CURRENT TOPICS. oxide; (2) to raise the tensile strength of the fabric: hard fine Para rubber, 4oo; paraffin (m. pt. about 66 ° C.), 4; magnesium carbonate, 26o; magnesium oxide, 36; and fine sulphur, 4 ° parts. All powders should be sifted twice; (3) to obtain impermeability to gas in cold-cured fabrics: fine hard Para, 4oo; paraffin (m. pt. about 66 ° C.), 5 parts. Benzine and benzol, free from water or suspended iron-oxide, are suitable solvents. The boiling point should be between 7 °o and

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... OO ° C., and not more than 8 per cent. should boil over IOO ° C. The rubbered fabrics are prepared and combined on a smooth calender. Vulcanization is done on drums by steam, or if sensitive colors or fabrics are used, by hot air under pressure. The fabrics must be protected from direct access of steam, 5o to 90 minutes cure at not exceeding. 133 ° C. and 2.2 atmospheres is suitable. With hot air I to 2~ hours at not more than 129 ° to 13 °0 C. at 4 to 6 atmospheres is suitable. It is best to aim at a slight undercure to allow for after-vulcanization.