Sentence:  The precipitate was washed twice with an 80 % saturated <WSD>solution</WSD> of * * f , dissolved in a small quantity 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:  a homogeneous mixture of two or more substances; frequently (but not necessarily) a liquid solution