212 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



equation, which may be called Esson's equation, on being 

 applied to the numerous exact observations recorded by 

 Gladstone, leads Dr. Mills to the conclusion that 54 per 

 cent, of the discordances between the theory and the obser- 

 vations are such as would on the average be found in any 

 very good analytical work, 33 per cent, occur in ordinary good 

 analytical works, and the remaining 13 per cent, lie on the 

 average within the limits allowable in such estimation of 

 colors as Dr. Gladstone made. The ordinary equations of 

 chemistry represent the result of distributing atomic weight, 

 and give no account of the work done. Esson's equation 

 and conclusions worked out by Gladstone, on the contrary, 

 represent a dynamic process as well as the distribution of 

 weight. 7 A, XL VIII., 246. 



WATER OF CRYSTALLIZATION. 



Professor Guthrie states that the absorption of heat, which 

 occurs when the salt is dissolved in a liquid, depends not 

 only on the relative specific heat of the salt in the liquid, but 

 also on the molecular ratio of the resulting solution. This 

 ratio declares itself, first, optically by the refractive index; 

 second, by the density; third, by the heat absorbed when a 

 saturated solution is mixed with the medium ; and, fourth, by 

 the heat absorbed when the salt itself was dissolved in a cer- 

 tain quantity of the medium. The conclusion which he draws 

 from his observations is that every salt soluble in water is 

 capable of uniting with water in a definite ratio, forming 

 definite solid compounds of distinct crystalline forms and con- 

 stantly melting and solidifying temperatures. 12 A, XL, 59. 



vidal's apparatus (ebulliscope) for the determination 

 of the amount of alcohol in wine, etc. 



The following instrument, an improvement on that orig- 

 inally devised by Yidal, it is claimed will indicate accurately 

 the percentage of alcohol in liquids in less than ten minutes, 

 using but little of the liquid. It depends upon the fact that 

 sugar, resin, citric and tartaric acids do not change the boil- 

 ing point of alcohol in which they may be dissolved, and 

 consequently the determination of the boiling point will show 

 the amount of alcohol present in an aqueous liquid. It con- 

 sists of a conical boiler, closed at the top with a screw-cap 



