How do u prove tat ur crystals r pure after re-crystallization ( do not contain NaCL)?
2007-06-04 04:08:07 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
In the pharmaceutical industry they prepare solutions of varying concentrations of a pure sample of the product. They then run these on an HPLC and plot the integration of each as concentration vs integration. They then run the sample of unknown purity and from its integration the purity is extrapolated from the plot of concentration vs integration. This tells you how pure the crystals are. If you do not have access to this method then a simple way would be to place some of your sample in a filter funnel and accurately record its weight. Next wash your sample with H2O then dry the filter funnel containing your sample and weigh it again. The difference in weight will tell you how much NaCl was in your sample. These methods assume your sample is organic. I hope this helps.
2007-06-04 04:39:58 · answer #1 · answered by Anonymous · 0⤊ 0⤋
It depends on what the crystals are: organic or inorganic? If you're trying to make KNO3 by crystallizing it from a solution of NaNO3 and KCl, you could dissolve a little of the product in water and add HNO3 + AgNO3. A white precipitate of AgCl shows that there's still some NaCl.
If you're worried about NaCl contaminating an organic compound, determine the melting point in a capillary tube and look a the melt. If it contains other crystals of NaCl, which do not melt at the low temperatures of organic compounds, then you know.
2007-06-04 11:23:05 · answer #2 · answered by steve_geo1 7 · 1⤊ 0⤋
How about dissolve a little bit of the crystals in distilled water and do a flame test? It's kind of crude, but quick.
The copper will burn blue and the sodium will burn yellow.
So if you get any green it's not pure.
2007-06-04 12:04:38 · answer #3 · answered by Sea Anemone 2 · 0⤊ 0⤋