mical (kemikal)

and n. [Earlier chym ical; Not only do worms aid indirectly in the chemical disintegration of rocks, but there is good reason to believe that they likewise act in a direct and mechanical manner on the smaller particles. Darwin , Vegetable Mould, p. 246. Also chemic . Chemical acetification. See acetification. -Chemical action. See action. - Chemical affinity, elective affinity, names formerly used for chemical force, and implying a property inherent in atoms of selecting other atoms with which to unite, or of preferring one combination to another. - Chemical analysis, the resolution of complex bodies into their elements. It is either quali tative or quantitative. Qualitative analysis consists in the determination of the component parts merely as re spects their nature, and without regard to their relative proportions. Quantitative analysis consists in the min at i on of the relative proportions of the components.Chemical black, bronze. See black, bronze. - Chemical change, as distinguished from physical change, a change which destroys the identity of the substance affected. A physical change is manifested without lo of identity by the substance. Thus, a ma of copper may be reduced to fine particles, drawn into wire, melted and cast into ingots or charged with electricity, without losing its identity as copper. But if copper is put into nitric acid, it di olves and is converted into another substance, copper nitrate. The copper, in consequence, has lost its identity, and has undergone a chemical change. - Chemical combination, the intimate union by chemical force of two or more elements or compounds to form a new compound differing in properties from either of its constituent bodies. It differs from mechanical mixture in that each element of a chem ical combination has a certain fixed and invariable com bining proportion, whereas mixture of substances can mechanical mixture the particles of each of its ingredients can usually be identified and separated by mechanical means; in a chemical combination the constituents are so blended that they cannot be identified. Thus, if chlorin and hydrogen gas are mixed in any desired proportion, the chlorin in the mixture will be evident by its characteristic color and odor. But if this mechanical mixture is exposed to strong light, a chemical combination takes place rapidly between the two gases, with evolution of heat. They combine, however, only in exactly equal volumes, and if an exce of either is present it remains uncombined. In the new compound, hydrochloric acid, chlorin cannot be detected by either color or smell, nor be isolated except by chemical means. - Chemical decomposition, the separation by chemical force of the component parts of bodies from one another, or the resolution of bodies into their elements. - Chemical equation, a symbolic expre ion used to represent a chemical reac with varying amounts of ingredients. In tion. The reagents, or bodies which enter into the reac tion, form the left-hand member of the equation, and the resultants of the reaction form the right-hand member. Thus, the fact that calcium chlorid and sodium carbonate foregrought together, ispred by the following equation: when in solution on each other, CaCl2 + Na2CO3 = CaCO3 + 2NaCl. This is a true equation in the algebraic sense, because the value of the two members is the same. Since matter is indestructible, nothing is lost in the reaction, and the weights of calcium chlorid and sodium carbonate which reacted must be precisely the same as the combined chemical weights of the resultant calcium carbonate and sodium chlorid. - Chemical equivalent, extinguisher, ferment, fire-engine, etc. See the nouns. - Chemical force, the force which binds together the atoms in a molecule, and causes chemical changes when di imilar molecules are brought within the sphere of its action under proper conditions. - Chemical formula, a symbolic expre ion used to represent the composition of a substance. In the formulas now generally adopted by chemists each elementary substance is indicated by the first letter or letters of its name, called its chemical symbol; and to expre the compounds of the elements, their symbols are arranged together, each denoting a single atom, and small numbers are written after a symbol and a little below (sometimes, and formerly always, above) the line, in dicating how many of them in the means 2 atoms of hydrogen united with 1 of oxygen, forming the compound water; KHO means 1 atom of pota ium (kalium), 1 of hydrogen, and 1 of oxygen, form ing the compound pota ium hydrate; and so on. If a number is placed at the beginning of the formula, it multiplies the entire formula like an algebraic coefficient; atoms element exist thus, 2H2O means 2 parts of molecules of water. So, too, a small number placed after a parenthesis multiplies the portion included; thus, Ca3(PO4)2 denotes 3 atoms of calcium combined with 2 equivalents of the radical PO4, forming tri calcium phosphate or bone phosphate. Chemical formulas are of two kinds, empirical and ration al. An empirical formula expre es simply the relative number of atoms of the elements present; a rational formula expre es not only the relative number of atoms, but also some conception of the mode of union of the atoms, the groups of radicals contained in the substance, the cla to which it belongs, etc. Thus, the empirical for mula of acetic acid is CoH402. Its rational formula (CH3 CO.OH) indicates that it may be regarded as made up of the and so suggests to the chemist many of its properties and radicals methyl (CH3), carbonyl (CO), and hydroxyl (OH) reactions. See graphic formula, under graphic. - Chemical harmonicon, hygrometer. See the nouns.Chemical kinetics, the science which treats of the phe nomena of bodies or systems of bodies when chemically active. Chemical match. See match . Chemical paper, paper used or suitable for use in the operations of chemistry, as litmus paper, etc. - Chemical rays of the spectrum. See spectrum. - Chemical statics, the science which treats of the phenomena exhibited by chem ical bodies or systems of bodies in equilibrium. chemicals. chemic a led (kem'i-kald), a. [ [Rare.] IMG:content-0235.jpg:[blocks in formation] chemically (kem'i-kal-i), adv. In a chemical manner; according to chemical principles; in a chemical sense; by a chemical proce or operation: as, a chemically active substance; a surface chemically clean.