82 PROVISIONAL METHODS FOR ANALYSIS OF FOODS. 



For the various determinations, a measured volume can be taken more conveniently 

 than a weighed quantity. The results can be calculated to per cent by weight by 

 dividing the results expressed as grams per 100 cc by the specific gravity. 



1. DETERMINATION OF SPECIFIC GRAVITY. 



Determine specific gravity at the temperature of 15.6 C. by means of the pycnom- 

 eter, small accurately graduated hydrometer, Westphal balance, or a Westphal plum- 

 met on the analytical balance. The pycnometer, when used, should be heated 

 quickly to room temperature after filling and before weighing, to prevent the error 

 due to the collection of moisture on the outside. A small hole filed in the cap will 

 permit the necessary expansion in the volume of liquid. 



2. DETERMINATION OF ALCOHOL. 



Measure 100 cc of the liquid into an Erlenmeyer flask of from 250 to 300-cc capacity ; 

 add 50 cc of water; attach the flask to a vertical condenser by means of a bent tube 

 and distill 100 cc. Foaming, which sometimes occurs, especially with new wines, may 

 be prevented by the addition of a small amount of tannin. If it be desired to deter- 

 mine alcohol in wines which have undergone acetic fermentation and contain a large 

 amount of acetic acid, 0.1 or 0.2 gram of precipitated calcium carbonate should be 

 added. This is unnecessary, however, in wines of normal taste and odor. Where 

 only occasional determinations of alcohol are made it is found convenient to use an 

 alembic Saleron. This apparatus is made of copper, and it can be readily taken apart 

 and placed in a small box. No rubber connections are necessary, and the setting up 

 requires but a few minutes. Determine the specific gravity of the distillate as directed 

 under Specific Gravity, and obtain the corresponding percentage of alcohol, by vol- 

 ume and grams per 100 cc, from Table II. 



3. DETERMINATION OF GLYCEROL. 



Evaporate 100 cc of wine a in a porcelain dish on the water bath to a volume of 

 about 10 cc and treat the residue with about 5 grams of fine sand and with from 1.5 

 to 2 cc of milk of lime (containing about 40 per cent of calcium hydroxid or 30 per 

 cent of calcium oxid) for each gram of extract present, and evaporate almost to dry- 

 ness. Treat the moist residue with 5 cc of 96 per cent alcohol (sp. gr. 0.81), remove 

 the substance adhering to the sides of the dish with a spatula, and rub the whole 

 mass to a paste, with the addition of a little more alcohol. Heat the mixture on the 

 water bath, with constant stirring, to incipient boiling, and decant the liquid into a 

 flask graduated at 100 and 110 cc. Wash the residue repeatedly by decantation with 

 10 cc portions of hot 96 per cent alcohol. Cool the contents of the flask to 15, 

 dilute to the 110-cc mark with 96 per cent alcohol, and filter through a folded filter. 

 Evaporate 100 cc of the filtrate to a sirupy consistency in a porcelain dish, on a hot, 

 but not boiling, water bath, transfer the residue to a small glass-stoppered graduated 

 cylinder with 20 cc of absolute alcohol, and add three portions of 10 cc-each of 

 absolute ether, mixing after each addition. Let stand until clear, then pour off 

 through a filter, and wash the cylinder and filter with a mixture of one part 

 absolute alcohol to one and one-half parts of absolute ether, pouring the wash liquor 

 also through the filter. Evaporate the filtrate to a sirupy consistency, dry for one 

 hour at the temperature of boiling water, weigh, ignite, and weigh again. The loss 

 on ignition increased by one-tenth gives the glycerol expressed in grams per 100 cc. 



"With wines whose extract exceeds 5 grams per 100 cc, heat to boiling in a flask the portion to be 

 used in the determination of glycerol, and treat with successive small portions of milk of lime until 

 it becomes, first, darker, and then light in color. When cool, add 200 cc of 96 per cent alcohol (sp. 

 gr. 0.8118), allow the precipitate to subside, filter, and wash with 96 per cent alcohol (sp. gr. 0.8118). 

 Evaporate the filtrate to about 10 cc, add about 5 grams of sand and from 1.5 to 2 cc of milk of lime 

 and proceed as directed above. 



