A POTENTIOMETRIC STUDY AND DETERMINATION OF COMPOUNDS CONTAINING POLY(OXYPROPYLENE) CHAINS

Ion-selective electrodes of the coated-wire type were used in potentio metric titrations of polypropylene glycols, copolymers of ethylene oxi de and propylene oxide and non-ionic surfactants based on oxyalkylated fatty alcohols and furfurylalcohol. The titration with a standard sol ution of sodium tetraphenylborate is based on precipitation of ternary compounds in the presence of bivalent metal ions; barium(II) salts ar e preferable. This compound is extractable to the membrane plasticizer ; the electrode potential is than governed by the extraction principle s. The signal-stabilization time during titrations depends on the leng th of the poly(oxypropylene) chain and thus, the results of manual tit rations are more precise than those of automatic titrations. Moreover, the results indicate that an average of 6.2 oxypropylene units corres pond to one tetraphenylborate ion, ie, 12.4 units per each barium(II) ion. For analysis of detergents or other samples of practical importan ce, the use of empirical titration equivalents is recommended.