Methylene blue powder, a phenothiazine salt, is a dark green bronze luster crystal or powder that is soluble in water and ethanol and insoluble in ethers. Methylene blue is relatively stable in air, and its aqueous solution is alkaline and toxic. Methylene blue is widely used in chemical indicators, dyes, natural dyes and drugs. In terms of chemical properties, methylene blue can form double salts with most inorganic salts. The aqueous solution is alkaline. Low toxicity, avoid skin and eye contact. Adding dilute sulfuric acid to the methylene blue solution will make the solution fade. It can be recovered if ammonia or dew is quickly added to the air.
It has many uses because of its active chemical properties, introduced below.
The first point is dyeing: it can be used to make ink and lakes and dyeing of biological and bacterial tissues. It can also be mixed with crystal violet and yellow dextrin in the ratio of 78:13:9 to form alkaline magenta blue.
Second, in terms of medical treatment:
Because methylene blue has reducibility, its injection is used to treat methemoglobinemia. Mild carbon monoxide poisoning can be detoxified by intravenous injection of methylene blue. It is clinically used to treat sulfanilamide allergy. Washing with its solution can treat cystitis and urethritis. In addition, methylene blue will be discharged from the urine within 30 minutes (injection) to a few hours (oral), resulting in the temporary blue of the urine, so it is also used to determine renal function in the cultivation of ornamental fish.
Third, chemical analysis and identification:
In chemical experiments, analytical pure methylene blue can be used as an adsorption indicator in chemical reagents and for the precipitation of perchlorate and rhenium and the catalytic spectrophotometric determination of selenium and molybdenum.
At the same time, methylene blue is also oxidizing. It can oxidize some substances with strong reducibility and be reduced to colorless methylene blue (some people call it methylene white). After being reduced, the reduced methylene blue has certain reducibility and can be oxidized by some oxidizing substances, such as oxygen in the air, to produce oxidized blue methylene blue. Therefore, methylene blue can be used for oxidation-reduction titration and demonstration of oxidation-reduction oscillating reaction. The most typical is the blue bottle experiment.
Methylene blue aqueous solution is blue in an oxidizing environment, but it will be reduced to a colorless state in case of reducing agents such as zinc and ammonia. When the concentration of methylene blue is high, hemoglobin is directly oxidized to methemoglobin. At low concentration, under the action of reduced coenzyme I dehydrogenase (NADPH), it can be reduced to reduced methylene blue, which can reduce high iron reduced protein to hemoglobin.