Document G5bDnVZZ2602w6o0XDq5kq73v

uuiKCn-j. c}i?::ic\-d. Division ox UjIKOYAL, Inc. * THE COLORS-STRIC LIEASGRZ-ZIiT OF PHOSC-Si'S III THE PRESENCE OF HYDFOG1I7 CHLORIDE Task force "C", of Minufacturing Chemists Association, has an assignment relating to the safety of vinyl chloride transportation. .More speci fically, the task force is examining the situation of ruptured and burn ing tank cars vith a view to estimating the prese?-ce of toxic gases such as hydrogen chloride, carbon monoxide and phosgene. Due to its partic ularly insidious nature, and the lack of pertinent information, phosgene has received the major attention. The portion of the investigation assumed by UklROYAL CHEMICAL was the testing of commercially available testing kits to ascertain their suitability for on-site detection of traces of phosgene in the presence of low concentrations of hydrogen chloride gas. If the hydrogen chloride was found to interfere, the feasibility of a scrubber tube filled with sine granules to eliminate the interference, was to be part of the investigation as well. Summary Tests were made vith three detection systems: 1) M.S.A. Universal.Tester, Model 1 with 6989O Detector tubes'1' 2) Unico kOO Precision Gas Detector with Ho. 146 tubes'^' 3) Scott-Drager Gas Detector Model.19/31> with 02?/b Phosgene detectcr tubes'3/ The detectors were used on air to which phosgene and hydrogen chloride were added in the following concentrations: 1) 2) 3) *0 5) 6) Q-5 -ppm 0.5 ppm 2.5 ppm 2.5 ppm 50 ppm 50 ppm phosgene, ti nt 11 > 11 7 11 > > no hydr; 50 ppu no 25O ppm no 500 .ppm 0 URL 17949 2- - The tube containing zinc was a medicine drover tube, 7 mm OD, and 75 mn long. It held a column 40 mrlong of Balers ''granular 40 ueshi. Reagent Grade zinc. The weight of the zinc was 4.0 grans. Glass wool plugs held the zinc in place. The tube was connected to the detector tubes with -very short rubber tubing sections so that there was a glass to glass butt. Observations We were unable to confirm MSA's claim that there was no interference from HC1 below its allowable limits. At 50 ppm EC1, the MSA tubes gave negligible response to 0*5 ppm phosgene. A zinc pre-tube did not help. When the KOI was 250 ppm and the phosgene is 2.5 ppm, the color formed was faint with or without a zinc pre-tube. However, when the HC1 is 500 ppm and the phosgene 50 ppm, good colors were formed with and without the zinc pre-tube. The Unico-Kitagawa tubes were even more sensitive to hydrogen chloride. At all three levels of phosgene and hydrogen chloride, there was no color when hydrogen chloride was present, and colors with much reduced intensity with the granular zinc pre-tube. The Drager tubes were sensitive to 253 ppm HC1 when the phosgene was 2.5 ppm, and gave no color. However, the zinc pre-tube restored the sensitivity of the system. At 500 ppm HCi and 50 ppm phosgene, the colora tion was good for tubes with and without a zinc pre-tube. Conclusions When the ratio of hydrogen chloride to phosgene is high (100:1), all the detection systems suffer interference. When the ratio of hydrogen chloride to phosgene is reduced (10:l), only tiie Unico-Kitagawa system fails to perform adequately. Probably "the most satisfactory system is the Scott-Drager equipment with the detector tubes protected with a zinc pre-tube. URL T7950 T -3- References ^^Expiration dates of two boxes, Oct. %10t May '71. Literature provided with detector tubes states that ,:other cornuon gases in the range of their allowable limits do not interfere with accurate measurements. (v 2)'Expiration date Mat. '70. Literature provided by Kitagawa with the tubes states that hydrogen chloride interferes by producing a similarly colored stain at concentrations over 50 ppm HC1. The Kitagawa detection system is also available from Matheson Co., Inc. ^^Expiration date Dec. 1971* A Drager bulletin (llo. 3^, May i960) indicates tolerance of their system to high concentrations 01 hydrogen chloride. "Where the concentration of phosgene was 2.5 ppm, and that of hydrochloric acid 35O ppm, the phosgene reading was 3 pom." JEN:mn 1/12/70 J. E. Newell URL 17951