On the Distillation of recent and of dried Vegetables, 1 69 



observed, that the produce of essential oil was excessively 

 small; notwithstanding the quantity of leaves which had 

 been operated upon amounted nearly to 40 pounds. 



Apprehending some mismanagement in the operation, 

 another quantity similar to the preceding was introduced into 

 the still : attending at the same time to every circumstance 

 which could possibly be imagined to facilitate the develop- 

 ment of the oil. A piece of basket-work was placed in the 

 bottom of the still, and a quantity of water was added suf- 

 ficient to give fluidity to the mass, and prevent the possi- 

 bility of empyreuma taking place; added to these, the boil- 

 ing point was attended to with care, and the first portions 

 of the distilling liquid were suffered ,only to drop slowly from 

 the condensing vessel. 



In this last operation, however, the value of the products 

 did not differ materially from that of the preceding; and the 

 result of several subsequent distillations appeared to show 

 that the essential oil could not be obtained from the dried 

 plant in a proportion equal to that afforded when in a recent 

 state. 



In the respective operations it was observed, that although 

 the produce of oil was comparatively inconsiderable, its ab- 

 sence seemed to be balanced by an abundant produce of 

 water highly impregnated, both with the taste and flavour 

 of the plant. 



This circumstance appears to warrant the presumption, 

 that the herb, notwithstanding the length of time which it 

 had been enclosed in the casks, had not suffered so much 

 deterioration as the diminished produce of oil might seem to 

 indicate ; for although the essential oil did not appear in an 

 uncombined state, its particles may* have undergone some 

 peculiar modification, in virtue of which it was rendered 

 more soluble, and hence the increased quantity of highly 

 impregnated water may be accounted for. 



The addition of alkaline substances in small proportions 

 has been supposed by some to accelerate the evolution of 

 volatile oils from their bases : in the present case this expe- 

 dient was not productive of any remarkable effect. 



XXVJTI. Re* 



