If you are looking at the Epsoma Garden Lime it is dolomite lime, which includes calcium and magnesium. You can crush some up into finer particles if you need it to act faster. Add it to your peat mix and let it sit damp for a week or two and your PH should be stable. 1 tbsp lime/gallon of your mix.

Pre mixed peat based potting soils already have dolomite lime added but if the soil will be used for a very long stretch or reused you may need to add more down the road.