Murexide
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Oxalic Acid Danger
Oxalic acid is quite frequently used to standardise potassium permanganate solutions. However, it is corrosive and toxic (kidney stones from calcium
oxalate build up). Initially I assumed that oxalic acid, with latex gloves and care, would be relatively safe to work with (similar to KMnO4 in
danger). However, further research shows that oxalic acid is rated at least a 3/4 and sometimes a 4/4 on health risk (!!!) as "extreme" (see http://www.chemicalstore.com/MSDS/MSDS_Oxalic_Acid.pdf). This is rather unsettling, especially for such a common chemical. Note that a 4/4 health
rating is normally reserved for extremely toxic chemicals e.g HF or dimethyl mercury
P.S Once the standard solution (0.1M) is made the health risk is obviously non existent. So, this obviously is relevant only for the powder and
concentrated solutions
[Edited on 28-12-2018 by Murexide]
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j_sum1
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Not sure what your health ratings are based on. There is no question that HCN is more toxic than oxalic Acid.
I think you are referring to the so:called fire diamond. The reality is that thos gives very little information. It was never intended to. It is for
quick assessment of potential hazards for containment purposes.
If you swallow enough OA, you will die. If you handle without gloves it will irritate skin. But follow routine handling procedures and there is
minimal risk.
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j_sum1
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Thread Moved
27-12-2018 at 22:15 |
Fulmen
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I've also seen OA listed as "extremely toxic", but Wikipedia has the following to say:
"In humans, ingested oxalic acid has an oral LDLo (lowest published lethal dose) of 600 mg/kg. It has been reported that the lethal oral dose is 15 to
30 grams"
That's about 5x the values for table salt, so I wouldn't worry.
We're not banging rocks together here. We know how to put a man back together.
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fusso
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Quote: Originally posted by Fulmen  | I've also seen OA listed as "extremely toxic", but Wikipedia has the following to say:
"In humans, ingested oxalic acid has an oral LDLo (lowest published lethal dose) of 600 mg/kg. It has been reported that the lethal oral dose is 15 to
30 grams"
That's about 5x the values for table salt, so I wouldn't worry. |
Wiki: 3 g/kg (oral, rats)[6]
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Sulaiman
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Here in UK Oxalic acid is restricted to 10% w/w (EPP)
I believe that the restriction is due to its potential for deliberate long term slow poisoning,
causing renal falure over a period of time, that would not be seen as 'unnatural' by a coroner.
- 'inheritance powder' for the patient poisoner.
[Edited on 28-12-2018 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
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morganbw
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We used Oxalic acid by the pallets where I retired from.
There were no real concerns about it.
I am not saying that it is completely benign just that we used no special care dealing with it.
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Fulmen
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Also, spinach contain appr 1% OA.
We're not banging rocks together here. We know how to put a man back together.
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XeonTheMGPony
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Rhubarb leaf has nice high concentrations as well
https://en.wikipedia.org/wiki/Rhubarb
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Fulmen
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True, but you don't usually eat the leaves. The stalks have only 0.25% or so, although plants damaged by cold can apparently have higher levels.
We're not banging rocks together here. We know how to put a man back together.
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Murexide
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I had a look at the UK restrictions for possession just then and they look rather surprisingly high. Especially 15% sulfuric acid and 3% nitric acid,
without your mineral acids it’s rather hard to do much Chemistry! Although oxalic acid could easily be concentrated by boiling and nitric acid by
distillation.
As for oxalic acid danger, it is looking more like it only causes renal failure and kidney stones and such after ingestion. It isn’t too corrosive
and doesn’t absorb through skin too well so as long as it isn’t eaten it should be fine I assume.
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Vomaturge
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I don't know how they come up with those (NFPA 704 fire diamond) ratings. I know that they're meant more for estimating immediate temporary hazards
than safe long term usage of chemicals, but some don't even make sense. According to Wikipedia, lead II acetate is just a "2 of 4." But it's hard to
think of an exposure scenario where a gram of oxalic acid would be more dangerous than the same amount of lead acetate. Maybe if the oxalic was
suspended as a fine dust, and caused a pulmonary burn?
I know which I'd prefer to have a gram of in my salad:
I love spinach!
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Murexide
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Rather surprisingly lead nitrate is a 3/4, somehow more toxic than lead acetate. And sodium Oxalate is a 1/4, presenting only a slight health hazard,
but oxalic Acid presents extreme toxicity hazards???
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