Phosphorous adj. (Chem.) Of or pertaining to phosphorus; resembling or containing phosphorus; specifically, designating those compounds in which phosphorus has a lower valence as contrasted with phosphoric compounds; as, phosphorous acid, H3PO3.
... rather meagre in nutriment; it contains but little phosphorous matter, with less carbon than other cereals, and is best and most generally employed as a diet ... — The People's Common Sense Medical Adviser in Plain English • R. V. Pierce
... two parts of finely pulverised manganese with one part of the phosphorous acid of urine in the same way as is indicated in the preceding paragraph, I ... — Discovery of Oxygen, Part 2 • Carl Wilhelm Scheele