OXYMURIATIC ACID, or as it is now more correctly termed CHLORINE, from its yellowish green colour, is an elastic gaseous fluid of a pungent disagreeable smell, and highly injurious to animal life, even when largely diluted with atmospheric air. Mixed with hydrogen, and exposed to light, they combine and produce a sour compound called _muriatic acid_ gas; this gas is greedily absorbed by water, which takes up 480 times its bulk, and has its specific gravity increased from 1 to 1.210. Thus dissolved in water it forms the _liquid muriatic acid_ mentioned in a preceding article. Chlorine forms combination, besides, with several other bodies; many of its combinations are termed _oxymuriates_, or more properly, _chlorides_: some of these are extremely useful in bleaching, dyeing, &c. The _muriatic acid_ appears to be the only acid of any consequence into which oxygen does not enter. OXIDE is the combination of oxygen with some base, without being in the state of acid; it is most commonly applied to the combination of oxygen with metals; most of the different rusts of metals are oxides. As oxygen combines with the metals and other bodies in different proportions, its combinations are distinguished by different prefixes, thus: _protoxide_ denotes an oxide containing the least quantity of oxygen: _deutoxide_ the next larger quantity; _tritoxide_ the next; and _peroxide_ the largest possible quantity of oxygen in the compound when it is not acid. For OXYGEN _see forwards_. POT-ASHES and PEARL-ASHES (one of the fixed alkalies) are both impure _carbonates of potash_ obtained from the ashes of innumerable vegetables, over which water is poured which dissolves the salts, and by evaporating the water leaving the salt, a dry powdery white mass is obtained. The chief difference between pot-ashes and pearl-ashes consists in the superior whiteness of the latter, and in the former being of a more dirty colour, and more caustic than the latter; hence it is not so highly saturated with carbonic acid. For many purposes in the arts such caustic potash is to be preferred. QUERCITRON, or AMERICAN-BARK is obtained from the _quercus nigra_ or black oak, a native of North America. It is used for dyeing yellow, and was brought into notice by DR. BANCROFT, who obtained the exclusive privilege of using it as a dye by an Act of Parliament, passed in the 25th year of the reign of George III. SAFFLOWER, _bastard-saffron_ or _carthamus_, is obtained from one or two plants, species of the _carthamus_ genus, natives of the South of Europe and the Mediterranean coasts. This dyeing material consists of two colouring substances, a yellow and a red. The former is of little value, the latter which is soluble in alkalies forms, by precipitation with acids, a beautiful red pigment sometimes used for silk dyeing, but more commonly in the preparation of _rouge_.