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.
“According to specification of liquor ammonia 30%
100mL liquor ammonia contains 30gm ammonia
Or, 1mL liquor ammonia contains 0.3gm ammonia” … you forgot the density (30 % NH3 by weight)
And finally the NH3 gas will be distributed between the 7 ml water and the 1,2 L gas volume (neglecting adsorption effects on the glass surface) if you evaporate the water in a closed vessel there will be an increase of the pressure and the gas law has to consider this effect. You can get the NH3 more quantitative in the gas volume if you put a few drops of a conc. KOH in this solution.
Very nice that you finally tell us where you use the ammonia for. I am curious about the sensor because our institute is leading in co-producing highly sensitive ammonia
detectors, Such instruments are for instance in the national network for air pollution,
However there are new developments with solid state detectors also. Still, all applications are for ammonia in air and not in vacuum.
Karl
The presence of water vapour would not change the concentration of the ammonia. However, it would change the adsorption of ammonia to the walls.
In case the solution would be added as liquid also (part of) the water would also evaporate anyhow.
Things would be easier when a larger vessel would be used, beacause then a smaller dilution of the solution is required with less interference by the water
Harry,
the evaporation of 7 ml water should increase the pressure of a closed vessel since the vapor needs more space; that was my point and therby the normal conditions of the ideal gas law...but maybe I am wrong with my opinion. By the way we have also developed potentiometric ammonia sensors going down to sensitivities that you can notice when a person entered a room (body smell). We got a patent for using a simplier system as a dosimeter for dirty bed linen. If interested I could send you more informations. But since we are both retired it will be too late to start a co-laboration unfortunately...
Karl
You just made me aware that he will bring 7 ml of water into the flask, equivalnet ot 7 grams of water. In 1.2 liter it would mean that not all water can evaporate, so he is left with liquid water and dissolved ammonia and fully wetted walls.
THe saturatiuon pressure of the water at room temperature by the way is small so that would not give a large differecne in the air composition.
As for the detector please send so I forward it to my colleagues.
I like to suggest to have quick look at the attached publication of the world leading expert on ammonia in the atmosphere
Erisman is also on Researchgate
Thanks all of you for your valuable suggesstion.
Please forgive me for a mistake.
kindly cosider the 7 µL instead 7 ml of liquor ammonia.
And Please tell me a easy and accurate procedure for vpm calculation for ammonia.
Kumar,
we bought a certified gas from the Linde Company and diluted the 10 ppm down to below 1 ppm with pure dry nitrogen. Under the biosensor topic I noticed that you are planning a biosensor for the analysis of ammonia traces in air. Those sensors are generally very delicate and it might well be that the stability does not allow the time for a serious calibration. Why will you develop an unstable biosensor, when a chemical one would do the job much better. Have a look in my book “Working with Ion-selective Electrodes” under the headlines: gas-sensing electrodes and how to build your own ISE. A very sensitive NH3 sensor consists of a NH4-ion-selective membrane electrode using nonactin as ion-carrier. This electrode is placed behind a gas permeable stretched Teflon membrane in a 0,001 M NH4Cl solution. This construction is much more selective than just using a pH-electrode behind the gas permeable membrane (commercial). Such a self-build sensor made from cheap PVC-tubes shows sensitivity below 1 ppm NH3 and is stable for months compared to a biosensor with only a few hours or days. Since I guess that you are working on your thesis, you should now be able to follow the direction without further help. If your advisor nevertheless demands a biosensor, ask why a good working system should be replaced by a worst one (biosensor experience since 1977).
http://www.linde-gas.at/pruefgase/pruefgase/10ppm_nh3_n2.html this is the Website from Linde for the NH3 gas
Gaurav
You have all the detailed answers in your QUESTION
"How we can calculate the concentration in ppm?"
A full calculation was done for you; why do you bother us a with your calculation in which you are a factor of 1000 off.
We also STRONGLY WARNED you: the dimension of your set-up is far too small. How do you want to deliver 7 microliter of solution? one drop from a buret is much bigger?
Dear all, I want to calibrate my NH3 gas sensor in a 0.343L airtight chamber by Liquor Ammonia of 25% NH3 concentration.
What amount (in volume) of liquor ammonia is needed to achieve 1 ppm (or more up to 50 ppm) concentration of ammonia in chamber to calibrate the sensor?
I will use micro-pipette for the drop-casting of diluted ammonia solution.
Mr. Gaurav, I want to know what does this "300" in the denominator stands for for the drive formulation given below?
Will you please help me to understand your proposed formula..
liquor ammonia (µl)= (0.833 ×ppm ×dilution)/300
Mr. Gaurav I have stuck to a similar problem...and your way seems to be convincing.
But the last statment says we take 7µL diluted (2500 times) liquor ammonia and placed in 1.2 L Airtight chamber?
Is that correct? Then why you said 7ml.....
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