Pot. Dich. & The Pea-Sausage or Erbswurst

[Grafist@aol.com]

A verbatim extract from "The Chemistry of Light and Photography" by 
Dr.Hermann Vogel published in 1876 by Henry S. King & Co. London.

Page 256       "The Chemical Action of Light and The Pea Sausage."

"In the campaign of 1870, the well known pea-sausage was one of the most 
important articles of food for the army, and was prepared daily by thousands. 
The fabrication of the interior portion caused little difficulty, but 
obtaining of so many skins created much difficulty. As the supply fell short, 
a substitute was soaught in vegetable parchment.  This paper, which was 
produced by dipping blotting-paper in sufuric acid for about a second, then 
washing and drying, is distinguished by its skin-like properties of 
resistance. It is impenatrable to water, and difficult to tear. It is 
therefore used for the production of bank-notes. It was attempted to make 
sausage skins of this paper, by doubling a sheet cylindrically and pasting it 
together.  No glue or gum can however resist the effect of the boiling water 
in which the sausage has to be cooked, and so the artificial sausage skin 
fell asunder.  Dr. Jacobson solved the problem by producing an adhesive 
substance, with the help of the chemical action of light, which could resist 
boiling water. He mixed the glue intended for the sausage skin with 
bichromate of potash, and exposed the glued parts to the light.  This made 
the glue insoluble, and now the artificial skin endured boiling water 
thoroughly well.  The number of sausage skins prepared in this way, by the 
chemical action of light, amounted to many hundred thousands.
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                     Something to lighten up a lecture or a thesis.
                                            Regards. John Grocott- 
Photographist.