Sciencemadness Discussion Board

Quick test to detect copper traces

Arthur Dent - 23-6-2018 at 14:40

Hello folks!
Is there a quick and dirty test to detect traces of copper in water?

I utfse'd the subject but found nothing under copper detection test.

Thanks :) - Bob

aga - 23-6-2018 at 15:18

Elemental copper or ionic copper ?

j_sum1 - 23-6-2018 at 15:27

My first thought would be to add a drop to a test tube of concentrated ammonia solution. If Cu2+ is present you will get the deep blue colour of the tetraamine complex.

But there are probably better and more sensitive tests than that one. Probably also based on the notion of complexing.

And aga, since when did elemental copper dissolve in water without forming ions?

aga - 23-6-2018 at 15:59

You're the First to mention anything about dissolving, including the OP.

Since when did copper dissolve in water in any appreciable amount ?


If it's Elemental copper, which does Not readily dissolve in water, boil the sample dry and look for black or brown dust then mess around with it. HNO3 would be a start.

If it's mysteriously dissolved copper of pretty much Any nature, add NaOH/Na2CO3 and basic copper carbonate will precipitate as a light blue dust.

The Ammonia thing would also be great, and a much nicer colour, although it'll all stay in solution.

If there is a huge piece of copper pipe in your sample, scrape off a small portion with a knife and see if there is a shiny copper colour underneath.

If so, this usually means the huge piece of copper pipe is in fact copper metal.

[Edited on 24-6-2018 by aga]

j_sum1 - 23-6-2018 at 16:12

I think "traces of copper in water" implies that it is dissolved. There is not anything visible there. If there was the possibility of metallic copper being present then the question would have been about detecting copper or copper compounds in dust or solid residue.

I think the question implicitly rules out macro sized pieces of copper pipe sitting at the bottom of the container.

unionised - 24-6-2018 at 00:33

If you dissolve a little calcium chloride (say 0.5g) in a litre of the water, mix it then add sodium carbonate any copper will be precipitated along with the calcium carbonate.
You can filter it off from the water.
If it isn't visibly blue then you are probably below the WHO drinking water limit for copper.

You can prepare "known" standards to compare the blue colour against by adding copier sulphate to distilled water and doing the same precipitation.

If the precipitate is dark coloured- brown or black- then you won't be able to see any blue colour.
However if you shake the filter with aqueous ammonia then the copper will dissolve and the blue/ violet colour of the copper ammine complex will be visible.
Again, if you make a series of known amounts of copper, you can do a comparison to get an indication of how much copper is in the water..

Arthur Dent - 24-6-2018 at 03:31

Thanks J_sum1, ammonia was exactly what I was looking for!
The reaction is very visible and that's exactly what I was looking for!

The reason for this request is to detect traces of copper in soil samples. Over a year ago, I read somewhere that small amounts of copper sulphate augment conductivity of soil and disrupt the ionic exchange of sugars in plants and trees. In that same article, they mentioned that for an adult tree that produces large amounts of fruit, it wouldn't affect the tree but reduce its crop of fruits.

I have a Ginko Biloba on my property, which produces outrageous amounts of yellow, cherry-like fruits every fall... it's quite unpleasant because the overly ripe fruits turn my walkway into a sticky, smelly marmelade mess. So I put a small amount of CuSO4 into the soil around the trunk of the tree.

Oh miracle! Last year, the tree produced less than 10% of the usual amount of fruits! SUCCESS !!!

But my neighbor, who I kept in the loop about this treatment, and who benefited greatly from the lesser amount of fruits in my tree, now accuses me of killing her shrub... located 15 yards from the tree!!! I told her its physically impossible for CuSO4 to migrate to the area where her shrub is, plus the minute amount wouldn't affect her shrub (an evergreen).

So my intent was to take a soil sample, and show here that there are no traces at all of Copper around the shrub.

I'll dissolve some soil in water, add ammonia, and show her that there is no color blue. But not before showing her some actual CuSO4 being mixed with ammonia, which produces a very satisfying dark blue color!

Thanks for the quick test. Even if it's not accurate at all, i'll have at least her off my back! ;)


j_sum1 - 24-6-2018 at 03:47

I hope it works. Persuading your neighbour I mean -- not the Cu test.
People can be funny about these kinds of things.

I would do a test with the soil on your property first to find out if it works at the concentrations that are present there.

It is not impossible that it could soak through the ground a distance of 15 metres. But it should dilute significantly before it gets there -- unless there is a plume extending in exactly that direction.

I actually think your strongest argument is that you did not add enough to kill your tree. You therefore did not add enough to kill another tree at that kind of distance.

unionised - 24-6-2018 at 04:41

Am I the only one who has spotted what might happen?
Here's a hint. If there was no copper in the soil, the plants wouldn't grow- they need traces of it.

Sulaiman - 24-6-2018 at 04:42

The last thing an amateur chemist needs is a neighbour upset with their chemistry,
so worst case ... buy her a new shrub, and help to plant it for her.

If I were your neighbour I too would suspect that your chemicals killed my shrub, due to the timing.
Negative hobbyist test results or explanations may not convince me.
To be 'innocent' you need to determine the actual cause of harm/death.

P.S. are you certain that there are no natural underground waterways and that the water table never reached your treated soil ?

P.P.S. I have used copper sulphate on my apple trees
but no more as I do not want too much copper in my soil - not good.

[Edited on 24-6-2018 by Sulaiman]

AJKOER - 25-6-2018 at 18:32

Here is a possible micro test for copper but not restrictive completely to just copper.

Have a credible third party add a clean soil sample (from your yard) to distilled water and a second sample to distilled water plus an amount of dissolved CuSO4 previously employed (and/or use samples of treated soil with copper sulfate). Let aqueous samples sit and then take a picture of the bacteria count in a drop under a microscope using standard methods for all samples.

Repeat with soil from several places around the shrub and also from around its roots.

Does the shrub sample look like the untreated version with respect to bacteria?

Basis of experiment: copper ions kills bacteria even in micro concentrations.

[Edited on 26-6-2018 by AJKOER]