268 ON THE HYDRARG YRO-BINIODIDES OF POTASSIUM, ETC. 
53.65 parts HgP C , . , , ) 1 atom HeP 454.6 
41.85 « KI ) which correspond^ u R » 
4.50 « HO pery nearly with C A a HQ ^ 
100.00 821.5 
It is, then, the di-hydrargyro-biniodide of potassium crystal- 
lizing with four atoms of water. 
In order to ascertain whether, by the use of alcohol, crystals 
of the double iodide could be obtained containing a larger pro- 
portion of Hgl 2 , to a saturated solution of KI in this liquid, 
as much HgP was added as could be dissolved. On evaporating, 
a considerable portion of HgP was gradually deposited, from 
which the liquor was poured off when itwas sufficiently concen- 
trated. The crystals thus obtained, were orange yellow, becom- 
ing orange red on drying, and evidently contaminated with free 
HgP. The proportional result of their analysis was 7 parts, 
HgP, to 5 parts KI, so that it nearly corresponds to the pre- 
ceding compound. 
A salt, however, may be formed, containing nearly one atom, 
HgP, to one atom, KI, by boiling down the hot saturated solu- 
tion as before stated, but if the temperature is allowed to di- 
minish during the evaporation, a portion of HgP is precipi- 
tated. 
The di-hydrargyro-biniodide of potassium is decomposed 
when dropped into water, a portion of HgP being precipitated 
which may be re-dissolved by agitation, or a gentle heat; 
and the solution thus formed is not again precipitated by dilu- 
tion. 
If the water is gradually added, so as to make at first a sa- 
turated solution, the double salt is dissolved without decom- 
position. 
100 parts of the crystals of HgP-f2KI, when dropped into 
water precipitated 13. parts HgP. The solution remaining was 
evaporated to crystallize. Crystals were thus obtained, which by 
synthesis (with which their analysis corresponded) are com- 
posed of HgP-f- 2h KI. These crystals were soluble in water, gra- 
dually added, but when dropped into water were decomposed, 
