418 COMPOUND PRODUCTS. CHAP. I. 



SUBSECTION IV. 



Malic Add. Malic Acid is found chiefly in the 

 juice of unripe Apples, whence it derives its name. 

 But it is found also in the juice of Berberries, 

 Elderberries, Gooseberries, Plums, and common 

 House-leek. It cannot be obtained in a crystallized 

 and solid form ; but if left exposed to the air it 

 becomes thick and viscous. It is decomposed by 

 heat and by strong acids. Nitric acid converts it 

 into oxalic acid. It combines with alkalies and 

 several of the metals ; and forms with lime a soluble 

 salt, by which test it is distinguished from other 

 acids. It has been used hitherto only for the pur- 

 pose of chemical experiment. 



SUBSECTION V. 



Gallic Acid. Gallic Acid, as it is obtained in the 

 greatest abundance, so it derives its name from the 

 nut-gall, from which it may be extracted by the 

 following expeditious process of Deyeux. 



Expose a quantity of the powder of nut-galls to 

 a moderate heat, in a glass retort ; and the acid will 

 sublime and form crystals of an octahedral figure. 



Its taste is austere and astringent. It strongly 

 reddens vegetable blues. It is soluble both in 

 water and alcohol ; and is distinguished by its pro- 

 perty of communicating to solutions of iron a deep 

 purple colour. When exposed to a gentle heat it 



