The determination of water in methanol by near infrared absorption

Abstract

Direct spectrophotometry at the 1·93 µm water band enables water in methanol solutions to be determined with a coefficient of variation of 0·4 per cent. and a detectability limit of 0·01 per cent. Use of the transmittance-ratio technique combined with scale expansion enables this coefficient of variation to be reduced to 0·04 per cent. At the optimum path length of 25 mm, the use of scale expansion lowers the detectability limit to 0·001 per cent.