This acid is found in apples and thejuices of similar fruits, and is also present in the mountain ash and garden rhubarb, to which it gives the peculiar tartness that is so agreeable to the palate. It is capable of being separated by the processes of the laboratory, but in its pure state no useful application has been found for it, although we think it might advantageously be employed in the manufacture of those summer beverages in which a sweet tartness is so cooling and agreeable. The difficulty attending its preparation may perhaps for some time prevent this, but that it will be more generally used we do not doubt.