Montgomery, T. L., Corn, M., “Aerosol Deposition in a Pipe with Turbulent Air Flow,”J. Aerosol Sci., 1,185 (1970). Postma, A. K., Schwendiman, L. C., “Studies in Micro-metrics: Particle Deposition in Conduits as a Source of Error in Aerosol Sampling,” HW-65308, Hanford Laboratories, Richland, Wash., 1966. Rouhiainen, P. O., Stachiewicz, J . W., “On the Deposition of Small Particles from Turbulent Streams.” J . Heat Trans.. 92. 169-77 (1970) Schlichting, H., “Boundary Layer Theory,” p 506, McGraw-Hill, New York, N.Y., 1960. Sehmel, G. A , , “Aerosol Deposition from Turbulent Airstreams in Vertical Conduits,” BNWL-578, Pacific Northwest Laboratory, Richland, Wash., 1968. Sehmel, G. A,, “Particle Deposition from Turbulent Air Flow,” J . Geophys. Res., 75,1766-81 (1970).
Sehmel, G. A., “Particle Diffusivitie: and Deposition Velocities Smooth Surface. J. Coll. Interface SCZ., 37. over a Horizontal ~. 891-906 (1971). Soo,S. L., “Fluid Dynamics of Multiphase Systems,” Blaisdell, Waltham, Mass., 1967. Wells, A . C., Chamberlain, A. C., “Transport of Small Particles to Vertical Surfaces,”Brit. J . Appl. Phys., 18,1793 (1967). Whitby, K. T., Liu, B. Y. H., Husar, R. B., Barsic, N. J., “The Minnesota Aerosol-Analyzing System Used in the Los Angeles Smog Project,”J. Coll. Interface Sci., 39, 139-64 (1972a). Whitby, K. T., Husar, R. B., Liu, B. Y. H., “The Aerosol Size Distribution of Los Angeles Smog,” ibid., pp 177-204 (1972b). ~~~
Received for review March 5, 1973. Accepted November 17, 1973. Based in part on PhD thesis of Ilori, 1971. Work supported under Contract AT (11-1)-1248,Atomic Energy Commission.
Formation of Bis(chloromethy1) Ether from Formaldehyde and Hydrogen Chloride Lawrence S. Frankel, Keith S. McCallum,l and Ledelle Collier Rohm and Haas Co., 5000 Richmond St , Philadelphia, Pa. 19137 ~
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The formation of bis(chloromethy1) ether from formaldehyde and hydrogen chloride in moist air was investigated by combining measured amounts of monomeric formaldehyde and hydrogen chloride with air in glass vessels or in Saran bags. The resulting amount of bis(ch1oromethyl) ether was determined by high resolution mass spectrometry and verified in some instances by gas chromatography/mass spectrometry or dual column gas chromatography. Very low yields of bis(chloromethy1) ether are produced by the reaction. and normally this finding would be of little interest, but for the recently reported carcinogenicity of bis(chloromethy1) ether. During the course of exploratory studies in our laboratories, bis(chloromethy1) ether (BCME) was observed to form under surprising conditions. This prompted a series of experiments to determine if BCME might be formed by the adventitious combination of formaldehyde and a source of hydrogen chloride. A preliminary announcement of this finding was made last year (Chem. & Eng. News, 1973). Initially, it appeared that threshold limiting value (TLV) concentrations of formaldehyde and hydrogen chloride yielded approximately 1 ppb bis(chloromethy1) ether. Subsequent work has indeed confirmed that bis(ch1oromethyl) ether is formed a t concentrations of HC1 and formaldehyde higher than the TLV levels, although yields are lower than originally thought. These facts are being reported now so that potentially hazardous operations may be recognized in situations where significant quantities of formaldehyde could react with chloride ion in the presence of moist air t o produce bis(chloromethy1) ether, a reported carcinogen (Laskin et al.. 1971); (Thiess et al., 1973). Apparatus and Procedure Gas phase reactions were carried out either in glass flasks or Saran bags. To whom correspondence should be addressed. 356
Environmental Science & Technology
Reaction Flasks. Three-neck, round-bottom flasks were provided with a septum and glass stopcocks. T o prepare a reproducible surface, the flasks were rinsed with water, then baked a t 200°C for at least a n hour prior to use. Gases were mixed by agitating several 4-mm glass beads with a Teflon-coated magnetic stirrer. The flask was partially evacuated. Aliquots of gaseous formaldehyde and hydrogen chloride were introduced through the septum. One of the stopcocks was momentarily opened to allow the contents of khe flask t o return t o atmospheric pressure. At the end of the reaction, the gases were flushed out through a n adsorber for analysis. Saran Bags. Saran bags (Anspec Co., P.O. Box 44, Ann Arbor, Mich. 48109) were equipped with a glass “T,” one arm of which was fitted with a septum. The bags were twice filled with air and emptied prior to use (Boettner and Dallos, 1965). The reactants were slowly introduced through the septum while air was being pumped into the bag. After filling, the bag was kneaded t o thoroughly mix the reactants. Experiments were planned so that bags were reused a t higher concentrations of reactants in subsequent experiments. Humidity Control. Reaction vessels were generally filled with air from a room held constantly a t 26°C and 40% RH. Some experiments were carried out under lower humidity conditions. The 100% relative humidity atmosphere was attained by drawing the air through water in tandem fritted glass disc scrubbers. A dry atmosphere was obtained by drawing room air through a n 0.5-in. diameter cartridge charged with 42 grams of Linde 4x Molecular S‘ ieves. Calibration and Gas Standards. The primary standard of calibration was prepared by adding a measured volume of BCME into a known volume of ethylene dichloride. Concentrations between 1/4-lY~ were convenient. These solutions are stable indefinitely and obviate the necessity of frequently handling liquid BCME. Gas standards were most conveniently and reproducibly prepared by pumping a measured volume of gas over a thermostated FEP Teflon (Du Pont) tube containing liquid BCME (O’Keeffe and Artman, 1966). The rate of dif-
fusion through the tube was determined by mass spectrometry. The permeation tube used for this work provided about 30 ng/min of BCME a t 35°C.
Reagents Formaldehyde was generated by heating a few grams of paraformaldehyde a t about 130°C for 2-3 hr in a 22-liter round-bottom flask stirred with a large Teflon paddle. After cooling a t least 2 hr, the formaldehyde vapor concentration was determined by drawing an aliquot through a Porapak Q (Waters Associates, Inc., Framingham, Mass.) adsorber tube, condensing it in a liquid nitrogen trap, and analyzing it by a chromotropic acid procedure (Altshuller et al., 1961). The calibration curve was prepared from appropriate dilutions of a 37% formalin solution. Formaldehyde samples for preparing reaction mixtures were also drawn through the Porapak Q adsorber tube. This adsorber removes most organic compounds and formaldehyde polymers, but formaldehyde monomer is not adsorbed (Frankel et al, 1972). Hydrogen chloride was Matheson anhydrous electronic grade. Analytical Methods Three highly selective analytical methods sensitive to less than 30 ng of BCME (
