413 



GLYCERIN. 



GLYCERIN. 



114 



This view of the constitution of glycerin is supported by an experi- 

 ment of Wurtz, in which he succeeded in obtaining glycerin artificially. 

 By the action of terbromide of allyl, C H 5 "' Br.,, on acetate of silver, 

 a body is formed which has the composition and all the properties of 

 triacetin. When this body is decomposed by baryta water, acetate 

 of barrta and glycerin are formed. Terbromide of aflyl is not a deriva- 

 tive of glycerin, it belongs to the allylic alcohol aeries. The following 

 re-actions exhibit the change : 



'it- i" ', 



Hydrate of 

 baryta. 



Glycerin. 



Acetate of baryta. 



In alcohol there if only one atom of hydrogen replaceable by a 

 radical to form a compound ether. In glycerin there are three atoms 

 capable of being replaced, and accordingly we may have three series of 

 ethers, thus : 



(c.n,r 



B 

 H 



II 



(C.H.,)" 

 R 



n 



H 



B 



i 



R 



All these three classes are represented by compounds, some of which 

 have been prepared directly from then- constituents, and some 

 exist already formed in nature. The glycerides which compose 

 the natural fata are almost all normal neutral glycerides, that ia, 

 they contain 3 eq. of hydrogen replaced by 3 eq. of an acid radical, 

 and the natural fats are almost all mixtures of several of these 

 glycerides. 



From the above view of the constitution of glycerin, it is obvious 

 that a great number of glycerides may exist, according as 1, 2, or 3 eq. 

 of hydrogen are replaced by 1, 2, or 3 of the same or different 

 acid radicals. We may also have glycerides of the following com- 

 position : 



(C.H,, 

 H 



(C.H,)"' 1 

 R O. 

 B 



It is evident that glycerin may give rise to the formation of a great 

 number of ethers, according as the atoms of hydrogen are replaced by 

 different monoatomic radicals, or by a biatomic radical, or by a ter- 

 atomic radical, where B" and B'" are respectively biatomic and teratomic 

 radicals. 



The natural glycerides have been named by adding to an abbrevia- 

 tion of the name of the acid, the termination in, thus we have stearin, 

 olein, &c. The artificial fats have been named in accordance with this 

 principle, and the prefixes mono-, di-, and tri-, express respectively the 

 proportions of the radical contained in them. Thus we have : 



C.H,'" 1 



(C,,H s .O,) O. 



Monmtearin . 



C.H,'" , 



CC..H..O.)' i 



Triiteirln. 



Similarly we have): 



C.H." 



(C 4 H,O t ) 



C.H, 



Monoacetin. 



Diacetin. 



According to Berthelot, the artificial fats are formed by heating the 

 hydrated acids along with glycerin in closed vessels for some time to a 

 more or less elevated temperature. Many of them are formed even 

 at the. ordinary temperature. The glycerides containing 1 eq. of acid 

 are mostly obtained by the continued heating of a mixture of hydrated 

 acid with excess of glycerin to a temperature of 392" Fahr. 



3f those containing 2 eq. of acid, some are obtained by continuously 

 heating glycerin with excess of acid to a temperature of 392 Fahr. In 

 'ases combination takes place at 212" Fahr. ; hi others the tem- 

 perature requires to be raised to 527 Fahr. 



The neutral compounds are obtained by heating the above com- 

 pounds with excess of acid to a temperature of from 464 Fahr. to 

 500* Fahr. 



In many cases the glycerides may be obtained by saturating a mix- 

 ture of glycerin and the acid with hydrochloric acid, and heating to 



The combination of glycerin with the acid takes place with the loss 



of water a double atom of water being separated for every equivalent 

 of acid. Thus : 



C,H 9 S + C.U.O, = 2HO + C 10 H 10 0, 

 Glycerin. Acetic acid. Monoacetin. 



C.H.O, -f 2(C.H 4 4 ) = 4HO + C 14 H 1S O 10 



Diacetin. 

 C 6 H S + 3(C 4 H 4 4 ) = GHO + C 18 II 14 O ia 



Triacetin. 



Besides combining glycerin with the fatty acids, Berthelot has ob- 

 tained combinations with the mineral acids. A brief notice of the 

 hydrochloric and nitric acid compounds will be given here ; and most 

 of the glycerides will be described under their respective heads. But 

 for further information on the subject, the reader must be referred to 

 the original papers of Berthelot which have appeared in the ' Annales 

 de Chimie et Physique,' vols. xli and xliii. 



Glycerin forms with hydrochloric acid three combinations, which 

 have been named monochlorhydrin, dichlorhydriu, and trichlor- 

 hydrin. 



/ 

 in C 



\ 



ifonoc/tlorltydrin C.H,C10 4 = 



H 2 

 Cl 



4 I is obtained by saturating 



glycerin with hydrochloric acid gas, and maintaining the solution for a 

 long time at a temperature of 212 Fahr. It is then neutralised with 

 carbonate of soda, and agitated with ether. On evaporating this solu- 

 tion, the body is left as a neutral oil, of a fresb and ethereal odour, and 

 a sweet but fragrant taste. It is miscible with water and ether. Its 

 density is 1 "31, and it boils at 441 Fahr. Monochlorhydrin acts on 

 ammonia, and forms the llydrochlorate of a base which Berthelot 

 names glycei'" / 



C,H,O 4) C1 4- Nil, 

 Monochlorhydrin. 



I C H,0, 



N{ H 4- uci 

 ii 



llydrochlorate of 

 glyceraminc. 



Dichlor/tydrin I C,H,C1.,0 2 = H > 2 I is obtained by exposing a 



\ Cl, ) / 



mixture of glycerin with ten to twelve times its bulk of fuming 

 hydrochloric acid to a temperature of 212 Fahr. for several days. It 

 is purified like the preceding compound. It haa a strong ethereal 

 odour ; dissolves readily in ether, but with greater difficulty in water 

 than monochlorhydrin. It boils at 352 Fahr. It is decomposed by 

 alkalies into chlorides and glycerin. 



( ' 

 TricMvrhydrin , C.H.C1, = n 



obtained by treating dichlor- 



hydrin with pentachloride of phosphorus ; it in a neutral liquid, boiling 

 at 31 1 Fahr. 



The formation of these ethers may be thus expressed : 



C,H,O, + 1IC1 = C.H-O.C1 + 2HO 

 Glycerin. Monochlorhydrin. 



C.H.O. + 2HC1 = C,H,0,C1, + 4110 

 Glycerin. Dichlorhydiin. 



C.H.O, + 3HC1 = C H,C1 S + <;ll<> 

 Glycerin. Trichlorhydrin. 



( ' TT '" T 



.\';t,-nr/lycer<7i, Glonoin X s . 3 V O, the nitric ether of glycerin. This 



substance is prepared by gradually adding glycerin to a mixture of 

 sulphuric and fuming nitric acids, carefully cooled. The glycerin 

 dissolves without any disengagement of nitric vapours. On adding 

 water to the solution, nitroglycerin.is precipitated as a heavy yellowish 

 oil, soluble in alcohol and ether, with a saccharine and aromatic 

 taste. It is a very instable compound. It decomposes with a loud 

 detonation when heated, and explodes even when struck violently. A 

 solution of nitroglycerin, left to stand for some time, decomposes into 

 glyceric acid. A drop of nitroglycerin placed on the tongue causes a 

 sensation of nausea, which lasts for several hours. 



Nitroglycerin appears to possess different properties, according to the 

 mode of its formation. Probably in some cases a basic nitrate is 

 formed. 



(Jlyceric Ether. The replacement of both the hydrogen atoms in 



alcohol by ethyl produces ether p'^' j-0,. The compound exactly cor- 

 responding to ether in the series of glycerin is not known, but a 



