Two analytical issues in the process of process qualification

"Industrial Analysis of Organic Intermediates" http://bbs.hcbbs.com/viewthread.php?tid=92738&highlight=%D3%D0%BB%FA%D6%D0%BC%E4%CC%E5%B9%A4%D2%B5%B7%D6%CE%F6

I will talk about my ideas 1. Detect the acid content in nitric oil after nitration of chlorobenzene with sulfur-nitric mixed acid. According to the density of nitric oil 1.23, roughly calculate the concentration of alkali and weigh the sample mass, and design the first plan: Weigh 50 grams of nitrate oil, add 300 ml of hot water, heat and stir, and then measure with 0.1 mol/L strong sodium oxide. Because of the interference of phenol, a pH meter is used to indicate the end point. By analyzing the actual sample, it is found that there is a large difference from the process estimation, and the reason is found.: After considering these factors, there are still differences in the sampling process and the sample melting process. It is found that it is not very stable near the end point, so it means that there is still acid in the oil phase. Therefore, the analysis method is improved, using back titration method, adding excess alkali, using acid back titration, and the problem is solved.

2. Detect the nitric oil content in the mixed acid after nitration of chlorobenzene with sulfur-nitric mixed acid (probably less than 1%) My idea: The final sample to be tested must be neutral, so it is decided where the neutralization should be carried out, first or last. Considering the amount of acid, it was decided to neutralize later. Take 100ml of waste acid and extract it with 10ml of chloroform. Neutralize with anhydrous sodium carbonate while forming crystal hydrate. After establishing the working curve, after the sample injection analysis passes the analysis, the difference before and after extraction is measured to calculate the extraction efficiency of chlorobenzene, which is 85% on average.