28 Mr. Teschemacher on the Crystalline Form of some Salts. 



will be observed. From this similarity of form I concluded 

 this new salt to be a sulphate of nickel and potash combined 

 with a small quantity of chromic acid, which is now further 

 confirmed by comparing the analysis of the former salt made 

 by Mr. Cooper, and inserted also in the same paper of Mr. 

 H.J.Brooke, with that of the new salt made by Mr. Stokes. 



Sulphate of Nickel and Potash. 

 Sulphuric acid . . 18*95 

 Oxide of nickel . 8*77 



Potash 10-24 



Water 12-04 



50- 



Chromo-sulphate of Nickel and Potash. 

 Sulphuric acid . . 18*260 

 Oxide of nickel . 8-200 



Potash 9-862 



Water 12-700 



Chromic acid . . 0-978 



50- 



Primitive form of both, an oblique rhombic prism. 

 Chromo-sulphate of Zinc and Potash. Sulphate of Zinc and Potash. 



P on M .... 101° 4-7' P on M . . . 102° 20' 



P on e 154 31 M on M' . . 108 40 



M on M' . . . . 108 45 



This latter salt, the sulphate of zinc and potash, I formed 

 by adding pure potash to a solution of sulphate of zinc, sepa- 

 rating the precipitate, and allowing the clear solution still 

 containing oxide of zinc to crystallize. Not having made the 

 analysis of this latter salt, I am unable to compare it with 

 the analysis of the chromo-sulphate of potash and zinc as 

 given by Mr. Stokes. 



These are further instances in which the combination of 

 minute quantities of matter vary the measure of the angles of 

 crystals, and which show the value of Dr.Wollaston's gonio- 

 meter in immediately detecting their existence. 



I take this opportunity of sending you the measurements of 

 the crystals of two other substances, which I am not aware have 

 been previously given. 



Hematin. 



Primitive form a square prism. 



1\ 



Pon M . 

 MonM' 



Moni. 

 M on c x . 



c 2 . 



c 3 . 



90° 



90 

 135 



122 10' 

 118 15 

 116 15 



M 



¥ 



This substance was found in the interior of a piece of log- 

 wood ready formed in a crystalline mass; I merely dissolved 



the 



