Лако-красочные материалы — производство

One mole of methylene blue (mol. wt. 319.6) requires two equival­ents of iron (112 grams) for reduction, and therefore 1 cc. titanium tri­chloride solution corresponds to:

0.007299 X 319.6 __ 0.02083 gram of methylene П2~ blue (C16H18N3SC1)

For example, exactly 0.2 gram of methylene blue (zinc-free) is dis­solved in about 100 cc. water in a 250-cc. round-bottomed flask. A

stream of carbon dioxide is passed into the flask and the solution is heated to boiling. Titanium trichloride solution is added from a burette to the boiling solution until the solution is just decolorized. Standard methylene blue (zinc-free, Geigy) required 7.86 cc. TiCl3 solution for 0.2 grams of the dye (average of three titrations). The dye content is, therefore:

0.02083 X 7.86 = 0.1637 gram of pure dye, or
0.1637 X 100/0.2 = 81.8 per cent purity

Methylene Green (mol. wt. 364.6). Methylene Green is a nitro methylene blue and its reduction requires 6 equivalents of iron. There­fore,.! cc. titanium trichloride solution is equivalent to:

0.007299 X 364.6 . r ,

——— —-————- or 0.00809 gram of dye

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0.2 gram of methylene green used 20 cc. titanium trichloride solution, and contained, therefore:

0.00809 X 20 or 1.618 gram of dye

The purity is therefore 80.9 per cent. The color change in this titration is not very sharp.