T. M. Chatard—Treatment of Gelatinous Precipitates. 247 
Found. Calculated. 
Stannic oxyd, 54°01 53°92 
Tungstic oxyd, 46°23 46°08 
100°24 100°00 
As it might perhaps be objected to the examples given ere 
that I employed only purely mechanical mixtures of stann 
and tungstic acids, and that this is not the case which occurs in 
practice, I made the following additional analyses: Portions of 
the two ona ie precipitated together from the solution by nitric 
acid with the usual precautions. The ignited mixed oxyds 
were then fused with potassic cyanid, as above. In this man- 
0°7292 2 gr. a a sp echine of SnO, and WO, gave 0°4211 gr. SnO, 
ct. 
0-9826. gr. a fhe same gave 0°5661 gr. SnO, = 57°61 pr. ct. 
Tin cannot be separated from molybdenum by fusing the 
mixed oxyds with potassic cyanid, as the molybdic acid is 
always more or less completely reduced to a lower oxyd. 
§ 3. 
On the treatment of gelatinous precipitates; by THomas M. 
CHATARD. 
The inconveniences and loss of time which attend the wash- 
ing of gelatinous precipitates are familiar to chemists. Even 
the methods of washing recently introduced by Bunsen are not 
always poe y nat sinatra in their japoks § ie applied 
this class of substances. The following method 
found, I think, to give results which leave nothing to be de- 
sired: The solution containing the substance to be determined 
muse anal will be sufficient to show the degree of pre- 
cision attainable by this process in the cases of some of the 
more familiar As une eee es oe tassic di- 
chromate were dissolved in y oy small porti water, re- 
esi with chloehyttte sod and alcohol, the a he of alcohol 
led, and ammonia added in ex ian After evaporation, in 
the manner above described, the chromic sesquioxyd presented 
a greenish blue granular powder very easily washed. 
