หมายเลขมาตรฐาน : ISO 3704:1976
ชื่อเรื่อง : Sulphur for industrial use — Determination of acidity — Titrimetric method
Applicable to products having acidities, expressed as H2SO4 , equal to or more than 0.01 % (m/m). Describes the extraction of acidic substances with a mixture of water and propan-2-ol (isopropyl alcohol). Titration of the extract with standard volumetric sodium hydroxide solution in the presence of phenolphthalein as indicator. The preparation of the sample from the laboratory sample is carried out by grinding a sufficient quantity of the undried material until it passes through a sieve of nominal mesh of 250 m.
Link : https://www.iso.org/standard/9179.html
