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Author: Subject: Toxicity of Chromium (VI)
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[*] posted on 3-2-2019 at 14:43
Toxicity of Chromium (VI)


How toxic really are chromium (VI) compounds? They don't have such a bad reputation as mercury or cyanides or arsenic but still when you read their SDS it seems that they are much worse.
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[*] posted on 3-2-2019 at 14:47


I believe the effects are chronic rather than acute. They are definitely carcinogens and will kill you with exposure over time. But you probably won't notice anything in the short term.

The famous one is the Hinkley case which was documented quite well in the movie Erin Brokovic.

[Edited on 3-2-2019 by j_sum1]
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[*] posted on 3-2-2019 at 15:03


Quote: Originally posted by ChemistryForever  
How toxic really are chromium (VI) compounds? They don't have such a bad reputation as mercury or cyanides or arsenic but still when you read their SDS it seems that they are much worse.

The symptoms a chronic more then anything else, although they are deadly carcinogens and should only be handled if you know exactly what you are doing and have the right PPE.
The fact you have to ask this says you shouldn't be handling it.




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[*] posted on 3-2-2019 at 16:01


It is not that I shouldn't handle them. Is because I am aware of their dangerous nature, but I didn't know how exactly dangerous they are. But the hazard statements such as "Fatal if inhaled" are sometimes a bit too much, I think they see a hazard on a chemical and they put it a degree further than it is ( like from toxic to fatal ). Basically the safety sheets make chemicals far more dangerous than they really are.
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[*] posted on 3-2-2019 at 16:06


Quote: Originally posted by ChemistryForever  
It is not that I shouldn't handle them. Is because I am aware of their dangerous nature, but I didn't know how exactly dangerous they are. But the hazard statements such as "Fatal if inhaled" are sometimes a bit too much, I think they see a hazard on a chemical and they put it a degree further than it is ( like from toxic to fatal ). Basically the safety sheets make chemicals far more dangerous than they really are.
They put chemophobic descriptions there probably not because they're chemophobic, they may just be afraid to be sued by some chemophobic dumbasses.



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[*] posted on 3-2-2019 at 16:11


Gloves, don't lick your fingers, use a mask if the powder is fine. Standard operating procedures. You should be ok.

When I handle Cr(VI) I am actually more conscuis of the environmental effect and the steps I take to protect my workspace also protect me.
Keep quantities small where possible.
Make solutions as dilute as practical.
Avoid spills. Choose containers carefully. Avoid double handling and transfer losses.
Collect all waste and convert to Cr(III)
Wipe down carefuly and treat wash-cloths to convert to Cr(III)
Spray surfaces with a reducing agent when done. I routinely keep a spray bottle of thiosulfate solution immediately at hand in my lab. Surprising how often it is handy. The spray bottle of ethanol is handy too.
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[*] posted on 3-2-2019 at 16:20


Well, perhaps they mean fatal from delayed effects. Pure concentrated dichromates might well be the death of someone who doesn't use the right precautions. I somehow think I'd rather do an experiment with an acute poison like cyanides or a sensitive explosive; If I were to make it to the end of such an experiment in good health, I'd know my techniques had been good enough to deal with the hazards at hand. That, or I was just really lucky. But with concentrated soluble hexavalent chromium, you could think you were being safe, while actually doing irreversible fatal damage to yourself.

Edit: doing some reactions with KMnO4 (as part of a chemistry set for an educational program) taught me a valuable lesson about losses and contamination when transferring powders. You can think that you got everything where you wanted it, but later while you're wiping down the test tube stand you find tiny streaks of purple. Needless to say, If that had been Cr VI I would have been in serious trouble.

I agree with Jsum; I'm sure it is possible to handle dichromates safely with the right precautions, but ChemistryForever, please make sure your precautions are really as effective as you think. You might be careful enough to never have any problems handling corrosive materials and moderate acute toxins, but still be gradually exposing yourself to dangerous milligrams of chemicals with chronic effects

[Edited on 4-2-2019 by Vomaturge]
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[*] posted on 3-2-2019 at 16:23


Quote: Originally posted by j_sum1  
Spray surfaces with a reducing agent when done. I routinely keep a spray bottle of thiosulfate solution immediately at hand in my lab. Surprising how often it is handy. The spray bottle of ethanol is handy too.
Why is thiosulphate used for destroying OAs? Why not sulphite?



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[*] posted on 3-2-2019 at 16:45


On a lab scale, the hazards can be mitigated with PPE and proper precautions, though I personally don't crack open the CrVI too often.

A more recent case than Hinkley was this case of poisoning of military contractors in Iraq through unprotected occupational contact with dichromate:

Quote:

KBR originally claimed it didn’t know about the deadly toxin until the spring of 2003. Documents produced in the lawsuit, however, revealed that KBR knew the chemical was being stockpiled and used in massive quantities at the water treatment facility as early as January of that year. Prior to the U.S. invasion, Iraqi workers would treat water at the plant with sodium dichromate before injecting it under pressure into the ground, driving oil to the surface. Sodium dichromate helped increase the life of pipelines and pumps by preventing corrosion.

Soldiers assigned to guard the facility said the chemical dust came from bags stacked both inside and outside the plant, which some soldiers would sit on or use for protection from the wind. Wind spread the orange powder from the thousands of 100-pound bags. Gentry estimated the dust covered about half the plant’s area.

“There were soldiers that actually brought it up, asked what it was, and they were told it was a mild irritant at first,” Rocky Bixby, 45, a plaintiff in the Oregon National Guard suit that bears his name, told HuffPost.

“They had this information and didn’t share it,” Gentry said in a deposition two days before his final Christmas, in 2008. “I’m dying now because of it.”

Another soldier, Larry Roberta, now 48, was exposed to the chemical after a gust of wind blew it into his eye and into a chicken patty he was eating. After washing his face and mouth, he tried washing the chicken, because it was the only food he had left for the day. “It tastes like a mouthful of nickels,” Roberta said. “I just kept washing my mouth and I couldn’t get that taste out.”

Roberta said he now requires an oxygen tank because he has less than 60 percent of his lung function and gets migraines stemming from the eye that was exposed to the chemical. He had surgery to fix the muscle at the top of his stomach that prevented food from coming back up.

...

A federal jury in Oregon found on Nov. 2 that KBR negligently exposed troops to the toxic dust and ordered the company to pay $85 million in noneconomic and punitive damages to the Oregon National Guard members.


https://www.huffingtonpost.com/2013/01/09/kbr-guilty-iraq-ne...




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[*] posted on 3-2-2019 at 17:28


Don't taste it.



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[*] posted on 3-2-2019 at 17:47


Quote: Originally posted by fusso  
Quote: Originally posted by j_sum1  
Spray surfaces with a reducing agent when done. I routinely keep a spray bottle of thiosulfate solution immediately at hand in my lab. Surprising how often it is handy. The spray bottle of ethanol is handy too.
Why is thiosulphate used for destroying OAs? Why not sulphite?

I have plenty of thiosulfate that's why.

What do you mean bu OAs? I have no experience with arsenic compounds and I did not think that was what we were discussing.
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[*] posted on 3-2-2019 at 17:52


Quote: Originally posted by j_sum1  
Quote: Originally posted by fusso  
Quote: Originally posted by j_sum1  
Spray surfaces with a reducing agent when done. I routinely keep a spray bottle of thiosulfate solution immediately at hand in my lab. Surprising how often it is handy. The spray bottle of ethanol is handy too.
Why is thiosulphate used for destroying OAs? Why not sulphite?

I have plenty of thiosulfate that's why.

What do you mean bu OAs? I have no experience with arsenic compounds and I did not think that was what we were discussing.
I mean oxidizing agents.



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[*] posted on 4-2-2019 at 07:14


Dichromates (and in general chromium(VI)) has two main risks:
- Acute sensitizer, some people react allergically to hexavalent chromium and can get nasty skin problems after exposure, even to small amounts.
- High inhalation risk. It is a known carcinogen when inhaled. At this moment, in the Netherlands, there are quite a few people, who are sick of inhaling hexavalent chromium dust. They had to sand objects, painted with yellow chromate-based paint. With the sanding, fine dust was released which they inhaled, day after day.

You must, however, see things in perspective. If you do one or two experiments with e.g. K2Cr2O7 and a few tiny dust particles are released into the air and you happen to inhale a few of those dust particles, then you are not screwed, as some people suggest. It is as with smoking cigarettes. A single cigarette will not kill you. But if you use dichromates frequently and are not too careful with using them, then you may be at risk.

My advice with this kind of things is: use common sense. Don't panic, try to work cleanly. In this particular case, prepare a working solution (e.g. dissolve 5 grams of K2Cr2O7 and make 100 ml of solution of this and use this for all kinds of experiments). In this way, you only have the dust-risk once (and it is even better if you do this preparation outside) and after that you can use your dichromate solution, without any risk of inhaling dust. If you get some of this solution on your skin, then quickly rinse with a lot of water and if you have a yellow stain, immerse in a dilute solution of slightly acidified Na2SO3 (e.g. a small spatula of Na2SO3, dissolved in 5 ml of 3% HCl). The stain then is removed at once and converted to the much less risky chromium(III). Through skin, there is no risk of cancer, but it can lead to allergic reactions.




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[*] posted on 4-2-2019 at 08:39


I like the idea of making up a dichromate solution to reduce the risk of inhalation.

I have 25g ammonium dichromate, what molarity would be generally useful ?

Is dichromate solution stable enough for years of storage ?

(or, ... why would it be more useful to keep it as a crystaline powder ?)




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[*] posted on 4-2-2019 at 09:38


Quote: Originally posted by Sulaiman  
(or, ... why would it be more useful to keep it as a crystaline powder ?)
To reduce storage space? I have a 2lb bag of K2Cr2O7 sitting in a corner. I'd like to not dissolve it all at once and have a few L of it as I don't have such a large container. Also, spilling it would be more disastrous than spilling 2lb of the solid.



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[*] posted on 4-2-2019 at 09:49


In the book Simple Chemical Experiments, there's a chapter entitled "Safe Fireworks" and a passage on making serpents eggs using a teaspoon of powdered sugar and one of KNO3 and two of powdered potassium dichromate. To that some mucilage is added drop by drop just enough to make a dough and thereupon shaped using your fingers into little cones like modeling clay.
"When lighted, these "eggs" will burn and a brow snakelike ash with a length of several feet will wriggle forth."
Anyway, it seems the long road to understanding what is safe is played out over and over in history and surely innocuous things even today will later in time be looked upon with obviousness.
http://www.sciencemadness.org/talk/files.php?pid=203290&...


[Edited on 4-2-2019 by Morgan]
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[*] posted on 4-2-2019 at 11:32


Quote: Originally posted by Sulaiman  
I like the idea of making up a dichromate solution to reduce the risk of inhalation.

I have 25g ammonium dichromate, what molarity would be generally useful ?

Is dichromate solution stable enough for years of storage ?

(or, ... why would it be more useful to keep it as a crystaline powder ?)

The concentration depends on what you want to do with it. If you use it for aqueous chemistry experiments, then I think making 250 ml of solution with your ammonium dichromate would be fine. That will yield an intensely colored orange solution.

I myself, however, would prefer the potassium salt or the sodium salt. Ammonium ion is not always a spectator ion. It can produce ammonia at high pH, which can coordinate to some ions or compounds or even be oxidized under certain conditions. So, dissolving the ammonium salt would be less useful in my opinion for general dichromate chemistry. Ammonium dichromate is interesting in its own (e.g. volcano reaction, making trichromates, which shows very interesting decomposition chemistry).

I myself have K2Cr2O7, CrO3, K2CrO4 and (NH4)2Cr2O7 (and some impure (NH4)2CrO4, which is contaminated with (NH4)2Cr2O7). I made a solution of the CrO3 in water and use that for aqueous hexavalent chromium experiments. I have 100 ml of the appr. 25% solution and it goes a long time, before I need to make a new solution.




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[*] posted on 7-2-2019 at 15:22


Quote: Originally posted by Morgan  
In the book Simple Chemical Experiments, there's a chapter entitled "Safe Fireworks" and a passage on making serpents eggs using a teaspoon of powdered sugar and one of KNO3 and two of powdered potassium dichromate. To that some mucilage is added drop by drop just enough to make a dough and thereupon shaped using your fingers into little cones like modeling clay.
"When lighted, these "eggs" will burn and a brow snakelike ash with a length of several feet will wriggle forth."
Anyway, it seems the long road to understanding what is safe is played out over and over in history and surely innocuous things even today will later in time be looked upon with obviousness.
http://www.sciencemadness.org/talk/files.php?pid=203290&...


[Edited on 4-2-2019 by Morgan]


Are you the author/related to the author? His name is Morgan too.
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[*] posted on 9-2-2019 at 09:31


Quote: Originally posted by Heptylene  
Quote: Originally posted by Morgan  
In the book Simple Chemical Experiments, there's a chapter entitled "Safe Fireworks" and a passage on making serpents eggs using a teaspoon of powdered sugar and one of KNO3 and two of powdered potassium dichromate. To that some mucilage is added drop by drop just enough to make a dough and thereupon shaped using your fingers into little cones like modeling clay.
"When lighted, these "eggs" will burn and a brow snakelike ash with a length of several feet will wriggle forth."
Anyway, it seems the long road to understanding what is safe is played out over and over in history and surely innocuous things even today will later in time be looked upon with obviousness.
http://www.sciencemadness.org/talk/files.php?pid=203290&...


[Edited on 4-2-2019 by Morgan]


Are you the author/related to the author? His name is Morgan too.


No, it was just an influential book I came across when I was about eleven. But yes, the author inspired my name on this forum.
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