REVIEW OF AMERICAN CHEMICAL RESEARCH. VOL. IX. No. 9.
WILLIAMA. NOYES,Editor. REVIEWERS : H. M. Goodwin, W. F. Hillebrand, I,. P. Kinnicutt, H. W. Lawson, G . N. Lewis, H.N. McCoy,
M. T.Bogert, E. M. Chamot, B. S. Cushman, Benton Dales, L.M. Dennis, A. H. Gill,
A. A. Noyes, J. W. Richards, S. P. Sadtler,
J. 0. Schlotterbeck, W. H. Seaman, F.P.Underhill.
GENERAL AND PhYSICAL CHEnISTRY. Determination of Vapor Densities in an Electric Furnace. BY W. NEBNST. Yrans. Am. ECecfrochemical Soc., Vol. 111 ( ~ g y ) . - T h e author describes a resistance furnace formed of an iridium tube, through the walls of which a current of 350 amperes is passed, heatingit up to between 2000' and 2200' C. T h e bulb with capillary tube is also of iridium, shaped after a Meyer vapordensity apparatus. Its capacity is 5 cc. T h e temperature is measured by comparison with a small, incandescent filament. T h e accuracy was tested by volatilizing mercury, whose vapor is monatomic, and for whose molecular weight at 2 0 0 0 ~ was found 2 0 6 and 204. Water, sodium chloride and potassium chloride slaved little dissociation a t 2 0 0 0 ~; carbonic acid gas gave a molalar weight of 44.1, 42.0, 41.9, which shows much less dissdatn than was anticipated, but the measurement was made in J. W. RICHARDS. presencof air in excess. An Exprlmental Study of Some Electrode Effects.
BY H .
M. TORYAND H T.BARNES. Trans. Am. EiectrochemicaC SOC., Vol. III (193 )---Measurements were made of the potential differences OF large number of metals, in pure water free from air, as againsl thesrtattt metal in water charged with either air, oxygen or hydrogen As a rule, the oxygen-charged acted the same as the a i t & g d water. T h e electrode in the gas-charged water was positive 'hothat in the gas-free water in all cases where oxygen was use& but often negative when hydrogen was used. T h e principal m l t d . a r e as follows, the E. M. F. being in volts :
- - 0.74 CadtQie............
Airehargtd to air-fm.
AlU&p@
** **
Iron
to 0.80
*
*
H-charged to air-free. 0.
0.125
-0.036
0.092
-0.175
-.. . ............. .... ......... 0.170 .... - ........ 0.284 to 0.140
Carbn $lamnt. co p a
&pd
** **
0.141
0. 0.
0.
380
Review of American Chemical Research. Air-charged t o air-free.
Lead ............... 0.074 Magnesium.. 0.020 Mercury. 0.068 Nickel .............. o.1gr Palladium 0.205 P l a t i n u m . . .......... 0.212 to 0.226 Silver ............... 0.105 Tin ................. 0.270 Zinc ................ 0.380
........ ............ ...........
H-charged to air-free 0. -0.206 0.
-0.151 -0.640 --0.44j t o +o.goS ~0.082 0.
$0.181
Tests of one metal in one gas against another metal in another gas (all in aqueous solution) gave numerical results corresponding with what would be calculated from above data. J. W. RICHARDS. The Electrolysis of Water. BY J. W. RICHARDSA N D UT. S. LAXDIS. ~i-u7ts. Am. Electrochemical Soc., Vol. I11 (1go3).Attempts were made to electrolyze dilute sulphuric acid in closed glass tubes and where the tubes was inelastic and would not explode, no current could be sent through with a potential of 3.5 volts. On breaking the seal, the current flowed from 0.3 volt upwards. Distilled water, boiled in a platinum dish, allowed no current to pass, but several micro-amperes passed a s soon as oxyhydrogen gas was bubbled into it. A calorimetric experiment was made, nieawring the watt-energy of the current which was setting free oxygen and hydrogen, and also :he sensible heat generated in the electrolyte. T h e difference between the two amounted to an absorption of 1.5 joules per coulomb of electricity passing, or 1.51 volts as the voltage absorbed i n decomposition. Under the microscope, gas was seen to form on the cathode at voltage. down to I .50, but not at I .45. With a cell 8.75 meters long, .d 0 . I per cent. sulphuric acid, the current passing from 0 . 3 t s . 2 5 volts, followed Ohm’s law within the errors of the expenlent, without disengagement of gas. T h e authors explain th by the fact that depolarization, i. e., re-formation of water, byJissolved hydrogen takes place, for such feeble currents, as fas& decomposition, and that in that case, as in refining copper,no voltage is absorbed in decomposition, and the current obeys )hm’s law. Ohni’s law gives the maximum current which can passif depolarizatiori is complete. If depolarization is not complete,Ohm’s law applies only to the portion of the current which is ac:ounted for by depolarization ; the rest of the current causes ultinate decomposition, with an absorption of 1 . 5 joules of energ] for every coulomb passing. J. W. RICHARDS.
Note on Electrical Endosmose. BY W. D. BANCK~FT. Trans. Am. Electrochemical Soc., Vol. I11 (1go3).-The ehdosmose of common salt through a porous diaphragm was largeiy prevented by placing the salt solution in a porous cup, placing a platinuln spiral in the bottom, and dipping the cup just benehth the surface of a caustic soda solution, the cathode being undprneath the
Anabtical Chemistry. bottom of the cup. This made a plane diaphragm of the bottom of the cup, and with this arrangement no chloride could be found in the cathode chamber after running forty minutes ( 2 amperehours). T h e author suggests that with proper arrangement of diaphragms the Hargreaves-Bird process could probably be run without steam, depending only on the water coming through the diaphragm by electrical endosmose. J. W. RICHARDS.
Thermo-Electromotive Force without Difference of Temperature. BY H. s. CARHART. Trans. A m . Electvochemical Soc., Vol. I11 (1go3).-When an electric circuit is composed of two or more metals, the thermo-electromotive force integrated around the circuit vanishes when the whole circuit is at one temperature. When the circuit is partly metallic and partly electrolytic, the author contends that the case is quite different, that changes in the electrolyte tend to limit the duration of the current, that the device as a thermal engine is self-limiting. A concentration cell can thus convert some of the equally diffused heat of its surroundings into electric energy, but it cannot do so continuously and can repeat the process only by having the cycle of operations reversed. T h e author then imagines a concentration cell carried through a complete Carnot’s cycle, and finds that when brought back to its initial condition, work has been done at the expense of the energy of the surroundings. Any voltaic cell with a positive temperature coefficient converts absorbed heat into electric energy. The conclusions are true only if the foregoing premise is true, and if the chemical reactions in the cell are ignored. J. W. RICHARDS. Concentration Changes in the Electrolysis of Brine. BY W. H. WALKER. Trans. A m . ElectrochemicalSoc.,Vol. 111(1go3).A study of these changes in the light of the relative velocities of the sodium and chlorine ions. But, as soon as any sodium hydroxide has been formed, hydroxyl ions conimence to take part in transporting the current with a velocity 2.6 times that of the chlorine ions. Therefore, while at the beginning, 65 per cent. of the salt decomposed comes from the cathode compartment, this proportion increases towards 85 per cent. as the electrolysis proceeds. This is leaving out of consideration the effect of diffusion through the partition. Electrical endosmose through the partition may also have some effect. J. W. RICHARDS. ANALYTICAL CHEIlISTRY. The Estimation of Copper in Ores, Ilattes, Etc. BY 0. H. PACKER.EZectrical Review, 42, 374-376.-Exact details are given for carrying out the aluminum strip ” cyanide method, which the author believes is sufficiently accurate for all commercial work and the best method for the ordinary analyst.
