382 CHEMISTKY. 



new compounds seem to belong to the rapidly increasing class of ''phys- 

 ical isomers," i. e., liquid or solid bodies whose chemical properties are 

 to be traced to the binding together of molecular groups, the individual 

 members of which occupy relatively difi'erent positions, the groups them- 

 selves acting as chemical units. The molecular volumes of metamers 

 do not favor the hypothesis proposed by Perkin. {J. Chem. Soc, August, 

 1881, xxxix, 409; Nature, October, 1881, xxiv, 542.) 



The rate at which chemical changes progress has been studied by 

 Kayander. He used magnesium plates about 2,000 square millimeters in 

 surface, immersed in various acids, the solutions containing 0.01 of the 

 molecular weight in grams in the liter of water. As to the influence 

 of time, he concludes that the reaction begins at the very moment the 

 I»late is immersed, the same action taking place when two acids are 

 mixed. The influence of temperature is precisely that exercised by it 

 on the diminution of the internal friction of the particles of the liquid 

 against each other. It does not seem to influence at all the chemical prop- 

 erties of the reacting bodies. His figures show that the velocity of the 

 reaction is inversely proportional to the internal friction of the medium. 

 {yature, June 1881, xxiv, 112.) 



Berthelot has stated that the chemical change which occurs wheii an 

 acid soluble in water acts on a soluble base or salt, or vice versa, or when 

 two soluble salts mutually react, is completed in a time not ai)i)reciably 

 greater than is required for completely mixing the two solutions. {Xa- 

 ture, February, 1881, xxiii, 373.) 



Thorpe has called attention to some cases of chemical reaction taking 

 place between solids. Thus, when perfectly dry j)otassium iodide and 

 mercuric chloride, or lead nitrate, or silver nitrate and potassium chro- 

 mate are rubbed together in a mortar, the characteristic color of the re- 

 action appears. {Nature, September, 1881, xxiv, 467.) 



Dewar has discussed the question of the alleged decomposition of the 

 elements in a paper read at York. He concludes thus: "The supposi- 

 tion that the diflferent elements may be resolved into simple constituents 

 and even into a single substance, had long been a favorite speculation 

 Avith chemists; but however probable that hypothesis may appear ajyri- 

 ori, it must be acknowledged that the facts derived from the most pow- 

 erful method of analytical investigation yet devised give it but scanty 

 support." {Nature, September, 1881, xxiv, 468.) 



Strecker has found that for chlorine, bromine, and iodine in the gas- 

 eous state, the ratio of the kinetic energy of the i)rogressive n)otion 

 of the molecules to the total energy is different from that observed with 

 other diatomic gases. These bodies seem therefore to form a group by 

 themselves, their molecules seeming to have a different reciprocal ac- 

 tion. The author doubts the validity of the suppositions of both Max- 

 well and Boltzmann as to the nature of the mobility of the atoms in the 

 gaseous molecule. ( Wied. Ann., 1881, II, xiii, 202.) 



Thomsen has sought to throw some light on the molecular structure 



