2 1, 2. INTRODUCTION. 



the methods of examination hitherto devised, either for the 

 estimation of a single constituent or for the separation of 

 several substances contained in a plant, I hoped to succeed 

 in inducing others to conduct investigations in a department 

 of chemistry at present so much neglected ; and it was in that 

 hope that I decided upon the compilation of this work. In it 

 I trust to be able to show that for the separate estimation of 

 many substances we have methods at our disposal which, in 

 point of accuracy, are nearly .abreast of the processes employed 

 for the determination of mineral constituents, and that we can 

 often obtain results really serviceable in the investigation of 

 the more important component substances contained in a plant. 

 I especially hope to succeed in showing that analyses of plants 

 possess in one respect an advantage over the analyses of 

 minerals, inasmuch as it often happens, in examining mixtures 

 or conglomerates of several chemical individuals, that in the 

 latter case a much less satisfactory insight into the constitu- 

 tion can be obtained than in the former. The elements, for 

 instance, of which a granite is composed can easily be deter- 

 mined by inorganic analysis, but it is exceedingly difficult to 

 ascertain with exactitude in what quantity each separate 

 mineral occurring in the granite is present. But in the 

 analysis of vegetable substances the endeavour is made from 

 the outset to separate the different chemical individuals from 

 one another, and by the use of various solvents this is fre- 

 quently possible. In this respect, therefore, the analysis of a 

 plant can often be made more complete than that of a mineral. 



2. The object that I have sought to attain in this work 

 was the compilation of a method of analysis applicable to the 

 qualitative and quantitative examination of vegetable substances 

 of both known and unknown composition, and of an introduc- 

 tion to the qualitative and quantitative determination of the 

 various more important constituents of plants with which we are 

 at present acquainted. 



I need scarcely observe that I have given the fullest possible 

 consideration to the question as to which tissues of the plant 

 contain the various constituents, and have therefore, for that 

 purpose, made use of microchemical analysis. 



With reference to tjie 'ar,vattgemon^ of the matter in the work, 

 I would remark that in the method of analysis contained in 



