chemicalmixer
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Merseburg Process
In light of all of the copper sulfate and sulfuric acid synthesis question threads, I was thinking that a discussion of a kitchen-friendly version of
the Merseburg Process (or rather, the Ammonium Carbonate-Gypsum Process) would be in order.
Merseburg Process:
(NH4)2CO3 + CaSO4 --> (NH4)2SO4 + CaCO3
Not unlike a modified version of the Solvay Process, the Merseburg Process utilizes aqueous ammonium carbonate to precipitate an insoluble - or less
soluble - carbonate precipitate, but instead of using sodium chloride as a feedstock, this process relies on the slight solubility of gypsum, in order
to eventually precipitate out calcium carbonate, leaving behind an ammonium sulfate solution. Furthermore, I see no reason why this process couldn't
be modified further to include the use of magnesium sulfate as well.
From the literature I could find on the subject, it seems that conversion rates of over 98% can be achieved when they slurry is left to react for 2-3
hours at 120F. Also, because the precipitate of calcium carbonate is highly insoluble, working with saturated solutions is less critical than with the
Solvay. Worth noting too, is that either the anhydrite, hemihydrate, or dehydrate of CaSO4 can be utilized, but in the literature, apparently the
CaSO4 used is first sifted through a sieve, in order to remove the less-than fine particulates.
Perhaps a procedure could be made, whereby one bottle containing sugar water and yeast would be used to generate CO2, which would then be directed
through a scrub bottle containing saturated NaHCO3 solution, and then finally the cleaned CO2 could be directed into a larger bottle containing a
slurry of ammonia water and gypsum. If one started out with 10% ammonia and plaster of paris, a fairly concentrated product could be achieved. Using a
digital scale, the mass of the reaction vessel bottle could be weighed until the appropriate mass of CO2 has been absorbed into the slurry/solution.
After this point, the CO2 generator could be removed, and the reactants left to interact with each other until the reaction is complete (possibly with
the aid of magnetic stirring). The process is exothermic, so it is probably unnecessary to add addition heat.
With the ammonium sulfate being the main product, copper hydroxide could then be reacted in order to form the tetra- and di-amine copper sulfate,
which, with careful heating, would afford the home experimenter with a convenient method of synthesizing copper sulfate. A solution of this CuSO4
could then be electrolyzed using a lead anode and copper cathode, or it could be reacted with oxalic acid solution, to eventually form H2SO4.
[Edited on 7-9-2012 by chemicalmixer]
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MrHomeScientist
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Interesting procedure, but for me copper sulfate is the only copper compound I can get easily. Is there an OTC source for copper hydroxide? Seems to
me that the sulfate is more readily available.
Mainly I just wanted to add this comment: As I noted in my "Calcium Sulfate and Titanium Thermite" thread, plaster of paris can have lots of additives
in it that may interfere with your reaction. The brand I found contained CaSO4, CaCO3, and SiO2, with the impurities in significant quantities.
Chemically these extras wouldn't do anything and could just be filtered off with the rest, but it would throw off your stoichiometry a bit. Just
something to watch out for.
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Hexavalent
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Probably not, as Cu(OH)2 quickly decomposes to copper oxide and other contaminants. When needed, it is usually prepared freshly from copper
sulfate and sodium hydroxide.
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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