Member Login

Remember Me
Forgot Password?
Join Us!

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

Join Eng-Tips
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Link To This Forum!

Partner Button
Add Stickiness To Your Site By Linking To This Professionally Managed Technical Forum.
Just copy and paste the
code below into your site.

Convert ppmw to ppmv for liquids

Convert ppmw to ppmv for liquids

There is some disagreement in the office on how to convert ppmw to ppmv for a liquid system.  The majority favors the following formula:

ppmv = ppmw * spgr (of the solution)

RE: Convert ppmw to ppmv for liquids

ppmv(stuff 1) = ppmw * spgr(stuff 1)/spgr(of the solution)

I like to look at formulas with the worst case to see if they make sense.  Suppose the stuff had infinite mass and tiny volume.  It could be 99% of the mass and .001% volume, the formula creates that.  And ther reverse no minimal mass huge volume.

RE: Convert ppmw to ppmv for liquids

It is not possible to directly convert a liquid mixture from/to ppmw and ppmv units. Firstly, to clear up any uncertainty, I assume you are talking about a mixture of two liquid, and not one liquid plus a solid or gas. The reason for my statement is that doing this type of "conversion" implies that the liquid volumes are simply additive. For many liquid-liquid systems, this would NOT be a good assumption. Mixing water and ethanol, for example, is not ideal, and the volume of the resulting mixture is not the sum of the two liquid volumes.

To put some numbers together for the sake of illustration, let's say we mix 100 liters of pure ethanol with 100 liters of pure water and ended up with 195 liters of ethanol-water mixture. What is the volume fraction of ethanol? Would it be 100/195? If you think "yes", then is the volume fraction of water also 100/195?

RE: Convert ppmw to ppmv for liquids

Ok, I think I'm with you.  More background - our lab is providing ppmw S in gasoline (or diesel for that matter) and a process analyzer is giving it as ppmv.  We are trying to reconcile the two values

RE: Convert ppmw to ppmv for liquids

It sounds as if the process analyzer was designed for use in gas service. Reporting sufur in a liquid hydrocarbon stream as ppmw is the correct way of reporting in my view. If you vaporize all of a sample of the liquid, then you will have a vapor which can be analyzed and reported on a ppmv basis. In this case, you would be analyzing the vapor constituents of the stream, such as H2S, SO2, etc.

You should note that ppmv and ppm on a mole basis are one and the same.


Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close