Hach Digesdahl 23130-20, Instrument Manual

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SECTION 4 OPERATION
4.1 Apparatus Preparation
See SECTION 3 for more safety information. Prepare to perform the
digestion either behind a laboratory safety shield or inside a fume hood. If
a fume hood is used, check the fume exhaust system to verify it is
working property.
Safety glasses and protective clothing are mandatory.
Turn on the water to the aspirator to maximum flow. Remove the
capillary funnel and place a finger over the opening in the vent trap cap. A
distinct suction should be felt.
4.2 Digestion
Procedures for using the Digesdahl Digestion Apparatus vary with sample
type. Most procedures use a two-phase digestion process involving
concentrated sulfuric acid and 50% hydrogen peroxide. Sulfuric acid
dehydrates and chars the sample. Hydrogen peroxide is added via the
capillary flow funnel to complete sample decomposition. The capillary
funnel feeds hydrogen peroxide into the digestion flask at a rate of 3 mL
per minute. This allows the analyst to control the amount of time sample
is exposed to the hydrogen peroxide (digestion time) by varying the
volume of hydrogen peroxide used.
DANGER
Wear protective eye glasses and clothing. A strong acid (concentrated sulfuric acid) and
a strong oxidant (50% hydrogen peroxide) are used in the digestion reaction. These
chemicals can cause burns if splashed on the skin or permanent eye damage if allowed
to contact the eyes. If the chemicals are hot, effects are considerably more severe.
Immediately rinse any affected area thoroughly with water and contact a physician.
DANGER
Porter des lunettes et vêtements de protection. Un acide fort (acide sulfurique concentré)
et un oxydant puissant (peroxyde d'hydrogène à 50%) sont utilisés dans la réaction de
minéralisation. Ces produits chimiques peuvent causer des brûlures s'ils sont projetés sur
la peau ou des blessures irréversibles aux yeux s'ils sont mis au contact des yeux. Si ces
produits sont chauds, les effets sont considérablement plus graves. Immédiatement rincer
toute partie atteinte abondamment à l'eau et consulter un médecin.
Use the Digesdahl Digestion Apparatus only behind a laboratory safety
shield or in a closed fume hood.
Some samples are more difficult to digest completely. In a careful study
of the minimal time required to digest a variety of materials, complete
nitrogen recovery was achieved for many samples immediately upon
clearing of the digest (when the digest becomes colorless). However,
resistant or refractory materials such as nicotinic acid require several
minutes of continued peroxide digestion after clearing to obtain 100%
nitrogen recovery.
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