GE Analytical Instruments ©2006 13-2 DLM 14291 Rev. A
NOA with the IFD filter in-line (not shown) to prevent liquid from entering the
reaction cell.
Silicon tubing is connected to the circulating water bath and the heating jacket
of the purge vessel. Hose clamps are used to secure the tubing to the purge
vessel and the fittings on the circulating water bath. Cold water from the tap,
a second circulating water bath or ice bath and peristaltic pump is connected
to the condenser on the purge vessel using rubber tubing and the tubing
secured with hose clamps.
Preparation of the Nitrate Reducing Agent
A saturated solution of VCl
3
in 1 M HCl is prepared and then filtered before use.
Vanadium (III) is oxidized slowly in air, and it is best to prepare small volumes
of the reagent to ensure that the reagent is active. Some researchers report
that the reagent may be stored with refrigeration for 2-4 weeks. To prepare
100 mL of the reagent:
• Use a balance to weigh approximately 0.8 grams of VCl
3
into a clean dry 100
mL flask. When water is added to solid VCl
3
, an exothermic reaction occurs
and the glassware will get hot. Use caution when rinsing the glassware with
water or adding the acid to the vanadium.
• Carefully add 1 M HCl to bring the level of the solution to the 100 mL mark.
Because this is a saturated solution, the dilution does not have to be exact.
• Cap the flask and invert several times. Not all of the solid will dissolve, but
the solution should turn blue.
• The solution MUST be filtered before use. Any filter paper (such as
Whatman #1) can be used to filter the solution. Store the solution in a clean
screw-cap bottle with a Teflon or aluminum foil seal.
Preparation of 1M NaOH
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