88 Dr. R. D. Thomson on the Coisodie Pine Resin. 



shows that two atoms of carbonic acid and one of water have 

 been removed by the action of the lime. That carbonic acid 

 is fixed by the lime, is proved by the effervescence which takes 

 place when acid is poured on the residue in the retort. 



Dr. French of London, in his * Art of Distillation,' pub- 

 lished in 1664, was aware that by means of lime, oils might 

 be extracted from " resins, gums, fat and oily things." To 

 obtain them, he directs 1 lb. of any of these to be distilled with 

 3 lbs. of the powder of tiles or unslaked lime. I have not been 

 able to find any notice of these facts in Glauber or any ante- 

 rior writer. 



The preceding experiments assist in carrying out certain 

 generalizations which had been deduced from a limited 

 series of data, and serve to confirm the idea of the analogy of 

 the resins, and of their derivation from an oil of the turpen- 

 tine type. The resins perhaps are more interesting to the 

 chemist than at first appears, from their analogy to other 

 bodies of vegetable and animal origin. Whether their basic 

 oils are derived from the deoxidation of other bodies in plants 

 supplied with a larger amount of oxygen, or are formed di- 

 rectly from their gaseous constituents, is a subject for inquiry. 

 If it be true that plants evolve no heat (although it is not easy 

 to comprehend how gases can be condensed without such a 

 disengagement), then it would appear that no combination of 

 carbon and oxygen, no proper combustion, such as occurs 

 in the animal system, takes place in plants ; and hence it 

 would follow that the essential oils are formed directly from 

 their elementary constituents. But the statement ( Brongniart) 

 which has been made that plants evolve heat in fertilization, 

 that oxygen is absorbed and carbonic acid given out, would 

 appear to favour the idea that combustion can occur in plants 

 as well as in animals. The admission of the operation of this 

 process in plants, would throw much light on the following 

 table, representing a descending series, with the exception of 

 the first, into which some bodies of animal origin are intro- 

 duced for the sake of comparison. 



Protein C 48 H^. 14 N 6 



Gum C 48 H^ O^ 



Starch . C 43 H 40 O 40 



Base of cane-sugar . C 48 Hgg O^ 



Fat C M H 40 4 



Bees-wax C 40 H 40 2 



Dammaran C 40 H 31 O s 



Cholesterin C 38 H 32 O 



Dammarone C 38 H 30 O 



Base of resins . . . C 40 H 32 



