6.65 x 56.1 / 1.8976 = 196.6 Saponification Value. The _ester_ or _ether value_, or number of milligrammes of KOH required for the saponification of the neutral esters or glycerides in 1 gramme of fat, is represented by the difference between the saponification and acid values. In the example given, the ester value would be 196.6 - 15.3 = 181.3. _Unsaponifiable Matter._--The usual method adopted is to saponify about 5 grammes of the fat or oil with 50 c.c. of approximately N/2 alcoholic potash solution by boiling under a reflux condenser with frequent agitation for about 1 hour. The solution is then evaporated to dryness in a porcelain basin over a steam or water-bath, and the resultant soap dissolved in about 200 c.c. hot water. When sufficiently cool, the soap solution is transferred to a separating funnel, 50 c.c. of ether added, the whole well shaken, and allowed to rest. The ethereal layer is removed to another separator, more ether being added to the aqueous soap solution, and again separated. The two ethereal extracts are then washed with water to deprive them of any soap, separated, transferred to a flask, and the ether distilled off upon a water-bath. The residue, dried in the oven at 100 deg. C. until constant, is the "unsaponifiable matter," which is calculated to per cent. on the oil. In this method, it is very frequently most difficult to obtain a distinct separation of ether and aqueous soap solution--an intermediate layer of emulsion remaining even after prolonged standing, and various expedients have been recommended to overcome this, such as addition of alcohol (when petroleum ether is used), glycerine, more ether, water, or caustic potash solution, or by rotatory agitation. A better plan is to proceed as in the method above described as far as dissolving the resulting soap in 200 c.c. water, and then boil for twenty or thirty minutes. Slightly cool and acidify with dilute sulphuric acid (1 to 3), boil until the fatty acids are clear, wash with hot water free from mineral acid, and dry by filtering through a hot water funnel.