Lovibond Tintometer MD 100 Manual De Instrucciones página 6

Removal of high Chloride concentration in COD samples
Chloride content may interfere during COD determination, if the tolerance level of
the used test will be exceeded. To overcome that problem the following sample
pretreatment can be used:
Equipment:
• 2 Erlenmeyer flasks 300 ml with NS 29/32 connection
• 2 HCl absorber according to DIN 38409
• 2 glass stoppers NS 29/32
• Pipettes for volumes of 20 and 25ml
• Magnetic stirrer and magnetic stirring rods
• Thermometer to measure 0 - 100 °C
• Ice bath
Reagents:
• 12 to 14 g of sodalime
• 50 ml H SO (95 - 97%, 1.84 g/ml, CSB free)
2 4
• Hydrochloric acid 10 % to clean absorber from residual lime
The work must be carried out under a fume hood!
20 ml
Put 20 ml homogenised
sample in the erlenmeyer
flask.
25 ml
Add slowly 25 ml
concentrated Sulfuric
acid each under cooling
and stirring.
EN Method Reference Book 1.0
25 ºC
15 ºC
Add the magnetic stirring
rod, and cool in the ice
bath.
Sample will be hot!
COD LR TT / M130
20 ml
Put 20 ml deionized
water in the second
erlenmeyer flask.
50 ºC
40 ºC
Temperature should not
exceed 40 to 50 °C.
EN
7