Quantitative Determination of Fatty Acid Salts and Alkyl Amine Salts by Infrared Analysis Method

Abstract

This paper describes an application of an infrared analysis method to quantitative determination of fatty acid salts and alkyl amine salts which are collectors used mainly in nonsulfide mineral flotation. Sodium oleate (NaOl) and sodium palmitate (NaPa) as a fatty acid salt, and dodecyl ammonium acetate (DAA) as an alkyl amine salt are used and for the measurement an infrared analyzer (nondispersion type) in the wave length range 3.4-3.5μm is used. The effect of pH on extraction of the reagents from aqueous solution into carbon tetrachloride phase is examined. Under a constant concentration, the indicated values in the fatty acid salts and alkyl amine salt are shown to be maximum and constant below pH 2.9 and above pH 10.6 respectively (Fig. 2, 5). Each calibration curve for NaOl, NaPa and DAA under such conditions of pH represents good straight line (Fig. 3, 4, 6).
The experimental results show that behavior of the extraction does not simply follow results of calculation based on the dissociation constant. In weakly alkaline range fatty acid salt is considerably extracted into carbon tetrachloride phase (Fig. 2), and the pH range is almost the same as that of acid soap formation. And also DAA is completely extracted at such lower pH as 10.6 (Fig. 5), it may indicate formation of amine ion-molecule complexes.
On the other hand, under higher concentration of NaCl even at pH 4, NaOl is extracted satisfactorily (Table 1).