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citric acid

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david simmo01/11/2013 16:52:17
33 forum posts

hi how do you stop mould growing in your citric acid it is in a close container(barrel)with sealed lid thanks dave

martin perman01/11/2013 17:16:57
2042 forum posts
86 photos


Can light get into the box, to stop mould it has to be light proof otherwise mould will grow.

Martin P

Thor 🇳🇴01/11/2013 17:42:55
1598 forum posts
45 photos

Hi David,

Try and get some benzoic acid and put that into the citric acid container. Benzioc acid will reduce/stop the growth if microorganisms. As Martin says, use a lightproof bottle.


Edited By Thor on 01/11/2013 17:44:44

Michael Cox 101/11/2013 17:53:46
549 forum posts
27 photos

Boric acid (also known as boracic acid) will also inhibit mould growth. This used to be available from chemists but I have not purchased any for 10 years or more so I am not sure whether it is still available.

Also copper in solution will also prevent mould growth. You could heat up some old copper tube to form a coating of black oxide. This should dissolve in the citric acid and it will turn slightly blue. Leave the copper tube in the liquid.


Ian S C02/11/2013 10:18:33
7468 forum posts
230 photos

I find that Tupperware gets infected with mould spores, the growth can be restricted, I'v got a large container in the kitchen for kitchen scraps, and it often gets furry.

Bleach in the acid would tend to neutralize the mixture. Forget the mould, it's doing no harm. Ian S C

Russell Eberhardt02/11/2013 11:05:37
2728 forum posts
86 photos

I even get algal growth in my sulphuric acid bath. It takes a lot to kill the little blighters! But as has been said, just ignore it.


DMB02/11/2013 11:44:45
1293 forum posts
1 photos
Ian and Russell,
Doing no harm? What do you think the bugs live on? In the case of Sulph. acid, I bet its the Sulphur content, thus steadily weakening the acid strength. Suggest you scrape `em out and maybe dose bugs with aa strong alkali to neutralise before diposal. As you say, could ignore till acid knackerred and replace with fresh.

Edited By DMB on 02/11/2013 11:46:14

Clive Hartland02/11/2013 15:54:33
2810 forum posts
40 photos

Looks like someone has discovered the origins of life. Fungus in Acid and Mould in Sulphuric, please dont mix the two together or you might make a new life form.

Makes one wonder how Primordal life started?


D.A.Godley02/11/2013 17:52:02
120 forum posts
39 photos

A splash of household bleach, added when the mix is made, prevents any unwanted growth, at least , this has been my experience when using citric acid.



Rik Shaw02/11/2013 18:21:01
1480 forum posts
398 photos

Try some sodium metabisulphate from your home brewing shop.


Rik Shaw02/11/2013 18:29:17
1480 forum posts
398 photos

Thinking again - what's all this with citric acid? If this is being used these days for pickling copper prior to silver soldering then it is a new one on me. Going back 30 years or so everyone seemed to be using dilute sulphuric acid - I know I did.

Fill me in someone please.


Stub Mandrel02/11/2013 18:56:17
4315 forum posts
291 photos
1 articles

Citric acid works fine as a pickle, it has the minor advantage that it won't melt you into a steaming puddle or burn holes in your clothes like sulphuric


mechman4803/11/2013 12:54:55
2947 forum posts
468 photos

Is Citric acid available on the local market...where do you get it from, Chemists, garden centre's,.. liquid, powder form etc..? Interested for future ref.


KWIL04/11/2013 09:18:06
3549 forum posts
70 photos

Elfin Safety could not care a toss about home workshops, only in Employment situations to protect the poor workers!

Russell Eberhardt04/11/2013 11:48:40
2728 forum posts
86 photos

Is sulphuric acid really more dangerous than citric.?

It has been stated that citric acid works slowly. This is because the solution is low in acidity (the PH is not very low). If you use a weak solution of sulphuric acid such that the PH is the same it will take equally long to work but should be no more dangerous than citric acid.

Sulphuric acid is available here (France) in all DIY stores and many supermarkets. It should be available in the UK as battery acid. I buy 30% strength and use it diluted 10:1 with water. It works in a few minutes. Dilute it more if you are worried about safety but always remember to add the acid to the water not the other way round.


Martin Kyte04/11/2013 13:57:09
2721 forum posts
48 photos

As I understand it, the issue is in the transportation of liquid acids (read that as by post). Parcelforce classify sulphuric acid as dangerous good so suppliers cannot just mail it as they used to. I suspect they don't sell that much anyhow so moved over to dry acid salts. That said battery acid packs are obtainable by post/courier but that would be diluted acid and fairly small quantities. For boilermaking especially in larger scales (or should that be de-scales) you tend to require quite large volumes which is why sulphuric acid was preferred as it could be diluted will a large volume of water.


John Baguley04/11/2013 14:21:48
503 forum posts
54 photos

One Shot (?) drain cleaner is easily available from B&Q etc. and is something like 90% sulphuric acid. Make sure you get the one that is sulphuric acid based though. It's available from Ebay as well so must be able to post it!

I do use citric acid but still prefer sulphuric acid for copper.


Rik Shaw04/11/2013 15:45:32
1480 forum posts
398 photos

Russell - yes sulphuric is much more dangerous than citric. You can lower a piece of copper tube into sulphuric and listen to it crackling as the acid burns of the scale and you get it on your flesh at your dire peril. Compared to the relative docility of citric acid, sulphuric is an angry beast - it does a lovely job though - and quickly!


Edited By Rik Shaw on 04/11/2013 15:47:12

Russell Eberhardt04/11/2013 18:51:11
2728 forum posts
86 photos
Posted by Rik Shaw on 04/11/2013 15:45:32:

Russell - yes sulphuric is much more dangerous than citric. You can lower a piece of copper tube into sulphuric and listen to it crackling as the acid burns of the scale and you get it on your flesh at your dire peril. Compared to the relative docility of citric acid, sulphuric is an angry beast - it does a lovely job though - and quickly!


Edited By Rik Shaw on 04/11/2013 15:47:12

As I said, it depends on the strength of the solution. A weak solution, less active and less dangerous.

You can buy battery acid ( about 35% w.w. sulphuric acid) by post. For example


Keith Hale04/11/2013 19:26:36
333 forum posts
1 photos


See Royal Mail website - Corrosive Substances

caustic soda, acids, dyes, metal cleaning products and other corrosive materials CANNOT legally be sent by post.

Acids include liquid soft solder fluxes.

Dry flux powders and salts are OK.

Other suppliers via ebay may think otherwise.


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