The absorption maximum8.5.1 The pri

The absorption maximum8.5.1 The principleThe chemical reaction (see appendix on the so-called Hantzschen: picture 2) withwhich dissolved formaldehyde reacts in solution react with Ammonia and Acetylaceton to form Diacetyldihydrolutidin (DDL). The absorption maximum of DDL is 412 nm. The reaction is specific for formaldehyde.8.5.2 Reagent8.5.2.1 Acetylaceton solution4ml of Acetylaceton are dispensed in a 1000 ml to measuring cylinder and ismade up to 1000 ml with distilled water. The solution air-tighted and can be usedfor 4 weeks if kept away from light.8.5.2.2 Ammonium acetate solution200 g of ammonium acetate is dispensed in a 1000ml measuring cylinder andmake up to 1000ml with distilled water.8.5.3 Reaction10ml of the absorbent solution (8.3) are taken with a pipette and are moved in a50ml bottle with 10 ml Acetylaceton solution (8.5.2.1) and 10 ml ammoniumacetate-solution (8.5.2.2). The bottle is closed, shaken and warmed up for 15minutes in a waterbath at 40ºC. The greenish-yellow solution is then cooled atambient temperature, protected from the sunlight (about one hour). The opticaldensity of this solution is determined with a wavelength of 412 nm by distilledwater with a Spectrophotometer (6.4). A control is determined in parallel withdistilled water and is taken into consideration with the calculation of the bottlesvalue (9.2).Remark: After every test, the PE flasks are cleaned in a lab washer. Should thisnot be sufficient, it is advisable that the flasks are kept at 70ºC openly in acirculating air warm chamber for approximately 16 h.