ESTIMATION OF THE PROCEEDING OF NEUTRALIZATION BY QUANTITY OF PRECIPITATE IN THE REACTION OF BARIUM HYDROXIDE AND SULFURIC ACID

Abstract

A revised course of study in the lower secondary school describes that the content of an existing item “effect of concentration and volume of the reagent solution on quantity of a reaction product” should be newly dealt with in the section “correlation between concentration and volume of acid and alkali in the completion of neutralization.” In connection with this alteration, the neutralization reaction of barium hydroxide and sulfuric acid, which appeared in the textbooks of the transitional period, was investigated to give some essential information as follows. 1) Though a majority of teaching materials (3/5) treated the neutralization of acid and alkali according to the new course of study, only one of them includes a student experiment emphasized in it. Even in that case, the end point of the reaction can hardly be determined by tracing the height of barium sulfate precipitate. 2) Similar particle size of barium sulfate is attained for three suspensions of acidic, neutral, and alkaline regions by the addition of cationic polymer flocculants, e.g. 50-100 ppm of C-620, which makes the height of the precipitate proportional to its quantity in a period of 10 min. 3) The use of barium hydroxide solution premixed with the polymer flocculant adds, by abolishing a troublesome explanation of the latter, a practical value to the teaching material when the completeness of neutralization is evaluated based on the height of the precipitate. Moreover, this teaching material was proved, after being conducted as an extra-curricular experiment in the lower secondary school, to be effectively utilized hereafter, since the trial yielded no problem, but it aroused much interest for students. It also has an advantage over another method of conductivity measurement because of the ease of interpreting its meaning.