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Cu ^247 Al 3092 Spectrogram A results from direct arcing of 1 rng. of U.iOs- Uranium spectrum obscures lines of impurities. Spectrogram B, obtained by tfxe carrier-distillation methodfrom 100-mg. samples of U-^Og, shows spectral line? e*/impurities
Carrier-Distillation Analysis of uranium 'ETAILS of a spectrograph^ method of the analysis of uranium and its compounds have recently been announced by B. F. Scribner and H. F. Mullin, chemists of the spectroscopy laboratory a t the National Bureau of Standards. Involving carrierdistillation of the sample, the method per mits detection of 33 impurity elements, some in concentrations as low as a few tenths part per million. The method was developed at the bureau i n 1942 and was used in the Manhattan Project. The bureau has applied the method to control and inspection in the production of ura nium compounds. Utilization of uranium as a source of atomic energy requiFes material of the Electrode assembly for carrier distilla tion analysis of uranium-base materi als. When a 10-ampere arc is struck the impurities of the charge are vap orized and swept into ~the arc by the **carrier"9 while the vt,ranium oxide remains unvolatilized
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highest purity. I impurities differ in their effects on the nuclear chain reaction. Some elements, sxich as boron and cad mium, may interef ere if present in concen trations as low a s a few tenths of a part per million, a n d many other elements should not exceeci a few parts per million. Rapid, sensitive, and accurate methods are therefore reqxaired for the determina tion of at least 6 0 chemical elements in a variety of uraniixxn-base materials. Prior to 1941, methods for the analysis of ura nium to the necessary sensitivity were un known. Even -fche established spectro graph^ methods of analysis, so useful in general for detecting minute amounts of impurities, were unsuccessful because of interference by tihe highly complex ura nium spectrum—s, spectrum in which more than 20,000 l i n e s have been observed. Early in 1941, tz-he bureau, at the request of the Office of Scientific Research and Development, undertook to adapt spec trograph! c mettLods to the analysis of uranium. In developing suitable methods it was evident ttLstt the interference of the spectrum of ura^nium, with the spectral lines characteristic of impurities, could be overcome only b y separating the impurities from the u r a n i u m . This was accomplished in the carrier-distillation method by con verting the uranixim sample to a refractory compound h a v i n g low volatility (the black oxide of u r a n i u m ΙΓβΟβ) and distilling the impurities from -fchis compound in a direct current electric a^rc. In order to sw^ep- out the minute quan tities of i m p u r i t y vapors from the sample without volatilizing the uranium, a small amount of a volatile material, termed a "carrier", is a d d e d to the sample. Gallium oxide, a compoixxid of a rare metal resem bling aluminum, was found most useful as a carrier and is a,
