when we do the quantitative analysis of oxygen . why we use iodine pentaoxide instead of fact that it have oxygen itself .i have got these details from NCERT book of +1 chemistry part 2. Please give your answer.when we refer this I2O5 we will have produced carbon dioxide containing oxygen from iodine.

In the process oxygen in the compound is completely converted to CO by passing over red hot coke; this CO is quantitatively converted to CO₂ by passing through I₂O₅ solution. This CO₂ is then reduced to STP and its volume is measured. Remembering one mole of CO₂ has one mole oxygen atom from the organic compound ,every 22.7 litre CO₂ corresponds to 16g oxygen (and not 32 g which would be the usual case). Then we can find the mass of oxygen and thus the % mass of oxygen in the compound.