I'll adress the questions I know something about:

Quote Originally Posted by Annie
1. Many of my images are of the ocean and I am intrigued by the idea of using sea water as the medium for the citric acid & platinum stock any obvious problems with this?
Not a good idea, I think. Sea water doesn't only contain sodium chloride, it also contains sulfate, carbonate, and lots of other stuff in small amounts. It is quite possible (probable) that some of these will form insoluble compounds with the platinum. You're welcome to try, but I wouldn't risk platinum in seawater myself.

Quote Originally Posted by Annie
3. Just how difficult and dangerous would it be to mix the Platinum Stock solution... Is this done with ingredients at room temperature?

My primary concerns are.... Explosions, invisible deadly gases, solutions that eat the flesh to the bone in a matter of seconds. Any insights or superior formulas are greatly appreciated!
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It won't explode. It won't give off dangerous gases. It won't eat flesh. But it seems very, very concentrated to me - are you sure it's 5 ml water? It will probably dissolve at room temperature if it dissolves at all.