CETYLIC ACID. 71 



Preparation. This may be readily inferred from what has been 

 stated regarding the preparation of caprylic acid. 



Tests. We must obtain a pure salt according to the method 

 described in our observations on caprylic acid, and then analyse it. 

 R. Wagner* has, however, discovered a method of detecting this 

 acid when mixed with other substances; for on heating such a 

 mixture with concentrated sulphuric acid, it always appears asso- 

 ciated with its aldehyde, and on supersaturation with potash, an 

 intense odour of oil of rue is developed. 



Wagner has in this way discovered this aldehyde in butter, in 

 cod-liver oil and other fish-oils, in old cheese, in a piece of her- 

 ring, &c. 



Physiological Relations. 



The remarks on the physiological relations of caprylic acid 

 apply equally to this acid. 



In the saponirication of butter we sometimes obtain only a 

 single acid, vaccic c^,C 20 H 18 O 5 .2HO instead of butyric andcaproic 

 acids. This acid reduces silver-salts, and taking up 1 atom of oxygen, 

 becomes converted into butyric and caproic acids (C 20 H 18 O 5 + O 

 = CgH 7 O 3 + C 12 H 11 O 3 ) ; it undergoes the same conversion when 

 exposed to the atmosphere, and so also does its baryta-salt. 



Delphic and hircic acids which were formerly regarded as inde- 

 pendent acids are probably identical with, or mixtures of some of 

 the acids of this group. 



CETYLIC ACID. C 32 H 31 O 3 .HO. 



Chemical Relations. 



Properties. The body, which is also known as ethalic acid, 

 forms colourless glistening needles, fuses at 57, but is solid at 55, 

 may be distilled without undergoing decomposition, and is inso- 

 luble in water. 



Composition. This acid, which is isomeric with the non-volatile 

 palmitic acid, obtained from palm-oil, consists according to the 

 above formula of: 



Carbon .... .... 32 atoms .... 



Hydrogen .... 31 



Oxygen 3 



Water 1 



100-000 

 * Journ. f. pi*. Ch. Bd. 46, S. 155-157. 



