U of S | Mailing List Archive | alt-photo-process-l | toxicity chrome alum?

toxicity chrome alum?

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  • Subject: toxicity chrome alum?
  • From: phritz phantom <phritz-phantom@web.de>
  • Date: Wed, 02 Sep 2009 22:08:54 +0200
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i just mixed up a 10% stock solution for sizing (used 0.2-0,3 gr/ 100ml 5% gelatin) and with the recent safety discussion, it's probably a good time to bump this question.
usually there are one or two chemists on the list. maybe can provide a final answer to the question below. and if there are any extra risks involved in handling the stuff (while taking the usual safety precautions like with every other darkroom chemicals: gloves, avoiding the use of powder/ breathing in, cleaning ... etc)
i assume that chrome alum has an unnecessary bad reputation (aka being as toxic as the dichromates). but i'd rather be safe than sorry.


phritz phantom schrieb:
Judy Seigel schrieb:

As for chrome alum & company, it's my understanding that they are quite poisonous, and remain so, and not what you want to drop into the water table (along with all those hormones and pthylates). Whether glyoxal is poisonous or not, it does break down (as I understand these matters, but admit that I am not a chemist), and certainly by the time I dispose of it seems entirely attenuated.
i saw this mentioned before, among others by sandy king. when i first ordered the chemical, i looked around, if there was any info available on the toxicity, precautions when handling... etc. but there wasn't much info available. to my understanding (from what i was able to find out), chrome alum is a chrome (III)-compound, which are not as toxic as chrome (IV)-compounds (such as the dichromates). there aren't any hazards mentioned on the english and german wikipedia pages. but i don't know, if there really aren't any, or if just nobody added them yet.
effects on the water table could maybe be neglected, since most of it should stay on the paper (within the gelatin size) anyway.

but maybe someone more chemistry-literate than me could shed some light on the whole thing.