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 <WSD>weight</WSD> of sodium tripolyphosphate or a mixture of sodium tripolyphosphate and tetrasodium pyrophosphate . 
Meaning of the word marked with <WSD> tags:  the vertical force exerted by a mass as a result of gravity