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Resources and Technical Data for Specialty Gases, Industrial Gases and Gas Handling Equipment from Air Liquide

Technical Resources

All the specialty and industrial gas product, technical and safety information you need in one convenient location.

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Conversion of PPM (mole basis) to Grams per Liter
for Gas Mixtures

Example – Given a 100 ppm (mole basis) gas mixture of Compound A in nitrogen, how much of Compound A will be contained in a 1 liter volume?

Key Assumptions:

  1. Temperature of sample is assumed to be at 21.1°C (70°F).
  2. Pressure of sample is assumed to be 1 atm just before injection. At around atmospheric pressure, gases behave in close to ideal manner.

Calculation:

Using the Ideal Gas Law (PV = nRT) for a temperature of 294.1°K (21.1°C), a pressure of 1 atm, and the gas constant R of 0.0821 liter x atm/mole x degree K, we find that 1 mole of ideal gas occupies 24.15 liters.

One liter of gas will then contain (1/24.15 ) moles. Since the concentration of Compound A is 100 ppm, the total number of moles of Compound A in 1 liter is:

(total # moles per liter) x (concentration of Compound A).

 

The concentration of 100 ppm (parts per million) is unit-less, and equals 100 mole-parts per 1,000,000 total moles = 0.000100 in decimal form; thus the amount of moles of Compound A in one liter of mixture is:

(1/24.15) moles per liter x 0.000100 = 
0.000004 moles of Compound A per liter

 

In order to find the weight of Compound A, we need to know its molecular weight. For example, if Compound A is hydrogen sulfide, with a molecular weight of 34.08 gram/mole, we obtain the following concentration:

0.000004 moles per liter x 34.08 gram per mole = 
0.000140 gram per liter or 0.140 milligram per liter


General Formula for Conversion of ppm (mole) to grams per liter for Gas Mixtures

(for temperature 21.1°C (70°F) and pressure 1 atm)

 

Converting Specialty Gases from ppm to grams/liters


Conversion of grams per liter to ppm (mole basis) for Gas Mixture:

(for temperature 21.1°C (70°F) and pressure 1 atm)

 

Converting Specialty Gases from ppm to grams/liters

 

The concentration expressed in decimal form is unit-less. To find the concentration of Compound A in ppm, multiply the answer from equation above with 1,000,000. For example, a concentration of Compound A of 0.000100 (decimal form from equation above) would be 100 ppm, while a concentration of 0.010000 would be 10,000 ppm or 1%.

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