Hydrogen chloride detection

Hydrogen chloride in air is an irritant, severely affecting the eye and the respiratory tract. The inflammation of the upper respiratory tract can cause edema and spasm of the larynx. The vapor in the air, normally absorbed by the upper respiratory mucous membranes, is lethal at concentrations of over 0.1% in air, when exposed for a few minutes. HCl is detectable by odor at 1—5 ppm level and becomes objectionable at 5—10 ppm. The maximum concentration that can be tolerated for an hour is about 0.01% which, even at these levels, causes severe throat irritation. The maximum allowable concentration under normal working conditions has been set at 5 ppm. 

Health and Safety. Remover formulas that are nonflammable may be used in any area that provides adequate ventilation. Most manufacturers recommend a use environment of 50—100 parts per million (ppm) time weighted average (TWA). The environment can be monitored with passive detection badges or by active air sampling and charcoal absorption tube analysis. The vapor of methylene chloride produces hydrogen chloride and phosgene gas when burned. Methylene chloride-type removers should not be used in the presence of an open flame or other heat sources such as kerosene heaters (8). 

Hydrochloric acid may conveniently be prepared by combustion of hydrogen with chlorine. In a typical process dry hydrogen chloride is passed into a vapour blender to be mixed with an equimolar proportion of dry acetylene. The presence of chlorine may cause an explosion and thus a device is used to detect any sudden rise in temperature. In such circumstances the hydrogen chloride is automatically diverted to the atmosphere. The mixture of gases is then led to a multi-tubular reactor, each tube of which is packed with a mercuric chloride catalyst on an activated carbon support. The reaction is initiated by heat but once it has started cooling has to be applied to control the highly exothermic reaction at about 90-100°C. In addition to the main reaction the side reactions shown in Figure 12.6 may occur. 

Unlike DDT, TDE does not lose one mole of hydrogen chloride when heated with ferric chloride, but rearranges to form an isomeric compound (31). It may be possible to develop this observation into an analytical method to differentiate between the two products or to detect the one in the presence of the other. 

Photolysis of an aqueous solution containing chloroform (314 pmol) and the catalyst [Pt(cohoid)/Ru(bpy) /MV/EDTA] yielded the following products after 15 h (mol detected) chloride ions (852), methane (265), ethylene (0.05), ethane (0.52), and unreacted chloroform (10.5) (Tan and Wang, 1987). In the troposphere, photolysis of chloroform via OH radicals may yield formyl chloride, carbon monoxide, hydrogen chloride, and phosgene as the principal products (Spence et al., 1976). Phosgene is hydrolyzed readily to hydrogen chloride and carbon dioxide (Morrison and Boyd, 1971). 

CCI4 = carbon tetrachloride EC = electrochemical detection ECD = electron capture detection GC = gas chromatography HCl = hydrogen chloride HPLC = high-performance liquid... 

Deprotection. The BOC group is easily removed under quite mildly acidic conditions, a feature which underlines its value in selective deprotection in peptide synthesis. Typically, treatment at room temperature for 30-60 minutes with a 1 m solution of hydrogen chloride in acetic acid, or with neat trifluoroacetic acid, is used. It is of interest that after t.l.c. of BOC-amino acids, brief exposure of the plates to hydrogen chloride fumes enables the ninhydrin reaction to be used to detect the presence of the liberated free amino acids. 

With these compounds the presence of the halogen will have been detected in the tests for elements. Most acid halides undergo ready hydrolysis with water to give an acidic solution and the halide ion produced may be detected and confirmed with silver nitrate solution. The characteristic carbonyl adsorption at about 1800 cm -1 in the infrared spectrum will be apparent. Acid chlorides may be converted into esters as a confirmatory test to 1 ml of absolute ethanol in a dry test tube add 1 ml of the acid chloride dropwise (use a dropper pipette keep the mixture cool and note whether any hydrogen chloride gas is evolved). Pour into 2 ml of saturated salt solution and observe the formation of an upper layer of ester note the odour of the ester. Acid chlorides are normally characterised by direct conversion into carboxylic acid derivatives (e.g. substituted amides) or into the carboxylic acid if the latter is a solid (see Section 9.6.16, p. 1265). 

As Table 2-1 shows, the treatment of the mustard agent (HD) resulted in stack concentrations, DRE, operating temperatures, carbon monoxide concentrations, stack particulate concentrations, and hydrogen chloride emissions that were all within required limits for all four test mns. At the time the trial bum report was prepared, no limits had been established for metals. However, the report notes that the measured concentrations were very close to the detection limits in all cases (U.S. Army, 1992). It is not clear whether the low concentrations were due to low metals content in the agent stream or to the effective removal of metals during processing. 

Readers are warned that the literature includes some incident reports originating from the emergency services which are undoubtedly in error. An example is the claimed production of hydrogen cyanide by fuels containing no nitrogen, but much chlorine (the ordinary gas detection tubes for cyanide actually generate and then measure hydrogen chloride for which they have very limited absorption capacity in the pre-layer). 

The ability of (67) to react with [2.2.1] bicycloheptene but not maleic anhydride is intimately connected with its strong electron affinity and this property is further emphasized by the observation that it can oxidize hydrochloric acid to chlorine. When dry hydrogen chloride is passed through a solution of (67) in dry ether, chlorine gas is readily detected and a quantitative yield of 1,3-diphenylpyrazol-4-ol hydrochloride is produced. The low-intensity carbonyl IR band of (67) is a manifestation of the compa-... 

Hydrogen chloride is the first chlorine-bearing interstellar molecule to have been detected. Its lowest rotational transition (J = 1 -> 0) at 625.9 GHz has been observed in the Orion Molecular Cloud (OMC-1) in emission with the Kuiper Airborne Observatory, (Blake, Keene, and Phillips, 1985) since atmospheric opacity at this... 

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