Wednesday, 13 May 2015

On Potassium Dichromate

My cytotoxicology work made me a bit more familiar with a reddish substance my instructor and occasional tutor claimed to be extremely dangerous for eukaryotic cells. K2Cr2O7 better known as Potassium dichromate. I only use it as a positive control because it has a well characterised response kinetics, to confirm cells are prone to die when intoxicated and as part of the  mixture composing the blank. But I know from the literature that this substance is so nefarious that if humans come across it they must handle it professionally or simply perish to a list of nasty effects.

Potassium dichromate is known by different other names, such as dipotassium (easy), potassium bichromate (still easy) or oxido-(oxido(dioxo)chromio)oxy-dioxochromium (even easier) [1]! This compound melts at 398 Celsius and boils at 500 Celsius. One of the properties that interests me the most is how soluble the compound is. The answer is exactly 4.9 gram per 100 CC at a temperature of 0 degrees Celsius and it is insoluble in alcohol [1]. Although, at a temperature of 20 Celsius its solubility increases to 125 g per liter of water [2].

This crystal powder is in between the orange and the red colour; it is odourless and has a bitter metallic taste. I wonder who was the first to taste it in order to report back on its flavour?!

Its LD50/LC50 tested on rats is of 50 mg per kilogram [3]. The lethal dose for men is 500 mg! And on what concerns direct health effects caused by Chromium (VI), these are quite impressive:

- Irritating to the skin and mucous membranes with poor tendency for ulcers to heal;
- Direct contact with the eyes may cause severe damage or even blindness;
- Ingestion may be fatal;
- Hexavalent chromium compounds have carcinogenic effects to humans;
- Repeated exposure may cause nasal perforation, skin ulceration, chronic rhinitis, pharyngitis, kidney and liver damage, inflammation of the larynx, increased risk of lung cancer [3]. Just good stuff!

As a matter of pure curiosity, tests on Sprague-Dawley rats revealed that potassium dichromate exposure can result in slight hematopoietic toxicity at 400 ppm [4]. Potassium dichromate poisoning is related to mitochondrial and lysosomal injury and treatment is only symptomatic [6].

If you're lined up to work with this substance you should definitely read the MSDS documents because it might, just 'might' save you from a lot of trouble. But if it ever comes to remediating then let me tell you what is there to save your...

... skin - 'wash with soap and flush with plenty of water without delay. After washing as directed, a 10% dilution of ascorbic acid can be a useful antidote for burns from chromic acid or hot chromate solutions'. Apply the ascorbic acid solution as a wet compress to the affected area.

The antidote for most ingested chromium preparations are demulcent solutions [5] and chelating agents (such as EDTA).

Ok, now you know a bit more, but bear in mind that this page is purely to guide you to what is out there, a simple throughput of ideas. It cannot be used as a technical guideline or a psalm from a toxicology bible. This is not a clinical page of comprehensive accuracy. For that, you really need to see a doctor!!!! I'm serious!!!

[1] Potassium dichromate, PubChem Open chemistry database, [], last visited on the 13th of May, last update unknown.

[2] Potassium dichromate, Chemical Book, [], last visited on the 13tjh of May 2015, last updated in 2010.

[3] MSDS Potassium dichromate, Air safety health and security department, [], last visited on the 13th of May 2015, last updated on the 16th of July 2001.

[4] Reproductive toxicity of potassium dichromate (hexavalent) National Toxicology program, [], last visited on the 13th of May 2015, last updated on the 16th of December 1996.

[5[] Curative Medicine, Part XV, Poisons and their antidotes, Medicology or Home Encyclopedia of Health, [], last visited on the 13th of May 2015, last update unknown.

[6] Goulle, J. P., Saussereau, E., Grosjean, J., Doche, C., Mahieu, L., Thouret, J. M., Guerbet, M., Lacroix, C. (2012). "Accidental Potassium dichromate poisoning. Toxicokinetics of chromium by ICP-MS-CRC in biological fluids and in hair". Forensic Science International. 217(1-3), pp. e8-e12.

1st image - Potassium dichromate salts, Source unknown.

2nd image - Potassium dichromate aqueous solution. Source unknown.

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