The Bucket Cell - Start to Finish

[WSM]

I am finally writing some articles on electrochemistry for the PGI Bulletin. They'll start appearing in the next one (out in a month or two) and will continue as long as I can keep it up. Once they're published there, I plan to take most of my notes and create some blogs here to add to what Swede started.

 

I'm trying to make them sort of a tutorial on starting electrochemistry but my overall goal is to describe making pyro chemicals generally, with the emphasis on doing it on a small (hobby) scale.

 

I look forward to any and all input from all of you and encourage creative thinking. Thanks.

 

WSM

[NeuroticNurse]

Hi NeuroticNurse,

 

My first successful cell was a one gallon (3.785 liter) pickle jar with a PVC pipe cap for a lid. It was a learning experience and I've grown a lot since then (in understanding and skill), but that old, inefficient and unregulated cell produced several kilos of potassium chlorate that summer. I think the efficiency was in the 40%-50% range, but it worked anyway!

 

I run my cell outdoors too (I don't like to see my expensive machine tools turn brown) and it works just fine. I don't run my cell very much but I love the challenge of making it better.

 

Welcome to the discussion.

 

WSM

 

Bugger

At the moment, I dont have a working pH meter, but I have ordered one from eBay, so hopefully that will arrive soon. Fingers crossed I'll be able to improve the efficiency of it a little bit. But at the moment its going okay. I'll also hopefully find the time to make a snazzy chlorate cell.

 

THanks for your kind words.

[WSM]

Bugger

At the moment, I dont have a working pH meter, but I have ordered one from eBay, so hopefully that will arrive soon. Fingers crossed I'll be able to improve the efficiency of it a little bit. But at the moment its going okay. I'll also hopefully find the time to make a snazzy chlorate cell.

THanks for your kind words.

 

Caution with inexpensive eBay pH meters. The simple pen type usually have single junction sensors and don't last long at all in the cell (In fact, the cell liquor is toxic to the sensors and poisons them; sometimes very quickly). Despite the bleaching effect the liquor has on pH paper, a quick dip should give you the pH of the cell before it bleaches out.

 

If you haven't already, read through Swede's blog (You'll shoot your eye out...) and see where his electrochemistry travels took him. I suspect, like us, you'll benefit from his experiments and avoid several pitfalls along the way.

 

WSM

[Arthur]

In photo processing the chemicals are replenished from "Cubitainers" by pipes and the fluid is moved by (typically) Iwaki bellows pumps each pumping for a controlled time and n adjustable volume per stroke. Remembering that dosing pumps can have several sizes of bellows and variable stroke length and can be run for 5 strokes or 500 strokes the range of delivery volumes is immense.

 

If you have a cell running then adding about 90% of the predicted HCL need by machine should enable you to test manually less often and top off the acid as needed ALSO adjusting the top off rate til it closes on the acid needed for perfect current efficiency. Two Iwaki pumps would enable you to add HCl to maintain pH and separately add water to maintain solution level.

 

Cubitainer is Kodak's own plastic bag in a box used for sending 20L of replenisher concentrate out to labs all over the world. As you pump from them the semi-stiff bag collapses keeping air out. They hold strong acids and strong alkali so should be suited to all we could ever need. They used to be used at big labs -I used to process 600 films a DAY! (but I'm no longer there and the firm has gone -get looking before digital takes over totally!)

[WSM]

In photo processing the chemicals are replenished from "Cubitainers" by pipes and the fluid is moved by (typically) Iwaki bellows pumps each pumping for a controlled time and n adjustable volume per stroke. Remembering that dosing pumps can have several sizes of bellows and variable stroke length and can be run for 5 strokes or 500 strokes the range of delivery volumes is immense.

If you have a cell running then adding about 90% of the predicted HCL need by machine should enable you to test manually less often and top off the acid as needed ALSO adjusting the top off rate til it closes on the acid needed for perfect current efficiency. Two Iwaki pumps would enable you to add HCl to maintain pH and separately add water to maintain solution level.

Cubitainer is Kodak's own plastic bag in a box used for sending 20L of replenisher concentrate out to labs all over the world. As you pump from them the semi-stiff bag collapses keeping air out. They hold strong acids and strong alkali so should be suited to all we could ever need. They used to be used at big labs -I used to process 600 films a DAY! (but I'm no longer there and the firm has gone -get looking before digital takes over totally!)

 

The surplus pumps from photo finishing equipment are first rate. I've bought several (both bellows and magnetically coupled) on eBay and they're excellent. I haven't seen the "cubitainer" offered, but if they hold up to the system the way you describe, they sound like a viable option for our pH control setups.

 

Thanks for the suggestions, Arthur.

 

WSM

Edited September 25, 2013 by WSM

[NeuroticNurse]

WHen I make my new one, I'll be putting in an IV line with dilute HCl in it, the problem with that is even that brittles the IV line plastic fairly quickly.

[WSM]

WHen I make my new one, I'll be putting in an IV line with dilute HCl in it, the problem with that is even that brittles the IV line plastic fairly quickly.

 

I thought the IV lines could handle HCl. If not, the substitution of an HCl compatible line would solve the problem. Do you have the specs of the IV line (ID, OD, length needed and material)?

 

I ask because someone here might have the material you need.

 

WSM

[taiwanluthiers]

I don't know, medical ones probably can't handle it... after all who in the right mind would inject someone with HCl?

[WSM]

I don't know, medical ones probably can't handle it... after all who in the right mind would inject someone with HCl?

 

Whether or not the IV line can handle HCl, various tubing materials CAN which are a direct replacement for it. I believe Tygon 2075 (or equivalent) is highly chemical resistant and would work if sized properly. Viton tubing might be another option.

 

WSM

Edited October 2, 2013 by WSM

[Arthur]

Cubitainers are what photo labs get concentrate chemicals in direct from Kodak/Fuji/Ciba etc they are a polythene thick bag in a card box. Contain 20l

 

Polymers that degrade under 35% HCL may survive 5 or 10%. Maybe you need to find an acid concentration that works for pH control and suits the available pipe. There is always a need to top up the water content so some water addition is essential just how much water, needs to be determined

Edited October 1, 2013 by Arthur

[NeuroticNurse]

IV lines are made of ordinary polyet

I thought the IV lines could handle HCl. If not, the substitution of an HCl compatible line would solve the problem. Do you have the specs of the IV line (ID, OD, length needed and material)?

 

I ask because someone here might have the material you need.

 

WSM

 

Dont have those specs. Sorry. I think they're just ordinary poly-ethylene tubes, I dont think they're designed to take anything particularly acidic, the most acidic thing that I can think of that would go through them in a normal setting would be Hartmann's solution, which has a pH of about 5, and I don't think they're designed for long term use either. It isn't a huge problem cost-wise, to me since I am able to get them for free from work, but I wouldn't recommend it to the average person who doesnt have access to them. But if you have any methods of making them resistant to brittling, that would be brilliant.

[WSM]

Cubitainers are what photo labs get concentrate chemicals in direct from Kodak/Fuji/Ciba etc they are a polythene thick bag in a card box. Contain 20l

Polymers that degrade under 35% HCL may survive 5 or 10%. Maybe you need to find an acid concentration that works for pH control and suits the available pipe. There is always a need to top up the water content so some water addition is essential just how much water, needs to be determined

 

I think polyethylene holds up to dilute HCl just fine. I plan to dilute the HCl 4:1 so I expect an 8% solution is what I'm using. The water is a plus since it's a consumable in the cell. The main thing is not to just dump it in (a cloud of chlorine is likely to be released), but to disperse it slowly, deep under the surface of the cell liquor (as per Swede's blogs).

 

WSM

Edited October 2, 2013 by WSM

[WSM]

IV lines are made of ordinary polyet

Dont have those specs. Sorry. I think they're just ordinary poly-ethylene tubes, I dont think they're designed to take anything particularly acidic, the most acidic thing that I can think of that would go through them in a normal setting would be Hartmann's solution, which has a pH of about 5, and I don't think they're designed for long term use either. It isn't a huge problem cost-wise, to me since I am able to get them for free from work, but I wouldn't recommend it to the average person who doesnt have access to them. But if you have any methods of making them resistant to brittling, that would be brilliant.

 

I thought the IV tubing would be either silicone or plasticized PVC. Polyethylene should work well for HCl, since it's usually bottled in it from the store.

 

WSM

[Mumbles]

Basically all the polyolefins (LDPE, HDPE, and PP) hold up well to all concentrations of HCl at room temperature. Polypropylene starts to degrade at high temperatures. If it's susceptible at high temperatures, I'd bet long term storage at RT might begin to brittle it or otherwise degrade it. I bet that's what your IV tubing is made from, or some co-polymer of it.. It looks like Polypropylene is a pretty popular material for the tubing here in the US, along with nylon and dynaflex.

 

I'd probably replace it with something like this: http://www.usplastic.com/catalog/item.aspx?itemid=90615&catid=634 I can't find the hydrochloric acid resistance for this particular type, but most tygon's are fairly resistant to HCl.

[NeuroticNurse]

I remember reading somewhere that LDPE in the sun is brittling to it, and my setup is outdoors. Would it make sense that it would brittle up after 10-12 days catching say perhaps 4-5 hours of afternoon sun that this might be the case? I can't really avoid moving it anywhere else, is there anyone who knows if this is the case?

[Mumbles]

I really doubt it. Sun brittling takes months to years generally. Maybe the combination of HCl and sunlight might have done something. It's hard to tell. In any case, you should replace the tubing with something more resistant, or change the line very regularly.

[NeuroticNurse]

Bugger its a mystery then. Regular changes aren't a problem for me, I guess I'll have to live with it.

[WSM]

Bugger its a mystery then. Regular changes aren't a problem for me, I guess I'll have to live with it.

 

If you can find tubing made of Viton B, it's UV, ozone and HCl resistant. No embrittlement or replacement headaches. The only downside is it's typically opaque, so you can't see through it; otherwise, it's ideal.

 

WSM

Edited October 5, 2013 by WSM

[pyrojig]

No need to see through it . If one where concerned about a "viewing glass" they could have a intermediate catch container of glass or other clear material that would receive the measured amount of dilute acid . This would then need to be plumbed into the cell via a dispersion tube as Wsm explained several posts ago. This would be under the liqueur surface ,it would allow for the acid to mix slowly to avoid it turning into a cloud of Cl gas. My only hang up with the bucket cell, is designing a holding tank for the acid and then plumbing the setup from a elevated point to utilize a gravity feed. Time seems to be very scarce , and I figure once the season slows down I can dedicate a lot more time and log results of the improved system that WSM designed .

[WSM]

I believe an acid reservoir can be fabricated from PVC pipe and sheet stock. I envision using 12" long piece of 6" diameter thin wall pipe and 1/4" sheet stock.

 

 

The lid is shown above the tank for clarity. It normally is down and sealed with the flexible tubing ring shown in blue.

 

The base is a square plate with the pipe cemented to it. Apply several coats of cement to both the pipe and base till they're properly softened, then put them together with a weight on top to get a good seal. After the glue dries for a day, fill any gaps with a disposable dropper and more cement. Repeat as neccessary (drying fully between coats) till the tank is well sealed. I prefer a heavy bodied cement with medium set for proper gap filling.

 

 

WSM

Edited October 30, 2013 by WSM

[WSM]

The lid is a bit more difficult to do (but worth it).



The first step is cut a circle of 1/4" PVC sheet a little larger than the OD of the tank. Next cut a 1/2" piece of the same pipe as the tank and split the resulting ring so it can overlap on itself. Determine how much of the ring to remove to allow just enough space for the tubular seal. Carefully heat the PVC ring with a heat gun (without scorching it) till it reaches about 275ºF where the PVC will be soft and pliable. Form the ring into a circle, matching the ID of the tank with enough of a gap for a snug fit of the tubular seal. Be sure the cut ends line up exactly. Let the ring cool till it becomes fully rigid again.

Center the support ring on the inside part of the lid and cement it in place, and let it fully cure.

The seal is formed from silicone or Viton tubing joined on the ends to form a ring to match the OD of the support ring (and the ID of the tank). The ring can be held in place on the support ring with silicone caulk and it'll be removable if the seal needs replacing.

Chamfering the inside edge of the tank rim slightly, will aid in seating the lid properly when closing it on the tank.


WSM

Edited October 30, 2013 by WSM

[pyrojig]

Wsm,

You always go above and beyond in your construction . You make masterpieces out of your work . I am jealous I dont have the equipment or time to construct such amazing pieces of work. I will have to take you advise and get this show on the road . I need to get this dang acid reservoir done so there are no more excuses to hang up the ;project . I feel bad sitting on such a masterful piece of work,. and not taking advantage of its ability to perform. I feel that Im doing you a disservice by not holding up my end of the project and keeping the ball rolling . Please take this as a sorry , and as winter approaches I believe time will permit me to get this thing operating.

[WSM]

Wsm,

You always go above and beyond in your construction . You make masterpieces out of your work . I am jealous I dont have the equipment or time to construct such amazing pieces of work. I will have to take you advise and get this show on the road . I need to get this dang acid reservoir done so there are no more excuses to hang up the ;project . I feel bad sitting on such a masterful piece of work,. and not taking advantage of its ability to perform. I feel that Im doing you a disservice by not holding up my end of the project and keeping the ball rolling . Please take this as a sorry , and as winter approaches I believe time will permit me to get this thing operating.

 

No need to apologize, I've got tons of projects half done around here. I'm hoping to be encouraging and offering suggestions to help you overcome the roadblocks so the project can progress.

 

As to the equipment and time; well, we seldom "find" the time, usually we "make" the time to do these things. Prioritizing our time correctly, family and work come first; after that we squeeze in a little time for hobbies. About the equipment,... it didn't all appear at once. It was accumulated slowly over time, one piece here and another there until it became the outrageous mess it is today. My life's work will be creating order out of chaos.

 

The bucket cell is sitting there, waiting. You'll get to it when time allows. I look forward to seeing it run and how it works out.

 

WSM

[WSM]

I talked to pyrojig recently and he says he's gearing up to run his bucket cell. I look forward to many postings from him here about how it goes. This is exciting!

 

WSM

[pyrojig]

http://i918.photobucket.com/albums/ad24/pyrojig/photobucket-13341-1388982245680.jpg

 

Here is the starting materials soon to be fabricated into a working cell.