Gooch and Beyer — Electrolytic Estimation of Lead. 59 



Art. IV. — The Electrolytic Estimation of Lead and of 

 Manganese by the Use of the Filtering Crucible ; by F. A. 

 Gooch and F. B. Beyer. 



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



In a former paper* we have shown that the filtering crucible 

 may be put to advantageous use in an electrolytic cell for the 

 treatment of deposits not compact and adherent enough to be 

 handled rapidly and conveniently by ordinary methods of 

 electro-deposition. Four devices were described : I, a closed 

 cell in which the perforated platinum crucible is adapted to 

 use as an electrode and to nitrations after interruption of the 

 electric current ; II, a closed cell in which the perforated 

 platinum crucible is used as an electrode and in subsequent 

 nitrations without interruption of the current; III, a cell in 

 which the perforated platinum crucible is adjusted to a filter- 

 ing flask for continuous filtration during electrolysis ; IY, a 

 cell in which a perforated porcelain crucible with included 

 electrode of platinum is arranged, like the platinum crucible 

 of III, for continuous filtration during electrolysis. It was 

 shown that by either of the devices described reasonably rapid 

 and accurate electrolytic determinations of copper may be 

 made without the use of rotating motors or expensive apparatus 

 of platinum. In testing these devices, copper sulphate was 

 electrolyzed, with an error ranging between + 0*0003 grm. 

 and —0*0003 grm. upon approximately 0*1274 grm. of copper 

 or 0*5000 grm. of the sulphate. The duration of the elec- 

 trolysis was about thirty minutes in the processes involving 

 continuous filtration and forty-five minutes in the processes in 

 which filtration was begun after electrolysis was completed. 

 The metallic copper deposited upon the cathode was partly 

 compact, partly spongy. In the work to be described the 

 apparatus has been tried in the more difficult determinations 

 of manganese and lead as the dioxides formed upon the anode 

 in very imperfectly adherent condition. 



The Determination of Lead as the Dioxide. 



In depositing lead dioxidef electroly tically, solutions contain- 

 ing nitric acid are employed ; precautions must be taken in 

 regard to concentration of acid, strength of current and tem- 

 perature ; and the liquid is siphoned off before interruption of 

 the current. With the rotating cathode making 600 revolu- 

 tions a minute and a sand-blasted platinum dish for the 

 anode, Exner obtained in ten to fifteen minutes adherent 



*This Journal, xxv, 249, 1908. 



f Smith, Electro-analysis, p. 101, edition of 1907. 



