Sentence:  These widely advertised products , which are used primarily for washing clothes , are based on high-sudsing , synthetic organic actives ( sodium alkylbenzenesulfonates ) and contain up to 50 % by weight of sodium tripolyphosphate or a <WSD>mixture</WSD> of sodium tripolyphosphate and tetrasodium pyrophosphate . 
Meaning of the word marked with <WSD> tags:  (chemistry) a substance consisting of two or more substances mixed together (not in fixed proportions and not with chemical bonding)