Formaldehyde Methylene Blue reactions

Experiment 12. Schardinger s Reaction.—Of two 25 c.c. portions of fresh milk one is boiled for a short time and cooled then 1 C.c. of the formaldehyde (prepared in an earlier experiment) and a few drops of an aqueous solution of methylene blue are added to each portion. When the two samples are now warmed to about 50° the dye in the unboiled milk is very rapidly decolorised and the same happens to further amounts added. In the boiled milk the colour remains unaltered. 

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