342 Mr. R. H. Brett on the Bromo-cyanide and 



the capsule : the whole was then slowly evaporated over a 

 sand-bath to dryness; the residue was then exposed to a dull 

 red heat for some time and weighed as bromide of potassium. 



The following were the results of two experiments. 



Exp. 1. Mercury 7*5 = bicyanide of mercury 9*43 



bromide of potassium 4*50. 



13-93. 

 Exp. 2. Mercury 7*5 = bicyanide of mercury 9*43 

 bromide of potassium 4*70 



14-13. 

 Calculated proportions, assuming the double salt to be com- 

 pounded of an atom of each of its constituents. 

 Bicyanide of mercury ... 10*241 

 Bromide of potassium... 4*758 



14-999. 

 Now as the quantity of mercury contained in the calculated 

 proportion of bicyanide is about 8*144, the difference between 

 it and the quantity obtained by actual experiment is only 

 0*644, for 8*144 — 7*5 = 0*644. In the 2nd experiment the 

 quantity of bromide of potassium obtained very closely ap- 

 proaches to the calculated proportion — as 4*70 to 4*758. It 

 may, I think, therefore be fairly deduced that the double salt 

 is composed of an atom of each of its constituents, and may be 

 represented thus : KBr-f Hg 2 Cy, or 

 Bicyanide of mercury 1 atom = 254 

 Bromide of potassium 1 atom = 118 



372 atomic weight of 



In 100 parts 68*279 the salt. 



31*721 



100*000. 



The Chloro-cyanide of Potassium and Mercury differs 

 scarcely at all in appearance from xhe salt last described, and 

 may be obtained precisely in the same way, substituting the 

 chloride for the bromide of potassium. It is however more 

 soluble in water than the bromo-cyanide, one part of the 

 salt requiring only 6*75 parts of water at 65° for solution. 

 The mineral acids and the alkalies do not decompose it. It 

 is however readily decomposed by sulphuretted hydrogen and 

 the hydro-sulphurets. 



In order to ascertain its atomic constitution it was analysed 

 in the same manner as the last salt. 



