274 ON THE HYDRARGYRO-BINIODIDES OP TOTASSIUM, ETC. 
exhibited by the ammoniacal biniodide of mercury, the fol- 
lowing experiments were tried, the great difficulty of procur- 
ing it clear of water, and free ammonia rendering it impossible 
to arrive at an exact analysis. 
1st. 10 parts HgP were digested with heat in aqua ammo- 
nia until it was dissolved, the liquor cooled, and the double 
salt, which crystallized from it, separated. These crystals 
upon drying, (by which they were decomposed,) gave 8.40 
parts, HgP. The liquor was then boiled until all the free 
ammonia was driven off, and fused nitrate of silver added until 
it ceased to produce a precipitate. This required 1.11 parts 
AgN, which, by calculation, indicates (170.15 : 1.11 :: 126.3: 
.824) .824 parts I, and as 1.60 parts HgP, which contain .90 
parts I, remained in solution, we may conclude there was no 
hydriodate of ammonia formed. 
2d. Into a tube, closed at one end and bent, was put a por- 
tion of the compound, still moist, and heat applied; the gases 
liberated were collected over mercury ; these, on examination, 
appeared to consist wholly of ammonia and aqueous vapor. 
The scarlet powder remaining was soluble in alcohol, and so- 
lution of iodide of potassium, and sublimed by heat in yellow 
crystals, which became scarlet red on cooling — being evidently 
biniodide of mercury. 
From this we may conclude that it is not an analogous com- 
pound to white precipitate. It appears to consist, as before 
stated, of 1 atom HgP, with 2 atoms NH 3 , probably directly 
united; if this be the case, its formula will be HgP + 2NH 3 . 
Not finding any notice respecting this compound in any of 
the chemical works to which I had access, I had at first sup- 
posed that it had not been hitherto observed, but have since 
seen, in the Annal. de Chimie et de Phys., a paper by Rose* — 
" on the combinations of ammonia with the anhydrous 
salts" — in the course of which, he states, that — " the red 
* Annales de Chimie et de Ph., tome lxii. Des Combinaisons de l'Am- 
moniaque avec les sels anhydres. Par Henry Rose. 
