# Last edited on 2016-12-19 21:42:52 by stolfilocal

Synthesis of anhydrous copper chloride CuCl2
from CaCl2 and CuSO4.

See the 00-LIBRETTO and 00-RECIPE

  copper_chloride.gawk > 00-RECIPE

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2016-09-??

In my first attempt, I mostly followed the libretto, but I tried to
prepare the reagent solutions at 100 C and carry out the reaction at
that temperature, in order to minimize the amount of water in the
resulting CuCl2 solution. According to the program, at that
temperature, only 46 and 21 ml of water were needed to dissolve the
CuSO4(H2O)5 (S1) and the CaCl2 (S2), respectively; and the final CuCl2
solution (S3) would have only 94 ml of water.

I prepared each solution (S1) and (S2) separately at 100C, with a little
excess of each salt, and decanted the right mass of the saturated liquid
to a separate beaker. Since these solutions cooled a bit after pouring,
some of the salt crystallized out. I then re-heated the two solutions
until the salts dissolved again, before mixing them.

When re-heating the two solutions before mixing, I overheated the calcium
chloride one (S2) to about 120 C. (A solution of CaCl2 that is concentrated
at 100 C will boil only at 120 C or more.) Impatient, I added it to the
CuSO4 solution (S1) while still at 110 C. But a saturated solution of CuSO4
still boils at 100 C, so there was vigiorous boiling that could easily
have splattered the mixture out of the beaker and resulted in burns.

The reaction worked, but the amount of calcium sulfate was so large
compared to the amount of liquid that they formed a thick paste (M3) of a
beautful lime green color. I had to add more than 200 ml of water to
make the mixture fluid enough for the calcium sulfate to precipitate
out.
    
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2016-09-??

The reaction mix (M3) of the previous experiment consisted of a paste of
solid CaSO4(H2O)2 in a solution of CuCl2, with some excess CuSO4 and
maybe some Ca.

The paste was diluted with water, decanted and filtered to produce ~400
ml of a clear blue-green solution (S3).

The CaSO4(H2O)2 precipitate (P1) was washed several times with water to give
about 580 ml of clear light blue-green wash (W1).

The CaSO4(H2O)2 ppt (P1) was dried, and weighted at 66 g. The predicted
amount was 64 g. Maybe still 2g of water adsorbed or trapped.

The copper in the wash (W1) was used in the "basic_copper_carbonate"
experiment.

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2016-09-11 [1]

Evaporated the concentrated CuCl2 solution (S3) from ~100 ml down to dryness,
using electric stove and hair dryer in a 600 ml beaker.

Reduced the crystalized blue-green CuCl2 (P3) to anhydrous by heating at
~120 C for tens of minutes.

Dissoved the anhydrous CuCl2 (P3) in ~100 mml of ethanol 99%, filtered,
washed with additional ethanol. Mass of filtrate and wash (S5), clear
but very dark yellow-green was 278 g including the round flask R1.

Residue (P4) left from etanol extraction and filtering of (P3) was white
crystalline. 

The residue (P4) was then trated with water. Most of it dissolved in
water to give light blue (turquoise) solution (W2), presumed to be
CuSO4. 

Added the (W2) solution to previous CuSO4/CuCl2 wash water (W1).
[**This may not be correct, see the "basic_copper_carbonate" experment.**]

The residue (P5) left after washing (P4) with water was white
microcrystalline. Maybe CaSO4(H2O)2 that was dissoved in (S3), plus
stuff added previously in attempt to control explosive boiling (SiC,
diatomite, and silica gel).

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2016-09-11 [2]

There is reason to suspect that hot CuCl2 solution (S3) oxidizes SiC to form
SiO2 or similar substance.

One of the things added to the main water solution (S3), in an attempt
to control boiling, was small beads (1--4 mm) of blue glass-like silica
gel. They apparently did not help with boiling. However, after drying
the CuCl2, the beads left in (P4) were black. On washing (P4) with
ethanol then water, they became clear green first, then colorless in
(P5). It seems that CuCl2 penetrates the silica gel beads to the core.

Stored the CuCl2 solution in anydrous ethanol (S5) in round flask R1.