Next, add a small amount of ascorbic acid, until you measure 0 PPM free ClO2 from your solution. Don't add too much. You simply want to use up the free ClO2 in the solution. Make a note of how much ascorbic acid you added.
Ascorbic acid is a powerful anti oxidant. It will react first with the free ClO2, and by limiting the amount added, it will have little effect on the chlorous acid. In a period of time, ClO2 will continue to be released and the concentration of free ClO2 will increase.
To determine if the release is linear, you can again add the same amount of ascorbic acid to use up the free ClO2 that has been generated, and then measure the length of time it takes to generate the ClO2 again.
Graphing the results will give an indication as to its linearity.