Sentence:  The precipitate was washed twice with an 80 % saturated solution of * * f , dissolved in a small quantity of 0.1 M neutral phosphate buffer , dialyzed against <WSD>cold</WSD> distilled water till free from ammonium ions , and lyophilized using liquid nitrogen . 
Meaning of the word marked with <WSD> tags:  having a low or inadequate temperature or feeling a sensation of coldness or having been made cold by e.g. ice or refrigeration