468 V. CHEMISTRY OF PHOSPHATIDES AND OEREBROSIDES 



thick oil, colored yellow with chlorophyll. The yield in cytoplasm amounts 

 to 0.6-0.97%, while the ether extract amounts to 0.1-0.2% of the fresh 

 leaves. The ether residue is dried in vacuo and taken up with anhydrous 

 ether, whereby a small amount remains undissolved. About 40% of the 

 dissolved material, which contains all the phosphorus, is precipitated from 

 this ether solution by the addition of 4 volumes of acetone. The precipi- 

 tate contains r?.-nonacosane and di-n-tetradecyl ketone, which may be ex- 

 tracted with boiling acetone. The luidissolved residue contains all the 

 phosphorus, which is present in quite similar proportions in different 

 preparations. It consists of the calcium salt of the phosphatidic acids. 



To remove the calcium, the ether solution of the calcium salt is shaken 

 with 0.5-0.25 A*" sulfuric acid, after which the calcium is removed Avith lead 

 acetate. The ethereal solution of lead salt is washed with water and con- 

 centrated in vacuo. The lead salt is precipitated with absolute alcohol. 

 It is redissolved in ether and reprecipitated with absolute alcohol, again dis- 

 solved in ether, and then shaken with 0.25 A^ hydrochloric acid to remove 

 the lead. The ether solution is washed with water and concentrated in 

 vacuo to a syrup. Afterward, through treatment with cold absolute alcohol, 

 a small amount of an insoluble iron-contaming impurity is removed, and the 

 free acid remains behind on evaporation of the alcohol. 



{3) Properties of the Phosphatidic Acids 



The phosphatidic acids are liquid oli\e-brown oils which remain un- 

 changed for long periods at room temperature, but which turn hard and 

 bro^^^l on exposure to air and become insoluble in organic solvents. The 

 unchanged acids are soluble in most organic solvents, cold acetone, and 

 especiallj^ ether, but are only slightly soluble in water. An alcoholic or 

 acetone solution can, however, be considerably diluted with water without 

 the development of an emulsion. 



Phosphatidic acid forms a number of salts. The sodium salt is soluble in 

 water, but only slightly soluble in cold alcohol, and is completely insoluble 

 in ether. The barium, calcium, and lead salts are hard plastic masses which 

 are insoluble in water but very soluble in ether, from which they may be 

 precipitated by alcohcl and acetone. 



(4) Hydrolysis of the Phosphatidic Acids 



Channon and ChibnalP^^ found that, on hydrolysis with barium hy- 

 droxide, a glycerophosphoric acid was formed which had a dextro-rotation. 

 Fatty acids were also recovered to the extent of 93% of the theoretical. 

 These had an iodine number of 136. Proof that the phosphatidic acid is 

 usually a mixture of several types of molecules is found in the fact that, on 



