Today, with precipitation in the forecast, I set up my mini-laboratory to measure the pH of the local rainfall in Stormstown, PA. First, I installed a standard rain gauge to collect rainwater.
I calibrated my pH meter, prior to taking any actual measurements, using standard reagents of pH of 4.0 and 6.86. I used a pH 7.0 reagent to verify.
After calibration, I waited for some rainfall and then collected my sample.
It had rained 0.20 inches over the past two days.
This was about 400 ml of liquid.
I measured the pH to be about 5.15, which is in the normal range for rainfall but still acidic. It is not considered to be acid rain.