SULPHURES, or SULPHURETS. Combinations of alkalies, or metals, with sulphur. See page 253. SULPHURETTED. A substance is said to be sulphuretted when it is combined with sulphur. Thus we say Sulphuretted hydrogen, &c. SUPER-SALTS. Salts with an excess of acid, as the supertartrate of potass. See page 215. SYNTHESIS. When a body is examined by dividing it into its component parts, it is called analysis; but when we attempt to prove the nature of a substance by the union of its principles, the operation is called synthesis. SYPHON. A bent tube used by chemists for drawing liquids from one vessel into another. It is sometimes called a Crane. T. TARTRATES. Salts formed by the combination of any base with the acid of tartar. See page 231. TEMPERATURE. The absolute quantity of free calorie which is attached to any body occasions the degree of temperature of that body. See page 81. TENACITY. Is a term used when speaking of glutinous bodies. It is also expressive of the adhesion of one substance to another. TEST. That part of a cupel which is impregnated with litharge in the operation of refining lead. It is also the name of whatever is employed in chemical experiments to detect the several ingredients of any composition. See Re-agent. TEST-PAPERS. Papers impregnated with certain chemical re-agents; such as litmus, turmeric, radish, &c. They are used to dip into fluids to ascertain by a change of colours the presence of acids and alkalies. THERMOMETER. An instrument to show the relative heat of bodies., Fahrenheit's thermometer is that chiefly used in England. (See page 81.) Other thermometers are used in different parts of Europe. For the difference in the scale of these thermometers, see the Table at page 468. TINCAL. The commercial name of crude borax. TINCTURES. Solutions of substances in spirituous menstrua. TORREFACTION. An operation similar to roasting; which see. TRITORIUM. A vessel used for the separation of two fluids which are of different densities. The same operation may be performed by a common funnel. TRITURATION. A chemical operation whereby substances are united by friction. Amalgams are made by this method. TUBULATED. Retorts which have a hole at the top for inserting the materials to be operated upon, without taking them out of the sand heat, are called tubulated retorts. TUNGSTATES. Salts formed by the combination of any base with tungstic acid. See page 229. TUTENAG. An Indian name for zinc. Chinese copper is also called by this name, which is a compound of copper, tin, and arsenic, much resembling silver in colour. V. VACUUM. A space unoccupied by matter. The term is generally applied to the exhaustion of atmospheric air. by chemical or philosophical means. VAPOUR. This term is used by chemists to denote such exhalations only as can be condensed and rendered liquid again at the ordinary atmospheric temperature, in opposition to those which are permanently elastic. VATS. Large chemical vessels, generally of wood, for making infusions, &c. VITAL AIR. Oxygen gas. The empyreal or fire-air of Scheele, and the dephlogisticated air of Priestley. VITRIFICATION. When certain mixtures of solid substances, such as silex and an alkali, are exposed to an intense heat, so as to be fused, and become glass, they are then said to be vitrified, or to have undergone vitrification. VITRIOLS. A class of substances, either earthy or metallic, which are combined with the vitriolic acid. Thus there is vitriol of lime, vitriol of iron, vitriol of copper, &c. These salts are now called Sulphates, because the acid which forms them is called sulphuric acid. VITRIOLATED TARTAR. The old name for sulphate of potass. VOLATILE ALKALI. Another name for ammonia. VOLATILE SALTS. The commercial name for carbonate of ammonia. See page 164. VOLATILITY. A property of some bodies which disposes them to assume the gaseous state. This property seems to be owing to their affinity for caloric. VOLUME. A term made use of by modern chemists to express the space occupied by gaseous or other bodies. U. UNION chemical. When a mere mixture of two or more substances is made, they are said to be mechanically united; but when each or either substance forms a component part of the product, the substances have formed a chemical union, 1 USTULATION. The roasting of ores, to separate the arsenic, sulphur, and whatever else is of a volatile nature that is connected with and mineralizes the metal. When the matter is preserved which flies off, the process is called sublimation; but when this matter is neglected, the operation is called ustulation. W. WATER. The most common of all fluids, composed of 85 parts of oxygen and 15 of hydrogen. See page 96. mineral. Waters which are impregnated with mineral and other substances are known by this appellation. These minerals are generally held in solution by carbonic, sulphuric, or muriatic acid. WAY dry. A term used by chemical writers when treating of analysis or decomposition. By decomposing in the dry way, is meant, by the agency of fire. WAY humid. A term used in the same manner as the foregoing, but expressive of decomposition in a fluid state, or by means of water, and chemical re-agents, or tests. WELDING HEAT. That degree of heat in which two pieces of iron or of platina may be united by hammering. WOLFRAM. An ore of tungsten containing also manganese and iron. WORM-TUB. A chemical vessel with a pewter worm fixed in the inside, and the intermediate space filled with water. Its use is to cool liquors during distillation. See Refrigeratory. WOULFE'S apparatus. A contrivance for distilling the mineral acids and other gaseous substances with little loss; being a train of receivers with safety pipes, and connected together by tubes. For a full description of this most useful apparatus, see Philosophical Transactions for 1767, and Chem. Catech. note 2, page 180. Z. ZAFFRE. An oxide of cobalt, mixed with a portion of siliceous matter. It is imported in this state from Saxony. ZERO. The point from which the scale of a thermometer is graduated. Thus Celsius's and Reaumur's thermometers have their zero at the freezing point, while the thermometer of Fahrenheit has its zero at that point at which it stands when immersed in a mixture of snow and common salt. See Notes, page 81. |