CELL-CONTENTS AND FORMS OF CELLS. 213 



TIGLIC ACID (C 5 H 8 O 4 ) occurs as a glyceride in croton oil, 

 and is soluble in water. 



HYPOG.THC ACID (C 16 H, O 2 ) occurs combined with glycerol in 

 peanut oil and in corn oil. It is soluble in cold alcohol and 

 crystallizes in needles. 



LYCOPODIC ACID occurs, as a glyceride, in lycopodium spores, 

 and is related to hypogadc acid. 



OLEIC ACID (C 18 H 34 O 2 ) occurs as a glyceride in many vege- 

 table oils. The glyceride of oleic acid occurs, as a rule, in larger 

 quantities in most fixed oils than any other glyceride, being present 

 in olive oil to the extent of 90 per cent. It is also found in a large 

 number of seeds, principally in cotton seed, hazel-nut, peanut, 

 sesame, walnut, corn, tea seed, almond, and the kernels of 

 apricot, peach, and plum. These oils are generally grouped to- 

 gether and known as the " olive oil group." The sodium and 

 barium salts of oleic acid are crystalline. 



RAPIC ACID (C 18 H 34 O 2 ) and ERUCIC ACID (C 22 H 42 O 2 ) occur 

 combined with glycerol in the oil obtained from rape or colza 

 seed and in other Cruciferous seeds. 



LINOLEIC ACID (C 18 H 32 O 2 ) is the principal acid of the gly- 

 cerides forming the "linseed oil group" or "drying oils." The 

 acid which is best known is that obtained from flaxseed or 

 linseed, the oil of which contains from 80 to 85 per cent, of 

 linoleic acid or its isomers. Linoleic acid is also present in the 

 fixed oil occurring in the seeds of the following plants : Hemp, 

 walnut, pine (Pinus sylvestris), fir (Abies balsainca) , poppy, 

 safflower, sunflower, and seeds of a number of species of 

 Aleurites. The seeds of Aleurites uwluccana yield the "candle 

 nut oil" of the South Sea Islands, and the seeds of A. cordata 

 yield the " tung oil ' (Chinese wood oil or Japanese wood oil) of 

 China and Japan. 



RICINOLEIC ACID (C 18 H 34 O 3 ) occurs as a glyceride in castor 

 oil, and is the principal constituent of this oil. It is also present 

 in the seeds of other Euphorbiaceous plants, being found in croton, 

 curcas, etc., and is also found in grape seed. Ricinoleic acid is 

 soluble in alcohol and ether and is insoluble in petroleum ether. It 

 forms crystalline salts with barium, calcium, and lead. 



JAPANIC ACID (C, 2 H 42 O 4 ) is the only dibasic acid occurring 



