to prevent trace contamination from wetted surfaces and from
the atmosphere. Specialized temperature compensation cor-
rects the measurement to 25°C, taking into accoun the
temperature effects on the ionization of water the contami-
nants, and interactions between the two. In the absence of
specialized temperature compensation, the sample temperature
is controlled to 25 ± 0.2°C. ... . ,
4.2 To determine the cell constant of a high purity conduc-
tivity cell with an instrument capable of accurate measurement
over the range of pure water to 150 fiS/cm with a single cell
constant, Test Methods D 1125 are used directly. Manufactur-
tivity cell with an instrument which does not accurately cover
the range from pure water to 150 pS/cm with a single cell
constant, a secondary standard cell is used that has an inter-
mediate cell constant with precise value determined by Test
Methods D 1125. That secondary standard cell is then used in
low conductivity water (not a standard) and readings are
compared with those of the low constant cell under test. In this
manner, the cell constant of the latter is determined. Manufac-
turers’ certification of cell constant traceability by this means is
an acceptable alternative.