330 CONSIDERATION OF CARBON COMPOUNDS. 



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

 potassium dichromateand sulphuric acid. After oxidation has taken 

 place the mixture is distilled, when valerianic acid with some 

 valerianate of amyl distils over. The change of amyl alcohol into 

 valerianic 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 0. 

 Amyl alcohol. Valerianic acid. 



Pure valerianic acid is an oily, colorless liquid, having a penetrat- 

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

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



Several of the salts of valerianic acid are official ; they are the 

 valerianate of iron, of ammonium, of zinc, and of quinine. The last 

 named three compounds are white salts, while the ferric valerianate 

 has a dark-red color ; the ammonium salt is easily soluble in water, 

 the other three compounds are insoluble or nearly so. 



Oleic acid, Acidum oleicum, HC 18 H 33 O 2 = 282. 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 . 



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

 olive oil is mainly oleate of glyceril. 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, 

 odorless, tasteless, neutral oily liquid, insoluble in water, soluble in 

 alcohol, chloroform, oil of turpentine, and fat oils, crystallizing near 

 the freezing-point of water; exposed to the air it decomposes and 

 shows then an acid reaction. Lead oleate is soluble in ether, lead 

 palmitate and lead stearate are not. 



The official oleates of mercury , zinc, and veratrine are obtained by 

 dissolving the yellow mercuric oxide, zinc oxide, or veratrine in 



oleic acid. 



_ 



QUESTIONS. 421. What is the constitution of organic acids, which group 

 of atoms is found in all of them, and how does an alcohol radical differ from 

 an acid radical ? 422. Give some processes by which organic acids are formed 

 in nature or artificially. 423. Mention the general properties of organic 

 acids. 424. Which series of acids is known as fatty acids, and why has this 

 name been given to them ? 425. Mention names, composition, and occurrence 

 in nature of the first five members of the series of fatty acids. 426. By what 



