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Re: Aquatic Plants Digest V4 #829
Roger Miller wrote
> The best procedure is to get (beg/borrow/buy) a reasonably accurate
> scale and measure the weight and volume of the chemicals you use under
> your conditions. That isn't a real satisfying alternative for most
> people, but I think it's the only solution that will make your
> calculations reasonably accurate.
Unfortunately, WEIGHING is the ONLY method that is going to give you a
reasonably accurate result. Every other method is an approximation --
sometimes you will hit it on the nose, other times you will be waay off!
Of course, it is nice to have an accurate analytical balance, but it is
NOT really necessary. A letter scale will give you quite good results,
IF you work with larger quantities of reagents, dissolve them in water
and then measure out the required volume of the solution.
Weighing out and dissolving 2-3 oz (57-85 grams) of K2SO4 in a liter of
water (initially dissolve the salt in a bit less water, then fill up to
the volume of 1 liter) will give you a stock solution that you can then
dilute further to make a working solution of known concentration and
measure out the meeded volume.
Of course, do NOT weigh out the chemicals on the bare scale pan (use a
tared piece of wax paper) and, as Roger mentions, watch out for the
water of crystallization! In commercial products water is not always
mentioned on the label!