| 摘要 |
1, 057, 984. Gas analysis. MINE SAFETY APPLIANCES CO. April 14, 1964 [July 2, 1963], No. 15353/64. Heading G1B. A free-flowing colorimetric indicator for determination of gases comprises a finely divided non-porous inorganic carrier coated with an adherent film of an inorganic absorbent material impregnated with a colorimetric reagent. The carrier may be glass beads, powdered glass, glazed ceramic chips or beads or metal shot of particle size between 40-100 mesh. The inorganic absorbent material is in the form of a binder and may be clay, acid treated clays, diatanaceous earth, bentonite, bauxite or Fuller's earth. Also absorbent material such as pulverized silica gel, which is not normally adherent, may be used when impregnated with a reagent containing a viscous liquid e. g. concentrated sulphuric acid. The binder or carrier may be neutral, acidic or basic as required, e. g. by use of basic soft glass beads, and also if desired the colorimetric reagent may incorporate a non-volatile acid or base. The reagent used depends on the gas to be detected, e. g. lead acetate for H 2 S, oxalic acid with a pH indicator e.g. thynol blue for ammonia, palladium sulphite salts with silica gel for CO, Congo Red indicator for HCl vapour, potassium dichromate and concentrated sulphinic acid with silica gel for alcohol in air-alcohol mixtures, and iodine with tetramethyldiamino diphenylmethane for SO 2 . The proportions of the constituents used are given in the Specification and the indicator is used in a sealed transparent tube with breakable ends. The tube may contain layers of guard chemicals to remove interferent gases. |
