some Silicates of Alumina, 365 



silicates of alumina into one class. But, it may be asked, 

 are none of these compounds as much true species as other 

 minerals with which we are acquainted, or, if they are 

 different states of decomposing felspar, are they not in this 

 respect analogous with many species, which have been pre- 

 sumed with considerable probability, to be the products of 

 decomposing rocks ? 



Article IX. 

 On JResins, By Henry Rose.* 



The remarkable phenomena of isomerism are observed in 

 much greater abundance in organic than in inorganic 

 bodies. The laws, however, which regulate isomeric 

 modifications among inorganic substances, can, from the 

 small number of atoms of which they are composed, be 

 more easily determined, than is possible with respect to 

 organic substances, which contain a greater number of 

 atoms; though these are probably more constant than 

 analysis has hitherto determined them to be. It is also 

 possible that this great number of elementary atoms may 

 occasion many discoveries on the laws of isomerism. At 

 all events it appears to me that the investigation of isomeric 

 organic substances, and their relations to other bodies, 

 belong principally to organic chemistry. 



In this point of view the experiments of Blanchet and 

 Sell,t on volatile oils, are incontestibly very valuable. 

 They found that a great number of those volatile oils, 

 which contain no oxygen, have the same composition, and 

 the experiments of other chemists, made at the same or a 

 later period, have increased the number. According to 

 Blanchet and Sell the following volatile oils are isomeric : 1st 

 and 2nd, the two oils which compose oil of turpentine, and 

 which they have named Dadylsmd Pencyl: 3rd and 4th, the 

 two oils called by them Citronyl and Citryl, which form 

 oil of lemons. To these may be added oils of turpentine 

 and lemons themselves, unless, as is very probable, we 

 consider them as mixtures. From the experiments of 

 Blanchet, it appears that we must add to the above the 



* Translated from PoggendorfF's Annalen, xxxiii. 33, 

 t Pogg. Ann., xxixi 133. 



