Hexavalent
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%v/v and %w/v calculations
A new department store opened near us today, and I noticed that they were selling 'concentrated formic acid' as a limescale remover. I purchased 400ml
for testing, and, after a quick acid/base titration using litmus blue indicator it was found to be of 13.02M concentration (13.02M/L), with some error
perhaps as I used a very strong base, NaOH, against the formic acid, which is comparatively weak. I also took a rough density measurement using a Mohr
pipette and my shitty drug dealer balance, and it was found to have a density of 1.06g/ml.
I used to be able to do this, but now I've just confused myself and some of the information on the web is incomprehensible from my perspective . .
.using this data above, how do I calculate the v/v and w/v percentages of my acid?
[Edited on 6-4-2012 by Hexavalent]
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peach
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The 'neutral' (equilivance) point of the titration is basic, because it's a weak acid with a strong base.
If you used blue papers, I would assume you drove it down until the paper turned red, which means you'll have overshot on the addition.
Weight over volume
Weight over weight
To be more sure, check the back of the pack carefully as it may have it's percentage written on it. Failing that, google the brand name and include
the word 'msds', as the safety sheet for the product often lists the percentage of corrosive or otherwise harmful things in the mixture.
[Edited on 6-4-2012 by peach]
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Hexavalent
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I used the litmus blue powder, which is dissolved into water to use as an indicator in the same fashion as phenolphthalein.
Is this correct;
13.02 moles/L
/10=1.302 moles/100ml
Mass=Moles*Mr
= 1.302*46.03
= 59.93 moles/100ml solution
=~60% formic acid w/v
[Edited on 6-4-2012 by Hexavalent]
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peach
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It's sometimes easier if you say 'acid indicating' or 'alkaline indicating', as I'm still unsure which you mean.
If the powder was blue, it'll indicate red - acidic. Whereas phenolphthalein (a word I still struggle to spell), indicates alkaline.
[Edited on 6-4-2012 by peach]
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Hexavalent
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Quote: Originally posted by peach  | It's sometimes easier if you say 'acid indicating' or 'alkali indicating', as I'm still unsure which you mean.
If the powder was blue, it'll indicate red - acidic. Whereas phenolphthalein (a word I still struggle to spell), indicates alkali.
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Litmus blue is blue under basic conditions, and red under acid.
When purchased, the powder was blue. It was dissolved in water, and upon addition to the aliquot of acid, it turned red. Base was added until it
permanently changed back to a faint blue.
[Edited on 6-4-2012 by Hexavalent]
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Hexavalent
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https://www.e-secure.biz/documents/897FG425JU/Safety%20Data%...
Thanks peach, found an MSDS.
What are the inhibitors likely to be though?
What do they do in this situation?
No information on their composition is given.
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peach
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| Quote: | Is this correct;
~60% formic acid |
Nah... because you've not specified if it's w/v, w/w or v/v. 
I'm teasing, partly.
Congrads on getting that close.
The inhibitors, I'm not sure.
[edit]: Having googled around corrosion and formic, I discovered that thiourea is sometimes added to it.
There is also this document regarding oil fields and formic, describing a corrosion inhibiting mixture. But I can't access the rest of the
document.
[Edited on 6-4-2012 by peach]
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Hexavalent
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Thanks for your help, as mentioned the titration was done very quickly, using a bench 1M NaOH solution and a rough aliquot of acid with probably some
level of overshoot.
If anyone's interested, it was 'The Range' shop I got it from . . .I was also tempted to get some sodium bisulfate and dichloroisocyanuric acid from
the pool section No NaBr, though, damn!!
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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peach
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I think I've seen the same stuff in B&Q too.
After some more googling, I discovered Rodine is a common series of acid corrosion inhibitors. It's some proprietary additive, they're called P3 and
the one for formic is 85 I think.
Unfortunately, you need to request the MSDS, they're not listed online.
Shoot them an email, telling them you've just drunk the bottle and need to know asap, and let us know. 
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Hexavalent
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Hmm . . .I think they'd be inclined to take further action if I did that
How could I pose the question without getting them concerned?
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peach
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| Quote: | | inclined to take further action |
A personalised stomach pump from Henkel, with Henkel on the tube. 
Just ask for it.
They have to give you it as a legal thing to ensure it's handled safely. The website actually suggests you read it prior to using the product.
Although they may only have to give you it if you have bought the product. Not entirely sure about the fine details there, which may
vary from place to place. Most companies list them up since it'd be a pain trying to collect receipts to then hand out the msds.
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CHRIS25
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Hexavalent and Peach, thanks for the question Hexavalent, you've just solved my headache with this question. The websites that have been recently
mentioned regarding maths are excellent, so just giving gratitude to the forum really.
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
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