Determination of Nickel Sulfate and Magnesium Sulfate in Electroplating Bath by Potentiometric Titration

Nickel sulfate plays an important role in electroplating. It is the main salt for supplying nickel ions. Its concentration affects the efficiency of the cathode current and the performance of the coating. When the content is low, the dispersing ability is good, the crystal is fine, but the deposition speed is slow, and the anode and cathode current efficiency is low. When the content is high, the high current region deposits quickly, but the dispersing ability is poor, and the consumption is also large; Magnesium Sulfate is used as a conductive salt in the electroplating industry, and the plating solution can have better conductivity after being added to the nickel plating solution. Make the coating white and soft [1]. The analysis of nickel sulfate and magnesium sulfate in the electroplating solution generally adopts the EDTA complexometric titration method. Compared with the atomic absorption spectrometry, the method is simple in operation, low in cost, and has obvious end point sharpness and high precision. EDTA complexometric titration analysis of nickel and magnesium content Generally, ammonium fluoride masking agent is used to mask Mg2+, EDTA standard solution is used to determine Ni2+ content; in another sample liquid, Mg2+ and Ni2+ content are determined, and Mg2+ content is calculated by subtraction method [2] ]. Or the dimethylglyoxime precipitation method, the precipitation reaction of dimethylglyoxime with nickel, first determine the Mg2+ content by EDTA standard solution; determine the mixture of Mg2+ and Ni2+ in another sample solution, and calculate the Ni2+ content by subtraction method. However, the former's masking effect and masking time of the masking agent will affect the accuracy and precision of the measurement results [3]; the latter is difficult to obtain correct results due to the entrainment precipitation problem during the precipitation process. In this paper, the complexing constants of Mg2+, Ni2+ and EDTA are different. Ni2+ is determined by EDTA standard solution in HAc-NaAc medium with pH value of 5.5-6. At this time, Ni2+ can form stable complex with EDTA, while Mg2+ does not produce. Interference [4]; In another sample solution, the combined amount of Mg2+ and Ni2+ was determined by EDTA in an ammoniacal slow solution medium with a pH of 10, and the content of Mg2+ was calculated by subtraction method, and good experimental results were obtained. And this method was compared with ammonium fluoride masking method. The obtained results prove that the determination of Ni2+ and Mg2+ content by pH adjustment method is simpler and more feasible.