Most often when you buy soil that has "African Violet" written on it, it is not really the best soil for your plants. This soil uses mostly peat moss which can cause your plants to become rotted very quickly.
Most growers prefer to mix their own soil which is actually a soil-less mix. The formula for this is:
One part peat moss - provides the soil with texture and water holding capacity.
One part vermiculite - a mineral called mica that is heated and puffed up to form lightweight, sponge-like granules.
One part perlite - a volcanic mineral expanded by heating to form very lightweight, porous white granules.
You can use an empty can or plastic container to measure. Some use additives such as charcoal but this is not absolutely necessary.
If you already have purchased soil with "African violet" on it, use that as your peat, then add the same quantities of vermiculite and perlite.
Peat must be watered before use or it will dry out very quickly. Perlite allows air to pass through the mixture and vermiculite holds the water for a time but also allows air to pass through the soil-less mix.
Many growers pasteurize the peat before mixing in order to kill soil-borne pests. Add water until the peat is damp then put into an oven at 180 degrees F. for one hour. The time should actually be counted from when the internal temperature of the peat reaches 180 degrees F. (This causes a very strong odor, so do this when no one else is at home or you may hear some objections!)