Oxalic acid: how strong.

[pcatterall]

I have some oxalic acid crystals and want to make up a strong mix but not too strong.
I would like to aim ayt the sort of strength which my rather leather like hands could tolerate for a few seconds provided it was washed off PDQ.
Any ideas? This is for wasing stains from hull and stainless parts.
Thanks

 

[boatbuilder]

About 50grams a ltr if I remember correct, anybody concur?

 

[duncan]

don't think you can make it too strong - I use it at full strength ie mix it with hot water until it won't disolve any more.

in practice this tends to be about 500g to a gallon of water.

 

[oldsaltoz]

<<<the sort of strength which my rather leather like hands could tolerate>>>

Have stopped making latex examination gloves, 100 pr for AU$8.00. ?

Also stay upwind if you don't have a respirator or you will have more than your hands dissolving......

 

[Talbot]

then mix a bit of wallpaper paste into the mix and it will spread on the intended area, and not drip off /forums/images/graemlins/laugh.gif

 

[Vara]

Not a good idea to use Oxalic acid without rubber gloves as it can be absorbed through skin and is quite poisonous.
http://physchem.ox.ac.uk/MSDS/OX/oxalic_acid_dihydrate.html

As to concentration as far as I can find out the concentration in most of the commercial products containing oxalic is 18%w/v.

 

[branko]

AND REMEMBER : DO NOT PUT WATER IN ACID ( i have a bad experience!)

 

[pcatterall]

Ah yes!! I'll do what I oughter 'add acid to water'
The point about rubber gloves is sensible of course but I have had a couple of nasty experiences where the gloves got a hole I couldnt feel anything until the acid really started to burn and by then it was too late.

 

[VicS]

It is suphuric acid to which the "add the acid to the water" rule applies but it is also good practice with other strong acids. No problems with oxalic acid but it may be more convenient to add the crystals to hot water. The instructions on the AG Woodcare website, however, are:
Pour 2-4 tablespoons of oxalic acid crystals in a heat resistant glass jar and add one pint hot water.

As far as I can find the solubility of anhydrous oxalic acid is only 90g/litre at 20C, thats 9%, and equates to 126g/litre (say 12½%) for the dihydrate but many recipies suggest it is more soluble.

The main hazard is its toxicity if ingested, it can can be fatal! It is also absorbed through the skin and by that route can affect the kidneys. It is aso an eye irritant.

You must avoid prolonged contact with the skin, washing splashes off promptly, so good gloves are required. They may be nitrile, butyl rubber, neoprene or PVC.

Goggles are a must to protect the eyes.

Make sure all waste is disposed of safely and that any unused material is properly labelled and stored safely.

 

[tillergirl]

The classic boat mix is 25 grams to 500cc water

 

[sparkie]

Has anyone any experience of using oxalic on a painted surface?? I've used it on gelcoat with some success but my latest boat is painted with 2pack acrylic and I'm affeared it might damage it.

Safe sailing

Sparkie

 

[duncan]

my practical experience seems to fit the theory pretty well.............

 

[Graham_Wright]

Used at high concentration it brought the glaze off our cast iron bath!

Careful!

 

[VicS]

You should not use any acidic cleaners on an enamelled bath as they attack the surface. You sould take care to only use a product labelled as suitable for such surfaces. Acid based cleaners will not, however attack a glazed surface, such as the toilet or wash basin, or plastics but you should nevertheless read the label.