Liam Lawless (lawless@vignette.freeserve.co.uk)
Tue, 09 Mar 1999 00:45:08 +0000
Hi all,
Judy asks about the dichromate reversal bleach. I have not tried saving
part-used bleach, mainly because I have several kilos of dichromate and 25
litres of sulphuric in the shed, but also because (as I'm sure you'll have
noticed) the bleach starts to put down a white sediment after very little
use. It is working satisfactorily as long as it still bleaches, and I doubt
very much if used solutions would deteriorate if kept in closed bottles
(protected from strong light) for a few weeks, but I like to start each new
session with a "clean" solution.
I mix with tap water, and while I have never used distilled, I cannot see
how it would improve the results I get without it. As for the question of
precision in weighing/mixing, many times when I have been feeling lazy I
have gone to the shed for a teaspoon of dichromate (or a tablespoon, if that
happened to come to hand first) and a dash of water in roughly a pint of
water, and it makes not a jot of difference. (Except perhaps to the
capacity of the solution - which I have never actually reached, except a
long, long time ago when I tried to work out what its capacity is. And
maybe doing things that way can be unnecessarily wasteful.)
My dichromate is pretty fresh (bought 2-3 months ago), and it's reassuring
to know that it'll still be working in 20 years. I also have some 32-year
old amidol which has turned black and is not quite as soluble as it used to
be, but otherwise works fine.
Liam
P.S. Dichromate solutions should NEVER be stored in the fridge in an
orangeade bottle.
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