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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1916 edition. Excerpt: ...ferric hydroxide, etc.) were unsuccessful. I have, however, been able to use emulsions composed of gamboge and mastic. Gamboge (which is prepared from a dried vegetable latex) when rubbed with the hand under water (as if it were a piece of soap) slowly dissolves giving a splendid yellow emulsion, which the microscope resolves into a swarm of spherical grains of various sizes. Instead of using the natural grains, it is also possible to treat the gamboge with alcohol, which completely dissolves the yellow matter (which makes up by weight of the crude material). This alcoholic solution, which looks like a bichromate solution, changes abruptly, on the addition of much water, into a yellow emulsion composed of tiny spheres, that appear to be identical with the natural ones. All resins may be precipitated from alcoholic solution in this way, but often the grains produced are composed of a viscous paste and gradually become stuck together. Out of six other resins tried mastic alone appeared suitable. This resin (which gives no natural grains) yields when treated with alcohol a solution that is transformed by the addition of water into a white emulsion, like milk, composed of granules of a colourless, transparent, glassy substance. 57.--Fractional Centrifuging.--The emulsion having been obtained, it is subjected to an energetic centrifuging (as in the separation of the red corpuscles and serum from blood). The spherules collect together and form a thick sediment; above the sediment is an impure liquid which is decanted. The sediment is treated with distilled water, which brings the grains into suspension once more and the centrifuging process is repeated until the intergranular liquid is practically pure water. But the purified emulsion contains...

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