Smart questions
Smart answers
Smart people
Join Eng-Tips Forums

Member Login

Remember Me
Forgot Password?
Join Us!

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips now!
  • 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.
Jobs from Indeed

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.

Converting an H2S analysis result in ppm (w/w) to ppm (v/v

nichs2 (Chemical) (OP)
14 Jan 09 7:29

I've got a sulphur survey in which results are presented in ppm (w/w) (i.e. mg/kg).  I need, in order to do some classifcation of our plant based on H2S concentrations, the results in ppm (v/v).  I thought I knew how to convert this using molecular weights and assuming ideal gases etc. but I don't believe some of my answers.  I have results for both gas-phase samples(e.g. H2S in propane product) and liquid phase samples (e.g. H2S in crude and produced water).

If anyone feels like doing an answer for me, H2S in produced water is 7.3mg/kg, H2S in propane is 1.5mg/kg!
MortenA (Petroleum)
15 Jan 09 1:20

Use mol weight of gas and mol weight of H2S to convert

Liquids: Hell i dont know. Imo it dosnt make the the same sence. Its like molality (molar koncentration in water). Here its costume to write number of moles pr liter of water - not number of moles pr. moles of water+moles og your compond - and whats the molality of water in water (when theres other compounds)? When its a coumpound that eventually becomes a solid e.g. like salts then your could use that refernce for ppm 8v/v) but H2S is a gas and when its free it take a lot of space - but the density of the water dosnt drop correspondingly. My feeling is that ppm (w/w) is more accurate here.

Best regards


Unotec (Chemical)
16 Jan 09 11:18
I am not completely sure, but for liquids I think you can correlate the gas equation MortenA posted but by densities:
ppm(v/v)liq=ppm(w/w)lliq*(density solution)/(density solid)
I might be wrong though, I have not done this in a while

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying " Damn that was fun!" - Unknown>>

MortenA (Petroleum)
19 Jan 09 6:43
I think you are wrong smile

H2S is not a solid at the given P and T!

Best regards

Unotec (Chemical)
19 Jan 09 10:40
.... yes, you're right... should read (density H2S)... it was a Friday, though.  

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying " Damn that was fun!" - Unknown>>

MortenA (Petroleum)
21 Jan 09 4:01
well you know what the Briths say:

Always check on mondays what was made on fridays after (pub) lunch smile

Anyway i still think its wrong: The density of H2S as a gas in the state AS A GAS is something you can calculate - but as a dissolev gas?

Best regards

Chacuncha (Petroleum)
11 Feb 09 14:27
you have to use the equation the Gram molecular weight of a gas occupies 22.4 Litres at STP. you need P and T to carry out the calculation, thus use P1 V1/T1 =p2 v2/t2, you get the volume of gas at the STP temperature, from this volume you can get the weight of H2S.
mxmaciek (Chemical)
12 Feb 09 8:21
H2S is dissolving with water. As it is forming the solution, not gas bubbles in the liquid.
Chacuncha (Petroleum)
15 Feb 09 11:31
I found the density of H2S is about 1.39 g/L, wouldnt this work for converting ppm w/w to ppm v/v?

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!

Back To Forum

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