Add 10 drops of one juice to 5 ml. of indicator solution in a test tube. Stir. Repeat for each
beverage. Line the tubes up from lightest to darkest. Record the rank of each beverage from
‘12’ being the lightest (with the most vitamin C) to ‘1’ being the darkest colour (with the least
vitamin C). (USDA Agricultural Research Service, 2005, p. 1)