Much care is required in mixing and sieving batches containing lead and other poisonous ingredients, to prevent the inhalation of the dust by the mixer. Therefore, where such materials are used, exhaust fans and ventilating ducts should be provided and fitted in the mixing rooms. A proper respirator should be worn by the mixer in charge to prevent any absorption into his system of the poisonous dust. Cases of poisoning are not unknown, but these are due to gross carelessness. A small regular weekly dose of Epsom salts should be taken by the mixers who have to prepare lead batches. This salt tends to remove any lead salts absorbed in the system by converting them into insoluble lead sulphate. ------------------------------------------------------------------------ CHEMICAL FORMULAE AND MOLECULAR WEIGHTS. ───────────────┬───────────────┬───── │ │_Molecular _Materials._ │ _Formulae._ │Weight._ ───────────────┼───────────────┼───── Alumina │Al_{2}O_{3} │ 102 Antimony Oxide │Sb_{2}O_{3} │ 287 Arsenic │As_{2}O_{3} │ 197 Bismuth Oxide │Bi_{2}O_{3} │ 468 Boric Acid │H_{3}BO_{3} │ 62 Borax │Na_{2}B_{4}O_{7}10H_{2}O│ 382 Calcined Borax │Na_{2}B_{4}O_{7}│ 202 Calcined Potash│K_{2}CO_{3} │ 138 Carbon │C │ 12 Carbonate of │BaCO_{3} │ 197 Barium │ │ Carbonate of │MgCO_{3} │ 84 Magnesia │ │ China Clay │2SiO_{2}Al_{2}O_{3}2H_{2}O│ 258 Chrome Oxide │Cr_{2}O_{3} │ 153 Cobalt Oxide │Co_{2}O_{3} │ 105 Copper Oxide │Cu_{2}O │ 143 (Red) │ │ Copper Oxide │CuO │ 79 (Black) │ │ Cryolite │6NaFAl_{2}F_{6}│ 210 Dolomite │CaOMgO2CO_{2} │ 184 Fluorspar │CaF_{2} │ 78 Gold Chloride │AuCl_{3}2H_{2}O│ 339 Iron Oxide │Fe_{2}O_{3} │ 160 Lime │CaO │ 56 Lime Spar │CaCO_{3} │ 100 Manganese Oxide│MnO_{2} │ 87 Nickel Oxide │NiO_{2} │ 75 Nitrate of Soda│NaNO_{3} │ 85 Phosphate of │Ca_{3}(PO_{4})_{2}│ 310 Lime │ │ Potash │K_{2}CO_{3}(2H_{2}O)│ 174 Carbonate │ │ Potash Felspar │6SiO_{2}Al_{2}O_{3}K_{2}O│ 556