Chemical Science. 397 



lignin contains most carbon, it is natural to suppose it is from 

 it the oxygen takes the carbon to form carbonic acid, that 

 change so indispensable to ripening*. 



Finally, the alteration the lignin suflers in the ripening, 

 continues during the decay of the fruit. It becomes brown, 

 and its decomposition occasions the formation of much carbonic 

 acid. Sugar is also decomposed at this time, and it is to its 

 disappearance, that the peculiar taste of decayed fruits is to be 

 attributed. The sugar in its decomposition also gives rise, no 

 doubt to the formation of carbonic acid. 



18. Crystallization of Sugar. — M. H. Braconnot has pointed 

 out the strong powers of crystallization in the sugar of barley, 

 and has shewn a remarkable instance in which that highly- 

 important arrangement of matter can take place without 

 liquidity. This sugar, when newly prepared, is perfectly trans- 

 parent, and of a very brittle and vitreous fracture, cfFering at 

 this time no traces of crystallization ; but when left to itself 

 for some days, its surface becomes dull and crystalline, and the 

 effect continues to increase until the whole of the sugar has 

 crystallized. It has then lost some of its transparency, and is 

 seen to consist of many rounded groups of needle-like crystals, 

 which are most generally separated from each other by empty 

 spaces. The sugar, thus crystallized, is much more brittle 

 than before ; its fracture presents a number of acicular diverg- 

 ing crystals, united in bundles terminated by the interstices, 

 especially when this arrangement has been produced at tem- 

 peratures below the common temperature. When held in the 

 mouth, it does not take on a bright smooth surface, but be- 

 comes rough, and by care small crystals may be separated, 

 which by the microscope appear to be flat tetrahedral crystals. 

 It was at first supposed that this substance had attracted 

 water from the atmosphere, and in that way been enabled to 

 have such motion produced among its particles as to allow of 

 crystallization ; but when placed in a close vessel with chloride 

 of lime, when it lost -jjjj of its weight, still it crystallized as in 

 the open air. It also crystallized when immersed in oil of 

 turpentine. 



Confectioners know, and have long feared, the effects of this 

 crystallization ; they considered it as a degradation of the 

 sugar in its nature, and search continually for means to jire- 



• M. Borard in a note says, it is flifTu-uif to suppose tliat in those fiuiis 

 tliat ripen early on tlic tree, all tlie sugar should be sent into the fruit liDni 

 the plant; it is more prohable tliat the fruit acts on the air, aii(M'orni* 

 sugar like the other fruits, but not in suflicicnt (juantity, and tliat tin le- 

 forc, it is necessary recourse slioiild be had to the tree, to loniplele its 

 rrpcning^. 



