How to Purify by Recrystallization

We show how to purify aluminum nitrate and strontium nitrate by recrystallization. This is important because those two substances must be extremely pure for our upcoming video on making glow in the dark powder.

First make aluminum nitrate from our previous video: http://www.youtube.com/watch?v=u4Ha1SJrazY

Dissolve the dry aluminum nitrate in water and filter off any insoluble materials. We could not filter it off before it dried in the previous video because the particles at that stage are much too small. It needs crystallize once to aggregate into particles large that can be filtered.

After filtering, dry off the aluminum nitrate. The desiccator bag might be useful here: http://www.youtube.com/watch?v=XJFfS_YbbYI

After drying, carefully weigh out the crystals. Then take that mass and add in 20% mass of water. So if you have 50g like me, you add 10g of water (or 10mL since density is 1g/mL).

It won't all dissolve, so carefully heat the mixture until it dissolves. Then cover it and let it cool down. Eventually it'll crystallize out purer crystals.

After the mixture cools to room temperature, and left for a few hours. The liquid is poured off and discarded, it has the impurities and is not needed.

The crystals are again weighed and once again they are recrystallized with 20% water.

Once this is done. Dry the final product. I started with 50g and ended up with 17g. But now it's very pure. Better than 99%

Strontium nitrate also needs to be purified. But it's solubility doesn't change that much with temperature so we'll have to purify by slow evaporation recrystallization rather than thermal cycle recrystallization.

First, make strontium nitrate like our previous video: http://www.youtube.com/watch?v=_rd8b6wNnKA

Once again, dissolve it in water and filter it. Then let it crystallize. But before it dries completely, let the liquid reduce to about 20% of it's saturated volume. So I started with a saturated solution of 10mL of strontium nitrate, i then waited until it evaporated down to 2mL of fluid. The crystals are not included in this assessment. Then discard the liquid. Repeat the recrystallization process.

Once again, use the desiccator bag to obtain extremely dry chemicals.

We are now ready to produce glow-in-the-dark powder.

Category:

Science & Technology

Tags:

• Strontium
• aluminum
• nitrate
• purification
• recrystallization
• phosphorescent
• glow
• in
• the
• dark
• powder
• chemistry
• science
• experiment

[fedaikn]

there is still liquid coating the crystals, even after the second purifying step. i think that one will not get rid of impurities unless one gets rid of the liquid phase. could you get rid of that by washing the crystals in a filter with some ethanol or isopropanol?

[NurdRage]

@fedaikn

the crystals are pure enough for the synthesis of phosphorescent powder.

And you do get rid of most of the liquid, and thus of the impurities, when you decant off the liquid.

[levikfc]

can u make any chemicals that are cheap and easy to make that dont make a really bad smell?

[NurdRage]

@levikfc

sorry, nope

[Igotdemburgerz]

@beaochi lol lets cook meth

[narusasu444]

question if the contaminants can crystalise out before the chemical you want does cant you pour the solution out then crystalise that?

[brandy1011]

Distilled water and deionized water are actually equally good for this process (unless the American deionized water is not completely deioninzed *scnr*).

[nikola96uf]

@NurdRage What means 90 % purity? For some tecnical chemicals like sulfuric acid are 90 % purity. I have technical grade H2SO4 and i did titration and it was 95 %. how then it is 90 % purity if it contains 95% H2SO4? Other is water.

Does that inpurity is 10 % of that 5 % that contains water in this case?

[azzy314159]

If I don't have distilled water, can I use pee. It is good enough, I am told, for car batteries.

[azzy314159]

If I don't have distilled water can I use pee? It is good enough for car batteries, I am told.

[feuerwerk1997hansl]

could you please tell me how much water i need for 100 gramms of bariumnitrat....and how can i find out how many water i need.....thanks

[shyvr]

How does one distill water?

[Helge129]

@MarcusTheReverent He has another video about doing that.

[MarcusTheReverent]

how do you purify or extract ammonium nitrate from fertilizer?

[DeanMalenko]

@darkpigion not sure if it's true but I think you could keep the liquid that you took away and crystalize that in order to not waste so much.