Sciencemadness Discussion Board

Lead cathode purity

If6was9 - 8-6-2003 at 07:21

In this hive thread here
https://www.the-hive.ws/forum/showflat.pl?Cat=&Number=43...
in the Chemical Reviews article it says:
Quote:

The purity of the cathode is of prime importance. It has been demonstrated (333, 334) that when lead is used as a cathode, its reducing power is nil when there is present as little as 3 mg. of copper, 0.5 mg. of silver, or 0.04 mg. of platinum per square decimeter of lead surface. The difference between 99.9 per cent lead and 99.99 per cent lead is often enough to cause failure in an electroorganic reduction (320). All leads, tabs, and connections of a metal different from the cathode were shown to be deleterious to the cathode activity.


Its interesting to compare this to this Japanese patent abstract which discusses the use of lead alloy cathodes:
Quote:

PAT-NO: JP406057471A

DOCUMENT-IDENTIFIER: JP 06057471 A

TITLE: ELECTROCHEMICAL PROCESS FOR REDUCING OXALIC ACID TO
GLYOXYLIC ACID

PUBN-DATE: March 1, 1994

INVENTOR-INFORMATION:
NAME COUNTRY
SCHARBERT, BERND N/A
BABUSIAUX, PIERRE N/A

ASSIGNEE-INFORMATION:
NAME COUNTRY
HOECHST AG N/A

APPL-NO: JP05122838

APPL-DATE: May 25, 1993

INT-CL (IPC): C25B003/04 , C07C051/00 , C07C059/153

US-CL-CURRENT: 379/177

ABSTRACT:

PURPOSE: To produce glyoxylic acid at a good current efficiency by using an
aq. oxalic acid soln. contg. a trace amt. of a mineral acid or org. acid and
salts of specific metals as an electrolyte and executing electrolytic reduction
using electrodes consisting essentially of Pb.

CONSTITUTION: The Pb alloy cathode contg. 80 to 99.9 wt.% Pb and 20 to 0.1
wt.% at least one kind of the metals among Sb, Sn and Cu, and the Pb anode are
immersed into the electrolyte of -20 to +40

COPYRIGHT: (C)1994,JPO




Putting this number JP6057471 in here http://ep.espacenet.com/

gives the following abstract:
Quote:

The present invention describes a process for preparing glyoxylic acid by electrochemical reduction of oxalic acid in aqueous solution in divided or undivided electrolytic cells, wherein the cathode comprises from 50 to 99.999% by weight of lead and the aqueous electrolysis solution in the undivided cells or in the cathode compartment of the divided cells in addition contains at least one salt of metals having a hydrogen overpotential of at least 0.25 V, based on a current density of 2500 A/m2, and a mineral acid or organic acid. The process according to the invention has the advantage that a highly pure, expensive lead cathode can be dispensed with and industrially available lead-containing materials can be used, for example alloys which, in addition to lead, comprise at least one of the metals V, Sb, Ca, Sn, Ag, Ni, As, Cd and Cu. Periodic rinsing with nitric acid can be dispensed with.


Its might be that the addition of a metal salt having a hydrogen overpotential of at least 0.25 V is used to plate out a pure metal layer on the cathode.

[Edited on 8-6-2003 by If6was9]


These are the equivalents in languages other than Japanese:

US5395488, BR9302036, CA2096901, DE4217338, EP0578946

http://ep.espacenet.com/



[Edited on 8-6-2003 by If6was9]

Organikum - 22-6-2003 at 10:13

If I interpret this right, this discloses an kind of "in situ" electroplating process which allows the use of a inpure cathode, yes? Probably this will beat every "pure metal" cathode as this purity can be only relative. (for the amateur this might make such electrochmical processes possible which have been out of reach by now...)

Is this portable to other electrochemical synthesises with other metals for the cathode? Yes, I guess - what speaks against it?

But organic electrochemistry is such a wonderanimal like the Grignard - often talked about but seldom seen in use.... ;)