Chemistry and Physics. 93 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. On the Vapor Pressure of reciprocally soluble Liquids. — It 

 has been pointed out by Ostwald that the question whether two 

 liquids are completely miscible with each other or only partially 

 so miscible is in general a question of temperature. Since all 

 vapors are completely miscible at all points above the critical 

 temperature, evidently liquids must be completely miscible at this 

 temperature. Below this temperature, however, a separation may 

 occur. In 1891 Masson showed that there is a temperature at 

 which this separation first occurs and which he called the " critical 

 solution temperature." At this particular temperature the two 

 saturated solutions formed by the liquids have the same composi- 

 tion and the same vapor pressure, and therefore give vapors having 

 identical composition. At this point, consequently, the composi- 

 tion of the liquid must be the same as that of the vapor which is 

 given off on boiling. Below this point, the composition of the 

 distillate obtained from a mixture of two partially miscible liquids, 

 maybe considered, according to the author, as also that of a liquid 

 mixture having, if homogeneous, the same composition as its 

 vapor. — Ann. Phys. Chem., II, lxiii, 336-341, December, 1897. 



G. F. B. 



2. On Electric Energy by Atmospheric Action. — An electric 

 generator has been devised by Warren" whose energy comes 

 from direct atmospheric oxidation. Plates of a special porous 

 compressed graphite are prepared, and about a fourth of each 

 plate is made active by immersion in platinic oxalate, drying and 

 igniting in an atmosphere of hydrogen. When placed in contact 

 with a ferrous sulphate solution, oxidation of the iron by the oxy- 

 gen of the air is effected through the agency of the platinum. 

 The circular lead beam to which these plates are attached sur- 

 rounds a porous diaphragm containing as the negative element a 

 rod of amalgamated zinc, the carbon plates being arranged so as 

 to allow the platinized portion to project above the solution, con- 

 sisting of strongly acidified ferric sulphate. On completing the 

 circuit a strong current is produced, which continues until the 

 complete reduction of the ferric salt has taken place, when the 

 action ceases. On withdrawing the zinc, the platinum surface 

 condenses the atmospheric oxygen and so steadily re-oxidizes the 

 ferrous salt, thus renewing the action. — Chem. JVeios, lxxvi, 200, 

 October, 1897. g. f. b. 



3. On the Significance of Ionic Reactions in Electrochemistry. — 

 In a recent lecture on the bearing of the ionic hypothesis on ana- 

 lytical chemistry, Kuster made some interesting experiments. The 

 electric exchange Cu + h + Fez=Cu + Fe ++ was shown by placing 

 pieces of iron near the top and of copper near the bottom, of a solu- 

 tion of sodium sulphate; on adding a few crystals of copper sul- 

 phate near the copper, a current flows at once from the copper to the 



