Consider 2mol (418g) of p-aminodimethylaniline hydrochloride, placed it right into a reaction kettle with a thermometer, add 6L of water to liquify, include 0.41 mol (40g) of focused sulfuric acid dropwise under mixing to make the service acidic, and also add Zinc chloride option, aluminum sulfate remedy, salt thiosulfate remedy, and also 300mL sodium dichromate service were included, and also the reaction service was heated up to 40 ° C within 10 minutes under stirring, and also the hydrochloric acid solution of N,N-dimethylaniline Put it into the reactor, then instantly add the remaining 600mL salt dichromate option, as well as heat it to 70 ° C within 10 minutes; when the temperature level reaches 70 ° C, placed 2.87 mol (250g) of manganese dioxide right into the reactor, warmth it to 85 ° C, as well as maintain The temperature was reacted for 30 minutes, the temperature was naturally reduced to 50 ° C, as well as 7.14 mol (700g) of focused sulfuric acid was gradually included under stirring; Wash with 600mL liquid sodium chloride solution; move the filter cake to a 20L beaker, add 10L water, stir as well as warm to boiling on the electrical heating mantle, suction filter while it is hot, add 1.84 mol (250g) zinc chloride and also 25.64 mol (1500g) Sodium chloride, stir to dissolve, after that place the remedy at 4 ° C for 24h, suction filter, as well as completely dry at 50 ° C to get 460g of Methylene Blue Trihydrate zinc chloride salt; liquify the obtained zinc chloride salt in 10L of water, add sodium carbonate 0.52 mol (55.2 g), cool to space temperature, filter with suction, clean the filter cake with a small amount of water, include 17.09 mol (1000g) of sodium chloride, stir and liquify, place it at 4 ° C for 12 hrs, filter with suction, and filter the cake at 40-45 After drying out at ℃ for 12 hrs, 320 g of the unrefined product of Methylene Blue Trihydrate was acquired (loss on drying out was about 15%, and also the return was 42.5% based on anhydrous matter). Put the crude methylene blue into a conical flask, include 1280mL of 0.1 mol/L hydrochloric acid (1:4), heat as well as dissolve in a water bathroom at 60 ° C, location formation at space temperature, filter with suction, as well as recrystallize the filter cake when in hydrochloric acid of the same volume and concentration. The exact same quantity of water was recrystallized when, and the filter cake was dried at 40-45 ° C for 12 hrs to acquire 205g of Methylene Blue Trihydrate, with a loss on drying out of 14.6% and also a return of 64.3% based upon anhydrous matter. The complete yield is 27.4% based on the raw material p-aminodimethylaniline hydrochloride.
