Table 2-6. Spectrophotometer, Controls and Indicators - Continued
Used to zero the meter when the light switch is held in
zero check position. This adjustment should be made at
the beginning of each series of tests. The light shield
must be closed.
Varies the lamp brightness thus determining the amount
of light reaching the photocell. It is used to standardize
the instrument before each measurement to compensate
for turbidity and/or color in the sample not caused by
the substance being measured.
Used to select the wavelength appropriate for the par-
ticular test. It is adjustable from 400 to 700 nanom-
eters (nm) and contains an individual filter for suspended
The range expander is not issued
with the spectrophotometer.
Receptacle used to electrically connect the optional
Expanded Low-Range Accessory to the spectrophoto-
Provide direct readouts for all calorimetric tests. The
appropriate scale for each test is inserted in the meter
while the remaining scales are stored in the meter scale
holder. The calibrations are printed on yellow, enamel-
coated card stock for easy reading.
Supplied with the spectrophotometer, are borosilicate
glass with two sides frosted. The bottles are placed in
the instrument cell holder with either clear side toward
the light source. Only clean, dry sample cells should be
placed in the instrument and when their surfaces become
scratched or nicked the cells should be discarded. The
25 ml mark is approximate but adequate for most appli-
cations. Greater accuracy will be assured however, if the
sample is measured in a graduated cylinder or by pipet.
Used in conjunction with meter scales, meter pointer
gives direct readout on meter scale card printed scale.