| 摘要 |
If the O-(5,6,7,8-tetrahydro-2-naphthyl)-N-(6-methoxy-2-pyridyl)-N-methylthiocarbamate used as an active ingredient of a medicine has yellowish discoloration, trace inorganic salt and heavy metal, which may be finally cause the medicine discoloration, deterioration and remaining of metal. The O-(5,6,7,8-tetrahydro-2-naphthyl)-N-(6-methoxy-2-pyridyl)-N-methylthiocarbamate having less than 0.1 wt.% content of O-naphthyl-N-(6-methoxy-2-pyridyl)-N-methylthiocarbamate has 90 or more than 90 whiteness (WB value, JIS standard), and no problem of discoloration of the medicine. Such the crystal is obtained by recrystallization under a condition of holding for 1h or more than 1h within a temperature range of 50-70 DEG C. The recrystallization is performed by filtering with preferable filter having a fine aperture of 20mum or less than 20mum. |
