Quantitative determn. of methyl bromide in gas, e.g. air - by passing as through two oxidising zones to form all bromide into bromine, and trapping on cuprous bromide indicator in third zone

摘要

Quantitative determn. of CH3Br in a gaseous mixt. comprises passing the mixt. through a carrier having 3 successive zones. In the first zone the CH3Br is oxidised to Br2 and HBr; in the second zone the HBr is oxidised to Br2; and in the third zone all of the Br2 is entrapped by CuBr indicator. The change of the indicator colour is used as a measure of the CH3Br content in the gas. In the first zone oxidn. is effected using (a) sulphuric anhydrie or oleum in the presence of (b) iodine pentoxide deposited on (c) an active silica gel carrier, these components being in the following percentages by wt. resp. 10.44-28.73:0.04-2.3:89.52-68.97. In the second zone oxidn. is effected using (a) KmnO4 in the presence of (b) iodine pentoxide deposited on (c) an active silica gel carrier, these components being in the following percentages by wt. resp. 0.02-3.09:0.05-4.61:99.93-92.3. In the third zone the indicator comprises (a) CuBr deposited on (b) act ie silica gel or glass powder, these components being in the following percentages by wt. resp. 0.09-2.92:99.91-97.08. The process is esp. used to control the CH3Br content of air in order to prevent poisoning during operations with it; as well as for sanitary measurements of the gas content in the ambient atmosphere at the sites of fumigation of vegetable and other prods. All the stages in the process are performed in a single indicator tube which allows determn. to be carried out under field conditions, e.g. in ship-bilges, stores houses and other premises. Determn. of CH3Br content in the air takes only 15-20 sec., and no special training is required.