Page:Encyclopædia Britannica, Ninth Edition, v. 24.djvu/485

Rh W A X W A X 459 sion indicate a close connexion between refraction and absorption, and Helmholtz has formulated a general theory of dispersion based upon the hypothesis that it may be connected with an absorbing iulluence operative upon invisible portions of the spectrum. Upon this subject, which is as yet little understood, the reader may con sult Glazebrook s &quot;Report on Optical Theories.&quot; 1 The limits of this article do not permit the consideration of the more speculative parts of our subject. We will conclude by calling attention to two recent experimental researches by Michelson, the results of which cannot fail to give valuable guidance to optical theorists. The first of these 2 was a repetition under improved conditions of a remarkable experiment of Fizeau, by which it is proved that when light is propagated through water, itself in rapid movement in the direction of the ray, the velocity is indeed influ enced, but not to the full extent of the velocity of the water (v). Within the limits of experimental error, the velocity agrees with a formula suggested by Fizeau on the basis of certain views of Fresnel, viz., VV ^-2-t&amp;gt; (2), V being the velocity when the medium is stationary. In the case of water, (jti 2 -l)//x 2 = 437. Conformably with (2), a similar experiment upon air, moving at a velocity of 25 metres per second, gave no distinct eii ect. From the result of the experiments upon water we should be tempted to infer that at the surface of the earth, moving through space, the aether still retains what must be coarsely called relative motion. Nevertheless, the second research above alluded to 3 appears to negative this conclusion, and to prove that, at any rate within the walls of a building, the aether must be regarded as fully partaking in the motion of material bodies. (R.) WAX is a solid fatty substance of animal and vegetable origin, allied both in sources and constitution to the fixed oils and fats. From fats or solid oils wax differs principally in its greater hardness and higher melting-point; but in the strictly chemical sense, while oils and fats are glycerides, a true wax contains no glycerin, but is a combination of fatty acids with certain solid monatomic alcohols. Of wax from animal sources there are in commerce beeswax, which forms wax par excellence, Chinese insect wax, and sper maceti. The more important vegetable waxes are Japanese wax, myrtle-berry wax, carnauba wax, and palm wax. Beeswax is secreted by all honey bees, and by them formed into the cell walls, &c., of their comb. It is separ ated by draining the honey, melting the drained comb in boiling water, and collecting the wax which solidifies on the top as the water cools. In this state it is formed into cakes of raw or yellow wax, good examples of which are of a light yellow colour, translucent, with a faint pleasant odour of honey. At ordinary temperatures it breaks with a granular fracture ; and in thin flakes or pellets it softens with the heat of the hand, and can be kneaded between the fingers. Its specific gravity is 960 ; it melts at about 62 C., and solidifies just under its melting-point without evolution of heat. It is soluble in hot ether, essential and fixed oils, benzol, bisulphide of carbon, and chloro form, and to some extent in boiling alcohol, but it is unaffected by water and cold alcohol. In chemical con stitution it contains 10 per cent, of cerin, an ether of O FT O ) cerotic acid and ceryl alcohol, 27 /~&amp;lt; 53 TT f O, and 90 per cent, of myricin ether of palmitic acid and myricyl alcohol, Yellow wax, on account of the colouring matter and other contaminations it contains, is unfit for many uses. The chief of these is candle-making. To remove soluble matter it is first melted over boiling water; and for bleaching it is formed into thin shreds and strips so as to expose the greatest possible surface. So prepared, it is spread out and frequently watered and turned in the direct sunlight, a slow but effective process. To hasten the bleaching action the wax may be mixed with about one-sixth of pure spirit of turpentine; and this preparation, on exposure, by its copious production of ozone, effects in four or five days a bleaching which otherwise would occupy three or four weeks. When the bleaching is complete all trace of turpentine oil will have disappeared. Bleaching may also be effected by chlorine, permanganate of potash, and other chemicals, but these injuriously affect the wax, in some cases forming substitution products which cannot be removed, and which in burning give off deleterious 1 Brit. Ass. Rep., 1886. In this matter, as in most others, the advantage lies with the lectromagnetic theory. See J. W. Gibbs, Amer. Jour., xxiii., 1882. 2 &quot;Influence of Motion of the Medium on the Velocity of Light,&quot; by A. Michelson and E. W. Morley, Amcr. Jour., xxxi. , May 1SS6. fumes. Wax is obtained in all parts of the world where there is vegetation sufficient to support bees ; but it is most largely forthcoming from tropical and subtropical regions. It is subject to extensive adulteration from powdered mineral substances, flour, cheaper waxes, paraffin, &c. Its uses are multifarious ; but it is most largely con sumed in making candles for the religious services of Koman Catholic and Orthodox Greek Christians, and for wax figures and models (see WAX FIGURES). Chinese Insect Wax, or Pe La, is a secretion deposited by an insect, Coccus ccrifcrus, Fabr. , in the twigs of a species of ash, Fraxinus chinensis, Roxb. The wax is, in its origin and the functions it performs in the insect economy, closely related to the lac produced by the allied species of Coccus (see LAC, vol. xiv. p. 181). When separated from the twigs which it encrusts, and purified, it is a hard translucent white crystalline body, similar to spermaceti. It melts at from 82 to 86 C., and in composition consists of cerin, one of the constituents of beeswax. It is little known in European commerce, but forms a highly important article of trade in China and Japan, where it is largely used for candle- making and for medicinal purposes. For SPERMACETI, see vol. xxii. p. 395. Japanese Wax is a hard wax-like fat which now forms an im portant export from Japan, principally to London. It is obtained from the small stone fruits of several species of llhus cultivated in Japan. For the extraction of the wax, which is present to the extent of about 20 per cent., the fruits are ground and treated by either of three methods (1) heating and pressure, (2) boiling in vater, and (3) maceration with ether or bisulphide of carbon. The wax is subsequently bleached, and as it comes into the market consists of yellowish hard cakes, covered often with a fine white powdery efflorescence. It has a resinous unpleasant rancid odour. It melts at about 54 C., and solidifies from melting at 41 C. with evolution of heat which raises the temperature about 5 C. Japanese wax becomes translucent about 12 C. under its melting-point, and when it has newly solidified from melting it can again be liquefied at 42 C., from which the melting-point rises by slow degrees with the lapse of time till it reaches the normal. It is not a true wax, but consists principally of the glyceride palmitin with small pro portions of stearin and disseminated crystals of free palmitic acid. It is largely mixed with and used as a substitute for beeswax, excepting for uses where its rancidity renders it objectionable. Myrtle-Berry Wax is obtained from the fruit of several species of Myrica in the United States, New Granada, Venezuela, the Capo of Good Hope, and other regions. It is a hard greenish substance, with a pleasant balsamic odour. Its melting-point is about 45 C. , and it consists principally of free palmitic acid with a little stearic acid and myristic acid, a very small proportion of these being combined as glycerides. It is consumed principally in the United States in combination with beeswax for candles ; and it is said the Hottentots eat it like cheese. Carnauba Wax is an exudation on the surface of the growing leaves of the carnauba palm, Coryplia cerifera, L., which flourishes in tropical South America. The wax is obtained by cutting off and drying the young leaves, from which it is then shaken as fine dust, and caked by melting either over an open fire or in boiling water. It is a true wax, consisting of ethers of myricyl alcohol and ceryl alcohol with cerotic acid, and its melting-point ranges from 85 to 90 C. Carnauba wax is a substance of considerable commercial importance in Brazil, whence large quantities are sent to Europe for use in the candle-trade and otherwise as a substitute for beeswax. Palm-Tree Wax is an exudation formed on the stems of two South American palms, Ceroxylon anclicola, II. and K., and Klop- 3 &quot;On the Relative Motion of the Earth and the Luminiferous /Ether,&quot; by Michelson and Morley, Phil. Mag., Dec. 1887.