Before I retired my work involved a lot of siler soldering, we used sodium bi sulphate

(sodium hydrogen sulphate) as a pickle. It would start to dissolve the tops of screw threads

if left in the pickle tank for a few days, but as most jobs took only 20-30 mins to pickle

this wasnt a problem. the mix ratio we used 28g to 100g of water, but found that

this ratio wasnt critical. as you say the chemical is used for lowering the ph in swimming pools

the ph plus dosnt work so well. Im sorry but i cant explain why the pickle reacts with the plastic pipe.

hope this helps,         Colin.

Edited By Colin Stewart on 13/03/2012 09:01:54

As a much retired chemist the following points may help.

1. The pickle used for "calcium deposits" may just have been neutralised so as to be ineffective. Try a fresh diluted solution.

2. The pickle is usually doing two things removing scale – essentially copper oxides – and removing/dissolving flux residues. The oxide should dissolve in any dilute acid, thus hydrochoric,sulphuric or citric will be ok. Sodium Bisulphate (aka Hydogen sulphate) is half neutralised sulphuric acid a should also work OK it is like citric acid a solid which may be more convenient.

3. Nitric acid will also dissolve the scale but even dilute nitric acid will slowly dissolve copper (sulphuric should not).

4. As an aside all acids will remove the zinc from brass leaving it copper coloured

5. Hydrochoric acid is a gas HCl dissolved in water it will tend to escape and attack bare steel and iron intiating serious and rapid rusting. Keep it out of enclosed workshops!

6. What do the elfins allow you to buy in 2012? Even citric acid, from health food shops, has moved under the counter but ask. Hydrochoric acid is sold as patio cleaner. Strongish Sulphuric acid is I guess still available as battery acid and will need carefully diluting acid to water. (pure concentrated 98% ,an oily dense liquid, is probably difficult to obtain and would need very careful diluting as adding the concentrated acid to water generates enough heat to boil the mixture if done too rapidly, AVOID)

You should be able to get hold of sulphuric acid at a builer's merchant, sold as drain cleaner. Some drain cleaners are however caustic soda so read the label. Dilute it to about 5% (up to 10% in cold weather) but remember to always add the acid to the water NEVER the other way round.

Russell.

Edited By russell eberhardt on 13/03/2012 20:52:54

Citric acid is freely available and has not 'gone under the counter', I regularly buy from my local pharmacist or homebrew store in the UK. Try eBay you can buy as much as you like and it makes a great pickle for copper.

If anyone wanted it for 'illegal substances' they could just squeeze a few lemons

T

Edited By Terryd on 14/03/2012 21:52:56

Terryd…..I think that what KWIL meant was that citric acid has been used by drug dealers to bulk out controlled drugs thereby making their already lucrative trade even more profitable. But thereagain drugs have been bulked out with everything from glucose powder to brick dust and there is no sign of these going under the counter. I must say that I find this self imposed, jobsworth type, petty regulation somewhat tiresome. I was once told by a Boots pharmacist that he could not sell me copper sulphate in case I was a terrorist (perhaps Pensioners' Liberation Army) and wanted to make a bomb with it !!!!!! At the same branch I had to do a covert deal "under the counter" to buy some hypodermic syringes after some interrogation as to whether I was a junkie. I bought some copper sulphate at a garden centre (can't say where in case the urban terrorists are tuned in) and got some extra syringes at a car boot sale (can't say where in case the junkies get in on it). Of course there is nothing illegal about buying these things which should be freely available. In fact if I were a junkie, needles and syringes are freely available at drop-in points.

Hi Mark,

Citric acid is not used to 'bulk out' drugs but to help dissolve heroin for injection as that drug is not soluble in water. Lemon juice or even vinegar can be used to acidify the drug for dissolving. Citric acid is preferred due to the possible impurities in juice etc but a desperate addict will resort to anything. The possibility of use of impure acids is the reason that citric acid is not banned as otherwise addicts will use such substances with possibly lethal effect.

It may be that citric acid is pre-added to heroin for those who inject, but it is not for 'bulking out'

Best regards

Terry

I buy both caustic soda and hydrochloric acid from my local hardware shop in Fenny Stratford. Both chemicals are supplied by Challs International of Ipswich http://www.challs.com

The hydrochoric acic is sold in 500ml plasitc bottles as " MAX super strength acid cleaner – spirit of salts" I have used this satisfactorily for pickling steel and brass items.

The caustic soda is in the form of pure granules and is sold in a 500g plastic bottle as "MAX strength caustic soda"

Hi try one shot from ebay it works well item no 190590736450 it is only £4.50 plus £6.00 PP but take care with it.

TY Kevin

Edited By Kevin Bennett on 15/03/2012 12:46:32