I. German Silver is an alloy primarily composed of copper, zinc, and nickel. It contains no silver, despite its name. II. Solder is typically a fusible alloy, traditionally made of lead and tin. Lead-free solders are now common, using tin with other metals like silver, copper, and bismuth. Tin is a primary component. III. Bleaching Powder is calcium hypochlorite (CaCl(ClO)), produced by reacting chlorine gas with calcium hydroxide. Its bleaching action comes from the available chlorine. IV. Hypo is a common name for sodium thiosulfate (Na2S2O3), a compound containing sodium. It is used in photography as a fixer.