218 
BRITISH PHARMACEUTICAL CONFERENCE. 
commence the operation, the upper funnel is filled as high as the top of the Tan¬ 
talus siphon, and thereupon discharges itself into the filter. The filter, then, 
with the weight thrown upon it, turns the scale and cuts off the supply, just 
as in the simpler apparatus. It will he seen that if the stirrup, k, completely 
closed the elastic tube on the emptying of the upper funnel the operation 
would come to a standstill after the first delivery ; and to avoid this a small 
screw, l, is introduced to prevent the weighted end of the board swinging 
back to its full extent, so that when the filter is emptied and opens the tube 
at f, a slow stream commences to pour into the funnel, i, increasing in rapi¬ 
dity as the augmented weight raises the wire at Jc. 
It is scarcely necessary to explain the principle of the Tantalus siphon—a 
contrivance familiar to many as the basis of a philosophical toy. It consists 
of a bent tube like a U, with one arm longer than the other. The longer 
arm is fitted into the tube of a funnel by means of an india-rubber washer. 
Its siphon action is brought into play directly the fluid in the funnel has 
risen above the level of the top of the bend, and it then draws off the con¬ 
tents as far as its shorter arm reaches. The figures will explain the rest. 
The application of the principle to the large filters used for manufacturing 
purposes will naturally suggest itself, and though the model exhibited was 
made for operations on a small scale, there is no reason that modifications 
to suit any variety of circumstances should not be introduced. 
The simpler form of apparatus is in regular use in one or two laboratories 
for filtering solutions. A multitude of cases occur to the pharmaceutist in 
which it is desirable that his filter should never run very low, as in the sepa¬ 
ration of essential oils from distilled waters, and in such as these its employ¬ 
ment would be of great advantage. 
The arrangement was designed by Mr. Wm. Rennoldson, of Newcastle, 
and the model shown was lent by Mr. A. Freire-Marreco, Reader in Chemistry 
in Durham University, by whom it has since been presented to the Museum 
of the Pharmaceutical Society at Bloomsbury Square. 
ON SPECIFIC GRAVITY OF TINCTURES. 
BY W. LAIRD, PH. C., DUNDEE. 
In the British, in common with other pharmacopoeias, after the formula for 
the preparation of a good many of the acids, liquors, and solutions, we have 
a note of the “ characters and tests ” of the various products. On looking 
over the P. B. it occurred to me that it was a pity that the compilers had 
not carried out the same rule in the section for tinctures. In two cases only 
is there any mention made of the characters the product is expected to 
possess,—Tinct. Opii and Tinct. Ferri Perchloridi. It is surely of as much im¬ 
portance for us to know the sp. g. of any of the other tinctures as of Tinct. 
Ferri. Why tell us that sp. g. of Syrupus is P330 and say nothing of that 
of Tinct. Opii; or why tell us that Syr. Rhamni is P32 and say nothing of 
Syr. Rhei, Scillse, or Zingib. ? If useful in the one case, it would be in the 
other. Being strongly impressed with this idea, I would suggest that the 
members of this Conference might aid in completing this portion of the P. B. 
by recording the sp. g., and also any peculiarity of tinctures as prepared by 
them, and forwarding their notes to the meeting. Some may be inclined 
to think this useless trouble, but I have a case in point, showing a knowledge 
of the sp. g. of a tincture to have been useful in at least one instance in the 
detection of unfair trading. 
Some time ago I was told of a person who was selling tincture of ginger 
