Sciencemadness Discussion Board - Where did I go wrong (KClO --> KClO3)

Where did I go wrong (KClO --> KClO3)

Varmint - 2-8-2013 at 05:07

I did the poor man's KClO3 production, boiling down until crystals of NaCl just started to fall out, removed from heat, let cool, then poured off the liquor into a fresh beaker.

I repeated the procedure a second time in order to have a larger volume to work with. Once the second batch had cooled, I added the liquour to that from the first batch. (Label Volume2)

To that I added an equal volume of saturated KCl solution, stirred, and was rewarded with a sizeable crop of presumed KClO3 that precipitated out, which I filtered, keeping the crystals, discarding the liquor.

Recognizing the still appreciable smell of hypochlorite on the still wet crystals, I decided to clean the beaker, add the crystals back, add the same amount of [distilled] H2O to get back to Volume 2, covered with a watch glass, and boiled for 15-18 minutes.

The solution lost virtually all of the hypo smell, but here's what I don't understand. At virtually the same volume, absolutely NONE, zero,zip,nada crystals fell out of solution.

I was expecting a loss in precipitate (figuring the missing NaCl left more "room" for KClO3 ), but nothing.

So, did I destroy some KClO3 by the boiling, or did the not missing NaCl really leave that much more room for KClO3 and all I need to do is boil off some more water to get my (lowered) yield back?

Did the remaining NaClO "eat" my KClO3?

I know this is something fundamental I'm missing, but I can't see what caused the apparent loss.

Even more perplexing is I did this sucessfully once before, but instead of trying to boil off the NaClO, it simply let the crystals dehydrate and the NaClO smell disappeared in sort order. I was then able to recrystalize the KClO3 2 passes, with better purity and prettier, larger crystals each time.

Thanks for any insight.

DAS

[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: corrected formulæ]

[Edited on 2.8.13 by bfesser]

Pulverulescent - 2-8-2013 at 05:44

Quote:

I know this is something fundamental I'm missing, but I can't see what caused the apparent loss.

Bleach weaker than advertised ─ interfering contaminants ─ lowered pH . . . take your pick . . .
NaClO₃ is still available as weedkiller, AFAIK, albeit with added fire suppressant which might be separated by selective crystallisation!

Varmint - 2-8-2013 at 05:55

Exact same bleach (same bottle), the disinfecting variety with "double the strength".

So, it's not the starting material, but something in my process that killed the KClO3.

DAS

[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: corrected formula, removed unnecessary quote(s)]

[Edited on 2.8.13 by bfesser]

SM2 - 2-8-2013 at 05:55

Concentrate on your solubilities. Especially as it comes to KClO3 in cold H2O. Now, you can buy USP grade KCl pellets from the home Depaux for <$10 for like 50Lbs. KClO3 really is not very soluble in freezing cold water. Use this to your advantage. You might consider switching to high test hypochlorite (H-T-H) from pool supplies. I've made lots of ClO4- and ClO3- using only either <del>salt</del> [NaCl] or KCl, and a bunch of 150W solar panels. The electrodes were Ti plated. Really, it's worth it to just order 5-10 K
lbs KClO4. Hope it helps.

[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: corrected formulæ]

[Edited on 2.8.13 by bfesser]

bbartlog - 2-8-2013 at 05:56

Without quantities, it's hard to say whether what you're seeing is supersaturation or just the fact that you no longer have the competing ion effect. As you suggest, there is 'more room' for KClO3 to dissolve when you use distilled water rather than a saturated solution of KCl. But whether this is enough to account for what you've seen depends on the mass of KClO3 and the volume of the liquid that was added. I would suggest that if you want to do something like this again, you should weigh the crude product and look up a solubility-versus-temperature chart so that you can estimate a roughly appropriate amount of distilled water (or other solvent) for recrystallization.
Anyway, it seems highly unlikely to me that your potassium chlorate was destroyed.

Varmint - 2-8-2013 at 06:15

bbartlog:

Got to be the competing ion issue. I'll just boil away some more H2O and see where that gets me.

SM2:

Your home depot is beter than mine! something like $22 for my 40lb bag (all softener salts seem to be 40lb qty here).

But when you figure the KCl + almost free electricity (by comparison to the chemistry) I can end up with some really good yields and high purity with none of the waste when my Pt clad [n]iobium screens get here!

I'll do the two tank route, 1st cell with chlorides always above 5g/100ml to preserve the anode, and I'll be recrystalising the KClO3 before it goes in the KClO4 cell.

Also going to try the KClO3 + Heat --> KClO4 path to see how that works out...

thanks,

DAS

[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: corrected formulæ]

[Edited on 2.8.13 by bfesser]

Pulverulescent - 2-8-2013 at 06:58

IIRC, thermal disproportionation of NaClO₃ is notoriously slow and difficult to drive to completion!
OTOH, the ClO₄ salt itself, is fairly pricey!

Fantasma4500 - 2-8-2013 at 07:54

im not sure if you wrote that you did try to cool it down, in which is the most beatiful and yield increasing step in this procedure, cant tell if the capitalization of the chemical formulas was too confusing (i have never witnessed NaCl written as NACL before, very new to me, lol)

as you recognize words by their shape when you read fast, i think its a must to write chemical formulas with correct capitalization..

anyhow..
when you add the KCl, boil it down again until you see NaCl crystals form, then add a littlebit of water to remove this effect, as NaCl does precipitate in small amounts when you cool it
cool the whole solution as much as possible and filter

Varmint - 2-8-2013 at 08:53

Formulas:
Depends on the forum I guess. Early on in many or most chem forums since subscript was nigh to impossible, folks just adapted and used all caps and didn't even bother with trying to subscript.

If this forum's preference is proper - NaCl - then I'm good to go, but keep in mind in the distant past I was chided for using that very smae thing.

Now all I've got to do is figure out subscript here...

With the BBS SW do it for me? (Test) KNO3 H2SO4

DAS

bfesser - 2-8-2013 at 09:01

I don't know what forums you speak of, but that's very unscientific and just plain wrong. Use proper notation, or you're going to anger a lot of people (particularly me!).

Quote: Originally posted by bfesser

I feel that there's now no excuse not to use subscript and superscript in posting. Some time ago, I coded up some buttons that you will see on the "Post Reply" page under the "Text Color:" dropdown (xy and xy

, and <a href="viewthread.php?tid=18651#pid242812">Polverone was gracious enough to fix my errors and implement them</a>. For those who can type BBCode tags, you can use [sub][/sub] and [sup][/sup]. Or for HTML junkies like myself, use and .

<a href="viewthread.php?tid=15528#pid201809">Subscript</a> thread

It's easiest to just type the tags out by hand, but you can also use these buttons: <img src="./images/xpblue/bb_subscript.gif" /> and <img src="./images/xpblue/bb_superscript.gif" />

[edit] Please stop writing HOH. I'm sorely tempted to just trash those posts...

[Edited on 2.8.13 by bfesser]

Varmint - 2-8-2013 at 09:14

OK, let me try this out...

H2SO4

Well, I can see I'm going to want to keep a notepad doc with common formulas open while posting because that's just not fun enough to do manually every time, and if people are going to actually get angry, well we wouldn't want to upset the apple cart.

DAS

bfesser - 2-8-2013 at 09:18

You get used to it. I can type out entire reaction equations properly formatted, about as quickly as I can type out a regular English sentence. I don't expect anyone else to be able to do this, of course, but a little effort would be nice. Thanks for your willingness to adapt, it's greatly appreciated.

Varmint - 2-8-2013 at 09:26

I'm adaptable! <del>You've since corrected SM2's use of HOH which is where I picked it up from, normally I woud have put H2O.</del>

But now it will be H2O from here on out.

I use HTML quite a bit actually, I write a lot of HTAs but the tags generally apply to whole lines or table cells, having to bounce around within a word would make me batty, ergo my notepad helper doc is already under construction...

DAS

[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: del]

[Edited on 2.8.13 by bfesser]

OK, so I jumped the gun.

Following a nice boil-down, I got back what looks to be a sizeable percentage of my expectation.

So, as bbartlog mentioned, it had to be the competing ion effect.

Since the liquor volume was so low I decided to use a graduated cylinder to watch the precipitation. Interesting to watch the size of the crystals grow then diminish as the cylinder cooled.

Thanks for all the input, positive and corrective!

DAS

[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: merged sequential posts]

[Edited on 2.8.13 by bfesser]

TheChemiKid - 8-8-2013 at 04:42

Quote: Originally posted by Varmint

Exact same bleach (same bottle), the disinfecting variety with "double the strength".

So, it's not the starting material, but something in my process that killed the KClO3.

Did you check the MSDS to see if anything else was added as a stabilizer that might change the reaction (such as phosphoric acid or sodium hydroxide)?

ElectroWin - 9-8-2013 at 15:46

the whole procedure from second batch onward, seems borked.

you should be washing with a saturated solution of your desired product, KClO3, not of KCl.
please check and review the principles behind washing crystalline product.

hyfalcon - 10-8-2013 at 03:53

Since KClO₃ has such a low solubility at cold temperatures, what he should be washing with is ice cold distilled or at least deionized water. This will help strip any sodium ions left from the metastasis reaction.

[Edited on 10-8-2013 by hyfalcon]

ElectroWin - 11-8-2013 at 12:43

ok, must be ice cold KClO3 solution, then

hyfalcon - 11-8-2013 at 16:40

Not if you are wanting to strip the remainder of the sodium ions left over from the metastasis reaction. There needs to be some room in the solution to do this. Look up the solubility curves for KClO³. You will loose very little at 0⁰C.

ElectroWin - 11-8-2013 at 17:41

there is plenty of room for sodium to be taken up, even if the solution is saturated with KClO3. please look at

http://www.tannerm.com/images/solution1.gif

[Edited on 2013-8-12 by ElectroWin]

hyfalcon - 11-8-2013 at 17:57

You get a cleaner product by stripping with an unsaturated solution. That's all I'm gonna say about it.

ElectroWin - 12-8-2013 at 08:28

either way, the wash solution you use must remain unsaturated w.r.t. the small number of NaCl crystals you have in your product, (and enough volume to dissolve all of those).

the reason to use a wash solution saturated with your desired product is so that you will not lose any of your desired product into the solution. instead, the NaCl, being more-soluble than KClO3, will replace it in solution. i believe this principle is well established in the literature, and is particularly effective for countercurrent extraction.

fyi, you can extrapolate from
http://www.freepatentsonline.com/3278275.pdf

[Edited on 2013-8-12 by ElectroWin]

hyfalcon - 12-8-2013 at 09:54

Anything that comes from that wash I recycle back to the cell for replacement electrolyte.

AJKOER - 14-8-2013 at 05:06

One path to Chlorate formation from NaOH (or KOH or Ca(OH)2...) requires high ionic strength, high pH and just mild heat (75 C).

Here is a design I am considering:

1. Place hot NaOH flakes (or be able to mildly heat) at the bottom of a large wide mouth container.

2. Place and start a Cl2 generator, from say, adding NaHSO4 to a solution of H2O + NaOCl + NaCl (chlorine bleach), in its own vessel in the large container.

3. Close/seal the large container and place in a tray of hot water.

Reactions:

In the Chlorine generator:
NaHSO4 + NaOCl --> Na2SO4 + HOCl

NaHSO4 + NaCl --> Na2SO4 + HCl

HCl + HOCl = Cl2 (g) + H2O

In the large vessel:
6 NaOH + 3 Cl2(g) --> NaClO3 + 5 NaCl + 3 H2O

Note, any pressure buildup in the container will help push the reaction to the right.

Reference for the last reaction: See section 5.14.2 at http://www.docbrown.info/page07/redox2.htm.
-------------------------------------------------------------------

Here is a path that I have actually done that requires first, however, the preparation of a soluble Silver salt.

1. Prepare Silver acetate from slowly dissolving Ag source in a solution vinegar and H2O2 over a period of days. Leave the salt in its Acetic acid solution.

2. Add NaOCl. If Chlorine Bleach is your source of hypochlorite, you will also be adding NaCl and possibly Na2CO3 depending on the brand of the bleach.

3. Filter out the white insoluble AgCl (that is formed immediately!) leaving a solution of just AgClO3. Note, any NaCl present will also generate Silver chloride so use sufficient Silver acetate.

Now, if you want KClO3 add KOH (or KCl). Filter again to remove new formed Ag2O or AgCl. Cool or evaporate to separate out your largely chloride-free chlorate salt.

Do not throw out the AgCl as it can be combined with sugar and NaOH to reclaim the Silver.

[Edited on 14-8-2013 by AJKOER]