feacetech
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SO2 in gas stream - interferances
SO2 + I2 + 2H2O -> SO42- + 2I- + 4H+
this is the general formula for the detection of sulphur dioxide in a gas stream.
My question is would acidic fluoride gasses interfere with this
if they do would passing through reagent grade 80% IPA and then Glass remove these?
Not so much IPA more for SO3
Glass wool for solids and acidic fluoride gasses
[Edited on 6-8-2013 by feacetech]
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subsecret
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Mood: Human Sadness - Julian Casablancas & the Voidz
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How is the gas stream being produced?
Fear is what you get when caution wasn't enough.
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feacetech
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from the addtion of sulphuric acid and HFA to phosphate rock
so the gas stream is not pure and i doubt a simple iodine reich test will work which is designed around a relaitivley pure gas stream
"For titrimetric or gravimetric determination of sulphur dioxide, the gases to be analysed are passed through a hydrogen peroxide solution, which
oxidizes sulphur dioxide to sulphuric acid; the sulphuric acid is either titrated with caustic soda solution against bromophenol blue or precipitated
as barium sulphate and weighed."
Gravimetric analysis may work and has shown no SO2 in the gas stream.
Titremetric analysis does not work as the acidic fluorides generate a false postive
According to Vogel barium sulphate can co-precipitate in the case of certain cations and this can give false results. However Fluoride was not
mentioned as an interfering species
Which is promising
so do you guys think the gravametric aproach is valid?
and my conclusion of using the reich test as a time waster is correct?
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feacetech
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The plot thickens
Gravametric BaCl
H2O2 acid base titration corrected for Flouride conc
mgSO2/m^3 - mgF/m^3*1.68
H2O2 BaCl titration (EPA method 8)
All yielded the same result
An I2 test yielded a result at about 0.25% of the above 3 tests results
I have since found that HFA will react with BaCl to form insoluable BaSiF6
so the two BaCl methods suffer from interferance
the acid base method corrected for Flouride is too simplistic and is missing a contaiminat thats is causeing a positive interferance
So it appears that maybe the I2 method is correct
Acid misit is minimal in the gas stream (from method 8's result)
CO2 is high in the gastream >3000ppm (gastek pull)
What do you guys think
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AJKOER
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Consider MgCO3 or Mg(HCO3)2. To quote (see "Effect of temperature and time on acid sulfite cooking for dissolving pulp" by Muhammad Adeel Shahzad,
page 11, at http://www.diva-portal.org/smash/get/diva2:578173/FULLTEXT01... ):
"Normally during the process, cation used is calcium, magnesium, sodium or ammonium.
Different sulfite solutions have different solubilites. These solubilites set the selection of
cation like calcium requires pH 2 to stay in solution, magnesium requires pH 4, sodium and
ammonium sulfite solutions may be strongly alkaline without precipitation. Acid process has
pH 2-3, bisulfate processes operated at pH range 3-5, neutral sulfite processes have pH range
6-9 and alkaline sulfite processes have pH range above 11. [18]
Usually sulphite cooking liquors are analyzed for total SO2, free SO2 and combined SO2.
These are determined by iodometric titration, followed by another titration with NaOH. Total
SO2 sums up the SO2- content in the cooking liquor of SO2, HSO3- and SO3 2-."
So, my proposed target reaction is when the pH is greater than 4 to neutral:
Mg(HCO3)2 (aq) + SO2 ---> MgSO3(s) + H2O + 2 CO2 (g)
If pH < 4, the MgSO3 dissolves, so add NaHCO3 to adjust the pH. It is also important that all water used in forming aqueous solutions be oxygen
free as:
MgSO3 (slurry) + 1/2 O2 --> MgSO4 (aq)
to limit so called forced oxidation.
Another source (see "Magnesium Oxide Wet Scrubbing System for Flue Gas Desulfurization" at http://www2.emersonprocess.com/siteadmincenter/PM%20Rosemoun... ) indicates at pH of 5 in place of 4 to quote:
"The pH of the slurry [consisting of MgO] must be carefully maintained between 4.5 and 5.0 because the MgSO3 has a very limited solubility above pH
5.0."
If any acid gas is present, like HF:
MgCO3 + 2 HF --> MgF2 (s) + H2O + CO2 (g)
However, MgF2 is described as " a white crystalline salt and is transparent over a wide range of wavelengths, with commercial uses in optics". Source:
http://en.wikipedia.org/wiki/MgF2 ). Apparently, NaF is also colorless.
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[EDIT] MgCO3.3H2O per this source (see http://magnesium.atomistry.com/magnesium_carbonate.html ) can be prepared, to quote:
"MgCO3.3H2O is produced by the action of sodium or potassium bicarbonate on magnesium sulphate solutions at ordinary temperatures "
Also, per the same source:
"Magnesium carbonate has an alkaline reaction, is rapidly decomposed by acids, and dissociates into MgO and CO2 when heated."
[Edited on 3-10-2013 by AJKOER]
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