[zorba9112]

How much NaF in water would make it form dangerous amounts of HF?

What would happen is somebody would pour NaF inside a swimming pool for example?

[chenbeier]

Sodiumflouride is a salt. To get hydrogenflouride you have to add a strong acid like sulfuric acid. In water its only dissolved, like sodium chloride, but its anyway very poisson.

[zorba9112]

Several sources I read claim that when Sodium Fluoride is dissolved in water it forms fluoride, hydrofluoric acid, and silicic acid.

[blackcat]

Several sources I read claim that when Sodium Fluoride is dissolved in water it forms fluoride, hydrofluoric acid, and silicic acid.

The key is concentration.

Sodium fluoride means "fluoride" ion in water, which overall is basic instead of acidic. Acids might form, but in tiny concentration in equilibrium

[AWK]

Several sources I read claim that when Sodium Fluoride is dissolved in water it forms fluoride, hydrofluoric acid, and silicic acid.

Either you read carelessly or you read unbelievable sources.

[Babcock_Hall]

If someone is interested in the toxicity of sodium fluoride, here is an older reference:  https://jada.ada.org/article/S0002-8177(85)02022-0/pdf

[blackcat]

If someone is interested in the toxicity of sodium fluoride, here is an older reference:  https://jada.ada.org/article/S0002-8177(85)02022-0/pdf

Indeed, I wrote a paper during my postdoc using fluoride as catalyst and I claim it to be non-toxic. But I also came across some sources stating that fluoride is toxic.

Well, whenever it comes to toxicity, it is the matter of dose. Don't forget toothpaste contains fluoride and also our tap water.

[Babcock_Hall]

If I recall correctly, fluoride ion is an alternate acceptor of a phosphoryl group in the reaction catalyzed by pyruvate kinase (the paper I cited mentioned glycolytic enzymes but did not go into detail).  As you implied however, the dose makes the poison, and I don't even know whether or not this reaction is the main reason.

[rolnor]

https://www.fishersci.com/shop/msdsproxy?productName=S299100&

LD50 in rat 52mg/kg

[rolnor]

I veru much hope you dont want to hurt anyone by pouring poison in a swimmingpool, please dont do that.

[zorba9112]

I veru much hope you dont want to hurt anyone by pouring poison in a swimmingpool, please dont do that.

Nope  Not a terrorist. I was just wondering if NaF in water would form any dangerous amounts of HF, that could cause the skin to burn.
While I still don't know for sure, my guess is that the amount of HF that forms is very minimal.

[rolnor]

Good! If you dissolve NaHF2 or KHF2 in water you get HF, NaF is as stable as ordinary salt NaCl.
https://en.wikipedia.org/wiki/Potassium_bifluoride

[chenbeier]

As I said in my first post, HF is developed if the fluoride solution is acidified.
But fluoride  is a poisson itself.

[hollytara]

HF has a pKa of about 3.2
HCl has a pKa of about -6

So when you dissolve a fluoride salt you do get some equilibration to get HF:

F-  +  H2O     HF  +   OH-   

and the pH is going to be higher than 7 from  the hydroxide formed.  If I remember right it can be as high as 9.
Is it enough HF to be dangerous?  It will depend on concentration, I suppose. 

Why silicic acid?  If you dissolve fluorides in glass, the HF that is formed starts to dssolve the glass!

[rolnor]

Yes, HF is a weaker acid but the equilibrium will be shifted very far to the left?