Chemistry
The metallic salt or binder used must be inert and insoluble in the vehicle, and it must be white or very neutral. It must have low tinting strength so that the dye itself determines which wavelengths are absorbed and reflected by the resulting precipitate. In ancient times chalk, white clay, and crushed bones were used, being sources of calcium carbonate and calcium phosphate. The salts that are commonly used today include barium sulfate, calcium sulfate, aluminium hydroxide, and aluminium oxide (alumina), all of which can be produced cheaply from inexpensive mineral ores.
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Famous quotes containing the word chemistry:
“For me chemistry represented an indefinite cloud of future potentialities which enveloped my life to come in black volutes torn by fiery flashes, like those which had hidden Mount Sinai. Like Moses, from that cloud I expected my law, the principle of order in me, around me, and in the world.... I would watch the buds swell in spring, the mica glint in the granite, my own hands, and I would say to myself: “I will understand this, too, I will understand everything.””
—Primo Levi (1919–1987)
“...some sort of false logic has crept into our schools, for the people whom I have seen doing housework or cooking know nothing of botany or chemistry, and the people who know botany and chemistry do not cook or sweep. The conclusion seems to be, if one knows chemistry she must not cook or do housework.”
—Ellen Henrietta Swallow Richards (1842–1911)
“The chemistry of dissatisfaction is as the chemistry of some marvelously potent tar. In it are the building stones of explosives, stimulants, poisons, opiates, perfumes and stenches.”
—Eric Hoffer (1902–1983)