# How does one test for lead in dry paint?

What analytical methodologies are capable of identifying lead in peeling paint? I am a hobby chemist owner of a Clinical Research Investigative Site. Please tell me if this site is only for professional chemists. If so, I will cancel my registration.

• The best way would be by a hand held x-ray fluorescence instrument. – MaxW Mar 19 at 20:54
• Lead test strips are available in hardware stores where I live and I think they are widely available. I do not know their limit of detection. – Ed V Mar 19 at 21:15

## 1 Answer

This site is not specialized and reserved to professional chemists. On the contrary. A lot of teenagers are using it every day.

Now if you want to identify lead in a dry paint, you may burn it in the flame of a Bunsen burner, and save the ashes. They contain a mixture $$\ce{Pb + PbO + Pb3O4}$$. Then dissolve the ashes in nitric acid (concentrated $$\ce{HNO3}$$ diluted with its own volume of water). Filtrate the insoluble part. Dilute the filtrate still more, by adding an equal volume of water. This gives you a lead nitrate solution, with which you carry out the following tests. Add some $$\pu{1 M}$$ $$\ce{HCl}$$ to a part of the obtained solution : it should produce a white precipitate of $$\ce{PbCl2}$$, if the solution contains some lead ions. Or add some $$\ce{KI}$$ solution : You would obtain a yellow precipitate of $$\ce{PbI2}$$, if the solution contains lead. The reactions are : $$\ce{Pb(NO3)2 + 2 HCl -> PbCl2(s) + 2 HNO3}$$ $$\ce{Pb(NO3)2 + 2 KI -> PbI2(s) + 2 KNO3}$$ A further proof is obtained by heating the solution containing the yellow deposit of $$\ce{PbI2}$$, because this substance gets redissolved at $$\pu{100°C}$$. And after slow cooling, $$\ce{PbI2}$$ will precipitate back and it looks like wonderful golden plates, floating in the liquid. It is amazing. If these precipitate do not occur, there is no lead in your paint.