10. Mix with half weight dry sodium carbonate and one-fourth weight of clean dry sand, and ignite.
IV. Gold Waste, α, Recovered.
1. Make just acid with hydrochloric acid, add solution containing 2 oz. pyrogallic acid, shake, let stand 24 hours; filter. Dissolve in aqua regia, and product after evaporation will be found better for toning than that precipitated by iron.
2. Acidify toning bath, and add sulphate of iron (2 grammes to 1 gramme chloride of gold.)
β. Separated from Silver.
1. Treat button obtained by fusing waste from hypo-toning and fixing baths with dilute nitric acid. Wash insoluble part with ammonia to remove silver chloride, if present, and dissolve in aqua regia.
2. Digest 20 grammes in flask with 1 fl. dr. hydrochloric acid, 15 m.m. of nitric acid, and 2 dr. of water. After quarter of an hour boil, add 2 oz. water; filter. Silver chloride with organic matter, &c. left undissolved. Reduced as III, above.
3. Add excess of pure potassium hydrate, and then boil in flask with excess of solid oxalic acid.
V. Paper Waste.
1. Soak paper in strong solution of saltpetre, and burn.