Sciencemadness Discussion Board

Vapor pressure of toxic solids?

Fyndium - 10-10-2020 at 15:36

Is there any risk that a solid could emit enough vapors to cause health risk? I thought this when handling lead acetate and after considering everything else I thought could I still be breathing it? Hydrates, especially in form of crystals do not appear to cause airborne dust particles, unlike some anhydrous powders which just float everywhere.

The vapor pressure of said substance is 0.1Pa.

[Edited on 10-10-2020 by Fyndium]

MidLifeChemist - 10-10-2020 at 18:42

Sure. Osmium tetroxide is considered dangerous for this reason.

Fyndium - 11-10-2020 at 02:03

The compound seems to have quite low boiling point of 126C, hence no wonder. Its VP is 7mmHG which translates to 1kPa, 10 thousand times higher than my reference.

unionised - 11-10-2020 at 04:43

Quote: Originally posted by Fyndium  

The vapor pressure of said substance is 0.1Pa.

[Edited on 10-10-2020 by Fyndium]

Which is about a millionth of an atmosphere.
Plenty of materials are toxic enough that breathing air containing 1ppm of them would be a bad idea.
Obviously, it's unlikely that you would actually reach the equilibrium concentration but...

Warm, but solid, naphthalene can generate enough vapour to exceed the TLV.

Herr Haber - 11-10-2020 at 07:00

Osmium tetroxide... vapor ? You probably thought dust right ?

MidLifeChemist - 11-10-2020 at 08:50

Quote: Originally posted by Herr Haber  
Osmium tetroxide... vapor ? You probably thought dust right ?


No, I thought vapor. The poster did not ask about dust.

Fyndium - 11-10-2020 at 15:09

Dust can be more easily controlled with good working practices and with simple breathing filters, but vapors need more.

What I was after here that how realistic or acute is the exposure to said low vapor pressure substances, if we are speaking minute exposures, no occupational? Is it possible to estimate the actual amount of material absorbed in the body? For lead, daily average intake is 100ug and tolerable limit for people is 250ug in their normal diet and life.

teodor - 12-10-2020 at 02:32

Quote: Originally posted by Fyndium  
Dust can be more easily controlled with good working practices and with simple breathing filters, but vapors need more.


I think the opposite. Many vapours could be vented out or neutralised but dust is a subject for more precise treatment.

But let specify which solids we are talking about. There are different nuances with each of them.



[Edited on 12-10-2020 by teodor]

Fyndium - 12-10-2020 at 04:38

This hazard came up because I were just recently handling lead oxide and lead acetate.

teodor - 12-10-2020 at 04:52

Quote: Originally posted by Fyndium  
This hazard came up because I were just recently handling lead oxide and lead acetate.


Micro quantities of lead will not make any harm, as you know people in past used its compounds everywhere. Only accumulation is the thing which matters, also it has direct danger to small and not born yet children.

So, if accumulation is the thing which matters then the dust, cleaning procedures & waste processing become most important.

As for vapours, I doubt PbO has any appreciable amount and PbAc2 has probably the same level as Pb(NO3)2 which is considered quite low at room temperature.

My most concern when working with lead compounds is my sleeves. I think they can accumulate a lot of micro droplets when I do washing etc. so my next safety measurement will be probably a lab coat.

As for wast processing I used a bottle but decided to buy a bigger plastic drum. I put NaOH solution inside and Na2Sx which converts all lead into PbS which is precipitated on the bottom on prolonged standing. I would not reccomend to use Na2CO3 because it cause effervescence (so many air-flying micro droplets) with acidic solutions. Also concentrated NaOH dissolves filter papers.
Na2Sx causes H2S smell so I will try replace this system with NaOH & Na(OCl)2 which causes precipitation of PbO2.

So, generally, I would more bother with splashing of solutions, washing procedures and dust accumulation in your lab and you should be alive if don't eat Pb salts on everyday basis.

But. If you process lead from e.g. batteries, it can contain other dangerous compounds with different properties as well.
0-2020 by teodor]

[Edited on 12-10-2020 by teodor]

BUT of course we were talking about lead (II) acetate because lead (IV) acetate is quite different thing and has a different level of danger.

[Edited on 12-10-2020 by teodor]

Herr Haber - 12-10-2020 at 08:10

Quote: Originally posted by MidLifeChemist  
Quote: Originally posted by Herr Haber  
Osmium tetroxide... vapor ? You probably thought dust right ?


No, I thought vapor. The poster did not ask about dust.


Well, I guess I'd have found out sooner or later since I have Osmium in my shopping list for the element collection but thank you for the heads up !
Sooner is always better :)
Darned interesting melting and boiling point though.