GLYCKUYI.. 



OLYCOL. 



418 



substance exist* which corresponds to the mixed ethers of Williamson 

 Thi is Jiaikyli*. It is prepared bv heating a mixture of glycerin, 

 caustic potass, and bromide of ethyl, to a temperature of 100* for 

 several day*. It is a colourless limpid oil, with a slightly aromatic 

 ethereal odour. Its sp. gr. is 0-920, and it boils at 376* Fahr. It* 

 formula is C,,H,,0,, and it is glycerin in which 2 equivalents of 



CH," ) 



hydrogen are replaced by 2 equivalents of ethyl (C,H,), > O r 



H ) 



Glycerin, when treated with sulphuric, phosphoric, or tartaric acids, 

 combines with them, forming compounds analogous to sulphovinic, 

 phosphovinic, and tartrovinic acids. 



Sulplogliittric Add (C,H.S,0 lt ). When glycerin is mixed in the 

 cold with double its weight of concentrated sulphuric acid, the two 

 substance* combine with considerable elevation of temperatare, but 

 without producing any colouring. The mixture is cooled, diluted with 

 water, and then saturated with baryta, by which a crystallisable sulpho- 

 glycerate of baryta is formed. By treating a solution of this substance 

 with sulphuric acid, sulphate of baryta is formed, and Sulphoglyceric 

 acid set free. The aqueous solution of the latter must be concentrated 

 in vacuo, and the concentration cannot exceed a certain limit, other- 

 wise decomposition takes place, even at 32* Fahr. The sulphoglycerates 

 are mostly soluble in water ; they are very readily decomposed by being 

 heated with water or metallic oxides, forming sulphuric acid and 

 glycerin. By dry distillation they are decomposed, with formation of 

 sulphurous acid, acrylic acid, acrolein, Ac. 



Sulphoglyceric acid is analogous to sulphovinic acid. If this latter 

 be considered as sulphuric acid in which one atom of hydrogen has 

 been replaced by ethyl, then the corresponding compound of glycerin 

 may be represented as sulphuric acid in which one atom of hydrogen 

 is replaced by the monatomic group 0,11,0, derived from glycerin. 

 The same remark would apply to phosphoglyceric and tartroglyceric 

 acids. The formation of Sulphoglyceric acid is thus expressed : 



C.H 



Glycerin. 



Sulphoglyceric 

 acid. 



Phoipkoglycenc acid (C.H,0,,PO,HO). This body is obtained by 

 dissolving glacial phosphoric acid in its weight of syrupy glycerin. 

 The solution is accompanied by considerable rise of temperature. It 

 is then diluted with water, neutralised with baryta, filtered from the 

 insoluble phosphate of baryta, and the concentrated filtrate mixed 

 with solution of acetate of lead, by which an insoluble phosphoglycerate 

 of lead is formed. To obtain the acid, this salt is decomposed with 

 sulphuretted hydrogen, and the filtrate evaporated and concentrated in 

 vacua It is an uncrystallisable liquid, which at its state of greatest 

 concentration has the consistence of a thick syrup. In this state it is 

 readily decomposed by an increase of temperature into glycerin and 

 free phosphoric acid. 



The phosphoglycerates are generally soluble in water, but little or 

 not at all in alcohol. Their solutions decompose by boiling, especially 

 in the presence of bases, into phosphates and free glycerin. 



M. Goblez has found that phosphoglyceric acid in combination with 

 soda and ammonia is contained in the cerebral matter, and in the yolk 

 of egg. 



When glycerin is heated with anhydrous phosphoric acid, acrolein 

 is produced. [ ACROLEIN.] 



OLYCEKYL (C.H,). The radical formerly assumed to be con- 

 tained in GLTCKBIS, the formula of which was then written C,H,0 5 , HO. 

 Recent researches prove that the compound group, which in glycerin 

 occupies the same position as ethyl in alcohol, is the teratomic radical 

 C,H , to which therefore the above term would now be more appro- 

 priately applied. 



GLYCOCIN. [OLTCOCOU..] 



GLYCOCOLL, Wycmn. Swjar of gdatint, C.NH.O,, is a com- 

 pound found amongst the products obtained by boiling gelatine with 

 potash or acids. It may also be prepared by heating hippuric acid 

 with hydrochloric acid, when benzole acid, water, and glycocoll are 

 produced. It forms transparent crystals, which are soluble in water 

 and sweet to the taste. It combines with acids and bases. Its easy 

 formation from the animal compound gelatine, has led to the sup- 

 position that it may play an important part in the animal body. 



GLYCOL (C,H,0 4 ). This is the type of a new class of compounds 

 discovered by Wurtz in 1856. In their chemical relations and properties 

 they occupy a place intermediate between the class of alcohols of which 

 common alcohol is the type, on the one band, and the class of bodies 

 of which glycerin is the type, on the other. The name glycol has 

 been given to express this relation, and that of bialomic alcohol to 

 xprcM that they have a capacity of saturation double that of common 

 alcohol 



We may consider alcohol as being derived from the type of a 

 double atom of water by the substitution of an equivalent of the 

 monoatomic radical ethyl for an equivalent of hydrogen. [OROAMC 

 RADICALS.] 



If now in two double atoms of water we replace two eq. of hydrogen 



>y a biatomic radical, such as ethylene, C.H., we shall obtain glycol. 

 ihe relations of alcohol to glycol may be thus seen. 



Alcohol. 



.-y .1. 



By the action of iodide of ethyl, for example, on acetate of silver we 

 obtain iodide of silver and acetic ether. Similarly by the action of the 

 riatomic iodide of ethylene (C.H, I.) on two equivalents of acetate of 

 silver we obtain acetate of glycol, the acetic ether of glycol : 



.-n. ...: i.: rirnr. 



cthylcnc. 



Acetate of gljcol. Iodide of 

 silver. 



It was by means of this re-action that Wurtz first obtained the 

 acetic ether of glycol, and from the ether, by decomposition with 

 alkalies, glycol itself. The method w suceptible of general application, 

 and by its means Wurtz has already obtained four members of the 

 series : ethyl glycol, propyl glycol, butyl glycol, and amyl glycol. 



We shall describe the preparation and properties of the typical 

 member of the group glycol itself. It will not be necessary to enter 

 minutely into a consideration of the others, inasmuch as they present 

 :he most perfect homology with glycol, not only in their properties, 

 out in their chemical relations. 



For the preparation of glycol, the best method is that proposed by 

 Atkinson. It is a modification of Wurtz's method, and consists in the 

 action of bromide of cthylene on acetate of potash. The products of 

 the re-action are bromide of potassium, free acetic acid, and mono- 

 acetate of glycol, as is seen by the equation 



2KBr 



About 2 ounces of acetate of potash, dissolved in 5 or 6 ounces of 

 alcohol, are placed in a soda-water bottle with 2 ounces of bromide of 

 ethylene : the bottle is lightly corked, and heated for two days on the 

 water-bath. The contents arc then filtered from the bromide of potas- 

 sium, which is washed with ether, and the united filtrates and washings 

 submitted to fractional distillation, those parts being collected which 

 distil above 356 Fahr. On being again rectified, the greater part, 

 consisting of pure monoocetate of glycol, distils over at 360 Fahr. 



To obtain glycol, the monoacetate of glycol is mixed with an equi- 

 valent quantity of potash, which decomposes it with evolution of heat. 

 The mixture after having been allowed to stand some time, is distilled 

 in the oil bath. On rectifying the distillate, a product is obtained, 

 boiling at 387 Fahr., which is pure glycol. The decomposition of 

 monoacetate of glycol by potash is expressed by the equation : 



KOHO = 



c.n a Ko, 



Monoacetate 

 of glycol. 



Olycol 



The following modification of this method has been used by Debus, 

 and although somewhat tedious it gives a larger product. Monoacetate 

 of glycol mixed with its bulk of water is heated for 12 to 16 hours in 



;, cl'-nl M-H-1 I" 111,' t,'lll]>i-l.lti:i.- l,f l.il!l:ur **. I'-.l I ll i - llllVlll-i it 



is decomposed into free acetic acid and glycol. The liquid is rectified, 

 and the parts collected which distil over above 374 Fahr. This con- 

 sists principally of glycol, but still contains acetic acid. 



An acetic acid determination, by means of baryta, is made in a 

 sample of this liquid, and then the proportionate quantity of potash 

 is added, and the mixture submitted to distillation. The distillate 

 consists of pure glycoL 



Pure glycol is an inodorous, somewhat viscid, liquid, with a slightly 

 saccharine taste. It has a density of 1 -125 at 32 Fahr. It boils at 

 886 to 887 Fahr. Exposed to the temperature produced by a 

 mixture of solid carbonic acid and ether, it becomes gummy without 

 solidifying. Its vapour density has been found to be 2-164. The 

 number required by theory is 2'146. 



Glycol is perfectly soluble in water and in alcohol, but only slightly 

 so in ether. In this respect it resembles glycerin. In its solvent 

 properties it stands between water and alcohol. In its chemical 

 re-actions it presents, as will be seen, the closest analogy with alcohol. 



Glycol is unaltered in the air ; but mixed with platinum black it 

 attracts oxygen with such avidity that the platinum becomes incan- 

 descent. By regulating the conditions of the experiment, however, 

 so as to produce a slow action, an aqueous solution of glycol is slowly 

 converted into glycolic acid. 



Potassium attacks glycol with energy; hydrogen is evolved, and the 

 heat disengaged is so intense as to inflame the gas, and blacken the 

 residue. The action of sodium is less violent hydrogen gas is dis. 



