n. Non-drying castor oil which has been converted into a drying oil by the catalytic removal of water from its principal fatty acid (80% ricinoleic acid), forming approximately equal quantities with 9–11 and 9–12 unsaturation. The term DCO rather than “dehydrated castor oil” has been suggested and is being used for this oil in order to reduce the tendency to confuse castor oil with DCO, which is entirely different in its properties from the oil from which it is derived.