Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: this_is_tom on March 27, 2019, 12:12:49 PM
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So, i am not a chemistry student (i study civil protection in europe) and part of my thesis involves doing chem work. My faculty doesn't have a lab and my thesis advisor told me to figure it out... But anyway that is not why I am here.
The stuff i am supposed to do is - measure how much NO2 is in car exhausts gases (data i found was mg/km and that is useless), then recreate the concentration and test if mixing it with LPG will cause it to ignite.
My questions are: What simple method can i use to measure the concentration? I found epa 7 and that is not possible. Is There a 'standard' method for testing ignition? Is There a quantifiable limit to 'iniciation' of LPG?
I am sorry for any mistakes and the simple english, its not my first language.
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Welcome, Tom!
I had never-ever imagined traces of NO2 could ignite LPG. It would take hard experimental evidence to convince me. Not only because of the extreme dilution: NO2 ignites amines, and if no amine is present, it may ignite unsaturated bonds, but these are rare in LPG.
Sensors exist to measure an NO2 concentration. As individual electronic parts to build a circuit around them, or as a complete apparatus.
The mg/km give you an idea of the NO2 concentration in the exhaust gas. Take some reasonable consumption in L/100km, convert to moles of C and H, and to moles of combustion products, remembering that air is mainly N2. Or take the engine's volume and rotation speed. This tells you how many mol/km of exhaust gas, which you can compare with the mol/km of NO2, and deduce the concentration. Not perfectly accurate because the proportion of NO2 varies a lot depending on the engine's effort, but already the power-of-ten may give you an idea.
When experimenting what concentration ignites LPG, I suggest to test a very wide range, because the exhaust concentration may very well be 103 or 106 smaller than the ignition limit. Don't forget to add a few additional causes: warm weather, sunlight, sand aerosol, fine particles.
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Thanks for them answer. I did some more research and came up with a plan on how to sample the NO2. Would you please take a look? NO2 reacts with water forming HNO3 and that in water forms NO3- and that i can measure. Does that make sense? Would that work? I know i need to calculate the conversion rate of NO2 to HNO3 but i already found some examples.
One question is, how do i know i dissolved all of the NO2?
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The problem ist NO2 soloubility is only middle to poor. And the reaction with water gives 2 NO2 + H2O => HNO3 + HNO2.
A mixture of nitric and notrous acid. Better is to use sodiumhydroxid as solvent. But also here you will have mixture of nitrate and nitrite.
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thank you, that was really helpful. I found a lot of info thanks to that. I found the saltzman method and I have more questions.
I found this Indicator Solution
1. Weigh out 5.0 g of anhydrous sulfanilic acid and add to a 1-L volumetric flask.
2. Add 500 mL of nanopure water.
3. Add 140 mL of glacial acetic acid.
4. Using a stir bar, stir the solution until the sulfanilic acid dissolves. This takes approximately 30 min.
5. Weigh out 0.020 g of N-(1-naphthyl)-ethylenediamine dihydrochloride and add to the volumetric flask.
6. Dilute to the mark using nanopure water.
my question is: compounds in step 1 and 5 are there to make it change color after the sampling right?
if so, do I get NO2-, NO3- or both?
and could I use those Nitrite/nitrate aquarium test kits just to get the ball park or would the acetic acid interfere?
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The receipe is an indicator which gives a red colour with nitrite. Also indication of reducing nitrate to nitrite.
https://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Sigma-Aldrich/Datasheet/1/73426dat.pdf
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https://www.google.com/search?q=NO2+sensor