JSP Gold Testing Acid

[Coincollector]

Hi, I am looking to purchase some new testing acid to test 9ct, 14ct, 18ct, and 22ct scrap jewellery.

The acid i currently have is running out/close to its use by date. With my old acid, I file and test the item directly. for example 9ct will fizz green if not gold and stain brown if 9ct gold, no reaction would mean a higher carat.

I can no longer find the acid for sale which I currently use as it was ex jewllers stock.

The JSP acid looks good because it has a different bottle for each of the Four carats, however I would like to test the item directly and not use the test stone which is provided with these acids.

My question is does any one use the JSP acids? and can you test the item directly or will the acids only work by putting lines on a test stone and seeing if the acid dissolves the gold lines?

 

[Pete]

Perhaps not of much help and speaking from ignorance - are these test acids not simply different concentrations of either nitric acid or a mixture of nitric and hydrochloric ( aqua regia ) ? The only acid that will dissolve gold is aqua regia. I am assuming nitric acid alone would dissolve the copper or other elements that are not gold. How you select a concentration to determine carat would require some research but if known would be cheap and simple to make. I did see gold testing kits for sale on the Bay a while back so might be worth checking.

9ct gold test acid is >50% conc. nitric acid
18ct gold test acid is an aqua regia mix of <50% conc. nitric acid with hydrochloric >50% conc. possibly in 1:3 volumetric ratios.

[Coincollector]

Thanks for your reply Pete, The JSP kits are sold on ebay, I was wondering if anyone on here uses them? and can you apply the acid directly to the gold item, or do you have to use the scratch stone? I would prefer not to use the scratch stone method because heavy plating could give false readings.

[Pete]

41 minutes ago, Coincollector said:

Thanks for your reply Pete, The JSP kits are sold on ebay, I was wondering if anyone on here uses them? and can you apply the acid directly to the gold item, or do you have to use the scratch stone? I would prefer not to use the scratch stone method because heavy plating could give false readings.

From what I have read the technique with jewellery is to nick or file a small groove in a concealed place in order to cut through any plating and then drop the acid directly onto the cut. Watch for the colour change then rinse in water to remove the tiny amount of acid.

[GoldBenj]

I use acid testing for un-hallmarked jewellery all the time, cooksongold or other jewellery supplies have acid testing kits that would be more than suitable.

I use a small abrasive "Buff Stick" which takes the plating layer off.

one thing I would say is to wash the acid off with soda to neutralise before washing with water, acid remnants can leave nasty burns.

[sovereignsteve]

http://www.quicktest.co.uk/acatalog/Gold_Testers.html