506 SCIENTIFIC RECORD FOR 1882. 



he used an electro-dynamometer of special construction, consisting of 

 two flat coils, in the center of which a cylindrical coil was suspended 

 from the scale-pan of a balance, the axes of the three coils being coin- 

 cident. As a result the author finds that a current whose strength is 

 equal to one C. G. S, unit decomposes 0.9373 milligram of water per 

 second, and, therefore, a fraction equal to 0.9373 -^ 9, or 0.10415 of the 

 equivalent of any other substance expressed in milligrams. Conversely 

 the current capable of producing in one second the electrolysis of one 

 equivalent of a body expressed in milligrams is 96 amperes. Taking 

 the gram as the unit of weight, the electro-chemical equivalent of water 

 is 9.373 X 10-*. {J. Phys., March, II, i, p. 109.) 



Streinitz has assigned to voltaic polarization the production of the 

 oxygen and hydrogen gases which appear at each of the electrodes 

 when the discharges of a Leyden jar are passed through water. By the 

 aid of a quadrant electrometer he has measured the difference of poten- 

 tial of the electrodes. He finds that when the electrodes are narrow 

 this difference changes sign if the number of discharges does not ex- 

 ceed a certain limit. The same inversion appears after a few minutes 

 with voltaic currents of short duration and disappears when the vol- 

 tameter is completely polarized. {J. Phys., April, II, i, p. 202.) 



Tommasi has given experimental evidence to disprove Bourgoiu's 

 statement that water is not an electrolyte. He maintains that water 

 can be electrolyzed by the current of a very feeble battery, provided 

 that the heat liberated by the battery is equal to that absorbed by the 

 water in decomposing into its elements (69 calories). {Comptes Rendiis, 

 April, xciv, p. 948; Phil. Mag., May, V, xiii, p. 377.) 



Berthelot has given the results of a large number of electrolytic ex- 

 periments in two important papers — one on the limits of electrolysis, 

 and the other on* the electrolysis of hydrogen peroxide. In both he 

 gives the thermo-chemistry of the action which appears to control the 

 results. {Ann. Chim. Phys., September, V, xxvii, p. 110.) 



Gore has investigated minutely the phenomena of the electrolysis of 

 copper sulphate, and finds that in this, as in nearly all cases of elec- 

 trolysis, chemical and electro-chemical forces coexist and operate in- 

 dependently at the same surfaces "of liquid and metal. The greatest 

 obstacle in finding the electro-chemical equivalent of copper is the difii- 

 culty of determining how much the ordinary chemical corrosion is de- 

 creased at the anode or increased at the kathode by the electric current. 

 The method does not admit of a great degree of accuracy, because the 

 chemical corrosion of cojjper, even in a cold neutral solution of copper 

 sulphate, causes a loss of that metal, and prevents the true weight be- 

 ing obtained. Hence the method of measuring the strength of a cur- 

 rent in electric lighting by the electrolysis of a solution of copper sul- 

 phate must be more or less inaccurate. {Nature, March, xxv, p. 473.) 



Bartoli and Papasogli have discovered that when dilute sulphuric 

 acid is electrolyzed with gas carbon positive electrodes, there is formed 



