Preparation of gas standard mixture

[bsxenia]

Hello everyone!

Does anyboby know if there is any equation for preparing vapour standard mixtures?

Thank you in advance

[AICMM]

Bsxenia,

Are you trying to make a standard of a solvent in some other gas? If so, what do you plan to contain it in? One of the easiest ways to make vapour standards is to but it in a static dilution bulb of a known volume. More difficult, but not really that hard, is to put it into cylinders with compressed gas like air or nitrogen.

Tell us more about what you want to do.

Best regards.

[bsxenia]

First of all, Iam sorry for not giving any further details.

Well, I just want to put a small quantity of different solvents in a bottle and close it with a valve. That means that after few minutes, there will be an equilibrium in the headspace of the bottle with a certain concentration (when I am using only one solvent, par example benzene) C=P/RT, but for making a mixture probably I have to add in my bottle different volumes of each compound. And here is my question, is there any equation to find out the exact volume of each compound? Let's say that I want to have a mixture of benzene and toluene.

Thanks a lot.

bsxenia

[Bruce Hamilton]

You really don't want to use multiphase mixture gas standards unless you have to.

There are a whole range of potential issues that can appear, including azeotropes, miscibility, mixing to saturation, maintaining the composition as gaseous samples are withdrawn etc. etc.

The normal method is to make gaseous standards ensuring that the pressure is never high enough to cause the less volatile components to condense. For petroleum gas mixtures, there is a procedure described in ASTM D4051 - 99(2004) Standard Practice for Preparation of Low-Pressure Gas Blends.

If you really must make multi-phase mixtures, there is a lot of information available for different families of gases which a good online literature search should locate, but the formulas can get quite complicated for muli-component mixtures,

Please keep having fun,

Bruce Hamilton