Another method which has been proposed is to run the liquid olein over a series of electrically charged plates, which effects its reduction to stearin. Stearic acid is also formed by treating oleic acid with fuming hydriodic acid in the presence of phosphorus, while other solid acids are obtained by the action of sulphuric acid or zinc chloride on oleic acid. Acids of Series II. may also be converted into saturated acids by heating to 300 deg.C. with solid caustic potash, which decomposes them into acids of the stearic series with liberation of hydrogen. This reaction, with oleic acid, for example, is generally represented by the equation-- C_{18}H_{34}O_{2} + 2KOH = KC_{2}H_{3}O_{2} + KC_{16}H_{31}O_{2} + H_{2}, though it must be really more complex than this indicates, for, as Edmed has pointed out, oxalic acid is also formed in considerable quantity. The process on a commercial scale has now been abandoned. One of the most important properties of this group of acids is the formation of isomeric acids of higher melting point on treatment with nitrous acid, generally termed the _elaidin reaction_. Oleic acid, for example, acted upon by nitrous acid, yields elaidic acid, melting at 45 deg., and erucic acid gives brassic acid, melting at 60 deg.C. This reaction also occurs with the neutral glycerides of these acids, olein being converted into elaidin, which melts at 32 deg.C. The lead salts of the acids of this series are much more soluble in ether, and the lithium salts more soluble in alcohol than those of the stearic series, upon both of which properties processes have been based for the separation of the solid from the liquid fatty acids. III. _Linolic Series:_-- -------------------------------------------------------------------------- Acid. | Formula. | Melting | Found in | | Point, | | | deg.C. | -------------------------------------------------------------------------- Elaeomargaric | C_{16}H_{29}COOH | ... | Chinese-wood oil. -------------------------------------------------------------------------- Elaeostearic | C_{16}H_{29}COOH | 71 | Chinese-wood oil. -------------------------------------------------------------------------- Linolic | C_{17}H_{31}COOH | Fluid | Linseed, cotton-seed and | | | maize oils. -------------------------------------------------------------------------- Tariric | C_{17}H_{31}COOH | 50.5 | Tariri-seed oil. -------------------------------------------------------------------------- Telfairic | C_{17}H_{31}COOH | Fluid | Telfairia oil. -------------------------------------------------------------------------- These acids readily combine with bromine, iodine, or oxygen. They are unaffected by nitrous acid, and their lead salts are soluble in ether. IV. _Linolenic Series:_--