Sentence:  After * * f and * * f were passed through Dowex-2-chloride twice and treated twice with healthy sweet clover tissue powder , nonspecific staining was greatly reduced but a disturbing amount of such staining <WSD>was</WSD> still present . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)