BEVERAGES 125 



Potassium ferrocyanide is sometimes used to clarify vine- 

 gars, and is said to be decomposed, leaving in solution an 

 unstable compound of prussic acid with the organic matter. 



Estimation of the Free Sulphuric Acid. Take 50 c.c. of 

 sample, add 25 c.c. N/io NaOH. Evaporate whole to 

 dryness, and ignite. To ash add 25 c.c. N/io, HC1 or 

 H 2 S0 4 , 25 c.c. aq. dest., and boil to expel CO 2 . Filter, 

 wash paper with hot water, and titrate whole nitrate with 

 N/io, NaOH, and phenolphthalein. The number of c.c. 

 of soda used x 0-0049 = ^ ree sulphuric acid in 50 c.c. of 

 sample. 



Barium chloride cannot be used to test for the free acid, 

 as vinegar is often made from hard waters containing 

 sulphates, which would also precipitate the barium. 



Microscope for vinegar eels, (i to 2*5 mm. in length.) 



Preservatives. Test as elsewhere. 



Vinegar, in doses of from a half to one ounce daily, is an 

 anti-scorbutic, but is inferior to lime and lemon-juices. 



BEER. 



Beer is usually denned as "a fermented infusion of 

 malt, flavoured with hops," but this definition must be 

 extended to include beers brewed from saccharine fluids 

 other than malt infusion, and flavoured with other bitters 

 than hops. The malt substitutes are such as malted 

 Indian corn, and starches chemically converted into 

 sugars (rice, potato, and other starches) by the use of 

 sulphuric acid. The latter may contain arsenic derived 

 from the acid used, and so contaminate the beer. This 

 happened in South Lancashire in 1900. The hop 

 substitutes are used only in a few breweries, of which a 

 list is published by the Inland Revenue authorities. They 

 are such bitters as quassia, gentian, calumba, chiretta. 

 Noxious bitters have at times been used, as nux vomica, 

 picrotoxin, and picric acid. 



Malt Beer is thus made: Barley grain is shot into a 

 cistern and covered with water to the depth of 5 inches 

 and soaked for 40 to 60 hours, until it has swollen up 

 and the process of germination has started. The wet grain 

 is then removed from the steeping-tanks, piled up in 



