_Procedure._—Add 4 drops of phenolphthalein indicator to 50 or 100 cc.
of the sample in a white porcelain casserole or an Erlenmeyer flask over
a white surface. Add N/50 sodium carbonate until the solution turns
pink. The total acidity in parts per million of calcium carbonate is
equal to the number of cubic centimeters of N/50 sodium carbonate used
multiplied by 20 if 50 cc. of the sample was used, or by 10 if 100 cc.
was used.