1904-5.] Crystallisation of Potassium Hydrogen Succinate. 449 
Variations in the Crystallisation of Potassium Hydrogen 
Succinate due to the presence of other metallic 
compounds in the Solution. ( Preliminary Notice.) By 
Alexander T. Cameron, M.A. Communicated by Dr 
Hugh Marshall, F.R.S. 
(MS. received January 9, 1905. Read January 23, 1905.) 
In the summer of 1902, while working as a student in the 
Chemistry Department of Edinburgh University, I prepared a 
quantity of potassium chromoxalate (Gregory’s salt) as an ordinary 
exercise, and this led me to attempt the preparation of a similar 
derivative of succinic acid, since such derivatives apparently had 
not been obtained. 
For this purpose a solution of potassium hydrogen succinate 
(prepared by half - neutralising succinic acid with potassium 
carbonate) was boiled for some time with freshly precipitated 
chromic hydroxide (prepared by adding ammonia to a boiling 
solution of chrome alum, filtering, and washing thoroughly). The 
undissolved hydroxide was filtered off, and the filtrate subjected 
to the same treatment with fresh chromic hydroxide ; the whole 
process was repeated two or three times, the final filtrate being 
dark green in colour. A portion of this solution was evaporated* 
to small bulk by boiling ; on cooling, potassium hydrogen succinate 
first crystallised out, and then a green crystalline powder was 
obtained. The remainder of the solution was concentrated only 
to about half its volume and allowed to stand for three days ; at 
the end of that time dark green crystals were deposited. These 
showed the striking peculiarity of being bounded only by curved 
surfaces, plane faces being entirely absent; from their shape they 
might be described as oblique elliptical double cones, possessing 
monoclinic symmetry (plane of symmetry with digonal axis normal 
to it). A perfect cleavage, yielding highly lustrous faces, was 
observed parallel to the plane of symmetry, and the parallelogram 
PROC. ROY. SOC. EDIN. — VOL. XXV. 29 
