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               Potassium dichromate from chrome metal or Cr(III)
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bHey chemists out there! This is a new synthesis of POTASSIUM DICHROMATE, a
potent oxidizer which can be used to make GOOD things. 
I cannot give you refs cause I have discovered this myself. The idea came
from a german chemistry lexikon, Römpp's, which said that Cr(OH)3 reacts
with NaOH/H2O2 to form chromate. 


WARNING: 
This file was written for informational purposes only. You should not
attempt to make it and to use this controlled (in Europe it is) stuff to
make illegal drugs or to poison someone. :) :) 
Potassium dichromate is toxic. A dose of 4-10 g of it can and will cause
the death of a man if ingested. 


Starting material can be: 
Chrome metal
Chrome-nickel wire
Any Chromium(III) salt


Synthesis:


Weigh out 104 g Chrome metal and dissolve it in 500 ml of fuming (37%) HCl
(or equimolar amount of dilute H2SO4) in a preferably large beaker. Add
the metal to the acid in small portions and warm if the rxn goes too
slowly. When it's all dissolved, filter the solution to remove insoluble
material the chrome was contained with. In another beaker, dissolve 245 g
pure NaOH in enough water and let the solution cool to 20-40 C. Add this
alkali solution slowly to the filtered chromium(III)-chloride solution. A
greenish or grayish precipitate of Cr(OH)3 will form. Filter this,
squeeze it out and wash it 3 times with distilled water. You don't need to
dry it, just put it into a clean beaker and add: 1) a solution of 160 g
NaOH in just suefficient water and 2) approx. 350 ml of 30% hydrogen
peroxide. Add the reagents carefully for that they don't splash. The green
Cr(OH)3 will dissolve and the soln will turn a very beautiful yellow of
sodium chromate. If you boil the solution for some time and then
crystallizate it, you can get Na2CrO4, but we want to proceed to potassium
dichromate now.
 
Add 164 ml of concentrated HCl. The color will immediately change to
orange. This is the color of the Cr2O7 anion. Now boil the solution down
to approx. 50% its original volume. After cooling white crystals of NaCl
can be removed and discarded. 
Now weigh out 149 g of Potassium chloride (or equimolar amount of either
K2CO3 , KOH , or KNO3). Dissolve it in 80 C hot water to prepare a hot
saturated solution. Pour this solution into the orange solution of sodium
bichromate. Orange crystals of the crude product will form. Filter them
after cooling to 10 C. 
Recrystalizate the product twice from distilled water. Store in
well-stoppered bottle.


If you started from chrome-nickle, then some insoluble nickle(II)-hydroxide
will remain undissolved after adding NaOH/H2O2. This can be filtered. If you
had Cr(III)-salts, then just dissolve them in water and add NaOH soln.

The solubility of K2Cr2O7 is only 7 g/100 g water, but that of Na2Cr2O7 is
more than 100 g/100 g. Therefore, if you add a potassium salt solution to
Na2Cr2O7 soln, K2Cr2O7 will crystallizate readily. 

The yield of this synth is almost quantitative, around 280-290 g if you
did it right ( 95%< ). There is only loss of material which remains on the
filter etc.   

I wish you good luck!

---Nitro

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