314 VINEGAR, CIDER, AND FRUIT- WINES. 



ishment offered to the latter. In acid fluid more succinic acid is 

 formed than in neutral. 



Succinic acid is quite readily soluble in a mixture of alcohol 

 and water, and consequently also in wine ; its taste is not very sour, 

 but disagreeable, and adheres for some time to the tongue ; hence 

 its presence can scarcely be expected to give an agreeable taste to 

 the wine. 



Glycerin. Glycerin being found in grape-wines, in which it is 

 formed from the sugar by fermentation, there can scarcely be any 

 doubt of its formation under the same conditions in fruit-wines. 

 According to Pasteur, the quantity of glycerin in wine is in a 

 definite proportion to the succinic acid formed, and, hence, more 

 glycerin would be produced with slow fermentation and in an acid 

 fluid. In red wines Pasteur found 4 to 7 per cent, of glycerin. 



Pure glycerin is a colorless, very viscid liquid having a specific 

 gravity of 1.27. It can be mixed with water and alcohol in all 

 proportions and possesses a very sweet taste. It is very likely 

 that the mild sweet taste of many ripe wines is due to a certain 

 content of glycerin. 



A solution of 7 parts of glycerin in 1000 of water (the pro- 

 portion in which Pasteur found glycerin in wine) does not possess 

 a sweet taste and differs from water only in being more insipid. 

 By adding to such a solution 100 parts of alcohol the mixture 

 shows a taste different from that of alcohol alone diluted in the 

 same proportion, the predominant taste of the latter being de- 

 creased by the glycerin and that of the mixture becoming milder. 

 Hence a certain importance has to be ascribed to the glycerin. 



Carbonic acid. The greater portion of the carbonic acid formed 

 by fermentation escapes as a gaseous body during the process, but 

 a certain portion remains dissolved in the wine as long as the tem- 

 perature of the latter is not raised. The temperature of cellars 

 generally increases, however, towards the end of spring, which 

 causes anew a slight development of carbonic acid in consequence 

 of which the wine again becomes turbid. The presence of car- 

 bonic acid is of advantage only in young wine, as it protects it 

 from the direct action of the air by forming a layer upon the 

 surface; in old wines it conceals, however, the fine aroma and 

 taste, making them appear younger than they actually are. 



