Gooch and Burdich — Electro-Analysis. 107 



Art. X. — Electrolytic- Analysis with Platinum Electrodes 

 of Light Weight ; by F. A. Gooch and W. L. Burdick. 



[Contributions from the Kent Chemical Laboratory of Yale Univ. — ccxxxii.] 



The present cost of platinum, which is the ideal substance 

 for anodes and cathodes in most processes of electrolytic 

 analysis, is now so considerable that. many attempts have been 

 made to substitute for that metal other less expensive materials. 

 Medway* has shown that a crucible of silver may replace the 

 platinum crucible used as a rotating cathode in determinations 

 of copper ; Shermanf has proposed the use of tin vessels for 

 cathodes in several processes ; Turrentine^: has shown that 

 dishes of graphite saturated with paraffine may be of service 

 for approximative purposes ; and other devices have been 

 suggested. No material has, however, been found so suitable 

 for general electrolytic work as platinum. Our attention has 

 been directed, therefore, to the devising of forms of apparatus 

 which, while suited to the purposes of exact electrolytic 

 analysis, require the least amount of this expensive metal. 

 We have experimented, first, with thin films of platinum 

 deposited upon glass, and, secondly, with diminutive electrodes 

 of platinum gauze or foil of ordinary thickness and stability. 

 All of these electrodes we're designed for use as rotating 

 cathodes, with a view to securing the best and most rapid 

 deposition. 



Electrodes of Platinized Glass. 



The ordinary method of making gas-electrodes (which con- 

 sists in painting glass with the usual platinizing solution, drying 

 the coating for a long time in the current of warm air above 

 a low flame, and finally heating strongly, even to redness) 

 does not produce films of platinum sufficiently adherent for 

 service as the cathode in the electro-deposition of metals. Such 

 films flake off in the electrolytic process and are removed from 

 the glass when the deposited metal is subsequently dissolved by 

 a suitable reagent. It was found, however, that a much more 

 1 closely adherent film may be obtained when a viscous mixture 

 of glycerine and dry chloroplatinic acid is substituted for the 

 usual plating solution. The mixture is applied by means of an 

 asbestos swab to the glass previously raised to a temperature suffi- 

 cient to volatilize the glycerine immediately, and the resulting 

 film of metal is burned into the glass at the softening point of the 

 latter. Various forms of electrode suitable for use as rotating 



*This Journal (4), xviii, 180. 



t Jour. Am. Chem. Soc., xxix, 1065. 



X Trans. Am. Electrochem. Soc, xv, 505, 1909 ; xvii, 303, 1910. 



