Aside from using calibrated gas mixes (available from all major gas suppliers) there are more unconventional approaches:

Now the 'trick' is to have an air stream that is low enough as not to disturb the equilibrium significantly.

Given the usual precision of MOS gas sensing devices the unconventional approaches will suffice in most cases. Especially when performing a simple 2-point calibration.

Hope this helps to start with...

P.S.: Sorry, I currently have no table of concentrations vs. temperature at hand. But such should be 'findable' in 'the net'.

Dear Dreher

I am not a chemistry guy but daring to understand what you explained. Thanks for that. But It will be better if you explain in layman's terms.

I have got that it should be an airtight chamber how much liquid ethanol is required in that volume (flask) that will result in 10 ppm, 100 ppm or 1000 ppm so on.

I read a post that has been appended below: Please comment. It would be of great help.

My Problem:- I am working on ammonia sensor. I want to calibrate this sensor in a 1.2 L Airtight Chamber by Liquor Ammonia of 30% concentration and Specific Gravity 0.89.

So, What amount (in volume) of liquor ammonia is needed to achieve 1 ppm concentration of ammonia in chamber to calibrate the sensor.

My Answer:-

Ammoin is very volatile hence I used a fan fitted in the chamber for better mixing of gas in chamber and also for total ammonia evaporation from the sample.

To make a calibration mixture for liquid ammonia, a known volume of liquid is vaporized in a known volume of dilutant air. The ideal gas law states that one gram mole of molecules will occupy 24,500 cc of volume at 25 degree centigrade and at 760 mm of mercury or sea level atmospheric pressure.

One part per million (by volume) is equal to a volume of a given gas mixed in a million volume of air.

1 ppm = (1 gas volume)/(〖10〗^6 air volumes)

A micro litre volume of gas in one litre of air would therefore be equal to 1 ppm:

1ppm= (1µL gas)/(1L air)

According to specification of liquor ammonia 30%

100mL liquor ammonia contains 30gm ammonia

Or, 1mL liquor ammonia contains 0.3gm ammonia

After dissolving 1mL liquor ammonia in 2499ml pure de-ionized water we obtained that:

2500mL liquor ammonia contains 0.3gm = 300mg ammonia

Or, 1mL liquor ammonia contains 1.2mg ammonia

Or, 1µl liquor ammonia contains 0.12µg ammonia

According to Standard Temperature and Pressure (STP) law

17 gm ammonia will occupy 24.5 Litre volumes

Or, 17µg ammonia will occupy 24.5 µL volumes

Or, 0.694µg ammonia will occupy 1 µL volume

Or, 0.833µg ammonia will occupy 1.2 µL volumes

We know that,

1ppm= (1µL gas)/(1L air)

And, We have an Airtight chamber of 1.2L volume

Hence

1ppm= (1.2µL gas)/(1.2L air)

Form above calculation we can derive an equation for ppm calculation for 1.2 liter gas.

liquor ammonia (µl)= (0.833 ×ppm ×dilution)/300

Therfore, If we take 7µL diluted (2500 times) liquor ammonia and placed in 1.2 L Airtight chamber

Then, We obtained 1ppm ammonia concentration in that chamber.

Topics

Is this the correct calculation for ppm calculation? - ResearchGate. Available from: https://www.researchgate.net/post/Is_this_the_correct_calculation_for_ppm_calculation [accessed Jan 16, 2017].

Hello Kumar,

if you can live with the airtight chamber approach, the above is transferable to ethanol. At least for low concentrations. Though I'm not sure whether the calculations are completely correct:

Thus you have to ascertain that you get the dimensions right: either Vol% or Mass% for both media (air and ethanol in your case): 1 µL of liquid ethanol gives more than 1 µL of ethanol (gas) - that's the way things work. What's sure: the volume of 1 Mol of ethanol (assumed as an ideal gas) @ 0 °C/101.3 kPa is 22,414 l. And the molar weight of ethanol (C2H6OH is 46.07 g.

The respective data for air (weight per volume at temperature) can be found @ wikipedia.

My own approach was targeting applications where you need a constant supply of gas for calibration - targeting the highest concentrations achievable to address the "extreme end(s)" of the calibration curve. And via the temperature control option you can get these concentrations sustained for long times. But I admit: it is different, requires more control etc. One thing I forgot to mention for my approach: it is best to let incoming air "bubble" through the ethanol to saturate the incoming air as fast and good as possible. Such bubblers are normally used for the air supply of (hobby) fish tanks but serve as well for other purposes (unless they are 'attacked' by the media).

Now you've got 2 options to fiddle with :)

Best regards

Thanks Dreher