PLANT AJSTALYSIS: 



QUALITATIVE AND QUANTITATIVE. 



INTRODUCTION. 



§ 1. An accurate qiialitative and quantitative analysis of a plant 

 or vegetable substance is not uofreqiiently referred to as one 

 of the most dLfficult tasks that a chemist may be called upon 

 to undertake. Attention is very properly directed to the great 

 number of species of plants that occur in nature, to the great 

 abundance and variety of their chemical constituents, and to the 

 circumstance that aJinost every skilful analysis of a plant that 

 has not previously been examined yields new, hitherto uidcnown 

 products. Prominence is also justly given to the fact that the 

 analysis of vegetable substances differs from that of minerals, 

 inasmuch as the elements present in the latter have in many 

 instances only to be separated and weighed or measured, either 

 as such or in the form of certain of their simpler, more easily 

 recognisable compounds, whilst in the analysis of plants it far 

 more frequently occurs that the proximate principles themselves 

 must be first sejjara ed before they can- be examined or weighed. 

 These reasons are all admissible ; we are, moreover, justified in 

 pointing out, amongst other numerous difficulties encountered in 

 the analysis of plants, the great proneness to decomposition of 

 many of the constituents of vegetable substances and. the errors 

 that may arise therefrom, not only in the estimation of these 

 bodies themselves, but also of such substances as may accompany 

 them. But surely these considerations should not tend to pre- 

 vent investigations from being carried out which are equally 

 important for scientific botany and chemistry, for medicine, phar- 

 macy, dietetics, agriculture, etc. By systematically arranging 



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