# Conversion approach ?

1. May 19, 2005

### sneez

I need to convert mol/cm3 into ppmv

how would i go about that if i know pressure and temperature ?

2. May 19, 2005

### dextercioby

What's "ppmv"? I have a hunch it comes from "parts per million",bt what does "v" stand for ?

1 mol/cm^3 is the cgs unit for concentration.

Daniel.

3. May 19, 2005

### sneez

parts per milion per volume , you just multiply ppm by 1.0e6

4. May 19, 2005

### pervect

Staff Emeritus
Are you using ppmv with gasses? A google shows that this appears to be the standard usage.

http://www.ch4.org.uk/glossary.php/Ppmv?term=p [Broken]

has the usage info,

http://www.rotronic-usa.com/datasheets/Ref/Def/ppm_v.htm [Broken]

has some sample calculations of how the term is used (with gasses).

If the term is being used for something other than gasses, the approach in the second url probably won't work - but I think it would be a bad idea to use the term for anything other than gasses.

Last edited by a moderator: May 2, 2017
5. May 19, 2005

### sneez

I think i can work with that. Thanx a much

6. May 19, 2005

### dextercioby

I hope u realize you can't make that conversion

dim (mol/cm^3)= S V^{-1}

dim (ppmv)=V^{-1}

Daniel.

7. May 20, 2005

### sneez

yeah i had to convert everything into SI units.

ppmv=[(Gas rho) /(air rho) ] * 1.0e6

Gas rho = P/(kT) from P=nkT

thanx very much guys