(A). Direct Ignition to Bismuth Oxid.—This method was abandoned because of the tendency to ignite suddenly during the incineration and the consequent loss of material.
(B). The Method of the Japanese Pharmacopeia, Third Revised Edition, Translated by the Pharmaceutical Society of Japan.—The method consists in treatment of the product with nitric acid, evaporation and subsequent heating to bismuth oxid. This method also was abandoned because of tendency toward sudden ignition with loss of material.
(C). The Method of Kollo (Apotheker Zeitung, 1910, p. 99).—The method consists in decomposition of the product by heating on water bath with normal sodium hydroxid solution, with formation of soluble sodium tribromphenate and insoluble bismuth hydroxid. The bismuth hydroxid is collected on a filter, washed with hot water until a few drops of the filtrate no longer turn litmus paper blue, dried and heated to constant weight and weighed as bismuth oxid.
(D). A. M. A. Method (Reports A. M. A. Chem. Lab., 1911, p. 18).—This method consists in dissolving the product in hot, strong hydrochloric acid, diluting, filtering and precipitating by saturation with hydrogen sulphid. The bismuth sulphid obtained is dissolved in nitric acid and from the solution obtained the bismuth is precipitated by addition of an excess of ammonium hydroxid and ammonium carbonate. The precipitate is collected and converted to bismuth oxid by heat.
The following tabulation shows the results obtained by Methods “C” and “D”:
TABLE 1.—BISMUTH CONTENT OF BISMUTH TRIBROMPHENATE
| Method | Gm. of Salt | Gm. of Bi2O3 | Per Cent. of Bi2O3 | |
| No. 1 Research Council Spec | C | 2.1312 | 1.1754 | 55.1 |
| No. 1 Research Council Spec | D | 0.5151 | 0.2772 | 50.03 |
| No. 2 (Merck & Company) | C | 2.0287 | 1.2543 | 61.8 |
| No. 2 (Merck & Company) | D | 0.5064 | 0.2634 | 52.01 |
| No. 3 (Heyden Chem. Works) | C | 2.0472 | 1.6020 | 78.2 |
| No. 3 (Heyden Chem. Works) | D | 0.5227 | 0.3546 | 67.8 |
It is seen from the tabulation that the results obtained by the Kollo method (Method C) are higher than those by the sulphid method (Method D) and that duplicate determinations show a rather wide variation. The results by the sulphid method are somewhat lower than those by the Kollo method, but duplicates agree fairly well. In view of the fact that the Kollo method will give excessive results if impurities such as talcum, etc., are present and in consideration of the satisfactory results obtained in previous work with the sulphid method, the figures obtained by this method are taken as indicative of the bismuth content of the specimens examined. Calculating the per cent. of bismuth oxid obtained to bismuth (Bi), the following values are obtained:
Bismuth Tribromphenolate, Research Council Specimen: Bismuth, 44.8 per cent.
Bismuth Tribromphenate-Merck, Merck & Co.: Bismuth, 46.6 per cent.
Xeroform, Heyden Chemical Works: Bismuth, 60.7 per cent.