/ 



6g 



/ 



last IS usually constructed with a mixture of clay, sand, and straw. Great care is taken that the sides of 

 the turnace should adjoui close to the copper, lest the smoke of the fuel should mix with tliat of the resinous 

 jmce; tor, without such a precaution, the heat of the furnace would not fail to set fire to the latter, and there 

 would be a great risque of losing the whole; as an additional safeguard, there is generally a vaulted canal, 

 tour or hye feet long, affixed to the mouths of the furnace, and terminated by a thick mud wall five or six 

 feet m height. When every thing has been thus prepared, a moderate fire is kept up with very dry .vood, 

 and the juice boiled five or six hours, the operators frequently stirring it about with a large wooden ladle to 

 prevent the impurities which sink to the bottom of the copper from taking fire, a circumstance likely to 

 occur. It IS said, without such a precaution. To ascertain whether the resinous matter is sufficiently boiled, 

 a small quantity of it is taken out of the copper, and poured on a piece of wood; if, when it becomes cold. 

 It may be reduced to powder by being pressed between the fingers, they know that the process is complete, 

 and then conduct it out of the copper into a large trough similar to what is used for receiving the raw 

 . juice from the pits, and placed in like manner on supports. It is necessary to filter the decoction, which is 

 done by pouring it hot on some long straw neatly stretched over wooden bars which form a kind of horizontal 

 grating; the thickness of the straw filter is generally four or five inches. The impurities and dregs remain 

 on the filter, and the juice runs through it pure into the trough. Before the juice becomes cold and fixed. 

 It IS let through a hole in the bottom of the trough into barrels, where it is suffered to harden; in this state 

 It assumes a brown colour and a brittle texture, and is called Bmi-scc, or Rase. To convert it into yellow 

 resin : instead of tunning the hot juice at once into barrels, an eighth part of fresh water is mixed with it in 

 the trough. The water is acted upon so briskly by the hot decoction, that the whole continues to boil an 

 hour or two, and the resin, from a brown colour, becomes at length of a fine yellow. It is afterwards 

 deposited in barrels and suflPered to harden like the Brai-sec. 



The yellow resin, as ordered by the London College, is the result of a difi-erent operation, but the pro- 

 perties of both these substances are so extremely alike, that they may be spoken of under the same head; 

 we shall therefore reserve our account of them until we have described the mode of preparing the 



H^ 



ESSENTIAL OIL. 



(Oleum esscntiale Pincum.J 



Oleum Terebinthinw . Pharm. Lond. & Ed. 



4 



Spiritus Terebmthince . Pharm. Wurt. &c. 

 Esprit de Rase, of the French. 

 Essential oil of Turpenline. 



The process for obtaining this oil, as directed in the London Pharmacopeia, consists in distilling five 

 pounds of the resinous juice with four pints of water, in a copper alembic. If one pound of the oil be 

 redistilled Avidi four pints of water, the result is called rectified oil of Turpentine, (Oleum Terehinthinm rectifi- 

 catum, of the London and Edinburgh colleges.) The process of rectification is not unattended with dano-er 

 for, unless the luting be very close, some of the vapour is apt to escape; and, if the latter should take fire, 

 the vessels will unavoidably burst. In some dispensatories, this rectified oil is denominated cetherecd. It 

 does not differ very considerably in specific gravity, smell, taste, or medical cpialities from the common 

 essential oil. 



The Oleum Terehinthince, as we have before remarked, seems to be by far the most active part of the liquid 

 resin of the Pine, and is, on that account, much more frequently employed in medicine than any other 

 preparation. Its exhibition, however, requires considerable caution, and the admonitions of Boerhaave, 

 Lange, &c. on this subject, cannot be too strictly attended to. The former of these authors, though its 

 panegyrist, speaks of its violently affecting the head, producing bloody urine, and dangerously irritating the 

 whole habit, when given injudiciously or in too large doses; and the observation of practitioners in general 

 tends to confirm this assertion. Hence, it is proper to employ a very few drops at first, and not to augment 

 the dose without great circumspection. The best vehicle of this powerful medicine is honey, which, with 



\ 



" Edinb. Dispensatory, (1797) p. 315, 



2 N" 



