PHARMACY. 



in the mixture, and drying it with a 

 gentle heat, the turpentine will be be- 

 trayed by its smell. Rut the more subtile 

 artists have contrived other methods of 

 sophistication, which elude all trials of 

 this kind. 



Some have looked upon the specific 

 gravity of oils as a certain criterion of 

 their genuineness. This, however, is not to 

 be absolutely depended on; for the genu- 

 ine oils obtained from the same subjects, 

 often differ in gravity, as much as those 

 drawn from different ones. Cinnamon 

 and cloves, whose oils usually sink in 

 water, yield, if slowly and warily dis- 

 tilled, oils of great fragrancy, which are 

 nevertheless specifically lighter than the 

 aqueous fluid employed in their distilla- 

 tion; whilst, on the other hand, the last 

 runnings of some of the lighter oils prove 

 sometimes so ponderous as to sink in 

 water. 



As all volatile oils agree in the general 

 properties of solubility in spirit of wine, 

 indissolubility in water, miscibility with 

 water by the intervention of certain in- 

 termedia, volatility in the heat of boiling 

 water, &c. it is plain that they may be 

 variously mixed with each other, or the 

 dearer sophisticated with the cheaper, 

 without any possibility of discovering the 

 abuse by any trials of this kind. And, 

 indeed, it would not be of much advan- 

 tage to the purchaser, if he had infallible 

 criteria of the genuineness of every indi- 

 vidual oil. It is of as much importance 

 that they be good, as that they be genu- 

 ine ; for'genuine oils from inattentive dis- 

 tillation, and long and careless keeping, 

 are often weaker both in smell and taste 

 than the common sophisticated ones. 



The smell and taste seem to be the 

 only certain tests of which the nature of 

 the thing will admit. If a bark should 

 have, in every respect, the appearance of 

 good cinnamon, ai>d should be proved 

 indisputably to be the genuine bark of 

 the cinnamon tree; yet if it tyant the 

 cinnamon flavour, or has it but in a low 

 degree, we reject it; and the case is the 

 same with the oil. It is only from use 

 and habit, or comparisons with speci- 

 mens of known quality, that we can 

 judge of the goodness either of the drugs 

 themselves, or of their oils. 



Most of the volatile oils indeed are too 

 hot and pungent to be tasted with safety ; 

 and the smell of the subject is so much 

 concentrated in them, that a small varia- 

 tion in this respect is not easily dis- 

 tinguished,; but we can readily dilute 



them to any assignable degree. A drop 

 of the oil may be dissolved in spirit of 

 wine, or received on a bit of sugar, and 

 dissolved by that intermedium in water. 

 The quantity of liquor which it thus im- 

 pregnates with its flavour, or the degree 

 of flavour which it communicates to a 

 certain determinate quantity, will be the 

 measure of the degree of goodness of 

 the oil. 



Medical use. Volatile oils, medicinally 

 considered, agree in the general qualities 

 of pungency and heat; in particular vir- 

 tues they differ as much as the subjects 

 from which they are obtained, the oil 

 being the direct principle in which the 

 virtues, or at least a considerable part of 

 the virtues, of the several subjects reside. 

 Thus the carminative virtue of the warm 

 seeds, the diuretic of juniper berries, 

 the emmenagogue of savin, the nervine 

 of rosemary, the stomachic of mint, the 

 antiscorbutic of scurvy-grass, the cordial 

 of aromatics, &c. are supposed to be con- 

 centrated in their oils. 



There is another remarkable differ- 

 ence in volatile oils, the foundation of 

 which is less obvious, that of the degree 

 of their pungency and heat. These are 

 by no means in proportion, as might be 

 expected, to those of the subject they 

 were drawn from. The oil of cinnamon, 

 for instance, is excessively pungent and 

 fiery; in its undiluted state it is almost 

 caustic; whereas cloves, a spice which in 

 substance is far more pungent than the 

 other, yields an oil which is far less so. 

 This difference seems to depend partly 

 upon the quantity of oil afforded, cinna- 

 mon yielding much less than cloves, and 

 consequently having its active matter 

 concentrated into a smaller volume ; 

 partly, upon a difference in the nature 

 of the active parts themselves : for though 

 volatile oils contain always the specific 

 odour and flavour of their subjects, 

 whether grateful or ungrateful, they do 

 not always contain the whole pungency: 

 this resides frequently in a more fixed 

 matter, and does not rise with the oil. 

 After the distillation of cloves, pepper, 

 and some other spices, a part of their 

 pungency is found to remain behind: s 

 simple tincture of them in rectified spirit 

 of wine is even more pungent than theii 

 pure essential oils. 



The more grateful oils are frequentlj 

 made use of tor reconciling to the sto 

 mach medicines of themselves disgustful. 

 It has been customary to employ ther 

 as correctors for the resinous purgatu 



