The common blue violet, Viola papilionacea, is found throughout the eastern U.S. This beautiful little wildflower, when in bloom, will be found often by the thousands, spread in fields, in woods, by flowing creeks and streams. Euell Gibbons called this healthy little wildflower, "nature's vitamin pill" (Stalking the Healthful Herbs). In fact he had it analyzed and found that 1/2 cup of violet leaves contained as much vitamin C as 4 oranges.
Violet leaves can be eaten raw in salads or cooked as a green. Similar to spinach in flavor. The extract made from the flowers can be used to make syrup and jelly. To prepare the extract fill a jar with flowers, cover with boiling water, seep for 12-24 hours and then strain. 1 cup of extract and two cups of sugar, along with juice from 1/2 a lemon are boiled for a few minutes, once cooled, a great syrup for pancakes or waffles.
When you add the lemon juice the violet extract changes turns reddish, indicating the addition of an acid.
Here is what happens when you add a acid to the violet extract.
Heart shaped violet leaves