Sentence:  Polyphosphates gave renewed life to soap products at a time when surfactants were a threat though expensive , and these same polyphosphates spelled the decline of soap usage when the synergism between polyphosphates and synthetic <WSD>detergent</WSD> actives was recognized and exploited . 
Meaning of the word marked with <WSD> tags:  a surface-active chemical widely used in industry and laundering