204 VINEGAR, CIDER, AND FRUIT-WINES. 



recommended when the working of one or more generators is to 

 be ascertained in a short time, perfectly reliable results being ob- 

 tained in connection with the determination of the acid by titra- 

 tiou. 



Determination of the Content of Acetic Anhydride in Vinegar, or 



Acetometry. 



The content of acetic acid in vinegar is sometimes ascertained 

 by a species of hydrometer termed an acetometer. The statements 

 of these instruments are, however, very unreliable. Vinegar 

 made from dilute alcohol or ripe wines in which no great excess 

 of albuminous or other matter is present might to a certain limit 

 be tested with sufficient accuracy by the acetometer, but vinegars 

 made from malt, poor wines, and such liquids as contain au ex- 

 cess of organic matters, do not admit of being tested with the 

 required degree of accuracy by this method, since the apparent 

 quantity of real acetic acid is increased by the presence of foreign 

 bodies which add to the density of the liquid. In some cases the 

 vinegar is saturated with chalk or milk of lime, the solution fil- 

 tered, and the specific gravity of the acetate of lime liquor ascer- 

 tained, by which a nearer approximation is arrived at than by 

 the direct testing of the vinegar, yet implicit reliance cannot be 

 placed on either of these two methods. 



The best method of ascertaining the percentage of acetic acid 

 in vinegar is by titration or volumetric analysis. For the execu- 

 cutiou of the test a few instruments are required, which shall be 

 briefly described as follows : For measuring off small quantities 

 of liquids, serve a burette and pipette, the latter a glass tube of 

 the form shown in Fig. 45. It is filled by dipping the lower 

 end into the liquid and sucking on the upper with the mouth 

 until the liquid has ascended nearly to the top. The upper end 

 is then quickly closed with the index finger of the right hand. 

 By slightly lifting the finger, the liquid is then allowed to flow 

 off by drops until its level has reached a mark above the convex 

 expansion, when it will contain exactly the number of cubic cen- 

 timeters indicated opposite to the mark. 



The burette is a cylindrical glass tube open on the top, gradu- 



