The stoichiometric equation of the photochemical reaction between acid chromateion and reducing agents such as ethanol and 2-propanol was obtained for the buffered aqueous solutions of ammonium dichromate and reducing agent, of which pH were about 4.5, 5.1 and 6.0.
In the dilute aqueous solution of dichromate ion, the photoactive species is acid chromate ion, HCrO4-, and by the irradiation acid chromate ion (Cr (VI)) is reduced to Cr (III) compound together with theformation of oxidation product of reducing agents.
The amount of unchanged acid chromate ion was measured by spectrophotometry and the oxidation product such as acetaldehyde or acetone was detected by gas chromatography. From these measurements it was confirmed that 1.5 moles of reducing agentswere oxidized against the consumption of one mole of acid chromate ion.
Thestoichiometric equation of the photochemical reaction, therefore, can be described as follows: H+ 2 HCr(11)04-+hP, 3 CH3CH2OH 2 CrOCOH2++ 3 CH, CHO + 6 H2O + 2 HCr(VI)04-+hP, 113 (CH3)2CHOH 2 Cr2++ 3 (CH3)2C0 + 6 H2O