ScienceHideout - 11-7-2012 at 12:27
Many salts in my lab are hydrates.
Recently I recovered an old bottle of aluminum chloride. The bottle was all clumpy and hard. I still managed to tap out some aluminum chloride and it
had a yellow color. You could also see how the crystals sorta sparkle.
Now- the manufacturer had no indication on if it was a hexahydrate or not- and I really can't tell!
Is there any easy way to tell anhydrous AlCl3 from the hexahydrate?
Hexavalent - 11-7-2012 at 12:42
It is almost certainly the hexahydrate; the anhydrous would have reacted with moisture very easily over the time.
barley81 - 11-7-2012 at 13:05
Carefully add a small amount to water (outside). The reaction will be violent if it is anhydrous. It was probably originally anhydrous, since this
kind of AlCl<sub>3</sub> is much more common and useful. If it's old, it will have reacted to form aluminum oxychloride/oxide/other crud
with moisture, producing HCl gas, and will not be simple hexahydrated aluminum chloride. You can also titrate it with NaOH and a suitable indicator or
determine chloride content by titration with silver nitrate/potassium chromate indicator (bring solution to neutral/slightly basic pH first).
[Edited on 11-7-2012 by barley81]