A Dictionary of Practical and Theoretical Chemistry: With Its Application to the Arts and Manufactures, and to the Explanation of the Phaenomena of Nature... : with Plates and Tables

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Richard Phillips, 1808 - 826 páginas
 

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a history of inventions @google, plz see ultramarine
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Página 8 - It sometimes happens, that jewellers, in letting precious stones, break oft' pieces by accident; in this case they join them so that it cannot easily be seen, with gum mastic, the stone being previously made hot enough to melt it. By the same medium cameos of white enamel or coloured glass are often joined to a real stone as a ground, to produce the appearance of an onyx. Mastic is likewise used to cement false backs or doublets to stones, to alter their hue.
Página 8 - The very long and durable operations of the ancient chemists rendered it a desirable requisite that their fires should be constantly supplied with fuel in proportion to the consumption. The athanor furnace was peculiarly adapted to this purpose. Beside the usual parts, it was provided with a hollow tower, into which charcoal was put. The upper part of the tower, when filled, was closely shut by a well-fitted cover, and the lower part communicated with the fire-place of the furnace.
Página 12 - The coarse bmpbuck of the shop* will not answer the purpose; but the ri.ie soot from the flame of a lamp or candle, received by holding a plate over it, mixed with clean size from shreds of parchment or glove-leather not dyed, will make an ink equal to that imported. The general composition of printers...
Página 7 - This nitre, which is called nitre of the first boiling, contains some common salt ; from which it may be purified by solution in a small quantity of water, and subsequent evaporation; for the crystals thus obtained are much less contaminated with common salt than before; because the proportion of water is so much larger, with respect to the small quantity contained by the nitre, that very little of it •will crystallize. For nice purposes, the solution and crystallization of nitre aie repeated four...
Página 12 - The distinctive characters of oil are inflammability, insolubility in water, and fluidity, at least in a moderate temperature. Oils are distinguished into fixed or fat oils, which do not rise in distillation at the temperature of boiling water ; and volatile or essential oils, which do rise at that temperature.
Página 8 - If the centre of gravity of the beam, when level, be immediately above the fulcrum, it will overset by the smallest action ; that is, the end which is lowest will descend ; and it will do this with more swiftness, the higher the centre of gravity be, and the less the points of suspension be loaded. But if the centre of gravity of the beam be immediately below the fulcrum, the beam...
Página 12 - ... leaves a small proportion of the iridium, but much less than in the preceding instance. Silver forms with it a perfectly malleable compound, the surface of which is tarnished merely by cupellation ; yet the iridium appears to be diffused through it in fine powder only.
Página 12 - ... and frequently turned, till the lac is liquid enough to pass through its pores ; when it is taken off the fire, and twisted in different directions by the men who hold it, at the same time dragging it along the convex part of a...
Página 12 - This is the produce of the amyris opobalsamum, L. The true balsam is of a pale yellowish colour, clear and transparent, about the consistence of Venice turpentine, of a strong, penetrating, agreeable, aromatic smell, and a slightly bitterish pungent taste : by age it becomes yellower, browner, and thicker, losing by degrees, like volatile oils, some of its finer and more subtile parts. To spread, when dropped into water, all over the surface, and to form a fine, thin, rainbowcoloured cuticle, so...
Página 12 - Boil the galls and logwood together in twelve pounds of water for one hour, or till half the liquid has evaporated. Strain the decoction through a hair sieve, or linen cloth, and then add the other ingredients. Stir the mixture, till the whole is dissolved, more especially the gum ; after which, leave it to subside for twenty-four hours. Then decant the ink, and preserve it in bottles of glass or stone ware, well corked.

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