RESINS. 907 



GUM RESINS. 



Many plants afford a milky juice when cut or pierced, such as the 

 dandelion and poppy, which when exposed to the atmosphere, 

 becomes solid, and assumes different appearances, according to 

 the plant from which it is derived. These concrete juices form 

 the gum- resins, which are important from their applications in 

 medicine. They are ^essentially mixtures of resins with gum 

 and an essential oil. They form a milky liquid or emulsion 

 with water, the gum only dissolving, while the resin and oil 

 remain in suspension together with various other matters with 

 which they may be accompanied. Alcohol dissolves only a 

 portion of them; but dilute alcohol is their best solvent, as it 

 takes up both the gum and resin. The dilute alkalies dissolve 

 them completely, leaving nothing but foreign matter. In their 

 number are, ammoniac, galbanum, assafoetida, olibanum, myrrh, 

 euphorbium, bdellium, aloes, scammony, gamboge, opium, 

 lactucarium, upas, and many others. Very few of them have 

 much chemical interest, and their treatment properly belongs to 

 pharmacy. 



The resinous acids produced by the action of nitric acid on 

 aloes have lately been studied by Mr. E. Schunk; they are 

 remarkable for their splendid red and yellow colours, and form 

 well crystallized salts. They are chrysolepinic acid, HO + 

 C 12 H 2 N 3 O 13 ; chrysamminic acid, HO-fC 15 HN 2 O 12 ; with 

 alsetinic and aloeresinic acids. (Liebig's Annalen, xxxix. 1 .) 



CHLOROPHYL. 



This name is applied to the green colouring matter of leaves 

 and plants in general, which is observed floating in their cells in 

 the form of green globules. Ether dissolves the colouring 

 matter of these globules, leaving a colourless substance, of 

 which the nature is unknown. Chlorophyl is prepared by di- 

 gesting fresh green leaves in ether, distilling off the latter, 

 digesting the green residue in alcohol which dissolves it, dis- 

 tilling to dryness, and then digesting the chlorophyl in concen- 

 trated hydrochloric acid. The fine emerald green solution in 

 that acid is precipitated by dilution with water. The precipi- 

 tated chlorophyl is again digested in a concentrated solution of 



