noun
calx; metal residue
Technical term in chemistry and metallurgy for the powdery oxide or residue left after heating a metal in air.
金属灰は、金属を空気中で加熱した後に残る粉末状の酸化物である。
Calx is the powdery oxide that remains after heating a metal in air.
酸化物 is the general term for oxide, while 金属灰 specifically refers to the historical concept of calx, the residue from heating a metal.
Compound of 金属 (metal) and 灰 (ash), literally 'metal ash', a calque of the historical chemical term 'calx'.