Sciencemadness Discussion Board

Growing Lead iodide crystals help!

Wrecking Bereserker - 11-5-2019 at 10:05

I reacted lead nitrate with postassium iodide to form lead iodide then i heated the solution to dissolve the lead iodide in water but the water just boils and spurts PbI2 all over!what should i do?

Ubya - 11-5-2019 at 12:22

lead iodide has a solubility of 0.41g/100ml of water at 100 °C. you need more water and to cover you vessel so you don't get lead splashes...

Boffis - 11-5-2019 at 12:28

You are simply boiling it too vigorously. Lead iodide dissolves quickly up to saturation but even in boiling water its solubility is only about 4g per litre. How much are you trying to dissolve? Did you measure the amounts of reactant you used? Did you mix them them in the correct Molar ratio? You will need to gives us a bit more information before we can help.

By the way excess lead nitrate depresses the solubility of lead iodide while excess potassium iodide increases it until finally no lead iodide will form at all on cooling only creamy yellow needles of a potassium lead iodide double salt.

@ Wrecking Bereserker

Sulaiman - 11-5-2019 at 12:46

just in case ... lead iodide is a cumulative poison,
(by mechanisms unknown to me) the iodine helps the lead enter your body, even through your skin.
Poisoning is (I've read) similar to lead poisoning.
Sorry if this is old news, just thought it best to mention it.

beeludwig - 11-5-2019 at 13:32

I've done this and have gotten the "golden rain" effect, I haven't tried making a larger crystal out of it although I'd like to. Wikipedia suggested making the crystals by reacting the chemicals through a permeable barrier. I tried this and it just made a mess. I haven't really tried anything else yet. Mostly because there's a limit to how much lead waste I want to make without a good way of remediating it.

woelen - 13-5-2019 at 23:28

If you boil the liquid with PbI2, cover the beaker or test tube loosely with a paper tissue. Any vapor/gases easily pass through, but small droplets get stuck in the paper tissue. In this way you avoid exposure to lead salts.

diddi - 14-5-2019 at 02:41

i do not boil it. as soon as the PbI2 begins to disappear, it is hot enough.

[Edited on 14-5-2019 by diddi]

woelen - 14-5-2019 at 03:27

But this only happens when you have a very small amount of PbI2 in the liquid. Otherwise you certainly will keep on heating, until the liquid boils.