Instruction Manual

4
General Notes
• Priortomeasurementensurethatthesampleissuitableforanalysis(nomajorinterference)and
doesnotrequireanypreparationi.e.pHadjustment,ltrationetc.
• Reagentsaredesignedforuseinchemicalanalysisonlyandshouldbekeptwelloutofthereach
ofchildren.
• Ensureproperdisposalofreagentsolutions.
• MaterialSafetyDataSheets:availableonrequest.
Chemical Method Notes:
Method:
The sample is heated at 150
o
Cfortwohoursinthepresenceofpotassiumdichromate,whichisa
strong oxidizing agent. Organic compounds in the sample are oxidized, reducing the dichromate ion
(Cr
2
O
7
2–
) to the green chromic ion (Cr
3+
).
IntheLowRange(LR)Test(0-150mg/L),theamountofremainingCr
6+
is measured; In the
MidRange(MR)(0-1,500mg/L)or(HR)(0-15,000mg/L),theamountofCr
3+
produced is
measured.Theresultsaremeasuredastheamountofoxygen(O
2
)consumedperliterof
water sample. The LR and MR test is displayed in mg/L while the HR test shows g/L.
TheCODreagentcontainsbothmercuryandsilver—themercurycontrolschloride
interferencesandthesilverfunctionsasacatalysttospeedthereaction.
Application:
Samplescanbemeasuredifthechloridecontentdoesnotexceed1,000mg/l(LR/MR)or10,000mg/l
(HR).
Inexceptionalcases,compoundscontainedinthewatercannotbeadequatelyoxidized.Thisresults
inlowreading,comparedwiththereferencemethod.
Differentmethodsofsampling,preparationofthesampleitselfandthetimeelapsedbetweentaking
thesampleandanalysiscanallaffecttheobtainedresults.
General Notes