Seeking a method for precipitating lead sulfate to determine lead content
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While conducting experiments, I found that the measured results were too high or inaccurate. My approach was as follows: the solution I was testing contained sodium hydroxide, zinc, and lead; the amount of sodium hydroxide was around 130 grams, zinc around 10 grams, and lead around 30 grams. 5 milliliters of the solution were taken, sulfuric acid was added; the precipitate was dissolved in acetic acid solution, and then EDTA was used for analysis – the results were all significantly high. I would appreciate some guidance: were substances such as barium and calcium also detected inside? And how can these impurities be removed? Thank you
The original poster is measuring the lead content, right? Here’s an idea for the original poster; it’s not necessarily accurate, but the poster might find it interesting to give it a try: 1. First, use the poster’s own method to completely precipitate out impurities such as lead, barium, and calcium. 2. Clean with dilute acid and then rinse with water. 3. Then dissolve lead sulfate with pure alkali. 4. Collect the insoluble precipitate to determine the lead content.
I’m not sure what pH value was used by the original poster during titration; based on what they mentioned, it seems that the pH value at the time of titration might have been too low. For such test solutions, precipitation is generally carried out first (with a sulfuric acid concentration ratio of about 5-10%), followed by filtration and washing (with 2+98 sulfuric acid), dissolution (in an acetic acid-sodium acetate buffer at pH=5.5), and titration. If you need detailed analysis procedures, give me your email address and I’ll send them to you.
I agree with the opinion from the 4th floor; it’s likely a systematic error. Otherwise, a consistently high value would be problematic. The influence of standard solutions could be taken into consideration, and it is recommended to perform re-standardization in order to rule this out
I took this into consideration; I suspected there was something wrong with my standard liquid. So I used pure lead powder as a sample, dissolved it and conducted tests, and the results were more or less the same, around 98%
I suspect that the reason for the inaccurate results you obtained might be interference from aluminum. You can refer to the materials I sent you to determine lead. The filtrate was analyzed for aluminum and zinc. The steps are as follows: Excess EDTA is added to a buffer solution with a pH of about 4–5, the mixture is boiled, and the excess EDTA is titrated using a zinc sulfate standard solution. Determine the volume and amount of zinc and aluminum. Then fluoride is added (it can be potassium fluoride, sodium fluoride, or ammonium fluoride) to debury the aluminum; the EDTA released is then titrated with a zinc sulfate standard solution, allowing the amount of aluminum to be determined. The difference in volumes corresponds to the amount of zinc. My opinion is for reference only; the detailed steps can only be proven through experimentation. I won’t go into the specific calculations. Wish you success!
A few years ago I tested lead sulfate, using ammonia and ammonium chloride as a buffer solution at that time!
I agree with the moderator’s suggestion; could the material be posted in the shared resources area so that everyone can also learn from it?*learn* Thank you first
It’s done, thanks to yang*anghui