raketpeter

Well i tested my cell this morning and i did the methylene blue test and the purple precipitate confirms my cell is now making perchlorate  ..

I am hoping to get chlorate down to 5 to 10 g a litre before i turn off the power..is there any tell tale indication of when all the chlorate as been used up?...I dont want to run my anodes to long with very low ClO3 level as this can corrode them very fast?..or will i have to use the indigo carmine test then from that work backwards to calculate how much ClO3 i have destroyed? via the amount of Bisulphite i have used?

I'm quite interested in this particular question having no hands on experience with GSLD anodes. With Pt anodes I always stop the cell when I can smell the O3. Might seem unpractical (who wants to "smell" their cell all the time ), but actually it's not a problem cause I can calculate when my cell will start smelling to within a cuople of hours out of a batch runtime of eight days.
I seem to remember reading *somewhere* that LD anodes have been used for O3 production in a NaClO4 electrolyte. If this is true you shouldn't have to worry about anode degradation. (Parts of your cell not made of LD, metal or PTFE might die VERY quckly once O3 forms - it's very agressive with many plastics, glues, etc.)
I will be most interested in hearing at what NaClO3 concentration you can start smelling the O3.

Best of luck

Very nice indeed Sasman. Could you elaborate a little more on your electrical anode connections - just how are you avoiding the "wicking" problem?

If the plastic screws you use are made of nylon - they WILL die. I know this for a fact since my cell initially used nylon. Now it's all replaced with homemade screws teflon - it's a pain to make M3 tefon screws, but worth it - they last forever - even when in direct contact with the Pt anode.

Once again - congratulations on your good progress!

I was referring to the crystallisation of the sodium salt only this salt is hard to crystallise out. I disagree that " it evapourates quite nicely" - I had to make a special concentrator for this purpose. Problems include: Boiling point is about 145 dec C (forget about std. hotmelt glue, polystyrene insulation, etc.), a thin crust of crystals from on the surface effectively preventing evaporation.

Regarding loss I estimate I lost some two kilograms of product (out of about 15kg total) due to aerosol losses. Also It does not take a flame to see that product is being lost - you can SMELL the perchlorate in the air (don't inhale ).

Raketpeter what voltage do you run your 3.3amp cell?..Does your perc perform well with making colours?...how many times do you have to recrystalize?

Alany mentions his first batch was not as good as his commercial  perc(obviously he can purify the product more)..Also what size PT anode are you using and what method of control are you using for current..

I am intrested in what that Black coating is on alany's Pt anode  very wierd?.. i have made small test batch's using my Pt Anode mesh and had no black coating..

.I have nearly made all my Lead Dioxide anodes...

My first Graphite anodes were 13 mm( 1.5mm PbO2 coating) diameter 15 cm long but these are made to use a current of about 10 amps each (Surface area approx 49 cm x 200 milliamps)..

I made these small electrodes because from what i have read passing large currents through a big anode tend to over heat the connections..etc..

    So i thought make small electrodes and share the current between them, so each electrode only has to take a small current..
From my experiments these GSLD anodes can easily take 10 amps so i scaled up my next batch and Now the ones i will be using are much bigger  ..

They are 34mm Diameter( 1mm PbO2) 15 cm long can take 25 amps (128 cm Surface area x 200 milliamps)..
I will post some pictures later .. very rare to see PbO2 anodes on the Net?..i have read lots but no photos ..

The actual coating on the rods is superb.. very smooth no pits or pinholes..much easier than i thought to make them..
The secret in making them is do it properly..I have read lots of people on the Rec.pyro ..were there PbO2 anode peel or dont last long..Also use Graphite not Carbon!! i tried Carbon gouging rods..Rubbish... dont bodge.. get Graphite...

The end result is well worth it...Rock hard Black crystaline PbO2 coating Sounds like ceramic when you tap it..

I am running in each electrode at about 25 amps in a Brine solution to test each one.. for a week or two .this also serves to leech out any chemicals that may have been absorbed by the PbO2 coating ..
The best test for the Anode is when the Chloride concentration gets really low even a Pt electrode dont like low levels of Chloride..

The only problem i have is when adding PbO to lower my Ph of my plating tank .. even though i have added lots of excess PbO and have left it stirring overnight at 60 centigrade.. it never reaches PH 7..?.. baffled me..
Also when PbO is added the colour of the solution is not the same pale blue as it was to start.. this worried me until i added a small amount of Nitric acid.. the colour then changed Back from a greenish blue to a nice pale blue...

To be continued....

Sorry for taking a while to respond - was out of town.
My cell runs at a voltage between [5.25;5.55]V.
The overvoltage for my Pt anode is higher than for PbO2 ditto.
The anode itself is essentially a Pt wire - about 100cm long and 0.4mm in diameter.

Haven't used the product for making colours (yet).
I have done a fair bit of experimentation with (re)crystallization and in short - I think it's a pain:
You must crystallize at minimum 52 deg C in order for nice crystals of anhydrous Perc. to form. Lower temperatures yields the mono- (or di-) hydrate which drains the mother liqour very poorly.
I have used centrifugation to separate the fluid (which is recyc'ed) from the anhydrous crystals. Works well - but VERY labour intensive.
Beware - product is LOST when you boil to concentrate to create the supersaturated solution for crystalization - losses are SIGNIFICANT - try placing a propane flame in the "steam" leaving your boiling vessel and the sodium colouration of the flame will demonstrate my point.

Bottom line - I'm dropping the step of crystallization of the sodium salt.

Btw. veeery nice work on your PbO2 sasman - congrat's!

Peter

I boil the dye and the acid first, then squirt in the sample, the same volume as the reagent.  My initial problem was my acid wasn't strong enough, but 300 g/l HCl seems to be fine.  I use 1 part dye to 5 parts acid and 6 parts solution under test.  I use a small boiling chip in the tube to make it easier to boil.

To destroy the chlorate I lower the pH to near 1 with HCl and boil which tends to destroy most of it by itself, I clean up the rest by adding sodium metabisulfite until the indigo carmine test is negative, then I add a little more to be sure.

I've written up the latest run but I haven't unhidden the article yet, I will once I add the tests on the product.  It is currently drying ready for weighing.

OK - your procedure is clearly different from mine. I looked at your (very interesting web page) and have a couple of questions:

1) Are you using copper wire is the cathode?? - Surely you are not going to make ammonium perch. with sodium perch. from a copper cathode??

I use Ti - no *chemical* corrosion, but there are problems with hydrogen embrittlement which gives rise to bending of the Ti and a small ammount of "physical" erosion of the Ti.

2) It seems you are running at VERY high amperage for such a small cell (and
anode) - also 75 deg C seems very high (I run at 25-35 deg C). What's the cell voltage under your cell conditions for the chlorate step and for the perch. step?

I run a 1900 mL batch size cell for about eight days at 3.3 A.
This, by the way, corresponds to over 95% current efficiency (but I cheat and start with the chlorate which makes a HUGE difference ).

Peter