506 CONSIDERATION OF CARBON COMPOUNDS. 



is, however, generally obtained by oxidation of amyl alcohol by 

 potassium dichromate and sulphuric acid. After oxidation has taken 

 place the mixture is distilled, when valeric acid with some valerate 

 of amyl distils over. The change of amyl alcohol into valeric acid is 

 analogous to the conversion of ethyl alcohol into acetic acid : 



C 5 H n OH + 2O = HC 5 H 9 2 + H 2 O. 

 Amyl alcohol. Valeric acid. 



Pure valeric acid is an oily, colorless liquid, having a penetrating, 

 highly characteristic odor ; it is slightly soluble in water, but soluble 

 in alcohol ; it boils at 185 C. (365 F.). 



Ammonium valerate and zinc valerate are official. Both are white solids hav- 

 ing the odor of valeric acid. The ammonium salt is readily, the zinc salt spar- 

 ingly soluble in water. 



Stearic acid, Acidum stearicum, HC^H^C^ = 282.14. The 

 official stearic acid is the commercial, more or less impure article 

 made from solid fats, chiefly tallow. It is a hard, white, somewhat 

 glossy solid without odor or taste. It is insoluble in water, but solu- 

 ble in alcohol, ether and alkalies. Both stearic acid and palmitic 

 acid, HC 16 H 31 O 2 , occur largely in solid fats. The general properties 

 of palmitic acid are nearly identical with those of stearic acid. (See 

 analytical reactions of fats.) 



Oleic acid, Acidum oleicum, HC 18 H 33 O 2 = 280.14. As shown by 

 its formula, oleic acid does not belong to the above-described series of 

 fatty acids of the composition C n H 2n O 2 , but to a series having the 

 general composition C n H 2n -2O 2 . 



These acids belong to the ethylene series i. e., they contain two 

 carbon atoms held together by a double bond, in virtue of which 

 they are oxidized more readily than the corresponding saturated 

 acids. They also form addition products ; oleic acid, for instance, 

 combines directly with 2 atoms of hydrogen, forming stearic acid, 

 and with bromine to form dibrom-stearic acid. 



Oleic acid is a constituent of most fats, especially of fat oils. 

 Thus, olive oil is mainly oleate of glyceryl. By boiling olive oil with 

 potassium hydroxide, potassium oleate is formed, which may be 

 decomposed by tartaric acid, when oleic acid is liberated. 



Oleic acid is a nearly colorless, yellowish, or brownish-yellow, 

 neutral oily liquid, having a peculiar, lard-like odor and taste. It is 

 insoluble in water, soluble in alcohol, chloroform, oil of turpentine, 

 and fat oils, crystallizing near the freezing-point of water ; exposed 



