196 VINEGAR. 



degree of sourness, and, in fact, before the acetous 

 fermentation is quite complete, it is racked off; this 

 is necessary to prevent it from passing into a state of 

 putrefaction, which would be sure to happen if it 

 were left too long in contact with the ferment (380). 



484. Vinegar, whether prepared from wine or 

 malt, has a great tendency to spoil by keeping, in 

 fact to putrefy ; this is merely caused by the impuri- 

 ties which it contains. As made from malt, it always 

 contains spirit, sugar, gum, and ferment, in greater 

 or less quantity. It is thick and turbid, and must 

 be clarified before it is fit for use Or can be kept ; 

 this is done by the use of isinglass or some sitnilar 

 fining. Sometimes also it is purified by filtration 

 through powdered charcoal. 



485. When vinegar putrefies, the change is not 

 confined to the impurities alone which it contains, 

 the acetic acid also is decomposed, and hence, as 

 soon as the putrefactive fermentation commences, the 

 liquid begins to lose sourness and becomes flat and 

 insipid. The impurities of the vinegar may of course 

 be wholly separated by distillation. Distilled vinegar 

 has no tendency to spoil by keeping ; it is quite as 

 strong and sour, or even stronger than it was before, 

 but its flavor is not quite so agreeable. 



486. Vinegar is sometimes conveniently strength- 

 ened by the addition of sugar. In this case the im- 

 purities which it contains, carry on the slow ferment- 

 ation of the sugar, and cause its conversion into 

 vinegar. The sugar must be added from time to 



