Sentence:  After * * f and * * f were passed through Dowex-2-chloride twice and treated twice with healthy sweet clover tissue <WSD>powder</WSD> , nonspecific staining was greatly reduced but a disturbing amount of such staining was still present . 
Meaning of the word marked with <WSD> tags:  a solid substance in the form of tiny loose particles; a solid that has been pulverized