Fidelmios - 18-5-2016 at 23:58
Hello all,
So I've began to dabble in Crystal growing, and I was curious about Double Salts. So I've got Ferrous Sulfate, and Copper Sulfate, and I decided to
try and crystallize them. So I just threw two saturated solutions together and mix them. The result is what is show on the right, compared to Ferrous
sulfate (left). http://imgur.com/AlmDEaP
It seems to maintain the crystal shape of Copper Sulfate, but with the color of a mixture of the two. Did I end up making a double salt, or something
like it? Will they make one if I use proper equimolar equivalents?
On a side note, whenever I look at people's Ferrous Sulfate crystals they are near teal, mine are a light green. Why?
Sulaiman - 19-5-2016 at 02:10
I think that you have crystalised your solutions too quickly,
all show signs of agglomeration ....
some of the solution and its contents get trapped in the mass of crystals.
Hence the colour is not 'pure'.
For purity and aesthetics a single crystal is required,
if pure it will be transparent I believe.
Fidelmios - 19-5-2016 at 10:28
The camera does not do this mass justice. The Ferrous Sulfate ones on the left are almost transparent. They have some minor discoloration due to the
oxide layer being deposited on them.
Hegi - 19-5-2016 at 11:15
As long as I know there is no double salt with structure of alternating Fe(II)/Cu(II) ions. 
DraconicAcid - 19-5-2016 at 11:36
I believe you cannot get a double salt unless the ions are significantly different, so that they occupy different locations in the crystal structure.
Otherwise you just get a mixed crystal.
Fidelmios - 19-5-2016 at 14:41
That was my question, it doesn't look like a double salt, so idk what I made.
Xenoid - 19-5-2016 at 15:05
From Mellor......
"It is interesting to note that copper sulphate normally crystallizes with 5H2O, but a salt isomorphous with the above series (Fe, Be,Mg, Zn, Cd, Mn,
Cr, Co, Ni sulphates - the vitriols) and of the composition CuSO4.7H2O is formed when copper sulphate in admixture with the sulphate of Fe, Zn or Mg
is allowed to crystallize."
Hegi - 20-5-2016 at 10:16
Actually, I was wrong. There exist a compound naturally found as a mineral PISANITE with a composition of
(Fe<sub>0.8</sub>Cu<sub>0.2</sub>
SO<sub>4</sub>.7H<sub>2</sub>O. The ratio Cu/Fe of found specimens is fixed 1:5. There was also found ferrous sulfate
heptahydrate (mellanterite) crystallizing as an overgrowth on pisanite.
Fidelmios - 25-5-2016 at 23:23
Neat! That is very interesting thank you Hegi