88 METHODS OF ANALYSIS. 



according to the modified Sachsse method for the determination of starch. (See 

 "VI. General Methods," p. 53.) 



20. Tannin and Coloring Matter. Official, 

 (a) PREPARATION OF REAGENTS. 



(1) Oxalic acid. Use tenth-normal solution ; 10 cc=0.04157 gram of tannin. 



(2) Potassium permanganate solution. Dissolve 1.333 grams of potassium 

 permanganate in 1 liter of water and standardize the solution with the tenth- 

 normal oxalic acid solution. 



(3) Indigo solution. Dissolve 6 grams of sodium sulphindigotate in 500 cc of 

 water with the aid of heat ; cool, add 50 cc of concentrated sulphuric acid, make 

 the solution up to 1 liter, and filter. 



(4) Purifled boneblack. Extract finely pulverized boneblack with hydrochloric 

 acid and wash with distilled water until the acid is entirely removed. The bone- 

 black is kept covered with water. 



(b) DETERMINATION." 



Dealcoholize 100 cc by evaporation and dilute with water to the original 

 volume. Transfer 10 cc to a porcelain dish of about 2 liters capacity ; add about 

 a liter of water and exactly 20 cc of indigo solution. Add tenth-normal potas- 

 sium permanganate solution, a cubic centimeter at a time, until the blue color 

 changes to green ; then add a few drops at a time until the color becomes golden 

 yellow. Designate the number of cubic centimeters of permanganate solution 

 employed as "a." 



Treat 10 cc of the dealcoholized wine, prepared as above, with boneblack for 

 fifteen minutes ; filter and wash the boneblack thoroughly with water. Add a 

 liter of water and 20 cc of indigo solution and titrate with permanganate as 

 above. Designate the number of cubic centimeters of permanganate employed 

 as " b." 



Then a b=c, the number of cubic centimeters of permanganate solution 

 required for the oxidation of the tannin and coloring matter In 10 cc of wine. 



21. Heavy Metals. Provisional. 



Lead and copper may be determined in 500 or 1,000 cc by the method given 

 under "IX. Canned Vegetables," page tiii. 



Copper may also be precipitated electrolytically & on 500 cc of the undiluted 

 wine by using as electrodes pieces of platinum foil 3 by 15 cm. Arsenic may be 

 detected or determined by one of the modifications of the Marsh method. 



22. Detection of Nitrates. 



(a) WHITE WINE. PROVISIONAL. 

 \ 



Treat a few drops of the wine in a porcelain dish with 2 or 3 cc of concen- 

 trated sulphuric acid which contains about 0.1 gram of diphenylamin c per 



" Neubauer Lowenthal method, Ann. der Oenologie, 2: 1. 



6 Fruhauf and Urslc, Bcricht Uber die Verzatnmlung Oesterreichischcr OnomikcM- in 

 Bozen, 188G, 1 : 66 ; Borgmann, Analyse des Weines, 2d ed., p. 146. 

 'Egger, Arch. Hyg., 2: 273. 



