Does lead have a bad rap?
Lead metal is easy to work with and resists corrosion which makes it a desirable metal for many purposes. Lead is used to create glass-like finish on walls, toys, or dishes. It also acts as a sealer to prevent moisture from damaging surfaces. These properties make it excellent for painting and coatings for walls and dishes. However, breathing in lead-based paint particles from the paint causes lead poisoning.
But first, let’s talk about lead poisoning
Lead poisoning occurs when lead enters the bloodstream and binds to enzymes in our body causing the enzymes to lose their critical functionality – everything from digestion to neural processing is impacted by lead poisoning. People suffering from lead poisoning may experience seizures and vomiting as their body functions are blocked by lead poisoning.
Today we have laws that prohibit companies from painting dishes or toys with lead paint. But some countries have no such laws and some companies ignore the law and use lead-based paint anyway. The only way to tell if paint contains dangerous lead is to test it. Below is a well-known oxidation-reduction reaction that can be used to test for the presence of lead.
How to detect the presence of lead experiment – method 1
Take several pieces of different dishware. Wet a paper towel with white vinegar. Rub the paper towel on the dishware to apply vinegar to its surface.
Next, dip a cotton swab in rhodizonic acid sodium solution. This acts as our indicator.
You can make rhodizonic acid sodium solution using rhodizonic acid sodium salt. This can be purchased from any science supply store or online at shops such as Amazon.
Rub the dish with the cotton swab. If the swab turns red, lead is present in the dish’s paint.
How to detect the presence of lead experiment – method 2
Here’s a similar method of detecting lead in paint. Soak a cotton swab with rubbing alcohol. Rub the swab against the dish. Allow the swab to dry. The alcohol will evaporate leaving residue collected from the dish’s surface.
On a white plastic plate, mix one drop of Rhodizonic acid sodium with one drop of vinegar. The mixture will be clear or slightly yellow.
Dip the dried swab in the solution and allow it to soak up the liquid. If lead is present, the swab will turn a pinkish-red color. The color change may take a while – between 1 and 10 minutes. The higher the concentration of lead, the quicker the solution will change color.
How lead detection works
White vinegar applied to a lead surface causes electrons to leave the lead bond, creating lead ions (Pb+2). Rhodizonic acid sodium is electron rich. When lead ions come into contact with Rhodizonic acid sodium solution, an oxidation-reduction reaction takes place. The lead ions are attracted to the Rhodizonic acid sodium solution resulting in a complex of atoms that are colored red.
Testing for gunshot residue
The same test can be used to test for gunshot residue. Police use this method to see if someone under suspicion shot a gun. The test for gunshot residue is called the sodium rhodizonate test. Since bullets contain lead and impact at a high velocity, they leave lead residue behind. The two tests described above can detect even the smallest amount of lead.
Notes about the “testing for lead’ experiment
When making the solutions above, make sure to mix the solution for about 5 minutes.
When you are finished with the solution, dispose of it in a drain using a lot of running water.