CHEMISTRY. (PHYSICS.) 



151 



names, expressing other than a distorted view 

 of the constitution of all but a few of the most 

 simple of organic bodies, are impracticable by 

 reason of their length and complexity. Hence, 

 to avoid the distortion inseparable from the use 

 of any single structural name for an organic 

 body, the only expedient is the assignment to 

 each body, in proportion to its complexity, of 

 an indefinite number of structural names a 

 proceeding almost tantamount to not assigning 

 it any particular name at all. With a view to 

 the prompt mental association of object with 

 name, brief empiric names, based on the origin 

 and properties of bodies, are, wherever prac- 

 ticable, to be preferred to structural names. 



Chemical Physics. Berthelot and Vieille have 

 experimented to obtain the specific heat of gas- 

 es at high temperatures. Their experimental 

 data were obtained by the combustion of cyan- 

 ogen mixed with sufficient oxygen to convert 

 it into carbon monoxide and nitrogen, two gas- 

 es which have sensibly the same specific heat. 

 From the pressure developed in the explosion, 

 the temperature referred to the air-thermome- 

 ter was calculated; and, from the total quantity 

 of heat produced and the temperature, the spe- 

 cific heat (at constant volume) of the resulting 

 gaseous mixture was derived, and hence the 

 specific heat of either of the resulting gases. 

 The results of the experiments showed that the 

 specific heat increases rapidly with the tem- 

 perature at such a rate that, in passing from 

 0. to 4,500 C., the mean specific heat of 

 the elementary and simple gases nearly doubles. 

 There is, however, another group of elementary 

 and of compound gases to be considered. Re- 

 gnault showed that the specific heats of chlo- 

 rine, bromine, and iodine were higher than that 

 of the other elements; and this specific heat is 

 closely the same as that of the compound gases 

 which are formed with a contraction of one 

 third in volume, as water, nitrogen monoxide, 

 and carbon dioxide. The mean specific heat 

 of chlorine at constant volume was found to 

 be, at 1,800, nearly three times that of hy- 

 drogen. Further experiments showed that, 

 the mean specific heat of water-vapor between 

 130 C. and 230 0. being 6'65 at constant vol- 

 ume, it is more than doubled at 2,000 and 

 tripled at 4,000. On comparing the element- 

 ary specific heat of the vapor of water with 

 that of its constituent elements, it appears that 

 the former value is in excess of the latter at 

 2,000 0. by 7, and at 4,000 0. by 5-1. This 

 excess represents a double work, that of the 

 molecular disaggregation of the compound gas, 

 and that of its chemical dissociation. Of car- 

 bon dioxide, the mean specific heat was found 

 to more than triple, and the elementary specific 

 heat to quadruple between C. and 4,300 0. 



Schramm has studied the influence of light 

 on the reactions of certain bromine compounds. 

 If the solution of bromtoluene in chloroform is 

 feebly colored with bromine and then placed in 

 the dark, no action takes place. But light de- 

 colorizes it at once, with evolution of hydro- 



gen bromide. The action of light upon the 

 bromination of ethylbenzine is of particular 

 interest, because not only is this hydrocarbon 

 under these conditions highly sensitive to the 

 action of light, but it yields different substitu- 

 tion products according to the intensity of the 

 light acting. If ethylbenzine is slightly col- 

 ored with bromine, no decolorization takes 

 place in the dark; but it loses its color at 

 once in daylight, or when exposed to burning 

 magnesium. If a molecule of bromine be made 

 to act on a molecule of ethylbenzine in diffused 

 light, a colorless liquid product is obtained which 

 does not solidify at 20. On distillation, HBr 

 is evolved, and a distillate is obtained at be- 

 tween 140 and 190, a dark-brown residue re- 

 maining in the retort. No bromine product 

 of constant boiling-point could be isolated. 

 When the ethylbenzine is treated with a mo- 

 lecule of bromine in direct sunlight the reaction 

 is violent, and the final product is a-phenyl- 

 bromethyl ; if in full sunlight, phenyl-brom- 

 acetene ; if in diffused daylight, dibrornstyrene. 

 It has been noticed that mixtures of salts 

 may often have a f using-point lower than that 

 of either of the constituent salts ; and a like 

 property having been observed in certain metal- 

 lic alloys, Dr. Guthrie, who has been making 

 the phenomenon a subject of special researches, 

 has given it the name of Eutexia, and desig- 

 nates a substance exhibiting such a property as 

 a eutectic mixture or alloy. A eutectic sub- 

 stance may. be defined as a body composed of 

 two or more constituents, present in such a 

 proportion to one another as to give to the re- 1 

 sultant compound body a lower temperature' 

 of liquefaction than that given by any other 

 proportion. This temperature of liquefaction 

 must, therefore, be lower than that of any of 

 the constituents of the compound ; and it is 

 plain that those substances only can be eutec- 

 tic which we can obtain both as liquid and 

 solid. Wljen a dilute aqueous saline solution 

 is cooled below the freezing-point of water, a 

 point will be reached, if the cooling is contin- 

 ued, where ice will be formed. If the ice is 

 removed, and pressed or carefully drained, it 

 will be found to consist of nearly pure water, 

 the liquid which has drained away being a 

 strong saline solution, which had become me- 

 chanically entangled among the crystals of ice 

 during solidification. As the brine which re- 

 mains is further cooled, ice will continue to 

 form till a point is reached at which the tem- 

 perature refuses to fall until the whole of the 

 remaining mother-liquid has solidified. The 

 solid result of this process, called a cryohy- 

 drate, possesses physical properties different 

 from those of either the ice or the salt from * 

 which it is formed. If the solution is saturated 

 when we begin to cool it, a deposit of surplus salt 

 takes place till the mother-liquor has reached a 

 condition of normal density ; but the tempera- 

 ture of the formation of the cryohydrate is the 

 same as in the former case. This temperature 

 is identical with the lowest temperature that 



