The Home Scientist
Element collection.
Wednesday, November 26, 2014
Golden rain.
- 1.0 g Potassium Iodide, KI
- 0.8 g Lead Nitrate, Pb(NO 3 ) 2
- 500 mL Distilled Water
28 comments:
Hi Dan, I watched a lot of your youtubes - great stuff! How can i find your email i wish to ask you something. Thanks in advance! Daki
Thanks! If you have a Youtube account, you can send me a message there. It's free and easy to make one if you don't, or you can post questions here.
Hi Dan, congrats on a great site and awesome blog. My name is Mark and i am from Ireland ;-) I would be very interested in talking to you about some products/problems tat i am incurring. New challenge for you lol. Would you be interested in having a chat about this opportunity ?? Feel free to email me to get the ball rolling [email protected] Kind regards and best wishes Mark
Hi Dan, How long does this experiment take exactly? Does it take a long time or can I get it done in an hour? Thanks!
Hi Dan, i tried this experiment before and i end up with too much precipitate after mixing the two compounds . what is my mistake ?
Dan, I used 2g of each compound and dissolved it with 150 ml in water it came out correct but the precipitate is too much at the bottom of the solution
hi dan, i wondered if golden rain can be enclosed and used like a snow globe, and whether the crystals would last for a long period of time. can you answer this? thanks, neil
That should work, yes! The flakes of lead iodide are so thin and fragile, though, I wonder how it would look after shaking it around many times. The compound itself is stable, but the flakes might break up into tiny bits (which might look even better!). A lead iodide snow globe, of course, would be a very dangerous curio to have; if it broke, you'd have a very toxic lead compound spill all over!
if you could email me at [email protected] i would be most appreciative. thanks. neil
HI could you help me out, i have science project due and i am trying to find the theoretical yield of both of the products. i am lost and in need of help. thanks HELP ASAP
To find theoretical yield, use stoichiometry and follow the chemical formula I gave in the post. I started with 0.8g of lead nitrate (Pb(NO3)2). Divide this by lead nitrate's molecular weight (given in g/mol) to get moles of lead nitrate. Divide by the coefficient in the equation for this compound (1) and multiply by the coefficient for the compound you want, lead iodide (also 1). Multiply by the molecular weight of lead iodide, and you find the theoretical yield in grams.
Can you touch the gold glittery crystals before you put them in the vile? or are they toxic too?
Dan, to make the reaction quicker, could I add distilled water at 100 degrees right at the beginning so I don't have to wait to heat it and cool it again? Please let me know fast as I'm thinking of doing this for a project and need to start quick. Thanks :)
Sure! It should all dissolve immediately.
Thanks for a great posting. After several tries using the boil and cool method which took 1-2 hours, I tried cold water (from the fridge) to initially dissolve the reagents. No lead iodide precipitates on mixing but wait 5 minutes and the golden rain effect begins. Might be easier for classroom demonstrations. Also I substituted Lead Acetate (0.9gm) for the Lead Nitrate in case that matters.
Thanks for the info!
What branch of chemistry does this experiment fall under?
I'd say inorganic.
Does this need to be done in a fume hood or can I do it as a demonstration in my classroom without one?
Nope! This reaction produces no gases so you don't need a fume hood. Very careful consideration of safety needs to be done, however. The lead salts used in this experiment are highly toxic and need to be handled carefully, and everything (the remaining liquid and any equipment that touched the solution) has to be neutralized fully before disposal. See the video linked at the top for more info. Good luck, but be very very careful!
where do you get the materials? specially the lead nitrate
I bought the potassium iodide from eBay, and made the lead nitrate myself by dissolving lead (also from eBay) in nitric acid (also made myself).
Hi Dan.. 1) We (me and my friends) performed this practical in our chemistry lab in college but we were not aware of the cleanup and disposal process, so we just simply washed all the apparatus used with water and thrown away the lead nitrate in wash basin. Is it fine or would cause harm later? 2) Adding up to above situation, me and my friend wanted to show this experiment to our parents and so we took the lead iodide solution to our home and started heating the solution in a glass cup which broke due to over-heating and the solution was all over the gas stove and as we were not aware of the safety to be taken we just cleaned it with water. Will it cause harm later?
Hi Dan, May I use one of the pictures for an education blog? I would like to link it with an artwork by Titian (Danae and the golden rain) http://kimikarte.blogspot.com.es/ Of course I would properly attribute your work. Thanks in advanced, Oskar
Wow sorry for the slow reply, I only just saw this! You can certainly use some pictures for your page, with attribution. Thanks for the interest!
What objectives would thisnexperiment was fall under?
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Is the potassium Nitrate seperate from the baking soda? I want to save it to make black powder with lol
Chemical Reactions: Lead Iodide & ‘Golden Rain’
Kicking off an occasional new series of graphics with today’s post, which’ll be looking at common chemical reactions encountered in schools. Today kicks off with one of my favourite reactions, the ‘Golden Rain’ demonstration, which involves the synthesis and recrystallisation of lead (II) iodide, and is commonly used to illustrate the recrystallisation process, as well as to demonstrate differences in solubilities.
This experiment starts with two soluble ionic compounds: potassium iodide, and lead (II) nitrate. These are dissolved in water to form colourless solutions, and then mixed together. This mixing leads to a double displacement reaction, essentially resulting in the metals ‘swapping’ their places in the two compounds, producing lead (II) iodide, and potassium nitrate. It also produces a rapid colour change, as the lead iodide is very insoluble in water at room temperature. When the solutions are added together, they immediately produce a bright yellow precipitate of lead iodide.
Whilst the lead iodide may be insoluble in water at room temperature, its solubility increases marginally with temperature. To put it simply, when ionic compounds dissolve in water, they dissociate into their component ions. This dissociation can either give in or take out energy from the surroundings. In the case of lead iodide, it dissociates into Pb 2+ and I – ions. This takes in energy, and so increasing the temperature of the solution will promote the dissociation of lead (II) iodide. Consequently, the solubility of lead iodide rises from 0.0756 grams per 100 millilitres of water, to a dizzying 0.41 grams per 100 millilitres of water.
The lead iodide dissolving produces a colourless solution once again. However, if this solution is then allowed to cool, the dropping temperature forces very pure crystals of lead iodide to precipitate back out of solution. These hexagonal crystals take some time to meander gently to the bottom of the flask, giving the reaction mixture a shimmering, glittering effect commonly referred to as a ‘golden rain’.
The effect can last for up to an hour as the crystals fall out of the solution, so it’s a great experiment to instill an awe of chemistry! The graphic images really don’t do justice to the magnitude of the glittering effect – to get the full impact, you should check out this video by Chemistry in Context , which shows it with great clarity, and also includes some further discussion of solubility.
In terms of practical uses of lead iodide, it was formerly sparingly used as an yellow paint pigment, though its instability in this form meant other pigments were generally favoured. Presently, crystals of lead iodide are sometimes used as a detector material for high energy photons.
As a final point: it’s worth noting that lead compounds are toxic, and should only be used by experienced chemists or teachers with the necessary safety precautions in place.
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The graphic in this article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License . Want to share it elsewhere? See the site’s content usage guidelines .
References & Further Reading
- Golden rain demonstration – Education in Chemistry
- Lead (II) iodide – LearnChemistry
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