Aidan Schurr asks:

>>Does anyone know of the origin of the term "hypo", as applied to 2.5% 
Sodium Thiosulphate?<<

Sodium thiosulfate was once called sodium hyposulfite. I don't know when the 
name was changed, or who changed it, but the old name was totally obsolete in 
1950.

Parenthetically, the USA spells it "sulfur", including all derivatives of the 
word, while the rest of the English speaking world spells it "sulphur". Both 
spellings are defensible historically.

Bob