1002 FOODS AND FOOD ADULTERANTS. 



RICHAEDS and PALMEK. A volumetric method based upon the work of Gerland. A 

 standard solution of tartrate of antimony and potassium is employed for the 

 titration. A solution of acetate of ammonium is prepared for use as de- 

 scribed below. In preparing this solution, saturate glacial acetic acid with 

 stronger water of ammonia. Exhaust a weighed portion of the sample as usual 

 with water, using such proportions to give approximately 0.3 to 0.9 gram 

 tannin per 150 to 300 cc. Divide this solution into three or four aliquot 

 parts. To one portion add the standard tartar emetic solution in slight ex- 

 cess, and to a second add less of the solution than is required to precipitate 

 the tannin. To each portion add 1 cc ammonium acetate solution per 25 cc 

 taken. After allowing time for the precipitate to settle, test a drop of the 

 clear liquid on a porcelain plate with a drop of sodium thiosulphate. An 

 excess of antimony is indicated by an orange-yellow precipitate. The tests 

 of the first two aliquot parts, more tartar emetic being added to the second 

 if necessary, indicate approximately the volume of the antimony solution 

 required to precipitate the tannin, and the remaining aliquot part or parts 

 serve to determine this volume with accuracy. The volume of the standard 

 solution taken X .01 == tannin as digallic acid. Ammonium acetate acts 

 similarly to the chloride in Gerland's method and prevents the precipita- 

 tion of the gallic acid. Arn. Jour. Sci., 16, 196 and 361; Allen's Commercial 

 Organic Analysis, Vol. in, Pt. 1, 123; Prescott's Organic Analysis, 471. 



RISLER-BEUNAT, H. A method based on the precipitation with stannous chloride. 

 Extract 10 grams of tea thirty minutes with 500 cc water; wash the residue 

 with about 500 cc boiling water; cool and complete the volume to 1 liter. 

 Precipitate 100 cc 'of this extract with 100 cc staunous chloride solution 

 containing 18 grams of this salt and 2 grams ammonium chloride per liter. 

 Collect, wash, dry, and weigh the precipitate, then ignite with ammonium 

 nitrate and again weigh. Calculate the resulting SnO; to SnO, and deduct 

 this from the weight of the precipitate ; the remainder is the weight of the 

 tannin, /eitsch. f. anal. Chem., 2, 287. 



SCHREINER, L. An apparatus for the absorption of tannin by hide powder. This 

 apparatus is so arranged that the first portions of the solution, which always 

 dissolve some albumin from the powder, collect in a small bulb placed below 

 by reason of their greater density. Der Gerber, 14, 244. 



SCHULZE, F. A volumetric method employing a gelatin solution standardized by 

 means of pure tannin disolved in a concentrated solution of chloride of am- 

 monium. The gelatine is also dissolved in a concentrated solution of chlo- 

 ride of ammonium. In the titration, the standard solution is added until 

 the precipitate formed will settle within half a minute, leaving the super- 

 natant liquid clear. Zeitsch. f. anal. Chem., 5, 455. 



SCHMIDT, E. A method employing a standard solution of lead acetate in dilute al- 

 cohol. A measured volume of the solution to be assayed is warmed to 60 C. 

 and titrated with the lead solution, using potassium iodide as an indica- 

 tor. Bui. Soc. Chem. [2], 21, 256; also, Jsb. d. Chem., 1874, 1035. 



SACKNER. Sackner commenting on various methods for tannin considers that of 

 Lowenthal the most accurate. Wagner's .Jsb., 1861, 625. 



SIMPKIN, S. J. A volumetric method based on the oxidation of tannin by perman- 

 ganate, and its precipitation by ammonium sulphate of copper. Chem. 

 News, 32, 11 ; also Jsb. d. Chem. 



TERREIL. An improvement of Mittenzwey's method. Terreil states that 0.1 gram 

 pure tannic acid will absorb 20 cc oxygen in twenty-four hours. Ber. d. 

 chem. Ges., 5, 362; also, Compt. Rend., 78, (!'.K); also, Zeitsch. f. anal. Chem., 

 13, 243. 



VILLON, M. A method involving extensive calculations based on the specific gravi- 

 ties of the original solution, the precipitant, and the solution after filtering 

 off the precipitate. Lead acetate with sodium acetate is the precipitant ein- 



