oxalic acid as grp cleaner - what dilution please

Furoner said:
Having followed the oxalic acid thread am now ready to lift out boat and wipe its bottom- will our chemist friends pls advise strength (or otherwise) of dilution with water for sponging on and with a hand sprayer. Have read the safety leaflet and will comply....seems nasty stuff.
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About 10pct by volume, assuming the powdered stuff you can get so cheap off ebay (citric acid is another one). I just rinse it off.
I cant say at this strength it is very scary.. wouldnt use it as an eyebath, but it isnt going to eat your flesh !
 
Beware of Oxalic acid cleaners, I had a nasty experience with this stuff.

When cleaning and degreasing my boats' topsides prior to painting ( the grp had ' chalked ' in sunlight ) the boat was up high on trestles and the acid / water residue ran down my bare arms; I had thought it must be quite feeble stuff as the instructions were ' to neutralise rinse surface with water'...

It was fine for a few minutes then my arms started burning, and the pain got rapidly worse - I ran to the club loo's and put my arms under the tap but the pain continued to build, I honestly thought it might burn down to the bone !

My then wife grabbed a club member who was a Hospital Matron, and Pat knew what to do; she filled a basin with cold water and had me keep my arms immersed for a good 40 minutes.

It was close to a hospital job, and getting it into ones' eyes doesn't bear thinking about...

Modern Oxalic acid cleaners may be a weaker solution ( this was off the chandlery shelf in 1991 ) but I'd exercise great care using them, most definitely with eye protection.
 
depending on concentration I would wear a face mask not nice at all to breath fumes in ... I use about 8 to 1 for wood bleaching . If it drys out and leaves dust dont inhale it !!
 
Daydream believer said:
Surely it depends on the dilution that it comes in to start with
One assumes that you will not be able to buy it in concentrated form
So if it is pre diluted then you would need to know by how much before you know how much more dilution you need
Or is that totally wrong?
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It is supplied as a crystalline solid, usually the dihydrate, COOH.COOH. 2H2O. It can be used at close to saturated.
 
VicS said:
It is supplied as a crystalline solid, usually the dihydrate, COOH.COOH. 2H2O. It can be used at close to saturated.
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VicS,

the stuff I used was a liquid, though as I mentioned may well be a weaker solution nowadays.

Also may I take this opportunity to apologise for something nasty I said about Sea Wyches, I had been wound up but that's no excuse; they introduced a lot of people to cruiser sailing, and we will always remember seeing ' Dutch Courage ' at Bembridge, better equipped than most chandleries !

Andy
 
nigelmercier said:
Any idea what that is, say at 20°C?
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Best thing is to use water that is hand hot for best saturation.

Seajet is often telling his tale of woe with Oxalic Acid, but I've been using it for years, mixing my own into the strongest concentration possible and beside it stinging a bit when it gets into open cuts I've not experienced anything like what he did.
 
Woodlouse; Seajet is often telling his tale of woe with Oxalic Acid said:
Woodlouse,

maybe you're ' well 'ard ' then or it's been diluted since as I suggested; I'm sure you'd agree with the gist of my warning though, it wasn't all that much fun and I'm probably not the only berk to underestimate oxalic acid cleaners, particularly with regard to eye protection.
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Seajet said:
Woodlouse,

maybe you're ' well 'ard ' then or it's been diluted since as I suggested; I'm sure you'd agree with the gist of my warning though, it wasn't all that much fun and I'm probably not the only berk to underestimate oxalic acid cleaners, particularly with regard to eye protection.
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I don't consider myself to be 'well 'ard' and all oxalic acid in liquid form is diluted since it's dry form is crystalline. If you're buying it off the shelf as a liquid then it's not going to be as strong as a batch you've made yourself but it will most likely be mixed with other chemicals, some of which won't be pleasant either.

I'm not the only one to refute your claims on the hazards of oxalic acid and you are the only one I've ever heard of to have experienced an excruciating burning sensation when getting it on skin. I won't disagree with you are regards getting it in your eye, it's something I've never tried and to be honest it's good advice with all cleaning products, even shampoo. But we'll have to disagree as regards getting it on your skin, unless you have eczema or leprosy or another skin condition since as I said, when it gets beneath your skin, then it can sting a bit.
 
VicS said:
According to Wikipedia the solublity at 25C is 14.3 g per 100ml for the anhydrous compound. So 20g/100ml for the dihydrate
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Interesting. The spec sheet for oxalic acid at the Sigma site says solubility is "ca.126.1 g/l at 20 °C". I wonder if the 143 g/litre is for the dihydrate version, or would it be the temperature difference? When I make up a solution of dihydrate I am pushed to get more than 140 g into a litre - not sure if I could get 200 g/litre.

http://www.sigmaaldrich.com/MSDS/MS...8+219853121+219853286&mode=match%20partialmax

Anyway, as far as cleaning off brown stains on the hull, it seems anywhere between 6-20% would will do the trick.

R.
 
rbmatthews said:
Interesting. The spec sheet for oxalic acid at the Sigma site says solubility is "ca.126.1 g/l at 20 °C". I wonder if the 143 g/litre is for the dihydrate version, or would it be the temperature difference? When I make up a solution of dihydrate I am pushed to get more than 140 g into a litre - not sure if I could get 200 g/litre.

http://www.sigmaaldrich.com/MSDS/MS...8+219853121+219853286&mode=match%20partialmax

Anyway, as far as cleaning off brown stains on the hull, it seems anywhere between 6-20% would will do the trick.

R.
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Dunno I find so many different figures. Some for the anhydrous acid some for the dihydrate, some at 20C some at 25 C.

All academic anyway. Make it the concentration you want or make it saturated at ambient temperature.
 
Woodlouse said:
I don't consider myself to be 'well 'ard' and all oxalic acid in liquid form is diluted since it's dry form is crystalline. If you're buying it off the shelf as a liquid then it's not going to be as strong as a batch you've made yourself but it will most likely be mixed with other chemicals, some of which won't be pleasant either.

I'm not the only one to refute your claims on the hazards of oxalic acid and you are the only one I've ever heard of to have experienced an excruciating burning sensation when getting it on skin. I won't disagree with you are regards getting it in your eye, it's something I've never tried and to be honest it's good advice with all cleaning products, even shampoo. But we'll have to disagree as regards getting it on your skin, unless you have eczema or leprosy or another skin condition since as I said, when it gets beneath your skin, then it can sting a bit.
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Woodlouse,

' refuting my claims ' is idiotic, do you think I made up the story for fun ?! :rolleyes:

I thought the whole point of these forums was to pass on tips and warnings, but do please feel free to gargle with Oxalic Acid if you reckon it so harmless...
 
We used to have a chemistry teacher who had us learn to recognise acids like hydrochloric by taste; he was mad as a box of frogs too and would probably be the subject of a whole series in the Daily Wail these days ! :)
 
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