GLUTIN. 27 



Three different compounds of glutin and tannic acidi liave been 

 discovered, and submitted to analysis ; they are, however, indi- 

 vidually of no particular importance in a physiological point of 

 view. The extreme facility with which tannin precipitates ge- 

 latinous matters gives a clue to the medicinal action of astringent 

 drugs on the human organism. They at once form insoluble 

 compounds, (for tannin acts similarly on the protein-compounds,) 

 and do not enter the blood ; and this is the reason of their being 

 comparatively innocuous. According to Mulder a less amount of 

 tannin than is contained in one ounce of cinchona bark would, 

 if conveyed dii'ectly into the blood, cause instantaneous death. 

 Acetic acid produces a slight turbidity, which speedily dis- 

 appears on the addition of an excess of the test. Alum either 

 produces no visible effect, or else throws down a veiy slight 

 precipitate, which soon disappears, and the other salts, which 

 have been mentioned as reagents for chondrin, yield no (or at 

 most, very slight) precipitates with glutin. Alcohol and creosote 

 act much the same as on chondrin, and no precipitate is occa- 

 sioned by the ferrocyanide or ferridcyanide of potassium. 



On boiling glutin in an excess of caustic alkali, till ammonia 

 ceases to be developed, sugar of gelatin (glycicoll) and leucin 

 are produced in the ratio of four parts of the former to one of 

 the latter. In order to separate these substances, the alkaline 

 solution must be saturated Avith sulphuric acid, evaporated to 

 dryness, and the residue boiled with alcohol. The leucin being 

 more soluble in alcohol than the glycicoll may be extracted from 

 the evaporated alcoholic solution by cold alcohol; the glycicoll 

 will remain in an impure condition in the residue. 



On treating glutin with concentrated sulphuric acid a colour- 

 less fluid is obtained, which, after prolonged boiling and satu- 

 ration with carbonate of lime, yields, in addition to certain un- 

 investigated compounds, leucin and glycicoll. This method is 

 stated by ISIulder to yield a less quantity of glycicoll, in pro- 

 portion to leucin, than the former. 



Glycicoll crystallizes in colourless prisms from a solution in 

 alcohol, and in rhombs from a spirituous solution. These crystals 

 possess a very sweet taste, are perfectly neutral, resemble 

 cholesterin in their appearance, dissolve in 414 parts of water 

 and in 931 of alcohol. 



' It must be remembered that tamiiii and tannic acid are svnouvmous terms. 



