Page:Popular Science Monthly Volume 21.djvu/681

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a hundred times less. The difference depended on one condition only. The former factory made white-lead in powder or in cakes; the other prepared and sold it exclusively ground in oil. In the former process much dust, in the latter none, was disengaged.

Another step in progress may be gained, perhaps, by substituting inoffensive substances for the compounds of lead employed in industry. White-lead has already a rival in zinc-white, but it is objected to that substance that it has an inferior coloring power. To meet this objection, Mr. Griffith, of England, has prepared a white coloring substance based on sulphuret of zinc, which combines the coloring power of white-lead with the inoffensive qualities of the salts of zinc.

A pharmacist of Brest, M. Constantin, has received a prize from the French Academy of Sciences for the discovery of substitutes for the use of oxide of lead in the glazing of pottery: glazes based on lime for the uncolored, on oxide of manganese for colored, glazings.

A number of inoffensive colors deserve mention as substitutes for poisonous colors. Such substances as eosine, fluorescine, and other products derived from aniline, have been fortunately introduced in later years for painting children's toys.

Nothing need be said of copper. It is as inoffensive as lead is dangerous; and it appears, according to the researches of Dr. Burq, to confer upon workmen who handle it an almost absolute immunity against cholera.

Mercury is as dangerous as lead. It provokes salivation, destruction and loss of the teeth, tremblings, paralysis, and death. The workmen exposed to injury from it are miners employed in its extraction, gilders, looking-glass makers, and hatters. The personal hygiene is the same as for lead; but in securing its application we are still opposed by the carelessness and foolhardiness of the workmen.

The principal means relied upon for preservation against accidents from mercury are the employment of ammoniacal sprays in the shops, and of iodide of potassium, as for lead. Both remedies were recommended by M. Meisens after a long series of experiments, and have been used with excellent effect. The division of the labor in its most insalubrious phases and an energetic ventilation are excellent measures. Operations in mercury have been, moreover, much alleviated by the introduction of new processes. Gilding with mercury has been replaced by galvanoplasty; silvering of glass with mercury by a plating process which is performed at half the cost, and is without danger to health. Mercury is used by hatters in a secret process for impregnating the fur of the hare and rabbit, to make it felt, with a mixture of mercury, nitric acid, and water. Efforts have been made to find a substitute for quicksilver, and Dr. Hillairet proposed in 1872 to use molasses, but the experiment was not satisfactory.

Phosphorus is but little used among us except in the manufacture of matches. The troubles which it occasions are cough, headaches,