* 
_ around the axis P 
188 M. McDonald on an apparatus for washing precipitates. 
Art. XVII.—Description of an apparatus for collecting and wash- 
tng precipitates in test tubes ; by M. McDonatp, Prof. Chem. 
Va. Military Institute. 
THE apparatus is shown in the figure in side elevation. Ais 
a bracket of hard wood or other suitable material, and serves 
as a support to the test tubes. It is firmly attached to the up- 
right D which carries the inverted syphon tube «, e’, @”. It has 
a shoulder at 1 which abuts against the fixed support ¢ and pre- 
vents oscillation. . 
Upon the bracket a rests the disk £ of porous biscuit ware, 
and upon this, several thicknesses of filtering paper. The test 
tube T is adjusted as shown in the figure, 
and held firmly in place by a clamp (which \ 
is not shown). There is an orifice through 
the center of A and E through which passes 
the shorter branch of the inverted syphon 
tube G, G’, G”. is is drawn to a capil- 
lary bore at @”’, and serves to introduce 
distilled water into the interior of the test 
tube for the purpose of washing the pre- 
cipitate. The apparatus is supported upon 
the stand Bc, and has a motion of rotation 
The disks of filtering paper have a di- 
ameter slightly less than the diameter of 
the disk E; their centers are perforated 
with holes a little less in diameter than the 
syphon tube at the point Fr. ! 
© use the instrument, several thick- 
nesses of filtering paper are slipped over 
@" and pressed evenly down upon E. The we 
eh is then inverted in its frame, the test tube containing 
1€ precipitate adjusted and secured in position by the clamps 
Usually this jet may be projected against the bottom of the 
tube with sufficient force to wash all the precipitate down upo® 
the filter. The test tube should fit very closely upon the sup 
port, or the pressure will force liquid and precipitate through 
together. 
iy sagt themes td any one of odiary ingeiy AT | 
