Turbidimetric titration procedure

Tanaka and co-workers [158] have used the high-temperature turbidimetric titration procedure originally described by Morey and Tamblyn [153] for determining the MWD of cellulose esters. This method has been applied to the measurement of the MWD of PP. They found that the type of MWD of this polymer is a log-normal distribution function in a range of I M) (cumulative wt%) between 5 and 90%. The effect of heterogeneity in the MWD of PP on the viscosity-molecular weight equation was examined experimentally - the results agreed with those calculated from theory. Strict temperature control ( 0.15 °C) is necessary in these determinations [159]. 

EXPERIMENTAL PROCEDURES AUTOMATED TURBIDIMETRIC TITRATION. A method for the automated aqueous turbidimetric titration of surfactants has been published (10) in which anionic surfactants are titrated against N-cetylpyridinium chloride to form a colloidal precipitate near the equivalence point. N-cetylpyridinium halides have a disadvantage in that they have the tendency to crystallise out of solution (15), consequently the strength of the solution may alter slightly without the knowledge of the operator, also the crystals suspended in solution may cause damage to the autotitrator. In view of these drawbacks hyamine was preferred as the titrant. 

Sodium Hydroxide, Standard Solutions (0.03 M)— Prepare by mixing 7 parts of water with 3 parts of standtud 0.1 A/sodium hydroxide (NaOH) solution. Concentrate 400 mL of 0.03 Af NaOH solution by evaporating to 30 mL, and determine any sulfate present in accordance with Appendix Al, Turbidimetric Procedure for Sulfate of Test Method D 1266. If sulfate is found, corrections must be made for any sulfur introduced by the reagent in the alkali titration following combustion. 

Amine oxides have cationic properties at low pH and so can be titrated with anionic reagents according to the procedures developed for cationic surfactants. Titrations with tetraphenylborate (81) and with dodecylsulfate (82) have been demonstrated, using a potentiometric end point. A turbidimetric end point has also been demonstrated (28). An am-perometric end point may be used in a two-phase system with dodecylsulfate titrant, if a suitable cationic indicator is added such as the iron(II) 1,10-phenanthroline complex (83). Long-chain amines, including any unreacted amine from synthesis of the amine oxide, will quantitatively interfere. 

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