Depending on the temperature 75 grams of citric acid will only make a saturated solution of around 100 ml of water. I'd just cover the part and tip in all the citric you've got . Suck it and see, then if you think a higher concentration is needed, get some more acid.

Eug

The last boiler I did was about 6 inches long and 2 inches in diameter. To pickle it I used 200g of citric disolved in 500ml of hot water. This worked very well, taking 20-30 mins to bring it all back to shiny copper.

John

Wikipedia (never wrong!) quotes the following solubility of citric acid in water:

117.43 g/100 mL (10 °C)

147.76 g/100 mL (20 °C)

180.89 g/100 mL (30 °C)

220.19 g/100 mL (40 °C)

382.48 g/100 mL (80 °C)

547.79 g/100 mL (100 °C

Sounds as if lemon juice is about 0.3 mol / litre. The molecular mass is 192g / mol ie so presumably lemon juice for comparison is only about 6g/100mL(?) ie about 4% concentration at room temp. Yes, it's years since I did any chemistry apart from making big fireworks.

Merry

I use a 25% viniger essence solution bought in a botle from the local supermarket.

Left in this solution a couple of hrs it comes out nice and clean.

The parts must be thoroughly washed after this treatment to avoid corrosion.

Ray

PS I only use this on Brass and copper parts.

Posted by john jennings 1 on 13/09/2014 17:09:56:

Citric acid is so soluble that a saturated solution at room temperature will consume vast quantities of acid and the resulting syrup will be very messy and difficult to handle.

What a load of claptrap.

Sorry I'm not sure what the claptrap is.

Using Muzzers figures a pint of warm (30 C) saturated citric acid solution would need over 2lb of solid acid.

This seems a really awful lot and if the solution evaporates or cools it will deposit excess solid acid.

The action of citric acid is quite complex partly due to the acidity of the solution (which at higher concentrations won't be proportional to the concentration) and partly forming soluble citrate complexes with, in this case ,copper atoms/ions.

End of chemistry tutorial for today!

However I guess it is a matter of experiment : I would still begin with weaker solutions.

John

I don't know about lemonade, but when we were kids we used citric acid, bicarb of soda, and icing sugar to make our own sherbet powder.
I guess it is safe enough as we are all still here.

Hello all, having read through this I am still a little unsure to the mixing ratio of citric acid to water to make a copper cleaning solution, could anyone help me ?, thanks in advance

Forgot to say that the residues are easy to dispose of.

Brian B

I use citric acid to remove soldering and brazing flux and (to some extent) scale & rust from bits.

I've never worried too much about "how much" – the main problem (in practice) is to be able to cover the part if it is large or awkwardly shaped. For these parts I first find a suitable (e.g. not too big) container – I have a few different shaped/sized ones (an old plastic bowl, ice cream containers, cut down milk bottles and a old home brew 'tub'  ) and fill it with hot water just sufficient to cover the part. Dependent on the amount of water used (which I simply guess), I put in about a heaped teaspoon per pint.

I then fish the part out after an hour or so and give it a bit of a scrub with wire wool and/or pick at any flux with a 'scratcher' (depends to some extent on the existing state of finish). Sometimes this is sufficient but usually it needs more time in the solution – but I keep checking fairly regularly and scrubbing/picking at the worst of the flux. So to my mind a fairly dilute solution works fine but what you must to do is monitor the part for progress and not leave it in over long. Having said that, I will often leave rusty steel parts in solution overnight – it's the non-ferrous stuff I watch more closely

I used to buy small packets of citric acid (50-75gms) from chemists but then discovered that for just a bit more I could get 1kg bags from eBay (look for Citric Acid & Indian Cooking). I use old plastic milk bottles to keep & store used citric solution and it seems to work fine (any 'muck' settles to the bottom) if I pour off the clear part of the solution and then top it up & cover the part with hot new solution… . Not too much science I'm afraid but it seems to work for me.

Hope this helps.

Regards,

IanT

Edited By IanT on 20/12/2015 10:09:18

Thanks for info' IanT & Ian SC

Have wondered abut this aspect for a while; have a couple of packets of Citric Acid from home brew shop for future use, now I have some idea of ratio.

George.