A rapid method for the production control of the non-ionic component in synthetic detergents

Abstract

A dilute solution of the detergent is slightly acidified and mixed with 20 ml of the cobaltothiocyanate reagent and 20 ml of dichloromethane, the mixture is shaken and allowed to separate.

The intensity of the colour of the dichloromethane is measured and the percentage of non-ionic detergent is calculated from straight-line calibration graphs.

Graphs are given for varying amounts of ethylene oxide units per molecule and also for varying hydrophobic molecules. In addition, poly(ethylene glycols) of varying molecular weights were checked by this method, together with synthesised fatty acid-poly(ethylene glycol) esters in an attempt to find a relationship between molecular weight and the slope of the graph. It was found that both the hydrophobic and hydrophilic portions of the molecule affect the slope.

Anionic detergents interfere in this determination, but a simple method to overcome this interference is given.