為何足金都只是9999

Pure gold (100% gold) is too soft so it may wear/damage away easily.

When mixed with another metal in small quantity, such as silver, platinum or even copper or zinc, forming a gold alloy makes it much harder wearing. Gold alloy is also easy to work with and to shape.

因為空氣會痴上舊金面頭,結果形成雜質

現實世界中，很難有百分百的完美東西，即使是鑽石，也有雜質。

蒸餾水，也會有一丁點的污染物。

完美，只存在於概念中。

2010-01-15 22:12:20 補充：
physics8801,

千足金是999，並不是因為太軟所以不製造100%純金，而是真的造不來。