Synthetic Fluorescent Halite

To produce crystals at home is an interesting experiment and if they fluoresce, could be “magic”.

Furthermore, it’s easy and cheap.

The only ingredient you have to use in big quantity is “patience”. Don’t expect to see crystals in a few hours.

Synthetic Fluorescent Halite consists on a recrystallized salt in presence of a particular activator and coactivator.

I don’t want to bore you with theory of fluorescence... so it’s sufficient to know that Halite fluoresces if into its cristal structure are present a small amount of manganese (activator) and lead (co-activator).

In this experiment I’ll drive you step by step from the choose of the elements to the final results.

The Elements

The elements we need are:

  • Water

  • Salt (NaCl)

  • Manganese (into the form of Manganese Sulfate)

  • Lead

Let me give you some suggestions about how to choose the right ones.

Water.

Unless you are living in high mountain and your domestic water is practically pure, do not use it because it contains too many impurity. The best choice is to use distilled water but an osmotic water works fine too. As example, you can buy for few euros the water for aquarius, for car batteries or for iron.

Salt.

In my experiment I used “coarse cooking salt” but remember that not all salts can be used because contains other elements (i.e. iodine).

How to discover if the salt is the right one?

If you have not time to waste (but money), directly buy “pure NaCl” for chemical purpose.

If you want to discover yourself if your salt is pure enough for the experiment, continue to read.

The method consists in crystallizing the salt under test and analyzing the shape of the crystals: they must be cubic.

It’s time to explain how to recrystallize the salt.

  1. Produce a supersaturated salt solution.In a container with lid (i.e. jam jar) put 100ml of hot water and 37g of salt. Close the container and vigorously shake for several minutes, until the salt is completely melt and the solution reaches the ambient temperature. Do not worry if a little salt does not melt. In this case, slowly pour the solution into a second container avoiding to pour the undissolved salt.

  2. Pour the solution into a dish and wait.... and wait......and wait again until some small crystals form on the bottom. Jokes aside, you should wait some days, so it’s better to leave the dish in a safe place and ensure that no dust or other impurity compromise the experiment.

  3. Remove the small crystals from the dish and observe them with a magnifier.

Wrong salt: crystals are not cubic!

Right salt!

This experiment give you an idea of how many kinds of salts exists and that just few of them are really "just salt".

Furthermore you learned how to produce a supersaturated solution. Consider that NaCl solubility is about 37g per 100ml of water. If you will produce a bigger quantity of solution, you must increase water and salt accordingly (example: 250ml of water and 92.5g of NaCl).

Manganese.

I suggest you to buy it online.

Small quantity of “Manganese sulfate monohydrate”

is available in sachets of tens grams for few euros.

Lead.