Use any water-miscible ketone, either acetone or methyl ethyl ketone, with acetone being the most economical choice. You only need to buy or electrolyze some sodium hypochlorite solution with a concentration of more than 10% by yourself, and then stir acetone into the sodium hypochlorite solution at low temperature. The temperature does not exceed 5°C throughout the process. Let it sit for a few hours and it will gradually clear up in layers and you can get some chloroform at the bottom. It is ready to use after drying and distilling. The yield of this reaction is almost quantitative, there are no side reactions and impurities, and the obtained chloroform is very clean.