InteUiaence and Miscellaneotts Articles. 391 



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Pectic acid possesses the singular property of dissolving in con- 

 siderable quantity in neutral or acid salts ; it then forms com- 

 pounds precipitable as jellies by alcohol ; these precipitates are 

 often mixed with pectin, render it gelatinous, and prevent by their 

 presence the recognition, by means of elementary analysis, of the 

 simple relations which connect pectin with the other gelatinous 

 bodies. 



5th. The gelatinous bodies may undergo a last period of trans- 

 formation, and be changed into two very soluble and energetic acids. 

 It is sufficient to boil pectic acid in water for a certain time to con- 

 vert it into an acid, called by the author parapectic acid, and 

 into another acid termed metapectic acid. The parapectic and meta- 

 pectic acids are also formed during the action of acids or alkalies on 

 pectin or pectic acid : the pectates may by long boiling be con- 

 verted into metapectates. These two acids are readily distinguished 

 from each other ; for the first precipitates barytes water, and the 

 second does not ; they decompose the double tartrate of copper and 

 potash, as glucose does. To be certain that this property was not 

 derived from the presence of sugar, the author had recourse to a 

 polarizing apparatus and the action of yest. Guided by the advice 

 of M. Biot, M. Fremy found that the parapectic and metapectic acids 

 effected no rotary action on polarized light, and that the presence of 

 yest produced no traces of fermentation. 



6th. After having examined all the properties of the gelatinous 

 bodies, and found that by employing very weak agents, comparable 

 to those which exist in vegetables, their acidity might be suc- 

 cessively developed, and from neutral bodies, which they originally 

 were, they might be transformed into energetic acids, the author 

 examined whether, during the act of vegetation, gelatinous substances 

 did not undergo changes comparable to those which he had pro- 

 duced artificially. On following for two years, with this intention, 

 the modifications which are effected in fruits during their matura- 

 tion, M. Fremy found that the gelatinous bodies which occur in 

 them could pass through the different intermediate states which he 

 has described ; thus green fruits contain abundance of pectose. As 

 maturation advances the pectose is changed into pectin ; and when 

 the fruits are perfectly ripe, the pectin is frequently completely con- 

 verted into metapectic acid. The modifications examined in this 

 memoir are then precisely those which occur during the maturation 

 of fruits. 



The author found in the numerous analyses which he performed 

 that the composition of the gelatinous bodies could not be repre- 

 sented by carbon and water, and consequently that they were far 

 removed from neutral bodies, properly so called. As experiment 

 always indicates a larger quantity of hydrogen than really exists in 

 organic bodies, the author states that he cannot attribute the differ- 

 ence which he has obtained to an error of analysis. 



The table presented to the Academy shows that all gelatinous 

 substances, similar to those which are derived from starch, are iso- 

 meric, or at least they differ only by the elements of water. This 



