ON THE HYDRARGYRO-BINIODIDES OP POTASSIUM, ETC. 269 
a portion of Ugh being precipitated as before. The liquor 
resulting was filtered, and when evaporated to dryness the 
product was not decomposed by water, but when slowly eva- 
porated, crystals of double iodide were obtained, associated 
with cubic crystals of free KI. 
Solutions were then made containing 1 equiv. HgP, to 2§, 
3, and 4 equiv. KI. These solutions were concentrated by 
slow evaporation, and in each case the crystals were associat- 
ed with cubic crystals of free KI; from these the crystals of 
the double iodide were separated, in each case were partially 
decomposed when dropped into water, and on analysis were 
found to consist of 1 atom HgP, with a little more than 2 
atoms KI, and about 4 atoms HO. 
A double salt was then examined, which had been prepared 
in considerable quantity, and crystallized by spontaneous eva- 
poration, from a large quantity of mother liquor. It was found 
to be readily soluble in any proportion of water, without de- 
composition. This being analysed gave 
50.65 parts HgP C nearly ^ latom HgP 
40.65 " KI < corresponding > 2-f" KI 
8.70 " HO ( with ) 8 " HO 
100.00 
The result of these experiments lead us to conclude that 
the double salt, containing the largest proportion of KI which 
can be combined, consists of HgP + 2KI, that it crystallizes 
with from 4 to 8 atoms of water of crystallization, that when 
crystallized with 4 atoms, it dissolves in water, which is gra- 
dually added, but is partially decomposed when this is sud- 
denly poured upon it, and that when it contains the larger 
proportion of water of crystallization, it is dissolved without 
decomposition in any proportion of water. 
To recapitulate the above results, I have been able to ob- 
tain two compounds only of biniodide of mercury, and iodide 
of potassium. 
1st. The hydrargyro-biniodide of potassium, HgP+KI. 
2d. The di-hydrargyro-biniodide of potassium, HgP + 2KI. 
