[ 201 ] 



XXXV. Some additional Observations on the Red Oxalate 

 of Chromium and Potash. By Robert Warington, Esq., 

 Secretary to the Chemical Society*. 



tTAVING in the year 1832 obtained this salt by the same 

 -■■•*■ method as that described by Mr. Croft, namely, in the 

 endeavour to prepare the dark blue oxalate of chromium and 

 potash by the process originally given by its discoverer Dr. 

 Wilton Turner, and having in my possession some crystals of 

 a much larger size than those usually obtained, I was induced 

 to avail myself of the kind offer of Professor Miller of Cam- 

 bridge, " to determine the form of any crystalline products 

 that the members of the Society might obtain in their re- 

 searches," and have great pleasure in laying before the So- 

 ciety the following letter and measurements : — 



" St. John's College, Cambridge, April 25,1842. 



" Dear Sir. — The crystals of the oxalate of chromium and potash 

 are represented in the accompanying figure. The numbers expressing 

 the angles between normals to the faces must be considered as rough 

 approximations only, for although I measured all the measurable 

 crystals you sent me, the variations of the angles between corre- 

 sponding faces showed that the crystals were by no means so perfect 

 as could be wished. 



" The angles given are however abundantly accurate for the pur- 

 pose of identifying the substance. One of the crystals was a twin, 

 the face (a) being the twin face or the face with respect to which 

 the two individuals were symmetrically situated. 



" Oxalate of Chromium and Potash. System Oblique prismatic. 



'*■ Angles between normals to the faces of 

 the crystal. 



" The faces ap rf q are all in one zone ; h p b are in one zone ; 

 k q b are in one zone ; a he k are in one zone. The other zones are 

 sufficiently well indicated by the parallelisms of the edges. 



" The symbols of the faces are, — a (100), b (010), c (001), h (101) 

 p (111), q (111),/(011), m (110), k (101), r (112). 



" I remain yours faithfully, 



" W. H. Miller." 



* Communicated by the Chemical Society, havinsr been read Mav 17 

 1842. J ' 



