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citric Acid mix.

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Clive Hartland27/04/2012 17:15:33
2820 forum posts
40 photos

Having read about the Citric acid being used for cleaniing up Brass and Copper I bought some Citric Acid Monohydrate from the chemist, it cost £1.02 for 50gr.

What i want to know is the mix rate with water. An initial try with 1 level teaspoon into a third of a jam jar of hot water cleaned up a couple of small components immediately.

Also is it stable and can it be kept for later use?


Edited By Clive Hartland on 27/04/2012 17:15:59

Brian Baker 127/04/2012 17:39:37
196 forum posts
36 photos

Citric is a very good pickling agent for model engineers. it will keep for months, (in a closed container to stop evaporation) and when it is no longer required may be safely poured down a storm drain, although a high copper content may not be welcome in a sewage works, depending on the ammount being disposed of.

As you use the solution, it will become blue with dissolved copper, but will still work fine. When it stops working,, say overnight, then it should be disposed of. If used to clean steel, it may deposit the copper onto the work, but this is easily removed.

Home brew stores sell larger quanties, up to one kilogram, but you should be prepared to prove that you do not want to use it to "cut" (dilute) strange & illegal chemicals.



David Littlewood27/04/2012 18:28:10
533 forum posts

Brian's last point is that several narcotic drugs are organic bases and need a weak acid to get them into solution; citric acid happens to be a cheap, stable and harmless example of this class, there are many alternatives but the paranoids who run the world are too ignorant to have heard of them. (BTW, I speak as a chemistry graduate, not as a person involved in drugs!)

If you want to remove the copper from the spent citric acid before dumping it (and that would be the responsible thing to do) then just add some washing soda solution; this will imediately precipitate the copper as copper carbonate, which should settle out. Alternatively, drop a few pieces of mild steel in it and this will precipitate metallic copper, rather more slowly. Of course, copper compounds make good fungicides, but that's probably been made illegal now by self-appointed bureaucrats.


Edited By David Littlewood on 27/04/2012 18:28:40

Clive Hartland27/04/2012 20:04:55
2820 forum posts
40 photos

Thank you lads, it answers all my questions. I use various chemicals for my bee keeping, Thymol and Oxalic acid. This for parasite treatment.


Gone Away27/04/2012 22:12:28
829 forum posts
1 photos

Another handy use for citric acid in the workshop is for passivating stainless steel parts .... bit safer than nitric.

Ian S C28/04/2012 10:00:59
7468 forum posts
230 photos

You'l find it in the supermarket, among the cooking ingrediants at half the price of the chemist, a bit dearer than the home brew shop. Can be got in bulk from agricultural suppliers.

In my days in nursing, we used citric acid to clean the serilisers, it was a brown colour, and fairly lumpy, it came in sacks of about10kg. Just a hand full or two in the boiler, and let it boil for an hr or so, more if things get busy, and you forget. Thats one of the things the night nurse does that the patients don't see. Ian S C

Stub Mandrel28/04/2012 20:58:25
4315 forum posts
291 photos
1 articles

"Of course, copper compounds make good fungicides, but that's probably been made illegal now by self-appointed bureaucrats."

Funnily enough Bordeaux Mixture which contains copper sulphate and is used as a fungicide in vinyards is one of the few fungicides approved for 'organic' growing (at least I'm sure it was some 15 years ago, when we had a certified organic nursery at work).


Russell Eberhardt29/04/2012 10:48:50
2737 forum posts
86 photos

You could use the spent solution to spray your roses against black spot!

Bordeaux mixture is still used in vast quantities here to spray vines and peaches so I have no qualms about disposing of used solution in the irrigation canal at the end of my garden.


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