CHEMISTRY. 



119 



tion of 



The oils marked $ sink in water. They yield also a fixed oil. 



Several of the gum resins, as myrrh and galbanum, 



C" \ likewise an essential oil, and likewise the balsam of 

 OI'HJ &c. 



SECT. XX. Of Wai. 



The upper surface of the leaves of many trees is co- 

 vered with a varniah, which may be separated and ob- 

 tained in a state of purity by the following process : 



Digest the bruised leaves, first in water and then in 

 alcohol, till every part of them which is soluble in these 

 liquids, be extracted. Then mix the residuum with six 

 times its weight of a solution of pure ammonia, and, 

 after sufficient maceration, decant off the solution, filter 

 it, and drnp into it, while- it is incessantly stirred, dilu- 

 ted sulphuric acid, till more be added than is sufficient 

 to saturate the alkdi. The varnish precipitates in the 

 form of a yellow powder. It should be carefully wash- 

 ed with water, and then melted over a gentle fire. 



Mr Tii.gry first di >eovrred that this varnish possesses 

 all the properties of bee* max. Wax. then, is a vege- 

 table product. Several plants contain wax in such a'<un- 

 dance as to make it wortli while to extract it from tln-m. 

 But let us, in the first pl.ice, consider the prop, rtirs of 

 bees wax, the must common and important species. This 

 subst* .ce, as Huber has demonstrated, contrary to the 

 generijlly tec- ivrd o,> ii">n, is prepared by the bees from 

 honey or *ugar, thf latter jricuhig the greatest propor- 

 tion of it. 



Wax, when pure, is of a whitish colour ; it is desti- 

 tute of taste, and h.'S scarcely any smell. Bees wax, 

 indeed, has a pretty strong ar .malic 'm>-ll ; but this 

 seems chit-fly owinr to sonv- substance with which it is 

 mixed ; for it disappears almost completely by exposing 

 the w jx, drawn t.ut into thm ribands, for some t' 

 the atmosphere. By this pr ceas, which is called bleach- 

 ing, t!ie yellow colour of the wax d sappears ai.d it 

 be' nrnes vt-ry white. Bleached wax is not affrcted by 

 the air. 



The sp'-cific gravity of unbleached wax varies from 

 0.9000 to 0.9650 ; that of white wax from 0.8203 to 

 0.966'2. 



Wax is insoluble in water ; nor are its properties al- 

 tered though kept under that l.q>iid. 



When heat is applied to wax it becomes soft ; and at 

 the temperature of 14.2, if imhlcacli! d. or of' 1.3.5 if 

 bleached, it melts into a colourless transparent fluid, 



which concretes again, and resumes its former appear- Chemical 

 ance as the temperature diminishes. If the heat be still ] 

 farther increased, the wax boils and evaporates ; and if 

 a red heat be applied to the vapour, it takes fire and 

 burns with a bright flame. It is this property which 

 renders wax so useful for making candles. 



Wax is scarcely acted on by alcohol when cold, but 

 boiling alcohol dissolves it. 



Ether has but little action on wax while cold ; but 

 when assisted by heat, it takes up about one-twentieth 

 of its weight of it, and lets the greatest part precipitate 

 on cooling. 



Wax combines readily with fixed oils when assisted by 

 heat, and forms with them a substance of greater or less 

 consistency, according to the quantity of oil. This 

 composition, which is known by the name of cerate, is 

 much employed by surgeons. 



The volatile oils also dissolve wax when heated. Thil 

 is well known, at least, to be the case with oil of tur- 

 pentine. A part of the wax precipitates usually as the 

 solution cools, but of a much softer consistence than 

 usual, and therefore containing oil. 



The fixed alkalies combine with it, and form a com- 

 pound which possesses all the properties of common soap. 

 When boiled with a solution of rtxe-d alkalies in water, 

 the liquid becomes turbid, and after some time the soap 

 separates and swims on the surface. It is precipitated 

 from the alkali by acids in the state of flakes, which are 

 the wax very little altered in its properties. 



The acids have but little action on wax ; even oxy- 

 muriatic acid, which acts so violently on most bodies, 

 produces no other change on it than that of rendering it 

 white. This property which wax possesses, of resist- 

 ing the action of acids, renders it very useful as a lute 

 to confine acids properly in vessels, or to prevent them 

 from injuring a common cork. 



Mr Lavoisier contrived to burn wax in oxygen gas. 

 The quantity of wax consumed was 21.9 grains The 

 oxygen gas employed in consuming that quantity amount- 

 ed to 66.55 grains. Consequently, the substances con- 

 sumed, amounted to 88.45 grains. After the combus- 

 tion, there were found in the glass ve-ssel 62.58 grains of 

 carbonic acid, and a quantity of water, which was tup- 

 posed to amount to 25.87 grains. These were the only 

 produ' ts. 



From this experiment he concluded, that 100 parts of Compoi- 

 wax are composed of lion ac- 



82.28 carbon cording ta 



17.72 hydrogen Lavoiuer. 



l.ussac. 



100.00 



But according to the experiments of Thenard and Gay- According 



Lussac, it is compose-d of * Theaaid 



Carbon 81.784 and Gay- 



Hydrogen 12.672 



Oxygen 5.544 



100 



The myrtle wax of North America is obtained from Myrtle 

 the myrica cerif-ra. The myrica ccrifera is a shrub wai. 

 which ,;rows abundantly in I. uiiun.a and other parts 

 of North America. It produces a berry about tin- s.ze 

 of a prpper corn. A very fertile shrub yieldb nearly 

 seven pounds. From the observation* of Cadet, we learn 

 thrft the wax forms the outer covering of the berries. 

 The wax thus obtained is of a pale green colour. Its 

 specific gravity is 1.0150. It melts at the temperature 

 of 109 : when strongly heated it burns with a white 

 flame, produces little smoke, and during the combustion 



