Originally Posted by
Fr. Mark
Not having the right references in front of me to be sure of vapor pressure, but Potassium Oxalate is a salt of Oxalic acid, as with most salts its vapor pressure will be very low. Smell could be impurities or depending on what else is in the solution, the free acid. Oxalates have some toxicity, but I don't think it is as bad as cyanide. IIRC oxalic acid is the toxic agent in Rhubarb leaves (not stalks, the part I love for pie). People don't usually measure the vapor pressure of salts of organic acids. The value will be a really high number if the material doesn't decompose upon heating before liquifying let alone boiling. Oxalates will probably give off CO2 and CO (carbon dioxide, more/less harmless, and carbon monoxide, very toxic) upon degradation, but again, I no longer have the reference books at my finger tips.
HCl (hydrochloric acid, muriatic acid) is pretty corrosive even in low concentrations and concentrated solutions give off fumes that will sting the eyes and nose/throat if not outright burn them. I was reminded of this when adding acid to water (always do it that way not the other way around!) last night to make cyanotypes. I miss having a fume hood to do chemistry in. that said, I do not ban HCl from my basement. It's a very useful chemical. I'd suggest handling concentrated solutions with good ventilation, splash protection for the eyes and rubber (nitrile) gloves, but that pretty much applies to anything we use for photo chemistry and might not be a bad idea for some kinds of cooking of food! BTW conc HCl is 30-37% so when you have a 5% solution, it's still pretty strong even though 5% doesn't sound like much. True, it will eat stainless (it's stain less not totally impervious unlike the german Rostefrei (rust free---hah!)). But if you dilute it enough, it won't harm your pipes, particularly if you have PVC drain pipes which are pretty much impervious to dilute HCl. Stomach acid is a few percent, maybe even 10% HCl, as anyone with acid reflux will tell you, you want to keep that acid where the body is protected from it (the stomach, not the esophagus) but it isn't immediately dangerous to life with proper handling. Don't bathe in it, but don't overly fear it either. If I've used a lot of HCl, and I have iron and copper drain pipes, I will neutralize it with baking soda first to double "bomb proof" the dilution thing. This makes a lot of fizz (carbon dioxide) so use an over-sized container.
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