The Vespiary
The Hive => Newbee Forum => Topic started by: bbeeasheets on July 06, 2004, 12:45:00 PM
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is there a cheap and easy method of checking concentration of sulfuric. I have both purchased concentrated h2so4 (instant drain opener) and distilled battery acid (came in 5 gallon bag in box). I would like to be able to check concentration. i looked into density meters and they are around $500 give or take. I really don't have proper glassware for titration yet.
thanks
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Just measure up a certain volume, weigh it and then calculate density (mass/volume)? As simple as that,
no need for fancy meters.
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against a strong base.
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accuracy - titration
close enough - weight of a accurate volume and check density... gives you a rough indication, or you could use vacuum disto to go a fair way over water bp at the vac and just wait until it stops boiling.
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Why do all peaple that titration is so hard to doo ???
It take max 5 min and you can titrate almost everyething. and alle the stuf is over the counter.
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Hest please post what you mean by all otc or pm me with details.
thx
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Titrations are quite easy and usually do not involve suspicious reagents, or equipment. The USP procedure for the titration of H2SO4 is below.
Materials:
H2SO4 Solution
Methyl Orange TS (100mg methyl orange in 100 mL dH20)
1N NaOH volumetric solution
Balance
Burette (easily found on auction sites, or chem suppliers)
Stirring Plate and Stir Bar
beaker (or glass stoppered flask as suggested in procedure)
Place about 1 mL of Sulfuric Acid in an accurately weighed, glass-stoppered flask containing about 20 mL of water, and weigh again to obtain the weight of the test specimen. Dilute with about 25 mL of water, cool, add methyl orange TS, and titrate with 1 N sodium hydroxide VS. Each mL of 1 N sodium hydroxide is equivalent to 49.04 mg of H2SO4.
This procedure as written works best for concentrated solutions of H2SO4. The procedure can be adjusted easily with different normalities of NaOH if so desired.
regards,
m_e
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are you sure about that indicator?
apart from being a shitty indicator (orange to red, yeehaw!) and not being the
most commonly available (phenolphtalein...) isn't it changing at some acidic pH?
somewhere where the second H+ of the sulfuric acid has it's buffer point?
i'm tired, so i may be talking nonsense, but wouldn't it be better to titrate both protons
and use a basic indicator?
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HSO4- has a pKa of about 1,9*
methylorange changes at about pH=4
so i guess it should work...
but i still think doing the right thing would be using a basic indicator,
wouldn't it?
*: i figured that the sulfate ion is stabilised by resonance, but that
HSO4- is a stronger acid than phosphoric acid came as quite the surprise!
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I always titrated my acids using baking soda. Once the solution stops fizzing, there are no more H+ ions in there, and the solution has become neutral. Don't overshoot this and add it slowly. Dilute your acid with sufficient water otherwise you'll get a sticky paste. Acid to water.
- Mass the acid to be titrated. (don't use too much)
- Dilute with enough water.
- Seperate the baking soda into gram portions and add them, one at a time, with stirring, allowing time for the bubbling to stop.
- Once the bubbling slows down, add half grams or less until the bubbling ceases.
- Add up the mass of NaHCO3 needed to titrate the acid, convert this to moles...
2NaHCO3 + H2SO4 --> Na2SO4 + 2CO2 + 2H2O
- Using that number calculate the number of moles of H2SO4 that reacted with the NaHCO3, convert this to mass.
- Take this mass and divide it by original mass of the H2SO4, multiply it by 100 and you should get the percent.
- For concentration, simply divide the number of moles of acid by the volume (in L for molarity), or g, or whatever you like.
This is quite crude but it's worked for me.
It's best to have an idea of how strong the acid is prior the titration so you can predict how much NaHCO3 you'll need. Most drain cleaners are >90% H2SO4...
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> I always titrated my acids using baking soda.
even if using an indicator you'd have to cook out the solvated carbonic acid to
get usable results.
> Once the solution stops fizzing, there are no more H+ ions in there
ouch. you figure that carbonic acid is quit soluble in water?
i can tell you from trying to neutralise reaction mixtures with carbonates
that fizzing is not a good indication.
verdict: not recommended. ;)
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If you have nothing to work with then boil the water off the acid until when a drop off a glass stir rod turns paper black as it eats a hole in it then you got about 95%. Calculate from there. Its geto but will get you close
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when a drop off a glass stir rod turns paper black as it eats a hole in it then you got about 95%. ;D
Is the volumetric test inaccurate due to likely impurities in the H2SO4?
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The density/concentration relationship for sulfuric acid is not linear, the density increases up to a certain point and then drops again. UTFSE.