From: Sandy King (sanking@hubcap.clemson.edu)
Date: 05/21/01-06:01:47 AM Z
Kaharine Thayer wrote:
>>
>As I've said before, although some dichromate ions have to be reduced
>in order to oxidize the gum, it's possible for there to be so few
>reduced molecules in proportion to the unreacted dichromate, that the
>green will not be visible to the eye.
I wonder if you might comment on the following. In carbon printing my usual
practice is to add liquid ammonia to the potassium dichromate solution to
the point where it changes in color from reddish/orange to a pale yellow
and takes on a distinctly ammoniacal smell. At this point the potassium
dichromate has changed from a dichromate to the double chromate salt,
potassium ammonium chromate. It is in fact no longer a dichromate but a
chromate, but of course chromates can tan and harden gelatin just as well
as dichromates. If this procedure could be adapted to gum would it not
eliminate the gum green problem?
Sandy King
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