VEGETABLE PRODUCTS. 153 



and Pinic acids. Canada balsam is from the Abies balsamea, 

 and is the clearest variety of balsams ; and on this account is 

 employed in putting up microscopic objects. Venice turpentine 

 from the Larix Europea ; Copaiva balsam, from the Copaifera 

 officinalis of Brazil and Antilles, consists of an oil and resin ; the 

 latter consists of Copaivic acid and an indifferent resin. San- 

 darach, from the Juniperus communis, consists of three acid 

 resins. Olibanum, from the Boswellia serrate, the frankincense 

 of the ancients, used for burning in churches and cathedrals. 

 Mastic, from the Pistacia lentiscus, comes from the island of 

 Chios ; consists of two acid resins ; soluble in alcohol, and makes 

 the finest varnish. Copal flows from the Hymencea verrucosa, 

 and is imported from Calcutta, Bombay, and Madagascar. It 

 is a mixture of several acid resins, which are soluble in alcohol 

 and spirits of turpentine ; hence its use in making varnishes. 

 Gum Lac, from species of Ficus of India. It exudes from punc- 

 tures of insects. It is an acid resin with various other sub- 

 stances : soluble in alcohol and acetic acid. The best non-electric 

 is Benzoin, from the Styrax benzoin, in the island of Sumatra. 



298. Gum resins are mixtures of various materials, a part 

 soluble and a part insoluble in water. The chief are Ammonia 

 Gum, which flows from the root of the Heracleum gummiferum, 

 or, according to others, from the Dorema ammoniacum. It 

 consists of 72 per cent, of resin, and the balance is gum, vola- 

 tile oil, &c. One of the ancient medicines ; not much used 

 now. Galbanum, supposed to come from the Berbose galba- 

 num : not of much importance. Asafostida, from the root of 

 the Ferula or Narthex asafcetida, growing in Persia, consists of 

 resin, gum, sulphurous oil, (fee. It is one of the most powerful 

 antispasmodics. Myrrh, from the Balsamodendron myrrha, a 

 tree of Arabia and Abyssinia, consists of resin, gum, and vola- 

 tile oil. The resin is neutral. Used as a tonic extensively in 

 medicine. Gamboge is from the Stalagmitis gambogioides ; 

 consists of gum 19 per cent., and 80 per cent, of acid resin. 



extensively as a yellow color. 



299. Closely allied to the preceding substances are Caout- 

 chouc (India-rubber) and Gutta Percha. Several families of 

 plants yield more or less caoutchouc from their juices. To ob- 

 tain the pure caoutchouc, the juice is washed with water, and 

 the caoutchouc rises like cream on the surface of the water. 

 The other materials of the juice remain in the water, or sink to 

 the bottom. When once it becomes thick, it can never be 



W hence Copal? Lac?— 298. What are gum resins? Mention some. 

 Of what does asafcetida consist? What gamboge?— 299. What is India- 

 rubber? How obtained? What are its properties ? 



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