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AQUA REGIA

A mixture of nitric and hydrochloric acidsa very powerful solvent. Gold and platinum, for example, can be dissolved by this mixture, which is commonly made of 18 parts and 82 parts of the respective acids.

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ANISEED OIL

contains a substance called arethol, is used in flavouring certain liqueurs, and is made from the seed of Pitnpinella anisum and the China or star anise by distillation with water. It is a thick yellowish, syrupy liquid of sp. gr. C975 to 0990, and refractive index 154 to 156, of peculiar aromatic smell and taste. The yield of oil from the seeds is about 24 per cent. Anethol is also obtained from fennel and tarragon.

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AZO DYES

A large class of dyes containing one or more socalled a/.o groups N: N linking together aromatic radicles. Many of them dye cotton without the use of a mordant, whilst others act as very fast mordant dyes on wool. They may be regarded as originating from the red crystalline parent substance, azobenzene, C6H5: N:N.

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ALLOYS

Many metals when melted together have the property of combining with each other to form either mixtures or definite compounds called alloys, a number of which are very useful in the arts and manufactures. At least some of these mixtures may be regarded as solutions of definite compounds in an excess of one of the metals employed, and may, therefore, be considered as solidified solutions. In this way, the metals aluminium, zinc, iron, tin, copper, and lead are largely used, and sometimes mercury, silver, gold, and platinum. Socalled German silver is a mixture of copper, zinc, and nickel; and brass consists of about 2 parts copper and 1part yinc. The British gold coin consists of pure gold 22 parts, and 2 parts alloy of silver and copper, and, until recently, silver coins consisted of 92

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AMIDOL

is used with sodium sulphate as a photographic developing agent.

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AOYL RADICALS

The radicals left after removal of Oil from organic acids for example, CH3.CO., C2H6.CO,, etc.

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ARGENTITE

A native form of silver sulphide occurring in cubic crystals, containing 87 per cent, silver, found in several of the United States of America.

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ADIPIC ACID

A member of the oxalic series of acids produced by the action of nitric acid upon oleic acid and other fatty acids. It is a solid crystalline body soluble in alcohol, ether, and hot water, which melts at 1530 C.

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ABRASIVES

Preparations such as aloxite, carborundum, corundum, emery, kieselguhr, pumice powder, tripoli, oilstone, and whetstone, used for cleaning or abrading by rubbing. Emery in the raw state comes from the Island of Naxos, in the Greek Archipelago; silicon carbide, corundum, and corundite are found in South Africa; and an aluminous abrasive is found in the south of France and the Pyrenees. All are used in making grindingwheels, etc.

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ARGON

Atomic weight, 3988. Argon is a recently discovered element found present in the gaseous state in the air to the extent of rather less than 1 per cent, by volume, and also in minute quantity in Bath and other mineral spring waters. It is isolated by processes which remove the oxygen and nitrogen respectively. It is a remarkably inert substance, and has been liquefied and frozen to a white solid. No chemical combinations of it are known. The density of the gas is ig94, and it is soluble in water to the extent of 4i volumes in 100 at 150 C. It boils at 187 degrees below o degreesC. According to Ramsay, the fractional distillation of argon yields traces of other gases having distinct spectra, and to these he gave the names of Neon, Xenon, and Krypton.

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