d. Effect of time on the formation of phospho
molybdenum complex
The formation of phospho molybdenum complex is time
dependent. Initially the rate of blue color formation is very
slow which gradually increases with time and remains
constant for certain period of time. Further increase
with time (after 60 minutes) results in the decrease in
absorbance. A plot of absorbance as a function of time is
shown in Figure 5. The absorbance value shows that the
maximum value of absorbance is observed at 35 minutes
which remains constant for about 25 minutes and after
1 hour the absorbance starts decreasing. This may be
due to the dissociation of phospho molybdenum blue
complex
6
. Hence the formation of phosphomolybdenum
blue is time dependent.