240 METHODS OF ANALYSIS [Chap. 



28 FIXED ACIDS.-TENTATIVE. 



Multiply the amount of volatile acids by 1.25 and subtract this from the total 

 acids, to obtain the amount of fixed acids, expressed as tartaric acid. 



29 TOTAL TARTARIC ACID'.— TENTATIVE. 



Neutralize 100 cc. of the wine with N/1 sodium hydroxid, calculating from the 

 acidity, 25, the number of cc. of N/1 alkali necessary for the neutralization. If the 

 volume of the solution is increased more than 10% by the addition of the alkali, 

 evaporate to approximately 100 cc. Add to the neutralized solution 0.075 gram 

 of tartaric acid for each cc. of N/1 alkali added and, after the tartaric acid has dis- 

 solved, add 2 cc. of glacial acetic acid and 15 grams of potassium chlorid. After 

 the potassium chlorid has dissolved, add 15 cc. of 95% alcohol by volume, stir 

 vigorously until the potassium bitartrate starts to precipitate, and then let stand 

 in an ice box for at least 15 hours. Decant the liquid from the separated potassium 

 bitartrate on a Gooch, prepared with a very thin film of asbestos, or on filter paper 

 in a Bijchner funnel. Wash the precipitate and filter 3 times with a few cc. of a 

 mixture of 15 grams of potassium chlorid, 20 cc. of 95% alcohol by volume and 100 

 cc. of water, using not more than 20 cc. of the wash solution in all. Transfer the 

 asbestos or paper and precipitate to the beaker in which the precipitation was 

 made, wash out the Gooch or Buchner funnel with hot water, using about 50 cc. in 

 all, heat to boiling and titrate the hot solution with N/10 sodium hydroxid, using 

 phenolphthalein as an indicator. Increase the number of cc. of N/10 alkali re- 

 quired by 1.5 cc. to allow for the solubility of the precipitate. One cc. of N/10 alkali 

 is equivalent, under these conditions, to 0.015 gram of tartaric acid. Subtract the 

 amount of tartaric acid added from this result to obtain the grams of total tartaric 

 acid per 100 cc. of the wine. 



30 FREE TARTARIC ACID AND CREAM OF TARTAR^.— TENTATIVE. 



Calculate the free tartaric acid and cream of tartar in the following manner: 



Let A = total tartaric acid in 100 cc. of wine divided by 0.015; 

 B = total alkalinity of the ash (sum of C and D) ; 

 C = alkalinity of water-soluble ash; 

 D = alkalinity of water-insoluble ash. 



Then 



31 



(1) If A is greater than B, 



Cream of tartar = 0.0188 X C; and 

 Free tartaric acid = 0.015 X (A-B). 



(2) If A equals B or is smaller than B but greater than C, 



Cream of tartar = 0.0188 X C; and 

 Free tartaric acid = 0. 



(3) If A is smaller than C, 



Cream of tartar = 0.0188 X A; and 

 Free tartaric acid = 0. 



TANNIN AND COLORING MATTER.-OFFICIAL. 



REAGENTS. 



(a) N/10 oxalic acid. — One cc. is equivalent to 0.004157 gram of tannin. *'• 



(b) Standard potassium permanganate solution. — Dissolve 1.333 grams of potas- 

 sium permanganate in 1 liter of water and standardize the solution against (a). 



