Richard Sullivan (richsul@earthlink.net)
Mon, 22 Mar 1999 11:18:27 -0700
At 10:47 PM 3/21/99 -0500, Judy wrote:
>I never had the patience to mix all the chemicals you needed with the
>Rochelle-salt developers, they really took huge amounts, at least the
>formulas I had. In fact I couldn't get them all into solution & then they
>didn't last very long.
I believe the old formulas called for sodium borate decahydrate which has a
molecular weight of 381.37 where the (dry) fused version has a molecular
weight of 201.22. None of the historical formulas specify which hydrate to
use but I strongly suspect that it is the decahydrate. I think most people
will end up today with the dry version. Thus if the old formula calls for
500 grams you would use only 260 gms of the dry stuff. This accounts for
why you have all that sludge in your tray when you try to mix the old
formulas.
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