AGRICULTURE AND PLANTING. 19 



On the component Principles of Ve-getables. 



of the bitter almond; in the seeds of aniseed, fennel, and card7vat/s,8i^ Sec. 



III. Concerning RB#^.:ts. * 

 The name of resin is used to denote iii^poiable substances soluble in alco- 

 hol, usually affording much soot by their combustion; they are likewise soluble 

 in oils, but not all in water. 



"All the resins appear to be nothing else but oils rendered concrete4»y t^tis 

 combination with oxygen. The exposure of these to the open air, and the decom- 

 position of acids applied to them, evidently prove this conclusion. 



Resins in general are less sweet than the balsams. They afford more volatile 

 oil, but no acid, by distillation. 



There are some among the known resins -which are very pure, and perfectly 

 soluble in alcohol, such as the balm of Mecca and of Copahu, turpentines, 

 tacamahaca, elemi : others are less pure, and contain a small portion of extract, 

 which renders them not totally soluble in alcohol; -such are mastic, sandaraclt, 

 guaiacum, laudanum, and dragoji's blood. 



If the roots, leaves, barks, &c. of several plants be put into spirit of wine, 

 suffered to stand a few days, and the spirit then evaporated ; the resinous principle 

 is obtained. Sometimes it exudes spontaneously in the form of drops, from the 

 bark of trees; as the gum mastic, anime, olibanum, benzoe, elemi, sandarach, guai- 

 acum, laudanum, tacamahaca, and sanguis draconis, which are found adhering to 

 the trunks of their respective trees. 



IV. Concerning B.vlsams. 



As the chemical analysis points out a sufficiently striking difference between 

 balsams and resins, I think it proper to treat them separately. 



The s.,ubstances called balsams are therefore rcsips united with a concrete 

 acid salt. We are acquainted with three principal kinds, viz. benzoin, tlie balsam 

 of Tola, and the storax calamita. 



If incisions be made in tlve trunk of balsamiferous vegetables, as the cojiaifc* 

 ra officinalis, amyris gileadensis, toluifera balsamum, pinus balsanica, &c< their 



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