J 68 On the Distillation rf recent and of dried Vegetables. 



render it difficult to trace the precise order of union which 

 those elements maintained in the original compound. Thus 

 it is found that vegetables, both of the noxious and escu- 

 lent kind, yield by that species of chemical decomposition 

 which is effected by fire, the same common elementary 

 principles; whence it follows, that the precise nature of a 

 vegetable cannot be determined by the mere knowledge of 

 its constituent parts. 



When the recent leaves of vegetables are exposed to a de- 

 gree of heat but little exceeding the medium temperature of 

 our climate, an evident change is quickly produced ; their 

 bulk becomes greatly diminished, their colour less vivid; 

 the fragrance, if they possessed any, is in most cases con- 

 siderably impaired, and in some instances totally destroyed ; 

 it will also be found that a considerable loss of weight has 

 been sustained. 



These obvious changes may chiefly be referred to the 

 evaporation of aqueous moisture, dissipation of the aroma, 

 and loss of a portion of the volatile or essential oil. That 

 this last effect does not take place is an opinion entertained 

 bv some practical operators, who maintain, that from those 

 vegetables containing essential oil, the greatest quantity may 

 be obtained by previous drying before they are submitted to 

 the process of distillation. 



It is not my intention either to combat this opinion or 

 to enter into a detail respecting the chemical composition of 

 vegetable bodies, but simply to state the following fact, 

 which has lately come under my observation. 



A quantity of the dried leaves or peppermint (mentha pi- 

 perita), which bad been included in casks well closed for 

 nearly two years, and apparently in a state of good preser- 

 vation, were exposed to distillation, with a view to obtain 

 the essential oil, The operation was conducted in a com- 

 mon still furnished with a connecting refrigeratory, and the 

 products received in an Italian recipient, such as is usually 

 employed for the separation of the lighter essential oils. 

 After a considerable quantity of the fluid had distilled, and 

 that which remained tasted but little of the plant, the pro- 

 cess was discontinued. On examining the receiver, it was 



observed, 



