140 
Proceedings of the Royal Society 
is done, and by turning the knee-piece downwards the pump will 
suck back the water again almost to the last drop. 
It is sometimes necessary in quantitative analysis to filter a small 
quantity of liquid directly into a small weighed platinum basin or 
crucible. For instance, in filtering the alkaline chlorides from the 
last traces of magnesia in a silicate analysis, or, to take another 
example, in the purification of minute quantities of alkaloids. 
This may be readily done by the arrangement shown in fig. 3. 
The small funnel I, instead of fitting into the large stopper at a, 
fig. 1, is fixed by means of a small cork into the wide end of the 
stout glass tube m (fig. 3). 
In order to avoid loss by spirting, the tube does not dip directly 
into the basin, but into the glass tube n. This tube may be made 
out of a broken pipette, and is supported by a loosely-fitting cork 
in the small bell-jar o, which may be most conveniently made by 
cutting olf the lower half of an ordinary wide-mouthed bottle. 
When the filtration is over the small funnel I and cork should be 
removed, and the wide part of the tube m washed with a very 
little water, which serves at the same time to wash down the inside 
of the tube n. By this means the amount of wash water is reduced 
to a minimum. In the estimation of alkaloids the solvent is often 
chloroform or ether, which dissolve india-rubber, so that in such 
cases a small ordinary cork should be substituted for the rubber cork 
in m. It may be further pointed out that with this apparatus it is 
an easy matter to filter liquids containing hydrofluoric acid, which 
attack glass, by using a platinum funnel and filtering directly into 
a platinum basin or other platinum vessel. 
A Convenient Method for Preserving Sidphuretted Hydrogen 
Water. 
A large bottle A (fig. 4) is fitted with a double-bored cork. In 
the one hole is the syphon tube a leading from the bottom of the 
bottle to any convenient point lower than the other end of the tube, 
and closed at this lower end by a short piece of rubber tubing and an 
ordinary nipper tap. Through the other hole passes the shore glass 
tube &, bent at right angles, and attached by means of rubber tubing 
to a piece of lead piping c fitted with a tap, below which tap c is 
soldered on to a pipe connected with the ordinary coal-gas supply. 
