In my lab we use a fabrication process involving BOE, which is 1:6 HF. For my specific process, we dilute the BOE 1:10, which gives a 1:60 total concentration of HF. I have been too paranoid to go near HF myself, so I have one of my more experienced labmates do it, but if I were to get some of this solution on me, how bad would it be?
Well, it will go through glass that can hold most other acids.
HF is not a strong acid, like HCl, but it does pose a hazard to skin even at low concentration.
From the MSDS (pdf)
Assuming you start with conc. HF at 40%. your 60 fold dilution is 0.67% HF. That’s too close to the nasty burn range for me to want the stuff anywhere near my skin.
Unless you are made of glass, I can’t see what relevance that factoid has. HF is actually a weak acid, and most available solutions won’t burn your skin unless you leave it sitting there for more than 15 minutes, and for really dilute solutions may not burn unless you leave it there for several hours.
And that is one of the biggest problems. With most other acids either the solution is weak enough that it does no harm, or it causes a burn within minutes if not seconds, and so is immediately washed off with no further harm. Because HF takes so damn long to burn it causes major probelms.
HF is dangerous mostly because it sucks the calcium right out of your bloodstream. When you couple that with the fact that the stuff will go straight through skin given enough time, and the fact that it take a long time to burn you have a major problem. The result is that HF is dangeorus not because it is corrosive and causes burns, as is the case for most acids, but because it is seriously toxic.
Ironically, the weaker the HF solution the more dangerous it usually is in practice. A strong solution will cause a burn within an hour, and the victim will then usually seek medical help. Weak solutions may not cause bruns for 10 hours or more. The victim goes home, goes to sleep and dies of a heart attack while asleep.
Which goes some way towards adressing the OP.
How bad would it be if you got it on you? If you noticed the spill it would be serious, but not life threatening. You’d rinse it off and get a couple of days off work and have regular tests for blood calcium levels, blood tests involving huge needles and gallons of blood (atcaully I have no idea how they test calcium levels).
If you didn’t notice the spill, which at that dilution you could easily not do, you could die. If you spilled it somewhere close to the bone, such as leaning in a puddle with your forearm, you could lose the arm due to the underlying bone being dissolved. You would almost certainly end up with a nasty burn and a scar.
I’m not trying to scare you. The point is to relaise that this stuff is nasty if misused, but so are boiling water or many of the herbicides availble at the local hardware store. All sorts of substances have potentially nasty health effects. The important thing is to apply basic safe handlingprocedures, including using appropriate PPE.
Don’t be paranoid, just be aware that it is dangerous, be sensible when handling it and you will have a better chance of being injured driving home than you do form handling this stuff.
I generally avoid HF, but proper hygiene will protect you very well. Wear nitrile gloves goggles and a lab coat at all times. It is very unlikely that you will spill enough on you to die of a heart attack without noticing if you are dressed properly like this.
FYI I would be careful of how you read percents when talking about acids. In my language, a 10% solution often means 10% concentrated acid by volume. In that mode your 1:60 solution is more like 1.7%. It’s rarely specified which, but experience usually makes it clear…usually.
I just wanted to clarify something. Weak acid does not mean it’s not corrosive. Weak acid at least in chem means it doesn’t release all it’s hydrogens to form hydronium ions. (HF is pretty corrosive stuff and toxic as you’ve pointed out.)
IANA chemist, but buy & distribute chemicals for a supply room in a major University chem department. 15-20 years ago, the American Chemical Society published a small safety pamphlet that listed as a symptom of HF exposure “long term excruciating pain.” It caught my attention.
A co-worker once got HF solution on his finger, and they ended up cutting out part of the finger. I don’t know how strong the solution or how big the finger part. the point is that it is an issue. I know that they now put calcium gluconate on it, which works wonders, I’m told. But i’d be extremely careful working with it – much more than other acids – and I’d seek help if I thought i’d gotten any on me.
knowing handling precautions and procedures for chemicals, in its form and concentration, is important. also you should know how to respond to hazards if an accident occurs. knowing what you are doing and being prepared first is important.
being prepared will help reduce anxiety. be nervous is not good for hazardous work.
I am a chemist and I’ve worked with concentrated and dilute HF in the past. At the dilution you are using, I would be cautious but not worried. Follow the proper PPE and handling requirements, including washing your hands after you are done working with it. Be knowledgeable and aware, but not afraid. Also, make sure your employer has Calcium Gluconate Gel available should there be an accidental spill.
Could you also treat it by sticking the affected body part in milk? (Just wondering because I remember that the treatment if you swallow fluoride from say tooth paste is to drink some milk. The mechanism for anybody that cares is that the calcium binds to the fluoride to make calcium fluoride which you would shit out instead of absorbing.)
I’m not sure, I doubt it would hurt but I believe the gluconate penetrates better. One of the reasons for inaction with HF is that it penetrates the skin faster than it burns, often resulting in muscle burns and bone damage. Most MSDS will recommend the standard water over milk.
I don’t think you can. I don’t think the calcium levels are high enough. If you don’t have any gluconate gel handy, you can however ingest large quantities of something like milk of magnesia or anything (tums) that has large amounts of calcium in it to help the situation.
I operate a pair of carwashes and we use an HF-based wheel cleaner. We have very strict safety rules about whom can handle changing out barrels, etc (only me!) and we also keep tubes of gluconate gel on hand just in case.
Our wheel cleaner is about 8% HF in the barrel, which is further diluted with water to where the chemical applicator that sprays it on the wheels it comes out at about 1-2 percent. Its extremely effective in eliminating brake dust.
I don’t understand why anyone would call HF a “weak” acid because it is extremely corrosive (I am not a chemist, though). In one of our washes the section of conveyor immediately in front of the chemical applicators is made out of stainless steel, at the other location its straight carbon steel. You can probably guess at which store we have been reinforcing the conveyor steel every couple of years due to it being eroded.
As an aside, there was a big stink in the carwash industry not too long ago over an Indianapolis-based chain of washes called Mike’s Express that proved that Mike’s was using HF not only in their wheel cleaner, but in their soaps, too. In the short term HF-based soaps do a great job, cars are really shiny and it sets up the car for drying very well. Unfortunately it will also etch your windshield over time, giving it what we call “starring”.
Check out this article from an Indy news channel (damn, there used to be a video that hilariously showed a reporter holding a beaker out of a partially opened car window to collect soap samples during the wash process). Also note the sheer ignorance on the part of the car wash owner that had the girl lose a part of her fingers. You don’t EVER use HF on wheels like that! She wasn’t even wearing gloves when she was scrubbing the wheels with it! It isn’t like these drums of HF-based cleaners aren’t CLEARLY labelled with “Warning: Corrosive” “Warning: Deadly” stickers all over them. Sheesh.
Think of it like this; 10M NaOH solution is an amazingly weak acid, but boy is it corrosive. Acidity ≠ corrosiveness.
Really? I once spilled a drop of concentrated HF on my hand. It hurt a lot in the 5 seconds max it took me to get my hand under cold running water.
Oh, boy; taking things kinda backward:
NaOH is not an acid in any common sense, and I think it’s idiotic to confuse people by talking about it that way. HF is a weak acid in the technical sense that it does not dissociate completely in water, but it dissociates very well compared to other “weak” acids, and it’s plenty strong enough.
Solutions of HF vary considerably, from very dilute solutions used by hobbyists to slowly etch glass, to the concentrated acid used in laboratories. There is no generalization between them, and it’s extremely irresponsible to say that there is.
Finally, BOE is NOT HF. It stands for “buffered oxide etching,” and the solution is a blend of ammonium fluoride and hydrofluoric acid. It contains roughly 60% fluoride ion as HF, but its pH is less acidic, and it’s less corrosive than HF.
I’m not at all certain of this next part, but I think that a 1:10 dilution of this stuff would have a pH of 2; with other mineral acids, this is quite mild, but it may not prevent the sheer HF nastiness from coming through.
Really? Liquids can penetrate skin like that?
Hmm. In a hypothetical murder scheme, could you hook up a barrel of dilute HF acid to somebody’s shower, have them bathe without noticing anything, and then dissolve from the inside out in their sleep?
They wouldn’t dissolve without noticing, but they could die without realizing exactly what was wrong. More of a biology question there. 
Oh, and here’s a handy pH calculator.
Well, I mean obviously they’d notice once their bones and muscles started dissolving, but could they conceivably take that acidic shower and not notice until hours later, when it’s most likely too late?
Well it’s a chemistry thing. (That link I gave earlier mentions what it means to be a weak acid in chemistry.) I mean alot of things in chem are like that. Lets see, in chemistry “organic” mean “containing hydrocarbons.” (You know, like gasoline and diesel.) Oh and “aromatic” means “having a conjugated ring system” and not anything with it smelling nice. (But hey, I’ve only had a few semesters of chem but I did learn quite a bit.)