Intelligence and Miscellaneous Articles. 395 



it is neutral to test-papers, and occurs in the juices of perfectly ripe 

 fruits. 



4. Parapectin is transformed, under the influence of acids, into a 

 substance which the author calls metapectin ; it has the properties 

 of a weak acid, reddens tincture of litmus, and precipitates chloride 

 of barium ; it may be named metapectinic acid. 



5. The preceding substances form compounds which are soluble 

 in a certain number of acids, and principally with sulphuric and 

 oxalic acids. These compounds are crystallizable, and form gela- 

 tinous precipitates with alcohol. 



6. There accompanies pectose in vegetable tissues, a peculiar 

 ferment called by M. Fremy pectase ; this has the property of trans- 

 forming pectin successively into two gelatinous acids, which are the 

 pectosic and pectic acids ; this change occurs without the presence 

 of air or the disengagement of gas, and constitutes the pectic fer- 

 mentation, which may be compared to the lactic fermentation. Pec- 

 tase exists in vegetables in two states, one soluble and the other 

 insoluble. 



7. When pectin is submitted to the action of pectase, the acid 

 first formed is a new acid, the pectosic ; it differs from pectic acid in 

 being completely soluble in boiling water. 



8. Pectosic acid is transformed into pectic acid by the prolonged 

 action of pectase ; the pectosic and pectic acids are also formed when 

 pectin is added to an alkali either free or carbonated, or under the 

 influence of lime, barytes, or strontia. 



9. Pectic acid dissolves in considerable quantity in neutral alkaline 

 salts, and especially in ammoniacal salts, which contain an organic 

 acid ; gelatinous double salts with an acid reaction are then formed, 

 which are precipitated in a gelatinous state by alcohol. 



10. Pectic acid, kept for several hours in boiling water, completely 

 dissolves, and is transformed into a new acid, the parapectic acid. 



1 1 . Parapectic acid changes, under the long-continued influence 

 of water, into a powerful acid, the metapectic acid. 



These two last acids arise under several circumstances, and prin- 

 cipally by the reaction of acids, alkalies, or of pectase, pectin and 

 pectic acid ; they possess the property of decomposing by ebullition 

 the double tartrate of potash and copper, like glucose. 



12. Gelatinous substances exposed to a temperature of 392° Fahr. 

 disengage water and carbonic acid, and are converted into a black 

 pyrogenous acid, which the author calls pyropectic acid. 



13. Gelatinous substances exhibit all the generic characters of 

 acids, the capacity of saturation and their power augmenting in 

 proportion as they recede from pectose ; they appear to be all derived 

 from a ternary molecule C 8 H* O 7 , and differ from each other only 

 as to water. 



14. The properties of the gelatinous substances of vegetables 

 afford an explanation of the alterations which a fruit undergoes 

 when submitted to the action of heat, as well as of the formation 

 vegetable jellies. Vegetable jellies may be produced — 1st, by the con- 

 version of pectin into pectosic and pectic acids under the influence 



2 D2 



