In 1876, methylene blue was first created as a synthetic aniline-based dye for the textile industry . Commercially, methylene blue is made by first oxidizing N,N-dimethylphenylenediamine with sodium dichromate (Na2Cr2O7) in the presence of sodium thiosulfate (Na2S2O3), then again with N,N-dimethylaniline. With the addition of 30% HCl and a saturated common salt solution to the dye solution, mixture is extracted; following filtration, the product is rinsed with a 2% common salt solution. Manganese dioxide and catalytic quantities of copper sulphate can be employed for the oxidation in place of sodium dichromate .