ME. GEORGE GOEE ON FLUORIDE OE SILVER. 
229 
55-44 grains of the brown fluoride was put into a platinum boat and heated to fusion in 
the retort-tube ; it lost -91 grain = T641 per cent. The boat and contents was then 
put into a tube of platinum 114 millims. long, in the middle part of another platinum 
tube 508 millims. long, and heated to low redness during 55 minutes in a slow current 
of gaseous ammonia previously dried by caustic lime. A very bulky white and deli- 
quescent sublimate of fluoride of ammonium, having the appearance of down, was pro- 
duced, and the silver salt crept over the edge of the boat at the exit end. The heat 
was continued some time after the sublimation ceased, and the boat was cooled in the 
current of mis. The whole of the salt was reduced to metal, and the amount of silver 
o 
found was 46‘09 grains. A small amount, -305 grain, had been carried forward into 
the long tube during the process, thus making a total of 46-395 grains, theory requiring 
46-610 grains, viz. 1-599 grains* of free silver, and 45-011 grains of combined silver, in 
the salt after fusion. After thoroughly digesting the boat in warm dilute nitric acid 
and washing, it was jet-black (whilst wet) in those parts which had been in contact with 
the fused salt, and when dry those parts were grey and rough with finely divided plati- 
num (see page 234); the boat had also increased 1-14 grain in weight, probably by 
absorption of metallic silver : igniting the boat did not alter this weight. The short 
tube enclosing the boat had, after similar cleaning, lost -05 grain in weight. The reaction 
which occurred in this case was probably in accordance with the following equation : — 
4H 3 N + 3AgF = 3(H 4 NF) + 3Ag + N ; 
the twelve atoms of hydrogen lose one atom of trivalent nitrogen and gain three atoms 
of monovalent fluorine by substitution. 
To ascertain the amount of free silver in a specimen of the brown fluoride, 43'04 
grains of the salt was dissolved in cold water, and the solution filtered in the dark ; a 
little grey powder of silver separated. The residue was well washed, ignited, and 
weighed; -575 grain of silver was found after deducting the weight of filter ash. 
The foregoing results show that 100 grains by weight of the brown fluoride contained 
1-336 grain of silver, -795 grain of aqueous hydrofluoric acid, and 97"S69 grains of pure 
fluoride. By fusing this quantity (7. e. 100 grains) of the brown salt in a nearly closed 
platinum vessel it loses 1-070 grain f, consisting of water and hydrofluoric acid. The 
fused residue contained 2-903 grains of free silver, of which 1-336 grain was in the salt 
when first taken, and 1-567 grain was set free during the fusion; it also contained 
96-027 grains of pure fluoride of silver. 
AgF . . . . 
Dried salt. 
97-869 
AgF ... . 
Fused salt. 
96-027 or 
Silver . . 
. 82-544 
Free silver about 
1-336 
Free silver about 
2-903 „ 
Fluorine . . 
. . 14-522 
Aqueous H F . 
•795 
100-000 
Loss by fusion . 
98-930 
. 1-070 
100-000 
Free silver about 2-934 
100-000 
* This number is necessarily variable owing to the salt suffering different amounts of decomposition in the 
process of drying. 
t This number is also variable. 
MDCCCLXX. 
q 
n 
