Additives for chlorate/perchlorate cells

[in_flames]

I will soon be building a electrolytic perchlorate cell and I was wondering what are the best chemicals to add to improve current efficiency.
While browsing other threads I have seen that (per)sulphate, fluoride and (di)chromate can be used but don't go into much detail.

I was wondering if anyone could comment on how well each of these or other chemical additives work to improve efficiency and in what concentrations they should be added.

My cell plan will most likely be a glass jam jar with a platinum wire anode and titanium bar cathode it that affects what can be added. These were acquired from ebay for very reasonable prices. More platinum wire is available for those who are interested. I am also planning to use a computer power supply on the 5V rail.

[Bacon46]

In my experience back yard chlorate cell efficiency runs between 40 and 50 percent at best. To make up for the poor efficiency I run larger cells.

The only chemical additives I have used are HCl and NaOH to control Ph.

The following specifications are from the last chlorate cell that I ran:

• Cell Body: 5 gallon plastic paint bucket

• Anode: 1 ¼”x 1 ¼” x 16” solid graphite bar coated with boiled linseed oil to slow corrosion. 10” of the anode was submerged. I purchased a graphite bar large enough to make 4 anodes this size from a local junk/scrap dealer for $5.00.

• Cathode: 4” x 5” x 1/16” solid copper plate

• Electrolyte: 4 gallons (15.14 liters) H20/NaCl. I dissolved approximately 13 lbs (5.89 kg) of NaCl in 4 gallons of water. I purchased in the NaCl in the form of water softener salt at the local hardware store. A 40lb bag was less than $5.00. 13 lbs of NaCl will not completely dissolve in 4 gallons of water. I filtered out the un-dissolved solids after the electrolyte had cooled to room temperature.

• Power Supply: 12 VDC, 12 amp, automotive battery charger modified to output 6 VDC by disconnecting one leg of the transformer. Voltage at the cell was 5.4 VDC

• HCl Drip: 6.5ml of 2% HCl

This cell ran for 28 days and produced 4lbs (1.8kg) of KClO3. That’s around 38% efficient.
Temperature control probably would have helped. I ran the cell outdoors in the winter. The highest temperature the cell reached was 40C.

A couple of drawbacks to larger cells is, the amount of chlorine gas released can be dangerous and may piss off the neighbors; especially at startup, and processing the electrolyte is laborious.

I am sure if you use the search engine you will find a great deal of useful information on this subject from people with more knowledge and experience than I have.

[Gammaray]

hi, you can look here http://www.vk2zay.net/article.php/63

or this http://www.wfvisser.dds.nl/EN/kclox_EN.html

[in_flames]

Thankyou for the links although I had already read them. My question was specifically about additives which those pages don't really go into any detail. I am interested in anyone's personal experience with them or more detailed information.

[alancj]

Gammary, you forgot the best site for chlorate's:
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/chlorate.html

Best of all... it seems the author, who I call "The Chlorate Guy", has come back from the dead, and has done some updating on his site in the past month.

To your question, in_flames, from what I've read (at the above site) that fluoride and/or persulfate is added in about 2g/L quantities. It increases current efficiency substantially. This page:
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/naperchl.html has several links to patents that describe the use of those additives with some actual data about what the effects are. Try viewing those patents on the freepatentsonline.com website, which is very good.

If you are using titanium as your cathode then you won't need to add chromate's; which are just used to protect mild and stainless steels from corrosion.

-Alan