The exchange loss of radioactivity from solid samplos of barium carbonate through the agency of carbonic acid and its ions has been investigated under a variety of conditions. It is concluded that the losses observed are greatly dependent upon the method of sample preparation, in particular the nature or any heat treatment which the sample materials undergo.

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During the course of a research problem involving hydrofluoric acid it became necessary to filter concentrated hydrofluoric solutions to remove various solid materials. The search for a suitable filter media finally led to the use of a commercially manufactured plastic material known as ``Sponge Teflon`` (polytetrafluoroethylone) which is produced by the DuPont Company. This material, which comes in 1/8 in. sheets, is used primarily as a gasket material in acid lines, and is impervious to all acids, including hydrofluorle acid.

This document is the report from a November 1948 meeting at Mound Laboratory on the measurement of the density of metallic polonium. Four determinations of the density of Polonium at 25 degrees C have been made. These values are 8.69 gm/cc, 9,34 gm/cc (twice) and 9.20 gm/cc. The probable error was 2%. The material used in the first determination was not subjected to a preliminary purification, which makes the value obtained doubtful. In this instance, production foils were used without a separation from their more volatile constituents. The difference in the reported value from that which appears in the Ad Interim Report is due to a recalculation based on the latest information on the physical constants of polonium. The value of using pure material and knowing the physical properties of polonium are clearly indicated.