(1) and (2). Use of magnesium oxide increases the pH of treated water samples between 10 and 11. The pH of the treated
water samples is adjusted to desirable limits (6.5 to 8.5) by adding known amounts of sodium bisulfate to magnesium oxide-treated water samples (0.15 to 0.20 g per litre). If the fluoride-contaminated samples contain bicarbonate ions in excess of 200 ppm, these ions interfere with sodium bisulfate used for lowering the pH of magnesium oxide-treated water samples.