Which analytical instrument is suitable for the determination of the gold content of gold plating bath?
Iodometric method for the destruction of cyanide with hydrochloric acid, and the dissolved gold aqua regia and converted to three gold chloride, and free iodide precipitate quantitatively, and then the standard solution of sodium sulfate free iodine thiosulfate titration, to determine the amount of gold.Reagentofuse: hydrochloric acid (relative density l.19), 1:3 HCl, aqua regia (3 volume of concentrated hydrochloric acid and concentrated nitric acid, l volume) 10% solution of potassium iodide, 1% starch solution, standard 0.025mol / L sodium thiosulfate solution.The methods of analysis are as followsThe pipet 2ml plating solution in a 300ml conical flask.Adding 20ml concentrated hydrochloric acid in the electric furnace evaporated to dry (in the ventilation cabinet)The adding chloroazotic acid 5 ~ 7ml, 70 ~ 80 DEG C to slowly evaporate into the slurry, but never dry.Then dissolve and wash the bottle wall with 80ml hot water. After cooling, add l:3 hydrochloric acid 10ml and 10% potassium iodide 10ml, placed in the dark 2min.Add 5ml starch indicator, titrate with 0.025mol / L sodium thiosulfate to blue, disappear as the end point
Weight weight method is cyanide decomposition with sulfuric acid and hydrogen peroxide, gold is reduced to metallic state precipitation, determination after separation by gravimetric method. The reagents used for sulfuric acid and hydrogen peroxide 30%. The analysis steps are as follows.Drain the solution with pipette, and lOml in the beaker of 250ml. Adding sulfuric acid lOml and 30% hydrogen peroxide 5ml.In the fume hood, heat up to three white smoke, and continue to run 3 ~ 5min.Rest cool, add water, lOOml, boil 2min, with ashless filter paper, precipitate and filter, wash with hot waterThe precipitation of the crucible and the filter paper together onto a known weight, dry ashing, burning to 600 degrees 0.5h, weighing in the dryer after cooling.
Traditionally, the weight method or the iodine method is used to measure the accuracy, but the operation time is testedIf you can on the instrument analysis, proposed by X ray fluorescence and the fastest lossless, the budget can be used to atomic fluorescence by atomic absorption.12g/l this concentration. If the original ceiling may also need to dilute the sample solution. With instrument analysis and manual method
