How to make Sodium Chlorate by Electrolysis of salt water?

[gary350]

I have a power supply for electrolysis of salt water brine, variable 3v to 6v up to 30 amps. Cathode is stainless steel, anode is carbon rods. Carbon rod surface area 42" sq. the Stainless steel cathode should be 21" sq. Salt is pure 100% salt dissolved into distilled water. I have been making saturated salt wrong. Today I learn saturated salt is, dissolve pure salt into 150°f water cool to 100°f pour into the 2 gallon brine tank. I find conflicting information about brine tank temperature some say, 40°C, or 60°c to 90°c, or 113°f. I Brine tank was 4.71volts 12.5amp running for 12 hours. Brine tank was 70°f and 12 hrs later 90°f. Lots of chlorine gas, hydrogen gas and oxygen comes from the brine tank no problem with 8'x8' door open. Sodium chlorate is suppose to fall out of solution below 40°C. I cooled 1 pint of brine water down to 0°f for 8 hours and no sodium chlorate fell out of solution. Something is wrong???

 

[sophiecentaur]

@gary350 Firstly, I really appreciate the intelligible circuit diagram you've given us., Too few of those around on PF!!

I know very little about electrolysis and my only experience was to try it with spent fixer from film developing. The place where I worked had loads of the stuff so I thought "money makes the world go around ...". I have to say, I came to it quite unprepared and all I ever got was a thin white film (silver, assumed) on the cathode, followed by horrible stains and warm water. I varied the volts but don't remember the current. This was pre-internet so information was not easily available.

From the vigorous activity you report, you are obviously electrolysing something so your circuit must be connected properly.

I did a quick search and a question about cathode material seemed worth asking. There was mention of titanium in one of the videos. Are you sure SS is suitable (at least the alloy you are using)?

 

[Borek]

Today I learn saturated salt is, dissolve pure salt into 150°f water cool to 100°f pour into the 2 gallon brine tank.

Could be that's just a lousy wording, but no, varying temperature is not what makes the solution saturated. You need to be sure there was an excess of salt present during dissolution.

 

[gary350]

Could be that's just a lousy wording, but no, varying temperature is not what makes the solution saturated. You need to be sure there was an excess of salt present during dissolution.

This is Google definition of saturated salt. To make a saturated salt solution, add salt to water and stir until no more will dissolve, and solid salt remains at the bottom. You can heat the water to dissolve more salt, stirring until no more dissolves, and then let the solution cool to create a saturated solution.

Today I made saturated salt. Dissolve as much salt as I can to 2 gallons of 70°f water. Heat water to 150°f dissolve as much salt as I can. Cool to 70°f again you have saturated salt.

I have been doing electrolysis for 6 hours, 4 amps at 4 volts. Electrolysis is no longer causing green color water and no excess chlorine gas.

I also learned I am using the wrong salt. A cooking show claimed canning salt is pure 100% salt but that is wrong. Kosher salt is 100% salt. When I heated canning salt to 150°f it turned dark dirty brown color. After 6 hours of electrolysis dirty waster has become clear. Maybe I should dump my salt water and start over???

 

[Borek]

stir until no more will dissolve

Yes, and that's what your original post was missing. You mentioned just dissolving and varying the temperature, there were not a single word about the excess left.

Kitchen salt is technically never 100% pure (actually 100% pure NaCl would be costly as hell, analytical methods can detect ppm level contaminations - and 99.999% leaves place for 10 ppm of other substances, removing them would probably put us in k$ per gram range).

We are most likely talking about several tenth percent of other substances. If the solution gets dark my bet would be on dextrose, used sometimes as a stabilizer for the added iodide.

Still, at these levels of contaminants I would expect the solution to behave as if it was just NaCl.

Sorry, I don't know the chemistry behind the chlorate synthesis good enough to be able to help. The general mechanism is chemically obvious, but apparently there are fine prints at work and of these I known nothing.

 

[gary350]

Yes, and that's what your original post was missing. You mentioned just dissolving and varying the temperature, there were not a single word about the excess left.

Kitchen salt is technically never 100% pure (actually 100% pure NaCl would be costly as hell, analytical methods can detect ppm level contaminations - and 99.999% leaves place for 10 ppm of other substances, removing them would probably put us in k$ per gram range).

We are most likely talking about several tenth percent of other substances. If the solution gets dark my bet would be on dextrose, used sometimes as a stabilizer for the added iodide.

Still, at these levels of contaminants I would expect the solution to behave as if it was just NaCl.

Sorry, I don't know the chemistry behind the chlorate synthesis good enough to be able to help. The general mechanism is chemically obvious, but apparently there are fine prints at work and of these I known nothing.

I built it and it works. I had to watch several videos and read several instructions to finally learn and understand how this works. Lots of information is not complete they don't explain in details I need to learn how this electrolysis works.

1. Bring 2 gallons of distilled water to a boil then and 8 lbs. of Kosher salt. Stir well only about 75% of the salt will dissolve into the hot water. When liquid cools to 70°f pour water and salt into plastic brine tank.

2. When brine is at 70°f turn on the power supply. Set to 4 amps DC and 7 volts DC. When electricity is turned on the load will pull 7 volts DC down to 4 volts DC. There should be several lbs. of salt in the brine tank that never dissolved.

3. Let the electrolysis brine tank run at, 4 VDC 4 amps for 18 hours. Keep watch on voltage about every 30 minutes volts will drop to 3.9 volts turn the variac up to keep volts at 4 volts. As sodium chlorite is slowly replaced with sodium chlorate voltage continues to drop and amps will stay at 4 amps for a while.

4. In about 16 to 18 hours electrolysis is getting very near being finished. Brine tank has 42 carbon rods, anodes surface area of all 42 rods is about 44 sq inches. Cathode surface area is 50% less than the anode. Stainless steel anode has a surface area of 21 square inches. Stainless steel metal plate needs to be bent into a C shape to expose electrolysis to both sides. When voltage starts slowly going up and amps are slowly going down almost all of the sodium chloride has been replaced with sodium chlorate. When volts are up to 6 volt and amps are down to 2 amp its time to stop. Brine will look dark gray dirty color from the carbon rods. If there is any salt = sodium chloride in the bottom of the brine tank remove it or add more water then turn on electrolysis again for 30 more minutes.

5. About 24 hours later brine will look clean all the carbon falls to the bottom of the tank. Syphon off the clean brine and filter dirty brine through a paper coffee filter.

6. Boil away the water. As water volume is reduced that forces sodium chlorate out of the solution.

My power supply is over kill it is 1200 watts and I only need 16 watts. It is nice to have 100% control of voltage and current.

 

[realJohn]

Safety first! Remember that chlorinated solutions are hazardous - chlorine + $\text{H}_2$ is dangerous.
$$\text{Cl}_2+\text{H}_2\rightarrow2\text{HCl}$$

 

[sophiecentaur]

I built it and it works.

Good one. I'm impressed. What exactly did you want to do with the stuff? More experiments? It's banned as a weedkiller and I remember playing with a Chlorate and sulphur mix which you could ignite (bang!!!) when hitting it with a hammer. Not the best explosive though.

You've obviously gone to a lot of trouble with this project so could it be a "just because it's there" venture?