1-21
REQUIRED APPARATUS
Description Unit Cat No.
Cylinder, graduated, 100 mL. . . . . . . . . . . . .each . . . . . . . . . . . . 508-42
Funnel, poly, 65 mm . . . . . . . . . . . . . . . . . . .each . . . . . . . . . . . 1083-67
Filter Paper, 12.5 cm . . . . . . . . . . . . . . . . . . .each . . . . . . . . . . . 1894-57
Flask, erlenmeyer, 125 mL . . . . . . . . . . . . . .each . . . . . . . . . . . . 505-43
The determination of metals requires acid and heat to pretreat the
sample. Because filter paper will disintegrate under these conditions,
vacuum filtration with glass fiber filter discs is recommended. Also,
glass filter discs do not retain colored species as filter paper would.
Reagent and Standard Stability
Most chemicals and prepared reagents do not deteriorate after
manufacture, but storage conditions and packaging have a great
influence on their stability. Absorption of moisture, carbon dioxide or
other gases from the atmosphere, bacterial action, or light (with
photosensitive compounds) may affect the reagent shelf life. In some
cases reaction with the storage container or interaction of reagent
components may occur.
Hach strives continually to prepare stable formulations and devise ways
of packaging them to provide maximum protection. Many unique Hach
formulations, methods of analysis and forms of packaging have resulted
from these challenges.
Chemicals supplied by Hach have an indefinitely long shelf life when
stored under average room conditions, unless designated otherwise.
Notations on product labels specify any special storage conditions
required. Otherwise, reagents should be stored in a cool, dry, dark place
for maximum life. It is always good practice to date chemicals upon
receipt and rotate supplies so the older supplies are used first. If in
doubt about the reagent shelf life, run a standard to check reagent
effectiveness.
Reagent Blank
The term "reagent blank" refers to that portion of the test result
contributed solely by the reagent and not the sample. This portion of the
test result represents a positive error. In several of the tests, the reagent
blank is of such magnitude that compensation must be made each time
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