Sentence:  The precipitate was washed twice with an 80 % saturated solution of * * f , dissolved in a small <WSD>quantity</WSD> of 0.1 M neutral phosphate buffer , dialyzed against cold distilled water till free from ammonium ions , and lyophilized using liquid nitrogen . 
Meaning of the word marked with <WSD> tags:  how much there is or how many there are of something that you can quantify