| CAS No.: | 61-73-4 |
| Molecular Weight: | 373.9 g/mol |
| Chemical Formula | C16H18ClN3S-3H2O |
Specifications of Methylene Blue are as follows:
Chemical Formula: C16H18N3CIS
Molecular Weight: 319.85 gm / mole (w/o water) 373.9 with water of crystallization
Chemical Name: 3,7-bis(Dimethylamino)-phenazathionium chloride Tetramethylthionine chloride
CAS Number: 61-73-4
C.I No.: 52015
Appearance: Dark Green Crystalline Powder
Assay (as is basis): 80 % - 85%
Assay (on dry basis): 98% -101%
Loss on drying: 10% -20%
Solubility: Clear Blue Solution
Ash content: 1% Maximum.
Residual Solvent: Nil
Aluminium: 100 ppm Maximum.
Cadmium: 1ppm Maximum.
Chromium: 10ppm Maximum.
Copper: 50ppm Maximum.
Tin: 10 ppm Maximum.
Iron: 100 ppm Maximum.
Manganese: 10ppm Maximum.
Mercury: Nil
Molybdenum: 10ppm Maximum.
Methylene Blue
C16H18ClN3S-3H2O -- 373.90
Phenothiazin-5-ium, 3,7-bis(dimethylamino)-, chloride, trihydrate.
C.I. Basic Blue 9 trihydrate [CAS 7220-79-3]
Anhydrous 319.86 [CAS 61-73-4]
Methylene Blue contains not less than 98.0 percent and not more than 103.0 percent of C16H18ClN3S, calculated on the dried basis.
Identification: Infrared Absorption 197K .
Loss on drying: Dry it at 75 and at a pressure not exceeding 5 mm of mercury for 4 hours: it loses
between 8.0% and 18.0% of its weight.
Residue on ignition: not more than 1.2%.
Arsenic: Prepare the Test Preparation by mixing 0.375 g with 10 mL of water in the arsine generator flask. Add 15 mL of nitric acid and 5 mL of perchloric
acid, mix, and heat cautiously to the production of strong fumes of perchloric acid. Cool, wash down the sides of the flask with water, and again heat to strong fumes.
Again cool, wash down the sides of the flask, and heat to fumes. Cool, dilute with water to 52 mL, and add 3 mL of hydrochloric acid: the resulting solution meets the
requirements of the test, the addition of 20 mL of 7 N sulfuric acid specified for Procedure being omitted. The limit is 8 ppm.
Copper or zinc: Ignite 1.0 g
in a porcelain crucible, using as low a temperature as practicable, until all of the carbon is oxidized. Cool the residue, add 15 mL of 2 N nitric acid, and boil for
5 minutes. Filter the cooled solution, and wash any residue with 10 mL of water. To the combined filtrate and washing add an excess of 6 N ammonium hydroxide, and
filter the solution into a 50 mL volumetric flask. Wash the precipitate with small portions of water, adding the washings to the filtrate, dilute the solution with
water to volume, and mix. To 25 mL of the solution add 10 mL of hydrogen sulfide TS: no turbidity is produced within 5 minutes (absence of zinc). Any dark color
produced does not exceed that of a control prepared by boiling a quantity of cupric sulfate, equivalent to 200 @g of copper, with 15 mL of 2 N nitric acid for 5 minutes
and by treating this solution as directed above, beginning with “Filter the cooled solution” (0.02% of copper).
Chromatographic purity: To pass the test.
Assay: Transfer about 100 mg of Methylene Blue, accurately weighed, to a 250-mL volumetric flask, dissolve in
and dilute with diluted alcohol to volume, and mix. Transfer 5.0 mL of this solution to a 100-mL volumetric flask, dilute with diluted alcohol to volume, and mix.
Transfer 5.0 mL of this solution to a 50-mL volumetric flask, dilute with diluted alcohol to volume, and mix. This solution contains about 2 @g per mL. Dissolve an
accurately weighed quantity of USP Methylene Blue RS in diluted alcohol, and dilute quantitatively and stepwise with diluted alcohol to obtain a Standard solution
having a known concentration of about 2 @g per mL. Concomitantly determine the absorbance of both solutions in 1-cm cells at the wavelength of maximum absorbance at
about 663 nm, with a suitable spectrophotometer, using diluted alcohol as the blank. Calculate the quantity, in mg, of C16H18ClN3S in the Methylene Blue taken by the
formula:
50C(AU / AS)
in which C is the concentration, in @g per mL, of anhydrous methylene blue in the Standard solution; and AU and AS are the absorbance of the solution of Methylene Blue and the Standard solution, respectively.
Methylthioninium Chloride BP or Methylthioninium Chloride Ph. Eur is also offered.
IUPAC name is 3,7-Bis(dimethylamino)phenothiazin-5-ylium chloride or 3,7-bis(Dimethylamino)-phenothiazin-5-ium chloride.
