Sentence:  Although the * * f calculation is obvious by analogy with that for gravitational field and <WSD>osmotic</WSD> pressure , it is interesting to confirm it by a method which can be generalized to include related effects . 
Meaning of the word marked with <WSD> tags:  (physical chemistry) the pressure exerted by a solution necessary to prevent osmosis into that solution when it is separated from the pure solvent by a semipermeable membrane