The Collaborative International Dictionary
Sulphophosphorous
Sulphophosphorous \Sul`pho*phos"phor*ous\, a. (Chem.) Of, pertaining to, or designating, a hypothetical acid of phosphorus, analogous to phosphorous acid, and known in its salts.
Wiktionary
sulphophosphorous
a. (context chemistry dated English) Of, relating to, or designating a hypothetical acid of phosphorus, known in its salts.