Colloidal gold / Коллоидное золото

To prepare the 1% solution of gold chloride 8 mg of gold foil was dissolved in aqua regia. Then the solution was evaporated under warming (about 100 ° C or below). The resulting a syrupy precipitate gold chloride (reminiscent of burnt sugar) has been moved by several portions of distilled water in a vial and acidified with a few drops of aqua regia. The total volume of the solution - about 1.0 ml.
In the porcelain evaporation dish poured 20 ml of distilled water. Add 4 drops of 1% gold chloride solution (this solution is rather pungent, so it can not pour a conventional syringe with steel needle - it will corrode it.). The solution was neutralized by adding sodium carbonate (reagent grade), control over the universal indicator paper (remember: the excess acid will be a hindrance in our experiment).
For colloidal gold we need to reduce gold chloride to the metal. For this purpose, on the prepared gold salt solution we sent butane burner flame. The reducing agent are products of incomplete combustion of butane. The reaction takes place in the surface layer of the liquid where the flame regard solution. It is seen as violet waves diverge from it. Meanwhile, the liquid begins to boil slowly.
The colloidal gold solution which we obtained contains the smallest particles of metallic gold. Because of their very small size liquid is purple. Other ways you can get a red or blue gold sol.
The solution, though colored, but transparent. After some time, it will destruct and gold will fall in the form of an almost imperceptible precipitate - because its very small concentration in solution.
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Видео Colloidal gold / Коллоидное золото канала Химия и Химики Сhemistry-Сhemists