Harper's new monthly magazine, 41 / 1870

An eminent German practical chemist has lately had his attention called to the defects of white-lead prepared by the so-called English method, especially to the comparatively slight covering property which it possesses. At some of our readers are aware, this method consists in calcining lead in a reverberatory furnace with one per cent. of its weight of sugar of lead dissolved in water, and placing the mixture in horizontal troughs communicating with each other and closed above. A current of carbonic acid gas is conducted through the troughs, obtained usually by burning coke. A sufficient pressure is produced by the bellows of the furnace in which the coke is burned to force the gas through cooling tubes into the mixture, which is continually stirred during the introduction of the carbonic acid. This process, however, according to careful experiment, is not sufficient to produce a soft white lead, of a suitable coating quality, as the product is found to contain too much hydrated oxide of lead. On this account the suggestion was made - with an excellent practical result - to use two and a half per cent. of neutral acetate of lead, dissolved in water, to one hundred parts of the oxide of lead, to which a slight quantity of vinegar is to be added. By acting upon this suggestion, it was found that the process of the fabrication of lead was greatly accelerated, and that a very much better article was produced, having an extraordinary coating power.

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