ANP QUARTERLY PROGRESS REPORT presence of sulfur. A colorimetric method4 was adapted to determine <strong>the</strong> concentration of sulfur quantitatively. In this method, sulfur is released from solution as H,S by acidification with HCI. The gas is adsorbed in a solution of zinc acetate solution, and, upon <strong>the</strong> fur<strong>the</strong>r addition of ferric ammonium sulfate, a reaction occurs between <strong>the</strong> organic reagent and sulfur to form methylene blue, an intensely colored dye. The absorbancy of <strong>the</strong> solution of methylene blue is measured with a photometer at 670 mp. The method is extremely itive with a workable range of from 5 to 50 pg 100 ml of solution. This range corresponds to a practical lower limit of determination of about 1 part of sulfur per million ports of sodium. Analyses of <strong>the</strong> sodium revealed that <strong>the</strong> sulfur was not mly distributed. In particular spots, <strong>the</strong> conc ion was of <strong>the</strong> order of 0.1 to 1% or higher. The sulfur content of <strong>the</strong> sodium sampled from <strong>the</strong> bulk of <strong>the</strong> trap was, however, much lower, 50 to 100 pprn, and that of <strong>the</strong> sodium in <strong>the</strong> system was less than 1 pprn. These results indicate that sulfur in sodium precipitates rapidly as sodium sulfide and can be effectively trapped and removed from <strong>the</strong> system. The solubility of sodium sulfide in sodium is evidently extremely small. Sulfur in Fluoride <strong>Salt</strong> Mixtures. The presence of sulfur in mixtures of fluoride salts which are being considered as proposed reactor fuels is considered deleterious, principally from <strong>the</strong> standpoint of corrosion. The major problem in determining sulfur in fluorides is that sulfur exists in at least two oxidation states, sulfate and sulfide, and, in order to adapt <strong>the</strong> methylene blue colorimetric method, <strong>the</strong> sulfate must be reduced to <strong>the</strong> sulfide. The reducing mixture recommended by Johnson and Nishita5 for sulfate in soils is used for this purpose. About 1 g of <strong>the</strong> fluoride mix is heated at <strong>the</strong> boiling point with 4 ml of a reducing mixture composed of 15 g of red phosphorus, 100 ml of hydriodic acid, and 75 mi of formic acid. Reduction of <strong>the</strong> sulfate is complete within 30 min, and <strong>the</strong>n <strong>the</strong> colorimetric method can be utilized. When sulfur is found in fluoride mixtures, <strong>the</strong> principal portion of <strong>the</strong> sulfur is in <strong>the</strong> form of sulfate ra<strong>the</strong>r sky, Anal. Chem. 21, 732-4 5C. M. Johnson and H. Nishita, Anal. Chem. 24, 736 132 Sulfur in H,-HF Gas Streams. The odor of H,S has often been noted in gas streams in <strong>the</strong> fuel production work. Two sources of this sulfur are known: sulfate contaminant in fluoride salts and fluorosulfonic acid, HSO,F, in hydrogen fluoride. Sulfur from <strong>the</strong> first source is known to be of <strong>the</strong> order of a few parts per million. A test of <strong>the</strong> sulfur content of hydrogen fluoride was made by dissolving <strong>the</strong> gas in a solution of NaOH, determining sulfur in <strong>the</strong> solution by boiling <strong>the</strong> basic solution in <strong>the</strong> presence of H,O, and precipitating <strong>the</strong> sulfate as BaSO, with BaCI,. The sulfur concentration was 2.7 mg per liter of HF. A semiquantitative method for determining sulfur as sulfide in off-gas from fuel production was set up in which <strong>the</strong> gas was passed through a 6% solution of NaOH. An equal volume of bismuth nitrate in glacial acetic acid was added to <strong>the</strong> scrub solution, and <strong>the</strong> turbidity, as Q result of formation of Bi,S, was compared with previously prepared standards. The procedure was made more precise by measuring <strong>the</strong> absorbancy of <strong>the</strong> turbid solution at 350 mp in a 7.5-cm cell with a total volume equal to <strong>the</strong> volume of <strong>the</strong> test solution. The concentration of sulfur found by this pro- cedure ranged from 2 to 35 pg per liter of off-gas. Determination of Fluoride in NaF-KF-LiF-Base Fuels J. C. White B. L. McDoweII Analytical Chemistry Division Investigation was continued on <strong>the</strong> feasibility of a spectrophotometric titration of fluoride based on <strong>the</strong> decolorization of a zirconium complex or lake. Zirconium alizarin sulfonate and zirconium Erio Chrome cyanine were tested as possible titrants. A titration cell based on <strong>the</strong> design of Sweetser and Bricker6 was fabricated so that <strong>the</strong> Beckman Model DU spectrophotometer could be used to meas- ure absorbancy. Although <strong>the</strong> data have not yet been thoroughly evaluated, <strong>the</strong> technique does not appear to be feasible for application to NaF-KF- LiF-base fuels because of <strong>the</strong> slowness with which equilibrium is reached. The procedure will be evaluated before fur<strong>the</strong>r work is done. 6P, 6. Sweetser and C. E. Bricker, Anal, Chem. 25, 253 (1953). 9' * '. -. - J '*
PETROGRAPHIC INVEST1 FLUORIDE FUELS G. D. White, Metallurgy Division T. N. McVay, Consultant Petrographic examinations were made of several hundred samples of fluoride melts. The majority of <strong>the</strong> samples were from alkali fluoride systems con- taining UF,. When small amounts of UF, (
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