152 
ON THE RIPENING OF FRUITS, ETC. 
tinous acids, which are the pectosic and pectic acids ; this 
change occurs without the presence of air or the disengage- 
ment of gas, and constitutes the pectic fermentation, which 
may be compared to the lactic fermentation. Pectase 
exists in vegetables in two states, one soluble and the other 
insoluble. 
7. When pectine 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 pectine 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 neu- 
tral 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. 
11. 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 principally by the reaction of acids, alkalies, or of pec- 
tase, pectine 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 con- 
verted into a black pyrogenous acid, which the author calls 
pyropectic acid. 
13. Gelatinous substances exhibit all the generic charac- 
ters of acids, the capacity of saturation and their power 
