COHESION OF LIQUIDS. 147 



It has been found, that several of the essential 

 oils ate hydrocarbons, as the essence of turpen- 

 tine, lemons, copaiva, burgamot, and camphene, 

 or camphogen ; but that most of them are com- 

 posed of hydrogen and carbon, united with oxy- 

 gen ; or that they are oxides of hydrocarbons, as 

 they have been termed by Dumas. 



The oil of mustard contains sulphur and nitro- 

 gen ; the oil of bitter almonds also contains some 

 nitrogen, according to Liebig and Wohler. When 

 perfectly pure, it is composed of 1 atom benzule 

 (Bz.) and 1 of hydrogen, the proximate atom of 

 which is 106. Their atomic weights have not 

 been accurately ascertained, owing to the fact, that 

 they do not combine with bases without decom- 

 position. They are of a pungent aromatic taste 

 and odour ; and many of them pass into the form 

 of vapour at the temperature of boiling water; 

 but some of them require a much greater heat. 

 Dumas observes, that the density of the volatile 

 oils is proportional to the quantity of oxygen they 

 contain. 



The specific gravity and chemical constitution 

 of the fixed oils are nearly the same ; yet they 

 require a temperature of about 600 F. to vola- 

 tilize them. Why then, it may be naturally in- 

 quired, if they consist chiefly of carbon and 

 hydrogen, is their cohesion greater than that of 

 aether, alcohol, water, and the essential oils? 

 The following facts may tend to throw some 

 gree of light on this question. 



