umesu , which contains citric acid as the main component , was used for metal plating and soldering and the oxidation coating treatment of bronze and iron ware (copper oxide (ii ) and iron oxide (ii ), an anti-rust treatment using an oxide film made of ferrous oxide called " kurodome " ), in addition to the sterilization of tools and bodily wounds . また、クエン酸を主成分とする梅酢は器具や人体の傷口の消毒の他、金属のめっきやはんだ付け、青銅器・鉄器の酸化皮膜処理(酸化銅(II)および酸化鉄(II)：酸化第一鉄による『黒留め』と呼ばれる酸化皮膜による防錆処理)のためにも用いられた。
