CONVERSAZIONE. 
551 
DONATIONS. £ d. 
A Friend, per Mr. Stephen Darby . 1 1 0 
Heanley, Marshall, Peterborough .. 2 2 0 
__ t 
Callaway, Lemuel . 2 2 0 
Horton, H. W. 0 10 6 
CONVERSAZIONE. 
May I9t/i, 1868. 
The invitations issued by the President and Council were responded to on 
the present occasion no less numerously than in former } r ears. The entire 
building was, as usual, thrown open for the reception of the visitors, amongst 
whom might be enumerated some of the most distinguished among the leaders 
in chemical, medical, and pharmaceutical circles. The exhibition of objects 
of beauty and interest provided for the entertainment of the members and 
their friends was such as to afford the greatest satisfaction to all who had the 
good fortune to be present, whilst it renders hopeless any attempt adequately 
to convey an idea of the brilliant and animated appearance of the various 
apartments. Amongst the most noteworthy of the numerous attractions were 
the experiments exhibited by the Master of the Mint. The researches pub¬ 
lished by this eminent philosopher during the last twenty years have been, 
and are, the admiration and wonder of the entire world ; the subjects of dif¬ 
fusion and dialysis he has absolutely created, whilst his more recent investi¬ 
gations into the absorption of gases by metals are perhaps the most wonder¬ 
ful and important of all. At the meeting on Tuesday night was exhibited 
the extraction of hydrogen from metallic palladium, which has the remarkable 
power of “ occiuding ” in its pores upwards of 400 times its volume of the gas ; 
this it again yields when heated in vacuo. All metals, it is found,exercise similar 
powers, but in lower degree. They also appear to possess a sort of power 
of selection, by w r hich they absorb certain gases more readily than others. 
Side by side with this was exhibited the dialysis of oxygen from atmosphe¬ 
ric air. By means of a Sprengel mercury pump, the air is completely re¬ 
moved from a thin caoutchouc bag; on continuing to exhaust, a gas passes 
through which contains about 41 per cent, of oxygen, and is capable of reig- 
nitiog a half-extinguished match. The cause of the accumulation of oxygen 
in this manner is different from ordinary gaseous diffusion ; it is a dialytic 
separation which occurs. In familiar language, the gas is believed to be lique¬ 
fied upon the exterior surface of the caoutchouc, to penetrate in this condition 
and reassume the gaseous state from the internal surface. The ingenious 
mercury-pump, by the aid of which the experiments are conducted, and without 
which, in fact, they could hardly be put into operation, is the device of Dr. 
Sprengel, and will be found described on page 377 of the present volume. 
The Couucil wrnre indebted to Sir C. Wheatstone for an alphabet telegraph 
and other electrical apparatus, and to Mr. C. W. Siemens, F.R.S., for a new 
electrical resistance meter. Mr. Siemens also contributed diagrams illustra¬ 
ting the construction of the gas-furnace by which steel may be produced 
direct from the ore. Messrs. J. J. Griffin and Sons exhibited Dr, Bussell’s 
new r apparatus for gas analysis. This apparatus is a modification of an instru¬ 
ment introduced some years age, in which the eudiometer, being surrounded 
by water, more rapidly acquires a uniform temperature, whilst in the present 
form reagents in the liquid state can be applied to the gas in the eudio¬ 
meter-tube itself. The time occupied in an analysis is thus much curtailed. 
Messrs. Hopkin and Williams maintained their renown as manufacturers of 
pure chemicals by an exhibition of specimens of thallium compounds and. 
