields the crystalline mercury compounds: Cl.Hg.S.CH2.CO.O.C2H5 and Hg(S.CH2.CO.O.C2H5)2, and is readily oxidised by nitric acid to sulphonacetic acid. Thio-diglycollic acid, S(CH2.CO.OH)2, is formed by heating chloracetic acid with potassic sulphide; its ethylic salt, S(CH2.CO.O.C2H5)2, a yellow oil boiling at 267°, is formed, together with mercapto-glycollic acid, by heating ethylic chlor-acetate with an alcoholic solution of potassic sulph-hydrate: CI.CH2.CO.O.C2H5 + HSK = KCl + HS.CH2.CO.O.C2H5 + S(CH2.CO.O.C2H5). The acid is solid and crystallises in readily soluble rhombic tables, melting at 129°. 715a. Sulphonacetic acid, CH2(SO2.OH).CO.OH, or sulpho-acetic acid, has already been mentioned as an oxidation product of mercaptoglycollic acid; it is further formed by bringing together acetic acid and sulphuric anhydride (comp. § 513): and by boiling an alkaline chlor-acetate with neutral sodic sulphite : By addition of sulphuric acid to the baric salt: it is obtained in the free state, and then forms colourless, deliquescent prisms, melting at 620-63°. Its salts are soluble in water. By heating with excess of sulphuric anhydride it is converted into methene disulphonic acid (§ 419): = 716. Glycolamide, C2H NO, CH2(OH).CO.NH2, is obtained by the action of ammonia on the ethereal salts of glycollic acid, and also by heating glycollide in an atmosphere of ammonia gas : It forms colourless crystals, melting at 120°, which yield ammonic glycollate on boiling with water, and are decomposed by alkalies into ammonia and glycollates. 717. Glycocine, glycocoll, or amido-acetic acid: is isomeric with glycollamide. As it is at once an amine and an acid, its true composition is in all probability that of a salt: this view being in complete accordance with its properties. Prior to the discovery of glycollic acid glycocine had already been obtained from different animal substances by boiling with mineral acids or alkalies-e.g. from gelatine (hence the name glycocine = sugar of gelatine), from hippuric acid, and, together with taurocholic acid (comp. § 528), from the glycocholic acid occurring in the gall. It is most readily obtained from hippuric acid (benzoyl glycocoll), contained in large quantity in the urine of herbivora, by boiling for some hours with concentrated hydrochloric acid. The solution is evaporated nearly to dryness, and the pulpy residue extracted with a little cold water, which takes up glycocine hydrochloride and leaves the resulting benzoic acid nearly untouched: The solution is then boiled with plumbic hydrate, filtered from the precipitated plumbic oxychloride, treated with hydric sulphide to remove lead, and evaporated to crystallisation. It is obtained synthetically by heating chlor or brom acetic acid with ammonia : but, as in the preparation of the alkylamines, the process goes in part further, diglycollamic acid and triglycollamic acid being formed. Glycocine forms large, hard, monoclinic prisms, unalterable in air, of strongly sweet taste and neutral reaction, which dissolve in four times their weight of cold water, but little in alcohol and not at all in ether. It melts at 170°, and decomposes at slightly higher temperature with carbonisation and formation of ammonia and some methylamine. The latter is especially formed on heating with baric hydrate: CH, NH3.O.CO 2 CO.O.NH2.CH, + 2Ba(OH), = 2BaCO3 + 2CH3.NH, + 2H2O, but not on employment of alkalies, which only give ammonia (comp. $ 16). Nitrous acid converts glycocine into glycolic acid. 718. As organic ammonic salt glycocine is altered by strong acids, bases, or the salts of both. By treatment with strong mineral acids glycocine salts are formed, which being at the same time free organic acids, have an acid reaction. These reactions occur in two stages. On dissolving a molecule of glycocine (C4H10N2O4) in a molecule of hydrochloric acid, colourless prisms of the formula: C4H10N204.HCl, crystallise on cooling, which, with excess of acid, yield the very soluble compound C2H¿NO2.HCI : The latter gives with platinic chloride a readily soluble, crystalline double salt, (HO.CO.CH2.NH3Cl)2,PtC14. The sulphate (HO.CO.CH,.NH,),SO, crystallises with difficulty. Strong basic hydrates give salts of alkaline reaction which are at the same time free amine bases: CH,.(NH,).O.CO CH.NH2 + 2KOH= 2 | + 2H2O CO.OK Glycocine yields with many neutral salts compounds which generally crystallise beautifully, to whose formation both the abovementioned reactions combine: CH,.(NH,).O.CO CO.0.(NH3).CH, + 2KCl = 2 | CH, NH3CI CO.OK 719. Weak basic metallic oxides or hydrates are also taken up by glycocine. They are mostly the oxides of metals which readily replace the hydrogen of ammonia and amides, such as copper, mercury, and silver. The resulting crystallisable compounds are therefore probably not analogous to those of the alkalies. Especially characteristic is the cupric compound, obtained by boiling a solution of glycocine with cupric oxide, which separates from the deep blue liquid in beautiful blue needles of the formula: 0.0(NH,)CH, Their water of crystallisation is lost at 100°. The analogous silver compound, C,H,Ag2N2O4, separates in colourless anhydrous crystals. 8 EE From these bodies the metal in union with nitrogen cannot be precipitated by alkalies. Copper glycocine dissolves in alkali solutions with deep blue colour, a compound of the formula: doubtless being formed. Cu(NH.CH.CO.OK), On heating an alcoholic solution of glycocine with ethylic iodide to about 120°, ethylic glycocine hydro-iodide is formed: CH,.(NH,).0.CO +2C2H,I= 2 5 CH..NHI CO.O(NH,).CH, It remains on evaporation in colourless, rhombic crystals, which are also readily soluble in water or ether. On shaking the aqueous solution with argentic oxide, hydriodic acid is removed, but on evaporating the ethylic amido-acetate, NH.CH.CO.O.C2H5, is decomposed by the water into glycocine and ethylic alcohol. 720. Diglycollamic Acid and Triglycollamic Acid. As already mentioned, these are formed in the preparation of glycocine from chloracetic acid and excess of ammonia. The resulting solution contains, in addition to ammonic chloride and glycocine, the ammonic salts of diglycollamic and triglycollamic acids. By evaporation the greater part of the ammonic chloride is removed, and the mother liquid is then boiled with plumbic hydrate until all ammonia is driven off. Plumbic triglycollamate separates, whilst the filtered solution contains glycocine and plumbic diglycollamate. This is then treated with hydric sulphide to remove lead, and boiled with zincic carbonate in order to separate diglycollamic acid as its difficultly soluble zinc salt. Diglycollamic acid, C,H,NO,, crystallises in large, colourless, rhombic prisms, not perceptibly soluble in cold water, insoluble in alcohol and ether. It tastes and reacts acid, and behaves towards carbonates as a monobasic acid, but by treatment with strong basic hydrates takes up two equivalents of metal. It is glycocine, in which the nitrogen is united to the methene carbonic acid residue of glycolic acid, CH2.CO.OH, in place of a hydrogen atom; therefore With strong acids it yields crystallisable salts similar to glycocine, e.g. HO.CO.CH2NH,Cl Triglycollamic acid, CH,NO, crystallises in very difficultly soluble small prisms. It is glycocine with two methene carbonic acid |