Sciencemadness Discussion Board

Caustic Vapor from adding Sodium Hydroxide to water?

FireLion3 - 11-4-2016 at 11:39

This has stumped me for years now and I've never really been bothered enough to look into it until now.

Every time I add Sodium Hydroxide to water, it seems to give off some very minor caustic vapor when its being stirred in, that is somewhat harsh on my lungs if I happen to get a whiff of it. Doesn't matter if it's distilled water or water from the faucet.

What is this? The only theory I have is that maybe somehow the sodium hydroxide particles are getting carried away in the water vapor, but I don't see how this is even possible, as it happens even if the water only heats up to about 40c. Plus, I didn't really think it could be carried up in vapor as a solid.

elementcollector1 - 11-4-2016 at 11:49

Probably a sodium hydroxide aerosol, or some such, created by the vapor and NaOH.

Velzee - 11-4-2016 at 11:51

It's NaOH being forced into the air.

A similar effect occurred to me:
Quote:

Following along Nile Red's method of boiling down the solution to dryness, I proceeded to empty the container on to a piece of paper, while using a t-shirt to protect me from inhalation(I didn't expect anything bad :( ) and I started coughing like a smoker with an itch in his throat, and when I exhaled, my breath would go directly in to my eyes, which I presumed shot microparticles into my eyes because I felt two or three small sharp pains on my eyes. After hurriedly putting the LiOH in a Ziploc bag, I opened my window (yes, I did this in my bedroom because I thought I would not encounter any problems)and turned on my fan and ran out, still feeling irritation when ever I'd inhale in the area.



And as a response to my prior experiments, a friend messaged me this:
Quote:

Were you properly ventilated? That reaction releases lithium hydroxide and loads of heat.

FireLion3 - 11-4-2016 at 12:05

I didn't realize something such as Sodium Hydroxide could be so easily volatile into the air, especially out of a solution that is being stirred very gently.

aga - 11-4-2016 at 14:13

Recently i found out that my local supply of NaOH contains a significant quantity of NaCl.

Screening incoming reagents appears to be necessary, yet i cannot imagine how to separate just NaOH from this mix.

Better to dump it and buy/make pure reagents ?

Sulaiman - 11-4-2016 at 14:31

since we normally add dry sodium hydroxide to water,
I guess it could just be very fine dust.

To test: pour a similar quantity of sodium hydroxide into another dry container.

[Edited on 11-4-2016 by Sulaiman]

unfrozen - 11-4-2016 at 16:16

I see this happen almost always when adding 337g NaOH to 787g H2O. The liquid gets hot, but probably well under 80C. I wrote to 3M, asking if P95 respirator filters are okay.

The reply was, "Yes. The 3M 6900 Full Facepiece with a P95 filter (3M 2071/2078) is a suitable choice for both NaOH dust and the fumes generated from mixing."

Magpie - 11-4-2016 at 17:17

I have choked also when adding NaOH to water. I agree that an aerosol must be formed which then moves upward into my breathing space. I have to step back quite a ways to get fresh air. I have learned to do this in my hood with the fan on. This way I don't get this choking aerosol.

NedsHead - 11-4-2016 at 17:48

I mostly use potassium hydroxide and have the same experience, could it be the water flash boiling in contact with the hydroxide and releasing a vapour? I've had an identical chocking cough from the caustic dust when transferring the dry potassium hydroxide flakes without proper ventilation or a mask

Loptr - 11-4-2016 at 18:40

The experience seems to be universal as it also happens everytime to me, especially if trying to use the solution immediately; which was a bad habit of mine, but then I started making sets of stock solutions.

I had an issue with temperature sensitive intermediates that were decomposing/dimerizing from the heat of hydration of the freshly mixed solution. I learned pretty quickly.

[Edited on 12-4-2016 by Loptr]

Ozone - 11-4-2016 at 18:48

Tiny droplets get carried up with the steam.

O3

CharlieA - 12-4-2016 at 17:53

Quote: Originally posted by FireLion3  
I didn't realize something such as Sodium Hydroxide could be so easily volatile into the air, especially out of a solution that is being stirred very gently.


This is not a question of volatility. The sodium hydroxide in the air is an aerosol: very fine particles, not molecules, suspended in air.

unfrozen - 13-4-2016 at 15:21

Quote: Originally posted by CharlieA  

This is not a question of volatility. The sodium hydroxide in the air is an aerosol: very fine particles, not molecules, suspended in air.

Thanks, that is good to know. So I can assume that my P95 filters are slowly getting clogged with sodium carbonate.

FireLion3 - 13-4-2016 at 21:57

But this all still begs the question, how is an aerosol getting created? I've had these caustic vapors hit me even if the temperature of the solution was only 30 degrees, with a very tiny amount of hydroxide added in. Certainly not enough for any appreciable steam to form to even carry particles in the air. I'm just having a little difficulty imagining how such an aerosol is forming from a room temperature or even cold solution.

Loptr - 14-4-2016 at 03:42

Quote: Originally posted by FireLion3  
But this all still begs the question, how is an aerosol getting created? I've had these caustic vapors hit me even if the temperature of the solution was only 30 degrees, with a very tiny amount of hydroxide added in. Certainly not enough for any appreciable steam to form to even carry particles in the air. I'm just having a little difficulty imagining how such an aerosol is forming from a room temperature or even cold solution.


I seem to recall it happening when the mixture has began to heat up substantially, and when the beaker is very warm to the touch.