99% Methylene Blue Powder Supplier

Methylene blue is a synthetic phenothiazine compound, soluble in water. It was first synthesized in the late 19th century and initially used as a textile dye. Later, it gradually played an important role in various fields such as medicine, scientific research, and aquaculture.

A method for synthesizing pharmaceutical-grade methylene blue, characterized by using p-aminodimethylaniline hydrochloride as a starting material, following the reaction pathway:

Weigh 2 parts of p-aminodimethylaniline hydrochloride (calculated by molar mass ratio) and add it to a reaction vessel equipped with a thermometer. Dissolve it in water, and add 0.41 parts of concentrated sulfuric acid dropwise while stirring. At room temperature, add a solution containing 4.95 parts zinc chloride, 1.00 parts aluminum sulfate, and 2.12 parts sodium thiosulfate, followed by a solution containing 0.72 parts sodium dichromate. Rapidly heat the reaction solution to 30–50°C while stirring. Add a hydrochloric acid solution containing 1.65 parts N,N-dimethylaniline to the reaction vessel, followed immediately by a solution containing 1.45 parts sodium dichromate. Rapidly heat to 60–80°C. Add 2.87 parts manganese dioxide to the reaction vessel and heat to 80–90°C. Maintain the temperature for 20–40 minutes. Cool to 40–60°C and slowly add... 7.14 parts concentrated sulfuric acid were stirred and the reaction solution was released. The mixture was placed at 4°C for 4–6 hours, resulting in a precipitate. The precipitate was filtered, and the filter cake was washed with a 10% sodium chloride aqueous solution. The filter cake was transferred to a beaker, water was added, and the mixture was heated to boiling with stirring on a heating mantle. The mixture was filtered while hot. 1.84 parts zinc chloride and 25.64 parts sodium chloride were added to the filtrate, and the mixture was stirred until dissolved. The solution was then placed at 4°C for 22–26 hours, filtered, and dried at 45–55°C to obtain methylene blue zinc chloride salt.

The obtained zinc chloride salt was dissolved in water, and 0.52 parts sodium carbonate were added. The mixture was cooled to room temperature, filtered, and the filter cake was washed with a small amount of water. 17.09 parts sodium chloride were added, stirred until dissolved, and the mixture was placed at 4°C for 10–14 hours. The mixture was filtered, and the filter cake was dried at 40–45°C for 11–13 hours to obtain crude methylene blue. This crude methylene blue was then recrystallized several times with water to obtain the final product.