PHARMACY. 



&n use which they do not seem to be well 

 adapted to. All the service they can 

 here be </f is, to make the resin sit more 

 easily at fir.st on the stomach : far from 

 abating- the irritating quality upon which 

 the violence of its operation depends, 

 these pungent oils superadd a fresh sti- 

 mulus. 



Volatile oils are never given alone, on 

 account of their extreme heat and pun- 

 gency ; which in some is so great, that a 

 single drop let fall upon the tongue pro- 

 duces a gangrenous eschar. They are 

 readily imbibed by pure dry sugar, and 

 in this form may be conveniently exhibited. 

 Ground with eight or ten times their 

 weight of sugar they become soluble in 

 aqueous liquors, and thus may be diluted 

 to any assigned degree. Mucilages also 

 render them miecible with water into an 

 uniform milky liquor. They dissolve 

 likewise in spirit of wine ; the more fra- 

 grant in an equal weight, and almost all 

 of them in less than four times their own 

 quantity. These solutions may be either 

 taken on sugar, or mixed with syrups, or 

 the like. On mixing them with water, 

 the liquor grows milky, and the oil sepa- 

 rates. 



The more pungent oils are employed 

 externally against paralytic complaints, 

 numbness, pains, and aches, cold tumours, 

 and in other cases where particular parts 

 require to be heated or stimulated. The 

 tooth-ache is sometimes relieved by a 

 drop of these almost caustic oils, received 

 on cotton, and cautiously introduced into 

 the hollow tooth. 



Among the volatile oils ought also to 

 be enumerated the empyreurnatic oils ; 

 for these also are volatile, but have a cha- 

 racter peculiar to themselves. The sim- 

 ple volatile oils exist ready formed in the 

 aromatic substances from which they are 

 obtained, and are only separated from the 

 fixed principles by the action of a heat not 

 exceeding that of boiling water. The 

 empyreumatic, on the contrary, are al- 

 ways formed by the action of a degree of 

 heat considerably higher than that of boil- 

 ing water, and are the product of decom- 

 position, and a new arrangement of the ele- 

 mentary principles of substances, contain- 

 ing at least oxygen, hydrogen, and carbon. 

 Their production is therefore always at- 

 tended with the formal ion of other new 

 products. In their chemical properties 

 they do not differ very remarkably from 

 the volatile oils, and are principally dis- 

 tinguished from them by their unplea- 

 sant, pungent smell, and rough, bitter- 

 ish taste. The following are the chief; 



Oleum petrolei, oil of bitumen, or tar. 



Oleum succini, oil of amber, which is 

 afterwards rectified. 



Oleum anhnale, animal oil, obtained 

 from hartshorn, which also is rectilied by 

 being again distilled with water. 



CLASS IX. Spiritus Distillati. DISTILLE'D 

 SPIRITS. 



The flavour and virtues of distilled wa- 

 ters are owing, as observed in the pre- 

 ceding chapter, to their being impregnat- 

 ed with a portion of the essential oil of 

 the subject from which they are drawn. 

 Alcohol, considered as a vehicle for these 

 oils, has tliis advantage above water, that 

 it keeps all the oil that rises with it per- 

 fectly dissolved into an uniform limpid li- 

 quor. 



Nevertheless many substances, which, 

 on being distilled with water, impart to 

 it their virtues in great perfection ; if 

 treated in the same manner with alcohol, 

 scarcely give over to it any smell or taste. 

 The cause of this difference is, that alco- 

 hol is not susceptible of so great a de- 

 gree of heat as water. It is obvious, 

 therefore, that substances may be vola- 

 tile enough to rise with the heat of boil- 

 ing water, but not with that of boiling al- 

 cohol. 



Thus, if cinnamon, for instance, be 

 committed to distillation with a mixture 

 of alcohol and water, or with a pure proof 

 spirit, which is no other than a mixture 

 of about equal parts of the two, the alco- 

 hol will arise first clear, colourless, and 

 transparent, and almost without any taste 

 of the spice ; but as soon as the more pon- 

 derous watery fluid begins to arise, the 

 oil comes freely over with it, so as to ren- 

 der the liquor highly odorous, sapid, and 

 of a milky hue. 



The proof spirits usually met with in 

 the shops are accompanied with a degree 

 of ill flavour, which, though concealed by 

 means of certain additions, plainly disco- 

 vers itself in distillation. This nauseous 

 flavour does not begin to arise till after 

 the purer spirituous part has come over, 

 which is the very time that the virtues 

 of the ingredients begin also to arise most 

 plentifully ; and hence the liquor receives 

 an ungrateful taint. To this cause prin- 

 cipally is owing the general complaint, 

 that the cordials of the apothecary are 

 less agreeable than those of the same 

 kind prepared by the distiller ; the latter 

 being extremely curious in rectifying or 

 purifying the spirits (when designed for 

 what* he calls fine goods) from all unplea- 

 sant flavour. 



