剂 appears as a suffix in many compound words:
药剂 (yàojì, 'pharmaceutical'),
清洁剂 (qīngjiéjì, 'cleanser'),
杀虫剂 (shāchóngjì, 'insecticide'),
调味剂 (tiáowèijì, 'seasoning/flavoring agent'). Once you know this suffix, you can decode many chemistry and medicine terms.
