From: Sandy King (sanking@hubcap.clemson.edu)
Date: 05/10/01-10:06:30 AM Z
Judy Seigel wrote:
>Actually not... it's many times *more* soluble than the other dichromates
>we use. In fact for an article in P-F #6 (justjustjust gone to printer,
>tadah!) I tried to FIND the solubility of sodium dichromate & after 3
>different answers in 3 different books, figured I didn't really really
>NEED to know -- but the lowest answer was 75% soluble at 68 degrees, and
>it went up to 150%.... another seemed to suggest it was INFINITELY soluble
>(as aren't we all).
The solubility of sodium dichromate is not the issue as regards its use in
colloid processes. As far as I know sodium dichromate offers no advantage
over ammonium and potassium dichromate for colloid processes (gum, carbon,
direct carbon, etc), but has one major disadvantage: its deliquescence.
That is, it absorbs moisture from the air, making it complicated and/or
difficult to mix accurate percentage solutions by weight.
A number of other chemicals have this quality, including potassium
carbonate and chromic acid, and the same problems pertain to their use.
Sandy King
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