AROMATIC ACIDS AND THEIR DERIVATIVES. 295 



Lactic acid is a colorless, syrupy liquid, of strongly acid prop- 

 erties : it mixes in all proportions with water and alcohol. 



Ferrous lactate, Ferri lactas, Fe2(C 3 H 5 3 )3H 2 = 287,9. Made 

 by dissolving iron filings in diluted lactic acid ; hydrogen- is 

 liberated and the salt formed. It is a pale, greenish-white, 

 crystalline substance, soluble in water. 



QUESTIONS. 



421. Name the more common organic acids found in vegetables 

 and especially in sour fruits. 



422. What is the composition of oxalic acid, how is it manufactured, 

 and what are its properties ? 



423. Explain the formation of crude tartar during the fermentation 

 of grape-juice, and how is tartaric acid obtained from it? 



424. Give properties of and tests for tartaric acid. 



425. State the composition and formation of cream of tartar, Rochelle 

 salt, and tartar emetic. 



426. What are Seidlitz powders, and what change takes place when 

 they are dissolved ? 



427. Mention some officinal scale compounds of iron, and give a 

 general outline of the mode of preparing them. 



428. From what and by what process is citric acid obtained ? 



429. Mention tests by which citric acid may be distinguished from 

 tartaric acid. 



430. From what, and by what process is lactic acid obtained ; what 

 are its properties ? 



44. AROMATIC ACIDS AND SOME OF THEIR 

 DERIVATIVES. 



Constitution of aromatic compounds. Aromatic compounds are 

 derived from benzene, C 6 H 6 , and the hydrocarbons of the benzene 

 series; they differ considerably in their behavior from the sub- 

 stances derived from the methane series, which latter are gen- 

 erally termed fatty compounds. Aromatic compounds cannot be 

 converted into fatty compounds or the latter into aromatic 

 compounds without suffering the most vital decomposition of 

 the molecule, and in most cases this transformation cannot be 

 accomplished at all. 



