Separation and Determination of Bismuth with Gallic Acid L. KIEFT AND G. C. CHANDLEE, School of Chemistry and Physics, The Pennsylvania State College, State College, Pa.
G
ALLIC acid as a reagent for the precipitation of bismuth was used in qualitative analysis by Das-Gupta ( I ) , but apparently no investigation of the quantitative possibilities was made. I n view of the small number of ions forming precipitates with gallic acid, it seemed worth while to determine what separations of bismuth from other elements were possible.
TABLEI. SEPARATION OF BISMUTH BiaOa Taken Gram
Pb Cd BirOa Present Present Found Gram Gram Gram Separation from Cadmium and Lead 0.083 0.04 0.1117 0.083 0.04 0.1118 0.083 0.04 0.1118 0.083 0.04 0.1118 0 083 0.04 0.1121 Seoaration from Aluminum and CODDer A1 cu Present Present 0.05 0.05 0.1116 0.06 0.05 0.1118 0.06 0.05 0.1117 0.05 0.05 0.1117 0.05 0.05 0.1110
0.1120 0.1120 0.1120 0.1120 0.1120
Reagents
Difference
-0.0002 -0.0003 -0.0002 f 0.0001
I
_.
The bismuth nitrate solution used was prepared from Bureau of Standards metallic bismuth and Baker’s analyzed acid. A 3 per cent nitric acid solution was used, The acid concentration in all work is expressed in percentage by volume. The gallic acid was Kahlbaum’s D. A. B. No. 5 grade.
0.1120 0.1120 0.1120 0.1120 0.1113
TABLE 11. SEPARATION OF BISMUTH
Procedure The 3 per cent bismuth nitrate solution containing the other elements was heated to 70” C., 50 cc. of gallic acid (1 gram of solid reagent) were added, and the solution was stirred for 1 minute. The solution was allowed to cool before filtering. The clear liquid was poured through the filter and the precipitate washed by decantation with 150 cc. of a solution containing 2 grams of gallic acid and 3 grams of ammonium nitrate per 100 cc. of water. The filter paper was transferred to the original beaker, 20 cc. of nitric acid were added, and the mixture was heated to dissolve the recipitate and break up the filter paper. The paper pulp was fhered and washed with 200 cc. of a 5 per cent nitric acid solution to free it from bismuth. The solution was evaporated to dryness and 10 cc. of nitric acid with 50 cc. of water were added. In order to separate bismuth from the other elements, a reprecipitation is necessary; consequently ammonium hydroxide was added until the solution was basic, then nitric acid to make it just acid. The solution was heated to 70’ C. and the bismuth reprecipitated with allic acid. The same procedure as described above was then use8 u to the point at which ammonium hydroxide was added. At tiis point the bismuth was precipitated as the subcarbonate and ignited to the oxide (8).
Biz08 Taken Gram 0.1120 0.1120 0.1120 0.1120 0.1120
0.1120 0.1120 0.1120 0.1120 0.1120
0.1113 0.1113 0.1113 0.1113 0.1113
0.1113 0.1113 0.1113 0.1113 0.1113
The results are given in Tables I, 11, and 111. Certain details of the above procedure require mention: (1) At a temperature above 85”, gallic acid starts to dccompose and among the products some compound, the exact composition of which is unknown, prevents the complete precipitation of bismuth. (2) It is necessary to evaporate to dryness in order to destroy any decomposition products of gallic acid; otherwise complete precipitation of the bismuth cannot be obtained. (3) Because of the ease with which bismuth compounds are reduced to the metal, the bismuth gallate could not be ignited to the oxide.
-0.0004 -0.0002 -0.0003 -0.0003 -0.0003
Cr BizOs Present Found Gram Gram Separation from Chromium 0.0312 0.1123 0.0312 0.1121 0.0312 0.1118 0.0312 0.1117 0.0312 0.1121 Separation from Nickel Ni Present 0.075 0.1118 0.075 0.1120 0,075 0.1122 0.075 0.1121 0.075 0.1120 Separation from Zinc Zn Present 0.08 0.1110 0.08 0.1111 0.08 0.1111 0.08 0.1111 0.08 0.1113 Separation from Iron Fe Present 0.01 0.1117 0.01 0.1112 0.01 0.1110 0.01 0.1110 0.01 0.1112
Difference
+O. 0003 ~-0.0002 0.0001 -0.0003 4-0.0001
-0.0002 0,0000 +0.0002 $0.0001 0.0000
-0,0003 -0.0002 -0.0002 -0.0002 0.0000
+0.0004
-0.0001 -0.0003 -0.0003 -0.0001
TABLE111. SEPARATION FROM SODIUM, POTASSIUM, CALCIUM, AND BARIUM Biz08 Taken Gram 0,2801 0.2801 0.2801 0.2808
Ca Na K Ba Present Present Present Present Gram Gram Gram Grant 0.08 0.08 0.09 0.08 0.08 0.08 0.09 0.08 0.08 0.08 0.09 0.08 0.08 0.08 0.09 0.08
BizOs Found Gram 0.2798 0,2799 0.2797 0.2809
Difference -0.0003 -0.0002 -0.0004 4-0.0001
Interfering Elements Mercury and antimony are precipitated partially with gallic acid. Tin interferes because it hydrolyzes in a 3 per cent acid solution. Silver cannot be removed with two precipitations.
Literature Cited Das-Gupta, P. N., J. Indian Chem. Soc., 6, 627 (1929). (2) Scott, W. W., “Standard Methods of Chemical Analysia,” 4th ed., Vol. I, p. 74,New York, D. Van Nostrand Co., 1925. (1)
REICEWED June 18, 1936.
Summary Bismuth can be separated and determined in 3 per cent nitric acid solution in the presence of lead, cadmium, copper, zinc, aluminum, chromium, iron, nickel, barium, calcium, sodium, and potassium. Bismuth cannot be separated from antimony, mercury, tin, and silver. 392
