VINEGAR. 63 



trol work arises from considering the weight of one cubic centimeter of vinegar to be 

 one gram. Where greater accuracy is desired, the quantities of vinegar employed 

 may be accurately weighed, or the weight estimated from a direct determination of 

 the specific gravity, or the average specific gravity of the kind of vinegar used may 

 be taken as a means of a closer approximation than that attained by regarding the 

 specific gravity of the vinegar to be 1.000. Blyth a gives the following figures: 



Range. Average. 



Wine vinegar 1.0129-1.0213 1.0175 



Spirit vinegar _. 1.008-1.013 1.0082 



Malt vinegar 1. 0150 



Sugar vinegar 1. 0100 



Wood vinegar 1.0070 



The writer has found in the case of cider vinegars a range of 0.997 to 1.029, with 

 an average of 1.015. 



3. DETERMINATION OF SPECIFIC GRAVITY. 

 Proceed as directed under wines (p. 82). 



4. DETERMINATION OF TOTAL SOLIDS OR EXTRACT. 



Evaporate 10 cc in a tared platinum dish of 50-mm diameter on the steam bath to 

 a sirupy consistency, dry for 2 hours in the drying oven at the temperature of boil- 

 ing water, cool and weigh. 



5. DETERMINATION OF ASH. 

 Use the method employed in case of wines (p. 83). 



6. DETERMINATION OF SOLUBILITY, ALKALINITY, AND PHOSPHORIC ACID OF ASH. 



Smith's method, modified by Frear: b Evaporate 25 cc to dryness, burn, cool, 

 weigh; extract the ash repeatedly with hot water on an ash-free filter; dry and 

 ignite the filter with undisBolved residue, cool and weigh, and calculate as insoluble 

 ash. Titrate the aqueous extract with decinonnal acid, using methyl orange as 

 indicator. Acidulate the neutralized solution with nitric and; also treat the insolu- 

 ble ash with nitric acid, and precipitate the phosphoric acid from the two solutions 

 separately by molybdate solution. The yellow precipitates, after solution in 

 ammonia, may either be treated with magnesia mixture, as in ordinary ash analysis, 

 or reduced with zinc and sulphuric acid, and titrated with standard permanganate 

 solution. Express the results in terms of milligrams of P 2 O 5 in the water-soluble and 

 water-insoluble ash, respectively, from 100 grams of vinegar. 



7. DETERMINATION OF TOTAL ACIDITY. 



Dilute 12 cc in a beaker until the solution appears very slightly colored when 

 viewed against a white background, add a few drops of phenolphthalein indicator, 

 and titrate with half-normal sodium hydroxid. Multiply the number of cubic cen- 

 timeters of half-normal soda solution required by 0.03 for the total acidity expressed 

 as grams of acetic acid. When 12 grams of vinegar are employed in the determination, 

 the number of cubic centimeters of half-normal alkali employed may be divided by 

 4 for the percentage of total acids expressed in terms of acetic acid. 



'Foods: Their comp. and anal., 4th ed., p. 682. 

 > Jour. Am, Chern. Soc., 1898, 20, 5. 



