Qualitative Detection of Titanium Dioxide in Rubber

Abstract

Abstract Titanium dioxide, either as such or in the form of the composite titanium whites, is now used to such an extent as a rubber pigment that a test for titanium is frequently necessary in the analysis of a compounded rubber. Owing to the insoluble nature of titanium dioxide, troublesome fusions are required to detect it by the normal qualitative tests in the ash remaining when a rubber is incinerated. The following method is offered as a quick and easy means of detecting titanium. A small portion (about 0.01 gram usually suffices) of the ash from the sample is placed in a clean glazed 15-cc. Porcelain crucible. One drop of concentrated sulfuric acid is then added, and the whole is heated on a hot plate for 30 seconds, i.e., until most of the acid is evaporated. The crucible is allowed to cool, and 2 drops of 6 N sulfuric acid added, followed by 1 drop of a 5 per cent aqueous solution of the sodium salt of chromotropic acid (1,8-dihydroxynaphthalene-3,6-disulfonic acid). A brownish red to purple coloration is obtained if titanium be present. In place of the chromotropic acid, 1 drop of 10-volume hydrogen peroxide is added in a second test, when the well-known golden yellow color is obtained.