Potassium dichromate uses

[Piccaso]

As we all know potassium dichromate is very useful in coating magnesium to prevent reactions. I have been reading else where that there are other uses for it beside the coating of magnesium. I have read that is is used in some comps as a oxidizer. I was wondering if anyone else knows of other uses for it pyrotechnic wise. I understand some peoples not wanting to mess with it because of it's carcenogenic properties.

[a_bab]

People are scared for no reason; it's no more dangerous than Ba nitrate IMO. Just make sure you don't eat or inhale the stuff.
This compound has a long history of use (in the leather industry). The workers that made this stuff were constantly exposed to large amounts of dust and the occupational disease was palatal perforation, much like in people with cocaine abuse. Plus it can cause dermatitis. These workers were exposed every day for years.

Now to answer your question, It is used in strobe fuel where besides protecting the magnalium it seems to act as a catalyst (some would say it's not the case).

With potassium chlorate and some organic fuel it makes deadly mixes that can explode spontaneously. I won't detail the amounts but I have a friend who nearly died; he used this mixture as a rocket fuel, when he was young. It exploded with extreme violence a few days after making it while being stored in a small plastic box.

I've also seen some patents that make use of it for slow fuses.

[WSM]

Besides the other uses mentioned, dichromates also catalyze the breakdown of perchlorates, which can enhance some formulations.

 

Always wear proper safety equipment (PPE) when handling dichromate compounds. Why take unnecessary risks?!

 

WSM

[Piccaso]

I am not worried about the dichromate risks, proper PPE and shop cleaning habits handle that. I was just looking for some more uses for it. I have a surplus of it that was given to me and I will never use it all up treating magnesium. I have heard tell of other comps using it as an oxidizer and along with other uses that are probably not appropriate for general forum posting because of safety issues. If any one has any comps they would be willing to share I would thank you for it even if you would just rather pm them to me instead of posting in the general area.

Edited February 3, 2020 by Piccaso

[ronmoper76]

I am not worried about the dichromate risks, proper PPE and shop cleaning habits handle that. I was just looking for some more uses for it. I have a surplus of it that was given to me and I will never use it all up treating magnesium. I have heard tell of other comps using it as an oxidizer and along with other uses that are probably not appropriate for general forum posting because of safety issues. If any one has any comps they would be willing to share I would thank you for it even if you would just rather pm them to me instead of posting in the general area.

I read the same thing in one of my fireworks books. The guy said he worked with and around it all his life with zero protection and had no health problems,as long as you don't throw a scoop in your coffee or start snorting lines of it you should be fine...I was surprised because the author is legendary in fireworks and the online community acts like the stuff is nuclear material,lol

[Carbon796]

That's because the majority of online users are more of the weekend warrior types. Rather than serious hobbyist. Its especially more prevalent on open and public forums. They hear or read about one bad thing. Then propagate it, like wild fire. Thinking their spreading real wisdom. Having never used, further researched, or gained any actual hands on experience.

[SharkWhisperer]

That's because the majority of online users are more of the weekend warrior types. Rather than serious hobbyist. Its especially more prevalent on open and public forums. They hear or read about one bad thing. Then propagate it, like wild fire. Thinking their spreading real wisdom. Having never used, further researched, or gained any actual hands on experience.

Carbon's right. As long as you practice good PPE hygiene, you're unlikely to run into health issues. That said, besides having a relatively low oral LD₅₀ (in rats; super low via inhalation), and being a Class 1 known carcinogen, dichromates also has been proven to cause heritable genetic damage, meaning it can cause problematic mutations in your sperm/ova DNA that can be passed on to your children. And it is a known teratogen, meaning that it can cause birth defects in children of women exposed during pregnancy. Barium nitrate, another indispensable pyro chem, is also highly toxic, but does not possess the proven genetic concerns of the dichromates. And both soluble barium salts and dichromates are ecological nightmares. But they have valuable uses in fireworking. If using typical (hopefully high-level) care/attention, then employing them is pretty much a non-event. Though I wouldn't grind dichromates or barium nitrate to airfloat indoors in a coffee/spice grinder, I will happily grind & open such containers outside (and standing upwind), with no inordinate concern. Just a matter of knowing precisely what you're working with and treating it with the appropriate respect that it deserves.

[WSM]

An old friend (who has since passed on, of old age) reported that in his youth, after WWII, successfully used it as an oxidizer for flash.

 

I have no experience in that regard and only mention it as an example of "outside the box" possibilities.

 

WSM

[EasyEstes]

When done with the chromium (VI) solution, it is necessary to surrender the liquid to a hazmat facility or further expose yourself to this nasty substance by destroying it yourself. I found a useful recipe in Sax's Dangerous Chemicals to eliminate one hazard (and create three more) using readily available reagents. Transcribed and abridged as follows: acidify chromium(VI) solution with drain cleaner, reduce to chromium (III) using stump remover, then precipitate a non-hazardous solid with antacids. The procedure doesn't have to be complicated if you do this outdoors in excessively large containers, go slow and understand which reagents can be used to excess. Also, I skipped filtration in favor of open air evaporation over a week period to end up with a pile of Epsom salts tinted green with "artists pigment." I am being intentionally vague to force use of the original source.

[SharkWhisperer]

When done with the chromium (VI) solution, it is necessary to surrender the liquid to a hazmat facility or further expose yourself to this nasty substance by destroying it yourself. I found a useful recipe in Sax's Dangerous Chemicals to eliminate one hazard (and create three more) using readily available reagents. Transcribed and abridged as follows: acidify chromium(VI) solution with drain cleaner, reduce to chromium (III) using stump remover, then precipitate a non-hazardous solid with antacids. The procedure doesn't have to be complicated if you do this outdoors in excessively large containers, go slow and understand which reagents can be used to excess. Also, I skipped filtration in favor of open air evaporation over a week period to end up with a pile of Epsom salts tinted green with "artists pigment." I am being intentionally vague to force use of the original source.

Then perhaps do the newbies a favor and provide a free & easy link to that chapter in Sax.

 

Because they are the only ones who would attempt this by guessing which of their commonly acquired drain cleaner (acidic and alkali and other?), stump remover (not all is KNO₃; some are rather nasty organic herbicides), and antacids (carbonates or hydroxides?) might work. And they're not going to pay $42 for access via Wiley online.

 

Sometimes intentional vagueness is not protective and can have unintended and potentially detrimental outcomes.

[MadMat]

What EasyEstes is talking about is reducing hexavalent chromium to trivalent chromium. If you do this, you have to remember that trivalent chromium is a heavy metal and still toxic. Reducing hexavalent chromium compounds is not as complex as what he posted and can be done with a number of different reagents. Sodium metabisulfite, sold as a sterilizer (commonly called Campden tablets) in wine making will do the job. Hydrogen peroxide will even reduce hex to tri, but the 3% sold at the drug store won't work. You would need a minimum of 35%, which IS available. The color change of reddish-orange/orange/yellow (depending on concentration) to green is the indication that the reaction took place. I used to work in metal finishing laboratories and part of my duties was waste treatment. Reducing hex chrome to tri chrome dropped the hazardous waste disposal costs about 70%.

Edited July 6, 2021 by MadMat

[SharkWhisperer]

What EasyEstes is talking about is reducing hexavalent chromium to trivalent chromium. If you do this, you have to remember that trivalent chromium is a heavy metal and still toxic. Reducing hexavalent chromium compounds is not as complex as what he posted and can be done with a number of different reagents. Sodium metabisulfite, sold as a sterilizer (commonly called Campden tablets) in wine making will do the job. Hydrogen peroxide will even reduce hex to tri, but the 3% sold at the drug store won't work. You would need a minimum of 35%, which IS available. The color change of reddish-orange/orange/yellow (depending on concentration) to green is the indication that the reaction took place. I used to work in metal finishing laboratories and part of my duties was waste treatment. Reducing hex chrome to tri chrome dropped the hazardous waste disposal costs about 70%.

Sodium metabisulfite is also the primary ingredient in a common stump remover (Bonide Stump-Out). Be sure to read the label/MSDS...

[MadMat]

Sodium metabisulfite is also the primary ingredient in a common stump remover (Bonide Stump-Out). Be sure to read the label/MSDS...

Hmm... The stump removers Ive seen were potassium nitrate. I was wondering why he mentioned stump remover. Well I guess I've learned something new

Edited July 6, 2021 by MadMat

[SharkWhisperer]

Hmm... The stump removers Ive seen were potassium nitrate

Bonide Product #BND272. Stump-Out. Sodium metabisulfate. $7.99/pound. Enough to treat one 12-18" stump. Or a bunch of dichromates. Amazon Prime'll get it to you by Wednesday. https://www.amazon.com/dp/B0001O0CMQ/?tag=best-stump-killer-20

 

Careful though because Bonide also make other formulations with various organics, likely toxic. I've never bought stump remover, so don't know who else uses KNO₃ besides Spectracide.

[justvisiting]

A word of caution from a guy that did not exercise proper care and did not use a respirator: I milled a partial strobe mix with potassium dichromate in a small mill jar, and the mixture stuck to the balls. It was a pre-weighed amount for a batch, so I wanted to get all of it off. Shaking and rubbing it through a sieve got the job done.

 

This one time careless exposure caused fits of sneezing, which gave way to extreme discomfort and bloody sores inside my nose that took several months to heal. Don't do what I did, you'll be sorry.

[SharkWhisperer]

A word of caution from a guy that did not exercise proper care and did not use a respirator: I milled a partial strobe mix with potassium dichromate in a small mill jar, and the mixture stuck to the balls. It was a pre-weighed amount for a batch, so I wanted to get all of it off. Shaking and rubbing it through a sieve got the job done.

 

This one time careless exposure caused fits of sneezing, which gave way to extreme discomfort and bloody sores inside my nose that took several months to heal. Don't do what I did, you'll be sorry.

Used to be the cool "science" demonstration to make a green ashy and sparky volcano with a couple of ounces of ammonium dichromate lit with Mg ribbon. Must've been 2 pounds of that stuff I lit off, mostly indoors and of course with no respiratory protection or gloves, before toxicity issues were well appreciated. Makes a cool volcano... Probably nicked the lifespan of a whole classroom of 5th graders, ack!

[EasyEstes]

Then perhaps do the newbies a favor and provide a free & easy link to that chapter in Sax.

 

Because they are the only ones who would attempt this by guessing which of their commonly acquired drain cleaner (acidic and alkali and other?), stump remover (not all is KNO₃; some are rather nasty organic herbicides), and antacids (carbonates or hydroxides?) might work. And they're not going to pay $42 for access via Wiley online.

 

Sometimes intentional vagueness is not protective and can have unintended and potentially detrimental outcomes.

Sure. Problem understood. The better case scenario is readers have fun generating fumes and kick over a jug of green Cr(III) solids rather than being jerks and dumping an aqueous solution of Cr(IV).

My experience is treating the collected rinse water from using Alodine 1201 (a commercially available chromic acid solution used to prepare aluminum for painting). What follows is based on my experience using Sax's Dangerous Chemicals:

Let stand liquid Cr(VI) waste solution until volume is reduced significantly through evaporation. Prepare a half normal sulfuric acid solution by adding 15 mL of ROOTO brand drain cleaner to one liter of water, then discard all but 100 mL down the sink (with the faucet running). It is easier and more accurate to make excess 0.5N H2SO4 solution rather than try to measure 1.5 mL of a syrupy acid. If the estimated mass of the problematic chromium compound is 5 g, then 10 grams of sodium metabisulphite (Bonide stump remover) is appropriate. Combination leads to rapid heating, sulfury gas generation and corrosive vapors, so add slowly, outdoors and always step away. Return to add excess Bonide, repeating until reaction is no longer evident. Neutralize this acidic Cr(III) solution by slowly adding small aliquots of Milk of Magnesia [Mg(O2)] until heat is no longer generated... then add to excess. Evaporate this solution for days until all liquid water is gone. The resulting solid should be hydrated crystals of magnesium sulfate and chromium (III) sulphate and excess Mg(O2), or as previously stated, green Epsom Salts. Someone who isn't me would have a clear conscious if they simply wrapped these solids in a bag and tossed it in the garbage, otherwise, do as I someone who is me would do and render this small mass of chemistry to a properly licensed HAZMAT facility with full disclosure. Hope this helps.