. . icances,and on their Combinations with the Alkalis. 2(Xi 



^so sufficient for the pearly matter itself dissolved in alcohol 

 seizing upon its alkali, and being converted into the combina- 

 tion of margarine saturated with potash. If we only obtain 

 peariv matter instead of this last combination, by boiling mar- 

 garine in tlie aqueous extract of turnsole, this ought not to be 

 surprising, if we recollect that the saturated combination is de- 

 composed by water, and consequently it cannot be formed in 

 the midst of a great mass of this liquid. This besides may be 

 easily demonstrated by pouring water into turnsole which has 

 been reddened by the alcoholic solution of pearly matter : at the 

 ijjoment of. the mixture, the colour passes to blue, because the 

 water determines the pearly matter to give up to the colouring 

 principle of the tiuns(^le the alkali which it had at first taken 

 from it. 



36. We have showni that margarine possesses a part of the 

 characters of the acids ; for it neutralizes the alkalinity, and at- 

 tracts the potash with more force than the colouring principles 

 do when employed as reagents. But are these properties suffi- 

 cient to entitle us to place it among the acids ? If we had fixed 

 the properties which are essential to those bodies, it would be 

 easy to decide this question ; but as this has not been done, it 

 is indispensable, before seeking to resolve it, to examine the most 

 general characters which have been ascribed to the acids. 



37. These characters are six in number ;yiz. 1. A sour taste. 

 2. Being capable of being attracted positively by electrified sur- 

 faces. 3. To neutralize more or less the salifiable bases. 4. To 

 tedden turnsole. 5. To redden the colour of violets. 6. To 

 turn yellovv- or redden hematine. 



. I. The sour taste was the first property which served to di- 

 >^tinguish the acids: and this ciuuacter is good; for it belong? to 

 the greater number of those bodies; and, so f;ir as I know, none 

 of the suljstances which are regarded by chemist.^ as non-acids 

 p<)s^.ess it. 



2. If tiie second character seems common to all the acids, it 

 is not exclusive to them; oxygon possesses it por excellence; 

 ^nd M. Berzelius asserts that sulphur, carbon, and arsenic act 

 equally towards the surfaces pos.itivclv electrihed. 

 . 3. Wiiile the sour taste was the first property assigned to the 

 acids, at a period when chemistry did not yet exist, so that of 

 neutralizing more or less the alkalis was one of the first which 

 was regarded as the chief property, when chemical phcenomena 

 began to l)e understood. It was even supposed that there nuist 

 be an acid principle in several bodies which united with the al- 

 kalis, and which in other respects differed extremely from the 

 acids.. . 



4. The property of reddening turnsole has been strongly in- 

 sisted 



