380 M. C. Lea on some new Manipulations. 
tube is closed with the finger and the funnel is quickly inverted 
in the vessel containing the mixture to be filtered. The other 
end of the tube hangs down into a convenient vessel placed on 
the floor. If it is desirable that water 
shall not be added to the mixture, the 
funnel is inverted empty, and the air is 
drawn out by a pipette inserted into 
the open end of the india rubber tube. 
It is evident that this arrangement is 
a combination of filter and siphon, and 
the pressure of the column of water in 
the longer leg of the siphon expedites 
the operation very much and leaves the 
solid portions much drier than ordinary. 
As the liquid begins to be exhausted, 
the solid portions are to be gathered 
round the funnel with aspatula. When 
the filtrate ceases to run, the funnel is 
left full:—in order that this may not 
return upon the solid matter, the funnel is lifted out of the ves- 
sel and the broad end quickly turned uppermost, when the con- 
tents of the funnel flow down the tube. 
When a precipitate is to be well washed this mode is evidently 
not applicable, although a tolerable washing is perfectly practi- 
cable. But when liquid and solid matters are to be quickly sep- 
arated on a large scale, it is very useful. When masses of small 
crystals strongly retaining the mother water, are to be freed 
from it, this may be done more quickly and more thoroughly 
than by ordinary filtration. Many other cases will readily sug- 
gest themselves. For example, when potash has been boiled 
with lime to render it caustic in large vessels, it is usually drawn 
off with a siphon into bottles and left twelve to twenty-four 
hours to settle, and then must be carefully decanted. It is far 
less trouble to filter it in the above manner in the act of re- 
moving it by asiphon. And so with many of the rough opera- 
tions which occasionally present themselves in the laboratory, 
and which are upon a scale rather exceeding the capacities of 
ordinary filtering funnels. 
Tn the i pha of crystals from the mother water, muslin 
. will general ly give a clear filtrate. In other cases it is necessary 
to place a piece of filtering paper inside the muslin. The paper 
must of course be of size sufficient to be secured by the twine at 
the neck of the funnel. But the force with which the column 0 
water acts upon the muslin over the mouth of the funnel, draws 
it to a concave shape, and sometimes breaks the paper. 1° 
avoid this, the paper may be folded so as to fit the inside of the 
funnel, turning the edges oyer and securing them as before de- 
