330 On the Definite Proportions in which Ike [Nov. 



II. On the Analysis of Organic Bodies. 



The analysis of organic bodies is much more difficult than that 

 of inorganic bodies ; because they are so easily altered by the 

 situations in which it is necessary to place them, in order to obtain 

 them pure, or in a state proper for experiment. It is often im- 

 possible to separate them from all the water of combination, the 

 elements of which mixing with those of the substance analysed 

 occasions an erroneous result. For these reasons I have preferred 

 making my experiments of analysis on combinations of the ternary 

 oxides with binary oxides, and I have almost always employed the 

 oxide of lead, because most organic bodies have an affinity for it, 

 and because the resulting combinations are almost always easily 

 separated from their w T ater of combination. I have chosen the 

 vegetable acids as the first substances to begin with, because they 

 constitute, as it were, the transition from inorganic to organic 

 nature. I propose to examine by degrees save substances belong- 

 ing to each class of ternary oxides, to ascertain what are the general 

 differences between the classes ; for example, between resins and 

 oils. These differences being ascertained, it will be next neces- 

 sary to examine the differences between the species themselves, as 

 between oils of lavender, cinnamon, anise, &c. 



As to the quaternary oxides, or those which contain nitricum, my 

 method of analysis explained here is not applicable to them. Hence 

 I shall in the first place pay attention only to the ternary oxides ; 

 convinced that it is necessary to know the more simple combina- 

 tions before we begin to study the more complex ones. 



It is very probable that in a course of study almost entirely new I 

 shall sometimes commit mistakes, and draw consequences which 

 will not be always confirmed by future researches; but 1 entreat the 

 reader, who will perhaps form his opinion of me at a time when 

 the subject will be better known and illustrated, to recollect that 

 this was not the case when these experiments were made, and that 

 it was scarcely in my power to profit by the information of any 

 predecessor ; but though I speak in this manner, I must, notwith- 

 standing, do justice to those chemists who have been employed 

 before me in the analysis of organic bodies. But among these 

 labours we can scarcely reckon the experiments of the phlogistic 

 chemists to decompose substances by naked distillation, in order to 

 obtain then* acid and empyreumatic spirits, their empyreumatic 

 oils, their essential salts, gases, &c. ; because they had no tendency 

 to decide the question under our consideration. 



When the theory of chemistry was changed by Lavoisier, that 

 illustrious chemist began to consider the composition of organic 

 bodies in a proper point of view; and he endeavoured to discover 

 the elements of these bodies, and to determine their proportions. 

 He discovered the nature of these elements, though he was not so 

 successful in determining their proportions. Lavoisier's mode of 

 analysis was to oxidize organic bodies till he converted them into 



