Hello All,
I’m setting up a designated safe work space for pickling platinum with hydroflouric acid. I was wondering what do other users use to lift the tree in and out of the pickle? Is there a particular type of metal tongs that are used that are resistant to hydroflouric acid?
Any help would be greatly appreciated.
Thanks,
Paul
HFl acid is EXTREMELY TOXIC, even in low concentrations… if it gets on your skin, neutralizing with baking soda will neutralize the acid but the fluoride ion is highly toxic and will continue to kill tissue…It will require immediate medical attention and an infusion at the site of contact with Calcium Gluconate to bind the fluoride ion into fluorite, which is stable and non toxic… Be careful PLEASE!!!.. HFl attacks everything including glass…it comes in polyethylene, fluorocarbon plastic, or lead bottles.
You will need to use polyethylene tongs or other pure resistant plastic material tongs to fish anything out of an HFl solution…the redox potential for Fl is the highest for an oxidant… it will burn up virtually all metals, except for pure gold and platinum… The only metal alternative would be a pair of platinum tongs or fine gold!..The fumes are HFl gas which is also deadly toxic… the cannot be inhaled as this type of acid requires ventilation outdoors or a fume hood with a specialized filter…if fumes are inhaled, irreversible lung damage will occur… this is a medical emergency. PLEASE BE CAREFUL!!!
@jsfandskh Many thanks for your reply. I have a fume cupboard in place and polyethylene containers. Trying to find polyethylene tongs or similar was the problem.
Thanks for your help.
please be careful… fume hoods should be rated to handle HFl…you must be a professional, this isn’t anything an amatuer do at at home should engage in… thanks… and stay safe, best of luck…
Just a bit of nit picking and since it is such a dangerous chemical I seem it is important.
HydroFluoric Acid is HF from H Hydrogen and F Fluorine.
Due to the inherit risks, some use a mix of hot strong Sodium Hydroxide and Potassium Hydroxide in stead. I found this information in a article in Ganoksin on casting Platinum.
It is a bit slower, but in the end you accomplish the same.
Just to emphasize things, this mix is also extremely dangerous, but since it is more in the immediate burn and etching injuries, not the long term slow injuries that may kill you, some prefer this in stead.
Any direction you decide to take, make sure you are equipped for the task at hand.
please excuse me Paul, but are you off your rocker? HF is an unforgiving liquid. please use other means
I completely agree, it is an unforgiving liquid. We have put in place a high level of health and safety protocols, along with purchasing a fume station specifically for handling the liquid.
Can you suggest another liquid/process for removing the investment that is baked on to the platinum castings? I am open to suggestions.
Some use a mix of Potassium and Sodium Hydroxide.
I think 50/50 and water to dissolve it.
It is used boiling hot, if I’m not mistaken.
It was mentioned in a thread here on Ganoksin regarding Casting Platinum.
I think it was here:
sand blaster??
A sandblaster will work for other precious metals but will not remove the residual investment that is ceramic-like following the high temperature burnout required for platinum.
NaOH and KOH are lye and potash lye… the pH for a 1 normal solution is 14… it’s the most alkaline substance that is readily available. at the concentrations used, it will burn skin quickly, you need to have a mild acid on hand to neutralize it if it splashes on you…flush with copious amounts of water, dilute vinegar or citric acid… handle with care!!! also!! Investment, as I understand it, has a lot of silica to give it heat resistance and fuse tightly. Platinum investment has no gypsum and is 90% silica in the form of a-quartz…requiring high burn out temperatures to fuse. Tridymite and cristobalite are high temperature polymorphs of alpha-quartz (different phases, with a different crystal structure), they are used in gypsum added investments for lower temperature gold and silver casting… Dental investment has Magnesium ammonium phosphate which acts as a binder and when heated turns into colloidal magnesium phosphate…
Silica dissolves in strongly alkaline solutions, but slowly… give it time…keeping at a simmering boil speeds up the process, but it will still work slowly…but it does work!
crystal lye is deliquescent. It needs to be kept in sealed containers to keep air and moisture out, otherwise it will absorb water and wet and dissolve itself… it also is exothermic when dissolved in water and will get hot…enough to nearly boil if mixed without constant stirring. As an aside, it does not attack ferrous metals as acid will… which is why pre dissolved lye is used as “liquid plumber” to clear drains of clogged organic material, like hair, which is very resistant to degradation…alkaline hydrolysis of organic matter including skin, is far more destructive than acid hydrolysis… KOH is even more reactive than NaOH…handle with care… but HFl is insanely toxic… even when neutralized with baking soda, the free fluoride ion is a cellular respiratory poison, like cyanide and will continue to kill tissue until bound with calcium… chronic fluoride exposure causes bone damage (fluorosis)…which is why there are warnings on tooth paste not to swallow it…
this is somewhat late, but if you are using HFl acid, a fume hood should be enclosed… like those in a chemistry lab when dealing with volatile toxic chemicals. If not, there’s still a risk of HFl gas escaping. Wearing a HFl rated canister respirator (gas mask type), eye protection (whole face guard), plastic gloves, and a disposable plastic gown is recommended… I worked in a hospital at one time and had to deal with patients with highly contagious diseases that were under droplet, airborn, and contact precautions… the entire room was a fume hood with negative pressure… there was an atrium where personal protective equipment was discarded… I would not work with HFl acid especially when contentrated and fuming without ALL of the proper precautions… even with precautions, chronic exposure has it’s own risks… florosis of bones in the body weakens them to the point of spontaneous fractures… this is counter intuitive since floride is use to treat tooth enamel to convert some of it from hydroxyapatite to florapatite to resist tooth decay… in bones, fluroapatite prevents bone remodelling… bones can’t adapt to stresses and weaken…
Just a heads up, it is HF, there is no such thing as HFl.
It is widely used in some industries, but it is a different level of dangerous than any Hydroxide.
Only comparable to boiling Sulfuric or Piranha solution.
You are absolute correct and I apologize for the misspell… hydrogen fluoride is HF…
the chemical symbol for fluorine is F… Flourine gas dissolves in water and spontaneously reacts to form hydrofluoric acid or HF… it dissociates into H+ and F- ions in water… but it’s considered a “weak” acid in that it dissociates less that hydrogen chloride…although it’s not as corrosive as HCl of Nitric Acid, it does attack glass and silicates. The flouride ion F- is highly toxic, it’s a cellular respiratory poison and is nearly as toxic as cyanide. Besides it’s corrosive acid effects, there in lies the toxicity… Flouride kill cells even after the acid is neutralized with baking soda. Exposure to skin for inhalation of fumes is a medical emergency. call 911!!!