130 PECTINE, PE.nC ACID. 



This matter may be obtained by means of alcohol. If into a quantity 

 of currant juice lately'' expressed, a portion of alcohol be poured, a 

 gelatinous precipitate is formed after a certain time ; this jelly, sub- 

 jected to graduated pressure and washed with diluted alcohol, gives 

 the gelatinous principle in a state of.tolerable purity : this is pectine, 

 discovered by M. Braconnot. 



Pectine dried is in membranous semi-transparent pieces resem- 

 bling isinglass. Thrown into about one hundred times its weight ot 

 water it swells considerably and at length dissolves completely, 

 giving rise to a stiff jelly. By increasing the quantity of water, a 

 mucilaginous solution, having a slightly milky aspect, is obtained. 



Pure pectine is quite insipid ; it does not affect the color of litmus, 

 the weaker acids have no effect upon it ; a slight excess of potash or 

 of soda does not change it obviously, and nevertheless pectine is 

 singularly modified under the influence of these alkalies, being chang- 

 ed into a particular body, having acid reaction ; for on saturating 

 the alkali employed, it immediately coagulates into a transparent 

 gelatinous mass — pectic acid. As pectine acted upon by the fixed 

 alkalies undergoes so remarkable a change, we may be allowed to 

 conclude, w-ith M. Braconnot, that the pectic acid which is found 

 ready formed in plants, has a similar origin ; a view moreover which 

 tends to confirm that formerly announced by A^'auquelin, when he 

 ascribed the development of the acids of vegetables to the presence 

 of alkalies.* 



Gelatinous pectic acid immediately becomes defluent upon the 

 addition of a few drops of solution of ammonia. By evaporating 

 this solution in a porcelain dish we obtain an acid pectate of am- 

 monia, which swells in distilled water, dissolves in it, and thickens 

 a large quantity of the fluid. As ammonia has no reaction upon 

 pectine, M. Braconnot has taken advantage of this negative property 

 to determine if pectic acid exists or not, ready formed, in certain 

 plants. Thus in treating carrots with cold water, rendered slightly 

 ammoniacal, a liquid is obtained, from which an acid immediately 

 throws down a precipitate of pectic acid.f Pectine and pectic acid, 

 therefore, may exist together in vegetables, and M. Jacquelain has 

 proved that the acid there is often in a state of combination as an 

 alkaline or earthy pectate. Tt is to these pectates that M. Payen 

 ascribes the origin of the carbonates of the same bases, which are 

 met with in the ashes of plants, the organic acid having of course 

 beon destroyed by the combustion. J 



M. Braconnot has described an easy process for obtaining pectic 

 acid in large quantity from carrots.^ 



M. Fremy has published analyses of pectine and pectic acid, which 

 present this remarkable peculiarity, that the cne has exactly the 

 fiame elementary composition as the other. 



* Braconnot, Annals of Chemistry, vol. xlvii. p. 274, Si icries 

 t Braconnot, op. cit. vol. xxx. p. 99. 



i Payen, Proceedings of the Academy of Sciences, vol. XV.p.90T 

 i Op. cit. VOL XXX. p. 97. "^ 



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