Put the cleaned cherries with their pits in a large pot and pour water over them, to cover them well.
Leave them to boil for 10 min., then remove and leave to cool. The fruits should have released their juice by this point. Next, strain the juice well by pressing the fruits or strain them a 2nd time through a cheesecloth.
Add 2 cups (500 g) sugar per 4 1/5 cups (1 L) of juice and return to boil again until the sugar melts. Finally, add the citric acid and distribute the juice into bottles, while still hot. Store the cherry juice in a cool area.