FOn DISTIKGUISIIIN'G SACCHARINE JCICES. 595 



2nd. That the proportion of potash or of any other oxybase neces- 

 sary to neutralize this acid being once known, it will not be necessary 

 to have recourse to experiments to ascertain the quantity of the other 

 oxybases which are capable of neutralizing the same acid, 



3rd. That the action of the acid upon organic colouring principles 

 may be predicted with a great degree of probability. 



13. There are properties which, without having the importance of 

 those which have been noticed, are interesting, inasmuch as they furnish 

 useful indications. For instance, if a substance precipitates without 

 alteration the animal matter of the water in which they are held in solu- 

 tion, it may be inferred with great probability that itwill preserve animal 

 matter, as is the case with the tannins ; and I shall show that nearly 

 all the substances of which this is predicable, though they may differ 

 widely in their elements, have notwithstanding many analogous pro- 

 perties ; among others a flavour more or less astringent. 



14. The pi-operties which have been considered may be remarked 

 (12 and 13), though under different relations, when a community of 

 characters is endeavoured to be established between a greater or less 

 number of chemical species, differing greatly with regard to their ele- 

 mentary composition. Let us now examine the properties which are 

 the best adapted for the definition of particular species. 



15. The properties the most suitable for this purpose are certainly 

 those which are manifested for our observation with equal intensity in 

 the different conditions in which the specimens of the species possessing^ 

 them may be placed. For example, acidity, which we have considered 

 as one of the most general properties of compound bodies, may become 

 a specific character of precision when considered in an acid body in 

 particular, with regard to the proportion in weight of the potash or any 

 other alkali, that a given quantity of this acid requires in order to its 

 neutralization. In fact this proportion will be constant as long as the 

 specific nature of the acid lasts. 



16. Properties which are manifested by obvious phaenomena of easy 

 production are also adapted to become specific characters; but I shall 

 show that these characters are specific in proportion to the small amount 

 of the alteration sustained by the elementary composition of the species. 

 With this circumstance in view, I have formed three groups of che- 

 mical properties from these three species : first, those which do not 

 undergo any sensible alteration in their composition ; secondly, those 

 which undergo an alteration which does not prevent them from resuming 

 their first composition ; and lastly, those in which the alteration 's suffi- 

 ciently profound to preventthe resumption of the original composition*. 



• Considerations genirales sur V Analyse organique. Levrault, Pavi», 1824, 

 p. 34 to 42. 



Vol, I.— Paiit IV, 2 s 



