[john13579]

I am trying to synthesize Chromium(II)Chloride for another project. I have taken chromium metal and added 15% hydrochloric acid. At first a green solution formed, which I presumed to be Chromium (III) chloride. I removed some of the green solution and allowed the reaction to continue. Chromium metal was still left and reacting slowly with evolution of hydrogen. After two days the solution became blue, which I presumed to be chromium (II) chloride formed by the reaction of chromium(III) with chromium metal. To confirm I added hydrogen peroxide to some of the blue mixture I presumed to be Chromium(II) chloride but there is no reaction, even on heating the color stays blue. Bubbling air thru the solution for a day also does not change the color to green as is described in literature. Is there a form of chromium III that is also blue? What is going on here?

[unsu]

Aqueous CrCl₂ is blue, and aqueous CrCl₃ is green.
As far as I remember, if you put the obtained solution of CrCl₂ in a test tube and let it stand in the air, it should eventually turn green. Your results confuse me too...

Try to add NaOH, then, Cr(OH)₂ is yellow (actually you will see a brown precipitate) and will not dissolve in excess alkali and Cr(OH)₃ is greyish green and it will dissolve in excess alkali because it is amphoteric.

Did you use a Bunsen valve or was the reaction mixture kept under an organic solvent like benzene to prevent oxidation by air?

[Borek]

I don't remember exact details but there are several isomers of the CrCl₃ (something like CrCl_n(H₂O)_6-n^(3-n)+). I believe some of them are quite kinetically stable. Doesn't have to be the case here, but I would check.

[john13579]

Thanks for the replies. Great insight and tips!
I did use a Bunsen valve.

Adding sodium hydroxide to the green solution causes a grayish cyan precipitate and a green solution on further addition as expected.

Adding a very small amount of sodium hydroxide to the blue solution causes it to turn green. At this point it behaves like the other green solution with formation of grayish cyan precipitate and a green solution on further addition.

The blue solution must therefore contain chromium(III). The solution is distinctly blue when shining fluorescent or an LED thru it, but incandescent light shone thru causes it to appear dull red. 

[unsu]

The solution is distinctly blue when shining fluorescent or an LED thru it, but incandescent light shone thru causes it to appear dull red.

That's what I like about CrCl₃
I remember it was dark green solution inside (regular tungsten bulbs light) and purple in the presence of sunlight. And if you are in the lab and staying next to the window, the sunlight makes it purple, and the "inside" part of the solution is dark green. This is really funny.