153 TEGETABLE PKODUCTS. 



absorption of oxygen, and of course impedes their drying, and 

 which is removed by boiling with oxide of lead (Htharge.) 



Sometimes they are lodged in intercellular spaces or cysts. 

 There are numerous hard or semi-fluid fats that occur in various 

 plants that differ in some respects from the general class. Palm- 

 oil, with the consistence of butter, comes from the Elais Gui- 

 niensis, and is imported mostly from Liberia. It is extensively em- 

 ployed in the manufacture of toilet soaps, and Ims jpalmitic acid 

 instead of stearic. The butter of Cacao is from the chocolate- 

 nuts of the Theobroma cacao, as also the butter oi Nutmeg, Shea, 

 Galam; and vegetable tallow is from the Stillingia Sibifera. 



295 • All these oils are composed of two or more salts which 

 have a common base, Oxide of glycyl : Cg, H3, 0. The acids 

 vary ; Stearic, Margaric, Oleinic, and Olinic, are the most com- 

 mon. The first two form solids with oxide of glycyl, the two 

 latter liquids. The relative quantities of the solid and liquid 

 salts give the consistence of the oil or fat. 



296. Volatile Oils. These occur in the leaves, stem, flowers, 

 seed, &c., of the plant. They occur in cavities formed especially 

 for their use, as in the vittse of the seed of the Umbelliferae ; 

 the sacs in the rind of the Lemon and Orange ; or in other cases 

 diffused through the cellular portions of the plant. Some of 

 these are simply hydro-carbons, as Oil of Turpentine from the 

 Pinus and Abies ; Oil of Juniper from the Juniperus communis ; 

 Oil of Lemon and Oranges. Some contain oxygen, as Oil of 

 Cinnamon, Peppermint, Rose, (fee. Some contain Sulphur, as 

 Oil of Mustard, Asafoetida, from Narthex asafoetida, and the 

 volatile oil of onions. Camphor is a solid volatile oil, from the 

 Camphora ofiicinarum of India, called stearoptene. 



These oils are usually obtained by distillation. Although the 

 boiling point of the oils is higher than that of water, yet from 

 their volatility they rise more rapidly than the water. 



297» Balsams and Resins. A balsam is a volatile oil with a 

 resin dissolved in it. Common turpentine, from the Pinus palus- 

 tris, is a balsam. By distillation we get Spirits of Turpentine ; 

 and we have left, in the still common rosin, colophony. 



Rosin, C40, H30, O4, is an acid, or a combination of two acids, 

 under different circumstances. When obtained by distillation 

 it is Silvic acid ; when by spontaneous evaporation it is Silvic 



What is with thcni? How removed from the drying oils?^ Mention 

 some other substances. — 295. Of what are all oils composed ? — Which form 

 solids? — 296. Where do volatile oils occur? What are some of them ? 

 Which contain oxygen? Which sulphur? What is camphor? How 

 usually obtained ? — 297. What is a balsam ? What is a rosin ? McntioL, 

 some other balsams. 



