Book I. VEGETABLE CHEMISTRY. 221 



fennel, angelica ; and of plants with compound flowers, such as wormwood. They are found also In the 

 flower itself, as in the flowers of chamomile, and the rose ; and in the fruit, as in that of popper and ginger, 

 and in the external integuments of many seeds, but never in the cotyledon. They are extracted by means 

 of expression or distillation, and are extremely numerous; and perhaps every plant possessing a peculiar 

 odor possesses also a peculiar and volatile oil. The aroma of plants, therefore, or the substance from which 

 they derive their odor, and which is cognisable only by the sense of smell, is perhaps merely the more 

 volatile and evaporable part of their volatile oil, disengaging itself from its combinations. Volatile oils 

 are characterised by their strong and aromatic odor, and rather acrid taste. They are soluble in alcohol, 

 but are not readily coverted into soaps by alkalies. Tiiey are very inflammable, and are volatilised by a 

 gentle heat. Like fixed oils, their specific gravity is generally less than that of water, on the surface of 

 which they will float ; though in some cases it is found to be greater than that of water, in which they 

 consequently sink. They are much in request on account of their agreeable taste and odor, and are pre- 

 pared and sold by apothecaries and perfumers, under the names of distilled waters or essences ; as well as 

 employed also in the manufacture of varnishes and pigments. 



1420. Wax. On the upper surface of the leaves of many trees there may often be observed a sort of var- 

 nish, which, when separated by certain chemical processes, is found to possess all the properties of bees'- 

 wax, and is consequently a vegetable wax. It exudes, however, from several other parts of the plant 

 besides the leaf, and assumes a more waxy and concrete form, as from the catkins of the poplar, the alder, 

 and the fir ; from the fruit of the myrica cerifera and croton sebiferum ; but particularly from the antherae 

 of the flowers, from which it is probable that the bees extract it unaltered. It was the opinion of Reaumur, 

 however, that the pollen undergoes a digestive process in the stomach of the bee before it is converted into 

 wax, though a late writer on the subject endeavours to prove that the wax is elaborated from the honey 

 extracted by the bee, and not from the pollen. It is found also in the interior of many seeds, from which 

 it is extracted, by means of pounding them and boiling them in water. The wax is melted and swims on 

 the top. Wax, when pure, is of a whitish color, but without taste and without smell. The smell of 

 bees'- wax is indeed somewhat aromatic, and its color yello\<^. But this is evidently owing to some foreign 

 substance with which it is mixed, because it loses its smell and color by means of bleaching, and becomes 

 perfectly white. This is done merely by drawing it out into thin stripes, and exposing it for some time to 

 the atmosphere. Bleached wax is not affected by the air. Its specific gravity is Q-9600. It is insoluble in 

 water, and in alcohol. It combines with the fixed oils, and forms with them a composition known by the 

 name of cerate. It combines also with the fixed alkalies, and forms with them a compound possessing 

 the properties of common soap. The acids have but little action on it, and for this reason it is useful as a 

 lute to confine them, or to prevent them from injuring cork. When heat is applied to wax it becomes 

 soft, and melts at the temperature of 142* if unbleached, and of 1m" if bleached, into a colorless and trans- 

 parent fluid, which, as the temperature diminishes, concretes again and resumes its former appearance. 

 At a higher temperature it boils and evaporates, and the vapor may be set on fire by the application of red 

 heat. Hence its utility in making candles. And hence an explication of the singular phenomenon ob- 

 servable in the dictamnus fraxinella. This plant is fragrant, and the odor which it diffUses around forms 

 a partial and temporary atmosphere, which is inflammable ; for if a lighted candle or other ignited body 

 is brought near to the plant, especially in the time of drought, its atmosphere immediately takes fire. 

 This phenomenon was first observed by the daughter of the celebrated Linnaeus, and is explained by sup- 

 posing the partial and temporary atmosphere to contain a proportion of wax exuded from the plant, and 

 afterwards reduced to vapor by the action of the sun. The result of its combustion in oxygene gas was, 

 according to Lavoisier, carbonic acid and water, in such proportion as to lead him to conclude that 100 

 parts of wax are composed of 8228 of carbon and 1772 of hydrogen. But owing to the little action of 

 acids upon it, there seems reason to believe that it contains also oxygen as an ingredient. 



1421. IVax possesses all the essential properties of a fixed oil. But fixed oils have the property of becom- 

 ing concrete, and of assuming a waxy appearance when long exposed to the air, in consequence, as it seems, 

 of the absorption of oxygen. Wax therefore may be considered as a fixed oil rendered concrete, iJerhaps 

 by the absorption of oxygen during the progress of vegetation. But if this theory is just, the wax may be 

 expected to occur in a considerable variety of states according to its degree of oxygenation ; and this is ac- 

 cordingly the case. Sometimes it has the consistency of butter, and is denominated butter of wax, as 

 butter of cocoa, butter of galam. Sometimes its consistency is greater, and then it is denominated tallow, 

 as tallow of croton ; and when it has assumed its last degree of consiBtency, it then takes the appellation 

 of wax. The following are its principal species : butter of cacao, butter of cocoa, butter of nutmeg, tallow 

 of croton, and wax of myrtle. 



1422. The butter of cacao is extracted from the seeds of the 1424. Btdler of mttmeg is obtained from the seeds of the 



theobroma cacao or chocolate plant, either by boiling them in '-^- '^~ '" ' * 



water, or by subjecting them to the action of the press after 



havinjf exposed them to the vapor of Iwiling water. sebiferum. 



1423. Butter of cocoa is found in tne fruit of cocos nucifera or 1426. T/te rvax.qf mjftile is obtained from the berry of the 

 cocoa-nut-tree. It is expressed from the pulp of the nut, and is myrica cerifera. 



even said to separate from it when in a fluid state, as cream 

 separates from milk. 



1427. Resins. Resins are volatile oils, rendered concrete by fmeans of the absorption of oxygen, or 

 rather perhaps by the abstraction of part of their hydrogen. They have a slight degree of transparency, 

 and their color is generally yellowish. Their taste is somewhat acrid ; but they are without smell when 

 pure. Their specific gravity varies from 1*0180 to 1'2289. They are non-conductors of electricity, and 

 when excited by friction their electricity is negative. The species of resins are numerous. 



1428. Roainis a species of resin, of which there are several 1435. OpoA(i/iamKm,or/)rt;mQ/'Gi/ea<i, which has been so much 



varieties From different species of the pine, larch, and fir- famed for its medical virtues, is the produce of the amyris 



tree, there exudes a juice which concretes in the form of tears. ^leadensis, a shrub which grows in Judaea and in Arabia ; but 

 Its extrication is generally aided by means of incisions, and it it is so much valued by the Turks that its importation is pio- 

 receives different appellations, according to the species from hibited. This is the balm of Gilead so much celebrated in 

 which it is obtained. If it is obtained from the pinus syl- Scripture. Pliny says it was first brought to Rome by the 

 vestris, it is denominated etrmmon turpentine ; from pinus generals of Vespasian. It is obtained in a liquid state from in- 

 larix, Venice lurnentine ; from amyris balsamea, IxUtam of cisions made in the bark, and is somewhat bitter to the taste. 

 Canada. It consists of two ingredients, oil of turpentine and 1436. Copaitia, or toisamo/copaii'a, is obtained from the co- 

 rosin. The oil is extricated by distillation, and the rosin re. paifera officinalis. 



mains behind. If the distillation is continued to drynes.s, the 1437. Dragon's blood is obtained from thedracoena draco, 



residuum is common rotin or colophonium ; but if water is pterocarpus draco, and calamus rotang. 



mixed with it while yet fluid, and incorporated by violent 1438. Guatac is the produce of the guaiacura officinale, 



agitation, the residuum is yellotii rosin. The yellow rosin is 1439. Botany Bay resin, the produce of the acarois resinifera, 



the most ductile, and the most generally used in the arts. a native of New Holland, and found in great abuuidance about 



1429. Pi/cAanrf<araremanufacturedfromtheresinous juices Botany Bay- 



of the fir. The trunk is cut or cleft into pieces of a conve- 1440. Greenrenn constitutes the coloring matter of theleaves 



nient size, which are piled together in heaps, and covered of trees, and of almost all vegetables. It is insoluble in water, 



with turf. They are then set on fire, and the resinous juice but soluble in alcohol. When treated with oxymuriatic acid, 



which is thus extricated, being prevented from escaping in a it assumes the color of a withered leaf, and exhibits the re- 



volatUe state by means of the turf, is precipiuted and collected sinous properties more distinctly. 



in a vessel beneath. It is partly converted into an empyreu- 1441. Cojial is the produce of the rhus copallinum, a tree 



raatic oil, and is now tar, which, by being further inspissated, which is found in North America. 



is converted into pitch. 1442. Anim^, is obtained from the hymensea coubaril, or 



1430. Maatich is extracted from the jiistacia lentiscus. locust-tree, a native of North America. 



P \A5\.iiandarach is obtained from the juniperis communis, by 1443. Lac is the produce of the croton laccjferum, a native of 



spontaneous exudation. the East Indies. 



1432. fi/emt is extracted from the amyris elemifera. 1444. Bloom. Upon the'epidermis of the'leaves'and fruit of 



1433. Tacambac is the produce of the fagara octandia and certain species of plants, there is to be found a fine, soft, and 



yristica officinalis, or nutmeg-tree. 



1425. Tallorv of croton is obtained from the fruit of the ( 



glaucous powder. It is particularly observable upon cabbage, 

 leaves, and wpon plums, to which : 



Labdanum is obtabied fxum. the citus creticus. leaves, and vpon plums, to which it communicatet a pen- 



