Analysis And Research Of Trace Lead In Electroless Nickel Plating Solution

High concentration nickel ions and citric acid will impact the measurement of lead ions. We skilled understand the important role of the lead salt stabilizer in the electroless nickel plating solution and the measurement method of the lead ions. Then we use the idea of applications from simple system to complex system to measure lead ions in different solution. Then we get a final method of measuring lead ions in the electroless nickel plating solution.We build spectrophotometry of measuring trace lead in the electroless nickel plating solution, mainly discussing the impact of high concentration nickel ions and citric acid. The methods were as follows:1. Lead solution containing little interferent:spectrophotometry using xylenol orange as the color reagent and phenanthroline as masking agent. By studying the impact of the optimal absorption wavelength, the amount of xylenol orange, the amount of phenanthroline, the optimal pH and the amount of hexamethylenetetramine, we established a xylenol orange spectrophotometry of measuring lead.2. Lead solution containing citric acid:citric acid can form clathrate with lead icons, impacting the measuring of lead icons. We found that increasing pH value or increasing the amount of the chromogenic reagent xylenol orange can correct the measuring result. We got the optimum pH and the optimum dosage of xylenol orange in this kind lead solution and corrected lead measuring curve in specific pH and amount of xylenol orange.3. Lead solution containing high concentration nickel ions:high concentration nickel ions made the value of lead measuring not accurate. By studying the influence curve of nickel ions on lead measuring, we got that when the Ni/Pb concentration ratio<120, the measurement error is small, so ordinary spectrophotometry can accurately measure the concentration of lead. When the Ni/Pb concentration>120, we can not get the accurate concentration of lead, so we used separation method. Nickel icons and lead icons react differently with excess strong base, so we added excess strong base to dissolve out lead icons for measuring. Because of nickel icons, we must dissolve three times to dissolve out80%known lead icons.4. Lead solution containing both citric acid and high concentration nickel ions: citric acid and high concentration nickel ions can both impact the measurement of lead icons. We first added a large amount of strong base to divide lead icons into two parts:lead icons in the supernatant and in the precipitation. To measure lead icons concentration in the supernatant, we should use the method for lead solution containing citric acid. To measure lead icons concentration in the precipitation, we should use the method for lead solution containing high concentration nickel ions. Because there is a little citric acid in the precipitation, we must dissolve five times to dissolve out80%known lead icons.In allusion to the method above, we discussed the changing of lead content in the supernatant and precipitation when we added different quality of strong base. We got that when adding more strong base, lead content in the supernatant will increase while lead content in the precipitation will decrease.In summary, the method established in this paper can relatively accurately measure the lead content in different solutions. This method is convenient to use and we want to extend this method among enterprises.