Bandil (Hive Bee)
05-17-03 17:15
No 433722
      Practical electrolysis chamber construction  Bookmark   


Swim was pondering on some construction ideas for membrane separated electrolysis chambers.

One ide was to take two L durable plastic containers(with an open top), that where formed like a perfect square. Then cut a hole in one of the sides of each container. The holes should be identical. Then a suitable exchange membrane would be glued  to cover one of the holes on cover it completely. Then the other container would be glued onto to the membrane to cover the hole. Then one would have a to compartment dived cell. Now for some performance questions:

1) The binding glue:
What kind of glue would be appropriate for this kind of work? I could imagine that regular epoxy glue would have a hard time in this kind of harsh environmet. Maybe cyanoacrylate would be more usable? It definately would make it alot easier using glue than using some kind of "press together mechanism".

2) The membrane.
If this system is built, the membrane cannot be replaced without rebuilding the whole lot. If a good "professional" cation-exchange membrane is purchased, how long will it last? For a single reduction, a couple of times or indefinately? I really have no idea on how long lasting such membranes are.

3) The plastic containers
What type of plastic should be used? There are often some evil solvents in contact with these, so it's essential to pick some good plastic. Maybe it should even be teflon coated metal in order to be really inert?



Cops are not there to help you, they're there to bust you.
(Hive Addict)
05-17-03 18:47
No 433728
      Glass is the best choice.  Bookmark   

I have found out that plastic containers usually arent chemically inert enough to perform organic electroylsis reactions especially from the heat of the reaction. I would use glass beakers or containers. I have also looked into electrolysis for reduction and found some useful patent #s on Google.

Here are the recent U.S. patents on Ion-exchange membranes:

6,359,019: Graft polymeric membranes and ion-exchange membranes formed therefrom
6,350,925: Perhaloethyl aromatic compounds and perhaloethenyl aromatic compounds therefrom
6,344,326: Microfluidic method for nucleic acid purification and processing
6,338,913: Double-membrane microcell electrochemical devices and assemblies, and method of making and using the same
6,337,120: Gasket for layer-built fuel cells and method for making the same
6,330,471: Iontophoresis electrode device
6,328,885: Current-efficient suppressors
6,328,875: Electrolytic apparatus, methods for purification of aqueous solutions and synthesis of chemicals
6,322,914: Method and apparatus for distributing water in an array of fuel cell stacks
6,322,690: Chemical method
6,315,886: Electrolytic apparatus and methods for purification of aqueous solutions
6,313,285: Purification of plasmid DNA
6,312,578: Method for extracting amine compounds from a liquid medium
6,300,381: Acid-base polymer blends and their application in membrane processes
6,284,124: Electrodeionization apparatus and method
6,274,020: Electrodialysis membrane and gasket stack system
6,268,532: Sulfonated perfluorovinyl functional monomers
6,265,224: Sample processing method using ion exchange resin
6,258,861: .alpha.,.beta.,.beta.-trifluorostyrene-based composite membranes
6,254,762: Process and electrolytic cell for producing hydrogen peroxide
6,248,469: Composite solid polymer electrolyte membranes
6,242,261: Assessment of ion availability in heterogeneous media using ion-exchange membranes
6,242,123: Solid polyelectrolyte membrane for fuel cells, and method for producing it
6,241,980: Sample processing method using ion exchange resin
6,235,186: Apparatus for producing electrolytic water
6,225,368: Water based grafting
6,221,923: Cross-linking of modified engineering thermoplastics
6,203,687: Method for shutting down an electrolysis cell with a membrane and an oxygen-reducing cathode
6,194,474: Acid-base polymer blends and their application in membrane processes
6,187,468: Electrodes for fuel cells
6,187,201: System for producing ultra-pure water
6,171,719: Electrode plate structures for high-pressure electrochemical cell devices
6,130,175: Integral multi-layered ion-exchange composite membranes
6,120,673: Method and device for regenerating tin-plating solutions
6,109,852: Soft actuators and artificial muscles
6,103,414: Blend membranes based on sulfonated poly(phenylene oxide) for polymer electrochemical cells
6,103,195: Micro-volume spin columns for sample preparation
6,103,075: Linear electrochemical conductor element
6,090,258: Ion-exchange spacer and processes for the preparation thereof
6,080,820: (Fluorovinyl ether)-grafted high-surface-area polyolefins and preparation thereof
6,080,298: Method for electrolysing a brine
6,077,434: Current-efficient suppressors and method of use
6,074,827: Microfluidic method for nucleic acid purification and processing
6,074,812: Method for desalting and dewatering of silver halide emulsions by electrodialysis
6,059,857: Ultrapurification of organic solvents
6,051,124: Zeta-potential determining apparatus
6,045,938: Linear electro chemical conductor element, process for its manufacture and apparatus for its use
6,045,684: Process and apparatus for the production of an aqueous solution of hydrogen peroxide
6,039,852: Bipolar plate for filter press electrolyzers
(Hive Addict)
05-17-03 20:40
No 433747
      Does electrochemical even work?  Bookmark   

does it even work? anyone had any practical effective xp w/ this?

Infinite Radiant Light - THKRA
05-17-03 20:42
No 433748
      Why not concentric vessels?  Bookmark   

Mount one cell within the other. Unglazed terracotta pots are reputed to work but their electrical resistance must be  high.

An idea is to construct the inner vessel by wrapping a cylindrical frame with goretex. This will give maximum membrane area (well almost) for the volume of electrolyte. This and circular geometry should create low electrical resistance: less heating and less voltage drop across the membrane.

Thinking about using clothing goretex put through a hot wash cycle with loads of detergent to remove the water repellent impregnation. The nylon laminate increases the strength of the membrane but not sure how this will react with whatever electrolyte (any ideas?). Goretex itself is expanded PTFE and chemically resistant, pore size around 20.

Making an SCE reference electrode looks fiddly but possible. For the counter electrode, I've been thinking about a graphite electrode mounted centrally in the inner cell. Several working electrodes could be mounted around the outside of the outer cell. Depending on the metal, the outer cell itself could form the working electrode. Wouldn't be too hard to find/make a suitable copper/lead/silver pot.

Any thoughts on this?
05-17-03 21:01
No 433749
      Does it work?  Bookmark   

All this sheep gut condoms with Mongolian silver dollar electrodes and a car battery sounds like pure BS to me. No one seems to have been successful with the kitchen electrochemistry recipes: I think this is more because the recipes are wrong or not detailed enough rather than 'it can't be done'.

There are loads of references to successful electrochemical reductive amination etc.

There seem to be many critical variables such as electrode composition, preparation and size, electrolyte composition, temperature, voltage and current and cell construction.

Proper setups do work, Frankenstein experiments do not.
(Hive Addict)
05-17-03 21:06
No 433750
      membrane possibilities  Bookmark   

In the industry, they use DuPont's Nafion, a thin porous plastic-like sheet to allow ion exchange and create current. This is obviously not easily obtainable (or cheap). Could porous plaster (plaster of paris) be molded and allow ion exchange? Other ideas are cork, cotton balls stuffed in a tube between the cathode and anode compartments, or salt bridges.
(Hive Bee)
05-17-03 21:16
No 433753
      Membranes  Bookmark   

Plaster of paris gets pretty soft and crumbly when wet. Why not just go with the plant pot method?

How reactive is cork? Might be good for the plug in the bottom of a reference electrode assembly.
(Hive Addict)
05-17-03 21:18
No 433754
      Organ Morgan you are correct  Bookmark   

Electrochemistry really does need to be exact. Current, voltage, temperature, anode and cathode choice selection DOES matter. You can't just stick two nails in a solution and hook it up to a car battery overnight to perform a succesful oxidation, it just wont work. You need a good adjustable power supply, watching the temperature carefully, and many other variables.

Promising Idea for MDP2NP->MDA synth, using NaNO3 salt bridge for electrolysis.
Electrochemical Cell For Reduction
Although I have seen many references to the use of electrochemical cells, the construction of them I have yet to see thoroughly described or for that matter where they can be purchased. This doesn't mean they are impractical, because for clandestine chemistry where the most reliable reduction reagents are watched like a hawk, electrochemical reductions could be the next breakthrough.

The cells are basically a container divided by some material which will allow charged ions to pass and therefore allow electricity to flow. The membrane also halts the flow (or reduces it considerably) of the material being reduced. This is necessary because if the membrane wasn't there, the reduced product could travel to the other electrode and become oxidized. The membranes are made of such materials as sintered glass, cellophane, porous ceramic plates etc.

This procedure was written for the analogous nitrostyrene which would lead to amphetamine. It should work equally well for MDA[46].

207g (1 mole) of the nitrostyrene is dissolved with a solvent prepared by mixing one liter of ethanol with 500ml of acetic acid and 500ml of 12N sulfuric acid. The solution is placed in the cathode compartment of a divided electrolytic cell containing a mercury, copper or metal of similar nature as the cathode electrode. The anode can be made of lead. 3N sulfuric acid is placed in the anode compartment. Current is passed equaling ~0.2 amperes/cm2 of cathode surface. The temperature is kept between 30-40C during the electrolysis until at least 8 Faradays of electricity have passed through the solution.

The number of square centimeters of your cathode surface (count both sides if both sides are in contact with the solution) times 0.2 is the amount of current you need flowing through your cell. 1 Faraday is equal to 96485.309 coulombs/mole of electrons and 1 Ampere is equal to 1 coulomb/second. The amount of time in hours the reaction should be run is then 771882.5 divided by the number of Amperes divided by 3600. If you have a total cathode electrode area of 40 cm2 then you need 8 Amperes running through your cell for 26.8 hours.

Remove the ethanol and ethyl acetate present through distillation (quit distilling when the temperature approaches 100C). Basify the remaining solution with 25% NaOH and extract the MDA from the solution with 3 portions of ether (or toluene or methylene chloride). Wash the extract with several portions of calcium carbonate solution, water and then dry with magnesium sulfate. Filter out the drying agent. Pass HCl gas through the solution until no more precipitate is formed. Filter the crystals and wash with ether and allow to dry.

Salt-bridge cell idea for reduction of MDP2NP to MDA
(Chief Bee)
05-17-03 21:23
No 433756
      Salt bridge amperage  Bookmark   

How much current can you push through a simple salt bridge? Wouldn't that have a too high resistance?
(Hive Addict)
05-17-03 21:43
No 433758
      Plenty  Bookmark   

Saturated salt solutions, or even slightly saturated salt solutions, are very strong conductors of electricity. So resistance is pretty low.
(Chief Bee)
05-17-03 21:48
No 433759 much is that in kilo-ohm?  Bookmark   

Good conductors compared to what? Could you give an approximate figure in kohm instead?
(Hive Bee)
05-17-03 21:49
No 433760
      Salt bridge  Bookmark   

That's a setup to measure the overvoltage of zinc against a hydrogen cathode isn't it? In that case, the current flow would be negligable and the resistance of a salt bridge unimportant.

If you want to push the reaction the other way, resistance might be too high.

Is hydrogen overvoltage the main criteria for electrode choice?
(Hive Bee)
05-17-03 21:54
No 433762
      salt water conductivity  Bookmark   

I remember from somewhere that a 2M, strong electrolyte solution has 10% of the conductivity of metal.
(Hive Addict)
05-18-03 01:32
No 433796
      membranes for electro  Bookmark   

Many of the usual plasticfoils can be used as cell dividers. One patent named PVC for example another PP. Depends on temperatures and electrolyte used. A clay pot perhaps in very hot conditions and also there fritted glass or glassfibre filters are preferable.
Design: the two boxes not glued together but hold together by springloaded screws  and a teflon (filled PTFE) seal holds the membrane.

Tip: many plasticfoils show no membrane qualities at first sight - but if you stretch them a little bit they work perfect. Try it!
(PVC-Analog Taste-Tester)
05-18-03 08:11
No 433855
      putty epoxy..  Bookmark   

Chemically, epoxy putty is some mean stuff. I've tested concentrated H2SO4, glacial acetic, etc. on it, and it refuses to break down. If you want to fix an anode/cathode in a glass cookie jar, then I highly recommend putty epoxy. Peace!cool

Love my country, fear my government.
05-18-03 11:56
No 433901
      membranes  Bookmark   

the electrochemical reduction of nitroalkenes in Ber. 124, 2303 (1991) was carried out with  membranes from glas frites  (G4)

Post 421272 (Vitus_Verdegast: "electrochemical reduction of nitroalkenes", Chemistry Discourse):
(Hive Addict)
05-18-03 20:02
No 433970
      hmmm no experimenters?  Bookmark   

I have the entire 8 vol set of electrochemistry sitting on my bookshelf... that's about 8 projects away from being cracked open..

  So i wondered who actually sucesssfully used this method? Since one of my more respected biochem buddies had no joy /w palladium electrodes and H2 reduction.. and he is a Membrane Filtration Specialist w/ all the stuff on hand!

Infinite Radiant Light - THKRA
(Hive Bee)
05-20-03 01:38
No 434226
      lets see now. Nafion is expensive.  Bookmark   

lets see now. 

Nafion is expensive. but so is everything.
AND i have given up on synthesizing any of the complexed sulfonates that are called cation/anion etc.
couldn't i just pee in a cup and stick it in the blender on frappe? lots of foam should do it.

then you must construct a membrane and apply the IONx to it
i like the bridge idea.
conditions may have to rather exact but then if this were sand castles everyone would want to play. and the sharks couldn't feed properly.
05-20-03 13:24
No 434312
      glass frit separator  Bookmark   

roger2003: Do you have any more information on their setup, glass frit isn't mentioned in VV's post?

Chemcast G4 is a zirconia-aluminia glass (alkali and thermal resistant).

Is glass frit the same as sintered glass?

HRH The Prince of Wales and Earl of Chester, Knight of the Garter, Rogerer of Servant Girls
05-20-03 14:10
No 434318
      All about glas frites you can read (also in...  Bookmark   

All about glas frites you can read (also in english) here:

One method for the setup is an u - tube (google and find)
05-20-03 14:58
No 434322
      All about glass frits  Bookmark   

Is this overkill for reductive aminations? As I understand, the separator does not need to be ion-selective; something that is unreactive, ion-permeable and prevents the solutions from mixing is enough.

A u-tube might be conductive enough. You can fill the tube with a salt solution thickened with agar to reduce mixing.

HRH The Prince of Wales and Earl of Chester, Knight of the Garter, Rogerer of Servant Girls
05-20-03 15:01
      U - tube with glas frit (G4) You can buy
(Rated as: no sources!)
05-20-03 19:26
No 434357
      Re: U - tube with glas frit (G4) You can buy  Bookmark   

That looks like it would have a cross-sectional area of several cm2. With several molar electrolyte concentration, the conductance would be low.

Reductive aminations seem to require low current densities at the electrode: a small setup might draw an Ampere or so. Hence, a u-tube looks doable! Some reductions I have seen used several hundred mA/cm2: I wonder whether the higher current will cause a problem? One way to find out, I suppose.

HRH The Prince of Wales and Earl of Chester, Knight of the Garter, Rogerer of Servant Girls
(Hive Bee)
05-21-03 02:48
No 434418
      You must remember, that for a reaction you...  Bookmark   

You must remember, that for a certain reaction you want to use a certain electrode potential (selects the reaction that is being affected) with proper current density (minimizes other side reactions, like hydrogen evolution) and current (you want to do it within a reasonable time). If you have a cell separator with a relatively high resistance, you need to give the cell higher voltage between the electrodes to get the electrode potential (the potential between the electrode and the electrolyte in the vicinity of the working electrode) high enough. This is why you really want to have a membrane with high mass transport abilites, ie low resistance. Read the british patent already mentioned (Post 231955 (foxy2: "Nitrostyrene or Nitropropene electrochem reduction", Chemistry Discourse)) and what they tell about the requirements for good yields. It is no bullshit either, I'm telling you.
05-21-03 03:58
No 434432
      Controlling the reaction  Bookmark   


Isn't that why a reference electrode is necessary? When you have a successful setup, it might be possible to dispense with the additional electrode and rely on current/voltage measurements across the remaining electrode pair.

Have you any experience of reference electrodes? Mercury chloride SCE looks nasty for obvious reasons, how about a silver chloride setup?

Imagining a laptop controlled current source for experimentation.

HRH The Prince of Wales and Earl of Chester, Knight of the Garter, Rogerer of Servant Girls
05-21-03 08:12
No 434499
      setup  Bookmark   

There is another setup:

Post 419410 (bottleneck: "Benzyl alcohols via electro. red. of benzoic acids", Novel Discourse):

with clay (maybe a flowerpot)

and another setup and reference for reductive amination

Post 343766 (Rhodium: "Electrochemical reductive amination of P2P's", Novel Discourse):
(Hive Bee)
05-21-03 15:38
No 434546
      That is exactly why you need a reference ...  Bookmark   

That is exactly why you need a reference electrode... well, one could do without it, but it wouldn't be reliable anymore. It is possible to use other electrodes than the saturated calomel electrode, the greatest difference being that they have a different potential and thusly you get a different voltage (potential difference) in your measurements, a matter of simple addition/substraction. Of course, you must know that the electrode survives your reaction conditions.

Edit: I think the silver electrode would work well, I have the potential somewhere as well but if you have a proper physical chemistry textbook, the data you need is most likely listed there.
05-21-03 22:51
No 434613
      Construction of an AgCl reference electrode  Bookmark   

In that case, here's something:

First, a Luggin capilliary - used to get the reference electrode to measure as close to the working electrode as possible.

Secondly, instructions below have been shamelessly ripped and edited from a college lab. practical that is at a few places on the web in pdf.

The instructions for this original experiment can be found in the Journal of Chemical Education (Volume 69, No. 1, Page 74, January 1992).


Part One; Reagent Preparation:

   1. Obtain a piece of silver wire from the instructor.
   2. Prepare the following solutions:

      -25 mL of 0.05 M AgNO3
      -50 mL of saturated KCl solution

   3. A solution containing 5 mL deionized water, 5 mL of concentrated hydrochloric acid and 5 mL of concentrated nitric acid. Remember to always add acid to water!

Part Two; Electrode Construction:

   1. Gently clean a 5 mm portion of one end of a silver wire with emery cloth. Dip this end of the  silver wire 3 cm into the 1:1:1 water, nitric acid, hydrochloric acid solution for 15 seconds. Remove the wire, rinse it thoroughly with DI water and set it aside to dry. This forms a AgCl ppt coating on the wire, providing both species for the AgCl(s) + 1e-   Ag(s) + Cl
      -(sat)  reaction in the reference electrode.

   2. Obtain a Pasteur pipet (thin-wall glass pipet) and triangular file. Score the tip of the pipet 1 cm from the bottom of the pipet body with the file and snap off the tip. Cover the pipet with a paper towel to prevent injury and perform this operation over a paper towel to collect small pieces of glass.

   3. Light a bunsen burner and slowly melt the tip of the broken Pasteur pipet. The goal here is to melt the tip sufficiently so that only a small pinhole (~0.1 mm or less) remains. This pinhole functions as the salt bridge and provides electrical conductivity between the reference cell and the metal electrode. Allow the pipet to cool. SEVERAL ATTEMPTS AT STEPS 2 and 3 will probably be necessary to get a suitably small hole without sealing the tip of the pipet.

   4. While the electrode is cooling, obtain cotton and wooden shaft cotton swab. Break the cotton  into small pieces about 5-6 mm in diameter. Also obtain about a dozen filter paper circles (5 mm in dia.).  These are made by punching holes in filter paper using a single hole punch.

   5. Using the wooden shaft cotton swab, force cotton balls into the bottom of the electrode body and compress them. Add cotton balls and compress them until they are ~1 cm thick. Compress this as tightly as possible without shattering the electrode body. Add 6 layers of filter paper circles and compress these on top of the cotton balls.

   6. Add saturated KCl solution to the electrode to a depth of 3 cm from the top of the electrode. Then add ONE drop of AgNO3 solution to the electrode. Place the electrode in a 50 mL beaker or graduated cylinder filled with saturated KCl solution and soak it for 5 minutes. This saturates the cotton fibers/filter papers with KCl.

   7. Remove the electrode and dry it. Hold it at eye level and examine it to see if solution is leaking from the pinhole. It should leak at no more than 1 drop every 4-5 minutes, if it leaks at all. If it leaks at a greater rate, the electrode body must be reconstructed until it leaks at the indicated rate. Do not be discouraged if many attempts are needed to properly assemble the electrode, it is a difficult procedure!

   8. Place the silver wire into the electrode (tarnished end first) until the wire extends to 5 mm above the filter paper circles. Seal the top of the electrode with a plug of rolled up ParaFilm (wax film) secured by tape. Seal the top as best you can, but be careful not to crack the electrode body and cut yourself. Store the electrode in a beaker or graduated cylinder filled with saturated KCl up to the level of the fill solution in the electrode. The electrode is now ready for use.

[blue]Finally, here is another method:]

Oh yeh, AgCl reference electrodes are fine in acid electrolytes but slowly degrade in strongly basic ones. Short periods look OK (reductive aminations of ketones seem to work best at pH 11-12).

HRH The Prince of Wales and Earl of Chester, Knight of the Garter, Rogerer of Servant Girls
(Hive Bee)
05-22-03 13:15
No 434717
      A lot of years ago i saw software  Bookmark   

A lot of years ago i saw software (and hardware) for controlling the electrochemical process. Anyone knows this software ?
(Hive Bee)
05-23-03 17:18
No 434976
      information to Nafion  Bookmark   

All technical informations:
05-24-03 01:47
No 435054
      Re: Control Software/Hardware  Bookmark   

I've had a quick scout on the web and potentiostats are extremely expensive. I imagine software is specific to the model.

It is relatively easy to make a variable voltage, regulated supply, but a PC controlled system would be ideal. There are some nice (cheap) hobby kits to add ADC and DAC interfaces to the PC.

HRH The Prince of Wales and Earl of Chester, Knight of the Garter, Rogerer of Servant Girls
05-24-03 02:03
No 435058
      Re: information to nafion  Bookmark   

Interesting stuff. Apparently fragile when wet. Expensive. Gore have developed a material consisting of goretex with nafion-filled holes: gives better strength when wet and excellent results with fuel cells.

Vanilla goretex I have found difficult to purchase by the square meter: resorted to cannibalising clothing. Dialysis membranes may also be good, but ones I have found are expensive. Seem to be 2 types of dialysis membrane: cellulose ester and regenerated cellulose. The latter has the best chemical resistance (e.g. acid/base/ketone).

A bastard elk just ate all my pot plants, so I have some terracotta pots to play with too.

HRH The Prince of Wales and Earl of Chester, Knight of the Garter, Rogerer of Servant Girls
(Hive Addict)
05-24-03 19:22
No 435198
      homemade membranes  Bookmark   

Post 325605 (Osmium: "> So what's the back-up plan?", Chemicals & Equipment)
for sulfonated membranes a la Osmium

and read the whole thread for more.

The information on the reference electrode is worth gold - thanks!

To the question at start: I dont think there is a universal perfect electrolysiscell design. It depends very much on the reaction if it shall be more than a educational experiment.

For a cell which is easy and works in many perhaps most electrolytic reactions you can use an electrolytic cell. Sounds stupid, but thats exactly what a car battery is. You get the fixation frames for your membrane(s) and electrodes for free this way and lead electrodes are also included.
Be careful with the acid and the lead.
(Hive Bee)
05-25-03 11:15
No 435356
      car battery  Bookmark   

anypne knows the kind of plastics (PP,PE etc.) from a car battery ?
(Hive Bee)
05-30-03 06:04
No 436466
      membranes  Bookmark   

membranes from PP, PE and PTFE