For several years we have been investigating trace amounts of metals in various rocks and minerals. Bromoform, diiodomethane (methylene iodide), and acetylene tetrabromide were used to separate igneous rocks into their constituent minerals. Because, in some cases, we were determining low level metal content (1 or 2 ppm.) in mineral separates it became important to know if the liquids could pick up enough metal to contaminate the minerals, and, if so, how the metal might be removed. The concern deepened when our colleage A. P. Pierce told us that bromoform picked up important amounts of uranium, and J. C. Antweiler noted that bromoform became laden with lead when used to separate ore minerals. Antweiler and I. C. Frost found that as bromoform cools the crystals that form first contain very little lead and when separated and melted give a very clean liquid. In a search for a more convenient cleansing procedure we treated samples of organic heavy liquids with Hcl-treated ion exchange resin (Amberlite IRA 400 and IRA 120 mixed in equal proportions) and also with fuller's earth. The fuller's earth had been used regularly to remove the tarry decomposition products that gradually darken bromoform and diiodomethane. Two fuller's earthsf rom differents ources gave equal results.

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