When using the speedstir, do you put a drop in and then turn the speedstir on for a couple of seconds and then turn it off before you add the next drop. And then repeat the procedure. Or do you keep the speedstir on while adding one drop at a time?
Leave the speedstir on the whole time. Start it up before adding any reagents and just let it whirl. Add drops about 1 per second until you reach the endpoint color change and the last drop does not change the color at all. Subtract the last drop that didn't change the color at all. Be sure to measure your volume BEFORE putting the stir bar in.