From: Greg Schmitz (gws1@columbia.edu)
Date: 05/23/01-09:33:07 PM Z
Perhaps this belongs on the Photo History list - but since the subject
is gelatine, cows and mustard from days gone by I thought I'd pass
this along (some of my notes on THE AMERICAN ANNUAL OF PHOTOGRAPHY:
1926):
Neblette, C.B. "Photographic Review for 1925: Emulsions. THE AMERICAN
ANNUAL OF PHOTOGRAPHY: 1926. Vol XL. Ed Percy Y. Howe. New York: The
American Annual of Photography, Inc. c1925., pgs 22-28.
Lamenting the lack of information available about emulsion manufacture
(from the manufacturers) and after noting "a growing tendency,
particularly on the part of the larger manufacturers, to the
circulation of reports of investigations on the basic problems of
emulsions, and not with the actual details of emulsion manufacture,"
Neblette remarks on a paper published by Dr. S. E. Sheppard dealing
with "the separation of gelatine-X." Neblette states, "presence of
which [Gelatine-X] in ordinary gelatine is chiefly responsible for
photographic sensitiveness;" and "This substance... was found to be
closely identified with allyl-mustard oil or allyl
sulphide... discovered to be allylisothiocyanate." Neblette adds,
"this [Gelatine-X ??] is present in ordinary gelatines in extremely
small quantities, not more than one part in a million and reacts with
the ammonia used in the digestion of the emulsion and with amines to
produce allylthiocarbamide, which is the active in producing
photographic sensitiveness." Neblette then goes on to sight numerous
papers concerned with the subject of emulsion sensitivity.
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