Лако-красочные материалы — производство

The content of matter soluble in water in pigments is determined by hot or cold extrac­tion of the pigments under prescribed testing conditions. For standards, see Table

1.1 (“Matter soluble in water”). The decision whether to use hot or cold extraction de­pends on the properties of the pigment and should be agreed between the interested parties unless otherwise prescribed.

The pH value of a pigment denotes the pH of an aqueous suspension of the pig­ment prepared in a prescribed manner. For standards, see Table 1.1 (“pH value”). Apparatus: pH meter.

The electrical conductivity (or resistivity) of an aqueous pigment extract is deter­mined from the electrical conductance (or resistance). For standards, see Table 1.1 (“Resistivity”). Apparatus: centrifuge with glass containers, resistance measurement bridge, electrolytic cell.

The acidity or alkalinity is measured as the quantity of cubic centimeters of 0.1 N alkali (NaOH or KOH) or acid solution that are required to neutralize an aqueous extract of 100 g pigment under prescribed conditions. Unless otherwise agreed, the pigment is extracted with hot water. If cold water is used, this must be specifically stated. For standards, see Table 1.1 (“Acidity/alkalinity”). Test reagents: 0.5 N HCl or H2SO4, 0.5 N NaOH or KOH, indicators (by agreement).

Water-soluble Sulfates, Chlorides and Nitrates. The procedures are applicable to pig­ments and extenders. The choice ofhot or cold extraction depends on the properties ofthe pigment and should be agreed. The anions are determined by the usual analyt­ical methods. For standards, see Table 1.1 (“Sulfates”, “Chlorides”, and “Nitrates”). Apparatus: Nessler tubes or spectrophotometer, equipment for pH measurement.

Water-Soluble Chromium(VI). Chromium(VI) is determined photometrically in an aqueous extract obtained by hot or cold extraction using the color produced with diphenylcarbazide, or directly as chromate. For standards, see Table 1.1 (“Matter soluble in water”). Apparatus: equipment for shaking conical flasks, photometer with glass cells, pH meter.

Matter Soluble in HCl. The pigment is extracted with 0.1 M hydrochloric acid under prescribed conditions to determine the content of As, Ba, Cd, Co, Cr, Cr(VI), Cu, Hg,

Mn, Ni, Pb, Sb, Se, and Zn. For standards, see Table 1.1 (“Matter soluble in HCl”). Apparatus: shaker for conical flasks.

1.2.2.4