PHYSICOCHEMICAL STUDIES ON BELGARD EV AND BELGARD EV-2000 SOLUTIONS .2. POTENTIOMETRIC AND CONDUCTOMETRIC ACID-BASE TITRATIONS

The two anti-scale agents BELGARD EV (BELEV) and BELGARD EV 2000 (BELE V 2) are titrated against standard NaOH solution. Both the potentiomet ric (pH metric) and the conductometric titration techniques are used. For the sake of comparison the reaction of the monomer (maleic acid, H (2)M) is also investigated. The two titration techniques reveal that H (2)M neutralizes along two equal steps. The pK(1) and pK(2) of the aci d are calculated as 2.9 and 6.1, in good agreement with the values quo ted in the literature. The potentiometric titration curves of BELEV an d BELEV 2 solutions are similar and show a single drawn-out inflexion. Computer analysis of the curves reveal four acid species in case of B ELEV and two in case of BELEV 2. The pK values, the percentage composi tion and the mean average molecular weights of all species are compute d. The consumption of NaOH till any one and the same pH value varies l inearly with the additives content in solution. This offers a simple m ethod for analysis of BELEV and BELEV 2 preparations. The conductometr ic titration curves of the two agents indicate the presence of three a cid species. Correlation with the pH curves is made in every case. Not all the inflexions in conductometric curves have correspondence in pH curves. The effect of addition of increasing concentrations of H(2)M to BELEV (BELEV 2) solutions and of increasing BELEV (BELEV 2) concent rations to H(2)M on the pH-metric curves is examined in detail. The tw o materials affect the neutralization pattern of one another. The resu lts suggest the masking of the free-acid protons through hydrogen bond ing with the polymers.