From: Sil Horwitz (silh@earthlink.net)
Date: 02/11/00-10:51:55 AM Z
At 2000/02/11 02:43 PM +0000, you wrote:
>I am a little confused about the history of HYPO.
>I know Sir John Hershel discovered fixer by accident when he added
>Sodium Thiosulphate to developer in the hope of increasing the action
>which in fact delayed it to such an extent that it arrested
>development, but why did he think it was Sodium Hyposulphate?
>The history books say that Sodium Thiosulphate was misnamed, so was
>Hershel adding a substance the he believed was Sodium Hyposulpahte
>because Sodium Thiosulpahte did not exist (had not been discovered) or
>did he put in the wrong substance by accident and then find out it was
>a different substance?
At the time hypo was first formulated (sulfur dissolved in sodium sulfite)
naming of chemicals was not uniform. The term "hypo" means "less than" as
opposed to "hyper" but there was no authority to establish nomenclature.
This did not occur until fairly recently, and the term "thiosulfate"
represents a sulfur compound with an excess of sulfur (sodium sulfite =
NaSO3, sodium thiosulfate = Na2S2O3 - the numbers should be subscripts, of
course). The "hypo" comes from the old name sodium hyposulfite,
incidentally, not a sulfate. No change in the chemical, just a nomenclature
change for uniformity.
Sil Horwitz, FPSA
Technical Editor, PSA Journal
teched@psa-photo.org
silh@earthlink.net
Visit http://www.psa-photo.org/
Personal page: http://home.earthlink.net/~silh/
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