Sentence:  The small amount of insoluble material which precipitated during <WSD>dialysis</WSD> was suspended in approximately 5 ml of starting buffer , centrifuged , resuspended in 2.5 ml of isotonic saline and tested for antibody activity . 
Meaning of the word marked with <WSD> tags:  separation of substances in solution by means of their unequal diffusion through semipermeable membranes