颜料和体质颜料的通用试验方法 第4部分:水萃取酸度或碱度的测定

[中文适用范围]： 该方法的原理在于按照 ISO 787/3 中规定的程序对材料进行热萃取，直至获得完全清澈的滤液。 用指示剂溶液进行测定（方法A）。 若加甲基红指示剂的溶液呈黄色（碱性），则用盐酸溶液滴定至橙色终点；如果加甲基红指示剂的溶液呈红色（酸性），则用氢氧化钠或氢氧化钾溶液滴定至橙色终点。 另一种方法（方法B）是电位测定。 取100ml测试溶液，插入pH测量装置的电极，读取pH值。 [外文原描述]： The principle of the method consists in the hot extraction of the material by following the procedure specified in ISO 787/3, to the stage of obtaining a perfectly clear filtrate. The determination is carried out with indicator solution (method A). If the solution with the methyl red indicator is yellow (alkaline), titrate it with the hydrochloric acid solution to an orange end-point; if the solution with the methyl red indicator is red (acid), titrate it with the sodium or potassium hydroxide solution to an orange end-point. The other method (method B) is the potentiometric determination. Take 100 ml of the test solution, insert the electrodes of the pH measuring device and read the pH value.