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Re: Salt vs copper sulfate for caps

Original poster: Mddeming-at-aol-dot-com 

In a message dated 4/21/04 10:00:21 AM Eastern Daylight Time, 
tesla-at-pupman-dot-com writes:
Original poster: pepperman-at-SoftHome-dot-net

Hmm, that's odd: 500 grams is  about 1 pound.  So that might actually be more
expensive than the price I quoted for 2 pounds.  But that raises another
why did 1 pound of copper sulfate make a saturated solution for 3 gallons
of water
for you, when it should take 2 pounds/gallon according to the MSDS?

What form of copper sulfate was the stuff you bought--was it copper sulfate
pentahydrate (which is what I was talking about), or might it have been
else?  Any other suggestions?

Michael Johnson

Hi Michael,

There are three forms of copper sulfate: Cu2SO4, CuSO4, and CuSO4.5H2O. Of 
these, Cu2SO4 decomposes in water.
Anhydrous Copper Sulfate CuSO4 has a solubility of 143g/liter at 0 C. 
increasing to 750g/liter at 100 C. or about 275g/l at room temperature.
CuSO4.5H20, the pentahydrate (aka blue vitriol to old folks) has a 
solubility of 361g/l at 0C. increasing to 2.03 kg/l at 100 C. making a 
saturation of about 670g/l at room temp.. Depending on the storage 
conditions, copper sulfate can exist as a mixture CuSO4.nH20 where n is 
between 0 and 5  Sounds like you both could be right.

Matt D.