I did a reaction and I measured the volume of gas produced against time. I need to find the rate constant of the reaction. 

I am trying to plot a graph of ln(vol of gas produced) against time so that the gradient will be equal to -k so i can calculate the rate constant k. I am using the equation ln[A]t = -kt + ln[A]o

The problem is I can't plot ln0. I timed the reaction every 5 mins and gas wasn't produced until 15mins had passed. This means that the volume of gas produced for time values 0, 5 and 10 mins is 0cm^3, but ln0 doesn't exist. 

How do I use my data to create a graph to calculate the rate constant?

My results were: 

Time 0\_\_\_5\_\_\_10\_\_\_15\_\_\_20\_\_\_25\_\_\_30\_\_\_35\_\_\_40\_\_\_45\_\_\_50\_\_\_55\_\_\_60 \_\_\_\_(in mins)

Vol \_0\_\_\_0\_\_\_0\_\_\_\_\_5\_\_\_10\_\_\_18\_\_\_\_22\_\_\_28\_\_\_36\_\_\_44\_\_\_51\_\_\_\_60\_\_\_\_70\_\_\_(in ml produced)