Why is it a change of gold? Now it's black and muddy
1., analysis of waste liquid: first, determine whether the waste liquid contains gold. In appearance, the gold waste liquid is mostly yellow. Then do a simple experiment, take the waste liquid on a clean filter paper and dry it slowly. If it is purple, it may contain gold2. reduction of gold powder: Gold liquor into the beaker, and then heated to 80-90 deg.C under stirring slowly adding ferrous chloride (or ferrous sulfate) solution, see the color of the solution changed from yellow to brown, and gradually see gold deposits at the bottom of the beaker. The precipitation, then add two drops of liquid, such as it may be considered that the blue precipitate, gold has been completely restored. Slowly pour out the liquid, spongy precipitate at the bottom of the beaker of yellow soil is the gold powder.3. purification of gold powder: in gold powder precipitation in the adsorption of some iron compound must be removed, in order to improve the purity of gold powder. With 1:2.5 hydrochloric acid into gold powder, boil, stirring for 5 minutes, then pour lotion. So 4-5 times, to the upper acid yellow for check (pickling, careful operation, reaction not too intense, so as not to spill). Then after pickling of gold powder were carefully rinsed with distilled water several times, and not so far (acidic with pH test paper).
Drying gold powder: after washing the gold powder into the porcelain evaporation dish, put into the oven drying, that is, orange sponge gold powder particles
Extraction principleThe use of ferrous chloride to gold reduction precipitation from waste liquor, the reaction is as follows: AuCl3+3FeCl2 and 3FeCl3+Au:
The gold ingot melting drying powder into a quartz crucible, the high temperature furnace is heated to 1200 DEG C (homemade coke furnace without high temperature furnace, use a hair dryer blowing), to be full of gold powder melted out into the pre made ingot graphite good. If the gold powder is pure, after melting adding a small amount of borax, at this time should be placed in the graphite crucible melting ingot. The purification, the purity of gold reaches more than 99.6%.
