278 Chemistry. [Lecture S4-. 



tree gum, and the mucilage contained in the 

 roots and leaves of several plants. 



Gum tragacanth is stronger than gum arabic. 

 It contains more of nitrogen and lime, perhaps 

 more oxygen and less carbon. 



Cherry-tree gum, as well as that which exudes 

 from most of our stone-fruit-trees, is very nearly 

 of the same qualities as gum arabic. It is, how- 

 ever, somewhat softer, and more easily melted. 



Mucilage is contained in great quantities in 

 bulbous roots, and in the foliage of those plants 

 which have fleshy leaves, such as the althea, 

 malva, &c. The bulbs of the hyacinth contain 

 so much mucilage that they may be used as a 

 substitute for gum arabic. 



3. Jelly is procured from many fruits, parti- 

 cularly from the juice of ripe blackberries and 

 currants. It must be carefully distinguished 

 from the colouring matter of the fruit, as well 

 as the sugar ; for in a state of purity it is nearly 

 colourless, though it has some taste, which is 

 rather pleasant. Dr. Thomson conjectures that 

 jelly is merely gum combined with vegetable 

 acid. 



4-. Sarcocott is contained in many plants, but 

 in greatest abundance in a plant which bears 

 that name. Liquorice and manna are classed 

 under this head, from resembling^sarcocoll in 

 taste, and being soluble in the same menstrua. 



5. Tan, or tannin, has been already noticed, 



