1823.] On the Crystalliiie Forms of Artificial Salts » 1:1<7 



Article VI. 



On the Crystalline Forms of Artificial Salts. 

 By H.J. Brooke, Esq. FRS. 



{Continued from p. 43.) 



The crystallographical characters of natural and artificial pro- 

 ductions appear to have received less general attention than the 

 other branches of science connected with mineralogy. I have 

 already alluded to the inadequate descriptions of crystalline 

 forms contained in Dr. Henry's excellent work on Chemistry ; 

 and I may refer to another recent and valuable pubhcation 

 which happens to lie before me, Dr. Ure's Dictionary, for abun- 

 dant evidence of the neglect which the crystallographical cha- 

 racter has experienced among chemists of the first rank. 



CrystaUine forms which are incompatible with each other are 

 frequently quoted in these works as belonging to the same sub- 

 stance ; and sometimes those forms are described in terms to 

 which no very definite meaning can be attached; as where Anda* 

 lusite is said, in Dr. lire's work, to crystallize occasionally ia 

 rectangular four-sided prisms verging on rhomboids. 



The crystalline form of morphia is given in Dr. Henry's work, 

 on the authority of three different chemists, as a rectangular 

 prism with a rhomhoidal base ; as a regular parallelopiped with 

 oblique faces ; and as a four-sided rectangular prism ; and Dr. 

 Ure quotes the form given by Choulant, as a double four-sided 

 pi/ramid with square or rectangular bases. The first of these 

 forms is impossible, unless we suppose the base oblique to the 

 axis of the prism, and then it is incompatible with the third and 

 fourth. The second is not very inteUigibly described. The last 

 two are not incompatible with that which is given below. 



If we inquire into the causes which have occasioned this neg- 

 lect of a science, not really difl^icult in itself, we shall perhaps 

 find that it is owing chiefly to the very profound manner in 

 which it has been treated by the late Abbe Haiiy, in whose 

 hands the subject first assumed a strictly scientific form. His 

 complicated analytical operations were probably repulsive to 

 most readers, and so much so^ that even in France there are 

 scarcely, as I have been very recently informed by one of his 

 friends, a dozen persons who have followed him in his re- 

 searches. 



Another cause of the little acquaintance which appears gene- 

 rally to exist with even the forms of crystals, may, perhaps, be 

 traced to the nomenclature which the late Abbe estabhshed to 

 designate them ; by this they were presented to the reader as 



