ee eg ek re ep he Pee as ag Pt 
Raat! See 
J. P. Cooke—Solubility of Chloride of Silver in Water. 221 
as the precipitate settles, pour off the clear hot water, dividing 
the solution between two precipitating jars. To one of these 
add a few drops of a solution of nitrate of silver, and to the 
other a few drops of hydrochloric acid. In both cases a pre- 
cipitate of chloride of silver will fall, and most chemists, cer- 
tainly, will be surprised at the effect; for it is not a mere turbid- 
; _ hess that results, but a well-defined precipitate, whose amount 
is easily estimated. Successive portions of boiling water poured 
upon the precipitate give the same reaction. In one experiment 
the reaction was still perceptible in the fourteenth wash-water. 
But under the action of the boiling water, the precipitate 
becomes crystalline or granular and the action lessens, until at 
_ last the water does not dissolve sufficient chloride of silver to 
cause even a cloudiness on the addition of nitrate of silver, as 
Just described. Mr. G. M. Hyams, a student in this labora- 
tory, washed two different portions of chloride of silver with 
boiling water until the action ceased, and then weighed and 
examined the residue. In the first experiment, 14561 grams 
of chloride of silver were washed with 66 liters of water. e 
chloride of silver was then collected and found to weigh 12320 
grams. Hence, 02241 grams, corresponding to 15°39 per 
cent had passed into solution. In the second experiment, 60 
liters of water were used, and 16-03 per cent of the chloride of 
Silver originally precipitated were dissolved. ‘These numbers, 
Owever, are only approximately accurate, for as the precipitate 
omes granular, it settles with less readiness, and there was 
hecessarily some loss in filtering off so large a volume of liquid. 
In the experiments above described the boiling water pro- 
duced only a very slight decomposition of the chloride of sil- 
ver. The precipitate, granulated by the washing, readily dis- 
solved in aqua ammonia, leaving less than a milligram of a 
black powder, which was proved to be metallic silver. 
_ The solvent power of water on freshly precipitated chloride 
of silver did not appear to be influenced by the presence of 
free nitric acid even in large quantities. We tried the effect 
both of dropping the nitric acid on the eer before pour- 
'ng on hot water, and also of previously adding nitric acid to 
the boiling wash-water. We used amounts of nitric aci 
(0 = 1:355) varying from five to two hundred cubie centime- 
ters to the liter of water, but without finding any marked dif- 
rence in the result 
The presence of a small amount of nitrate of silver in the 
Water entirely prevented its solvent action, so far as we could 
discover. In order to determine the limit of the action, we 
added different quantities of nitrate of silver to the boiling 
Water before pouring it on to the precipitated chloride of sil- 
er. With one centigram of nitrate of silver to the liter of 
