Sept. 15, 1870] 
to Hoffmann, ‘‘of metallic hydrogen, a white magnetic metal?” 
and yet now, through his labours, the fact of the condensation 
of hydrogen in the solid state by metallic palladium, and toa 
less extent by other metals, has become familiar to all of us. 
Then, again, I would remind you of Graham’s recent discovery 
of the occlusion of hydrogen gas in certain specimens of meteoric 
iron, whilst earth-manufactured iron contains, not hydrogen, but 
absorbed carbonic oxide gas, proving that the meteorite had 
probably been thrown out from an atmosphere of incandescent 
hydrogen, existing under very considerable pressure, and there- 
fore confirming in a remarkable degree the conclusions to which 
‘spectrum analysis had previously led us. The position in the 
ranks of British science left by Graham’s death will not be easily 
filled up. He accomplished to a certain extent for dynamical 
chemistry what Dalton did for statical chemistry ; and it is 
upon his experimental researches in molecular chemistry that 
Graham’s permanent fame as one of England’s greatest chemists, 
will rest. 
As closely connected with the above subjects I have next to 
mention a most important research by Dr. Andrews, of Belfast, 
which, marking an era in the history of gases, shows us how our 
oldest and most cherished notions must give way before the 
touchstone of experiment. No opinion would appear to have 
‘been more firmly established than that of the existence of three 
separate states or conditions of matter, viz. the solid, the liquid, 
-and the gaseous. A body capable of existing in two or more 
of these states was thought to pass suddenly from one to the 
other by absorption or emission of heat, or by alterations of the 
superincumbent pressure. Dr. Andrews has shown us how 
false are our views on this fundamental property of matter, for 
he has proved that a large number of, and probably all, easily 
condensible gases or vapours possess a critical point of tem- 
perature at and above which no increase of pressure can be 
made to effect a change into what we call the liquid state, the 
body remaining as a homogeneous fluid. Whilst below this 
critical temperature certain increase of pressure always effects a 
seperation into two layers of liquid and gaseous matter. Thus 
with carbonic acid the point of critical temperature is 30°'92 C., 
and with each given substance this point is a specific one, each 
vapour exhibiting rapid changes of volume and flickering move- 
ments when the temperature or pressure was changed, but 
showing no separation into two layers. Under these circum- 
stances it is impossible to say that the body exists either in the 
state of a gas or of a liquid; it appears to be ina condition 
intermediate between the two. Thus carbonic acid under the 
pressure of 108 atmospheres, and at 35° §’C., is reduced to 
= of the volume which it occupies at one atmosphere: it has 
-undergone a regular and unbroken contraction, and it is a 
uniform fluid. If we now reduce the temperature below 31° C., 
the liquid condition is assumed without any sudden change of 
volume or any abrupt evolution of heat. We can scarcely too 
highly estimate the value of the researches of Andrews. 
As examples of the power which modern methods of research 
‘give of grappling with questions which only a few years ago 
were thought to be insoluble, I may quote the beautiful observa- 
tions, now well known, by which Lockyer determined the rate 
of motion on the sun’s surface, together with those of Frankland 
and Lockyer respecting the probable pressure acting in the 
different layers of the solar atmosphere ; and, lastly, the results 
obtained by Zollner respecting solar physics, and especially the 
‘probable absolute temperature of the sun’s atmosphere, as well 
-as that of the internal molten mass. These last results are so 
‘interesting and remarkable, as being arrived at by the com- 
bination of recent spectroscopic observation with high mathe- 
matical analysis, that I may perhaps be permitted shortly to state 
them. Starting from the fact of the eruptive nature of a certain 
‘class of solar protuberances, Zollner thinks that the extraordinary 
rapidity with which these red flames shoot forth proves that the 
-hydrogen of which they are mainly composed must have burst 
out from under great pressure ; and, if so, the hydrogen must 
have been confined by a zone or layer of liquid from which it 
breaks loose. Assuming the existence of such a layer of in- 
_candescent liquid, then applying to the problem the principles 
and méthods of the mechanical theory of gases, and placing in 
‘his formulae the data of pressure and rate of motion as observed 
by Lockyer onthe sun’s surface, Zollner arrives at the conclusion 
that the difference of pressure needed to produce an explosion 
capable of projecting a prominence to the height of 3°0 minutes 
above the sun’s surface (a height not unfrequently noticed) 
‘is 4,070,000 atmospheres. This enormous pressure is at- 
stained. at a depth of 139 geographical miles under the sun’s 
eo, * 
NATURE 
407 
surface, or at that of the s}; part of the sun’s semi-diameter. In 
order to produce this gigantic pressure, the difference in tem- 
perature between the enclosed hydrogen and that existing in the 
solar atmosphere amounts to 74,710°C.! In a similar way 
Zollner calculates the approximative absolute temperature of the 
sun’s atmosphere, which he finds to be 27,700° C.; a temperature 
about eight times as high as that given by Bunsen for the oxyhy- 
drogen flame, and one at which iron must exist in a permanently 
gaseous form. c 
Passing on to more purely chemical subjects, we find this 
year signalized by the redetermination of a most important 
series of chemical constants, viz. that of the heat of chemical 
combination by Julius Thomsen, of Copenhagen. This con- 
scientious experimentalist asserts that the measurements of the 
heat evolved by neutralizing acids and bases hitherto considered 
most correct, viz. those made with a mercury calorimeter by 
Favre and Silbermann, differ from the truth by 12 per cent. ; 
whilst the determination by these experimenters of the heat of 
solution of salts is frequently 50 per cent. wrong. As the result 
of his numerous experiments, Thomsen concludes that when a 
molecule of acid is neutralized by caustic alkali the heat evolved 
increases nearly proportionally to the quantity of alkali added 
until this reaches 1, 4, 4, ¢ of a molecule of alkali, according as 
the acid is mono-, di-, tri-; or tetra-basic. Exceptions to the law 
are exhibited by silicic, and also partly by boracic, orthophos- 
phoric, and arsenic acids. In the two latter, the heat of com- 
bination is proportional for the two first atoms of replaceable 
hydrogen, but much less for the third atom. A second unex- 
pected conclusion which Thomsen draws from his calorific 
determinations is, that sulphuretted hydrogen is a monobasic 
acid, and that its rational formula is therefore HSH. : 
Another important addition made to chemistry since our last 
meeting is a new, very powerful, and very simple form of 
galvanic battery discovered, though not yet described, by Bunsen. 
In this second Bunsen’s battery only one liquid, a- mixture of 
sulphuric and chromic acids, and therefore no porous cells, are 
employed. The plates of zinc and carbon can all be lowered at 
once into the liquid and raised again at will. The electromotive 
force of this battery is to that of Grove (the most powerful of 
known forms) as 25 to 18; it evolves no fumes in working, and 
can be used for a very considerable length of time without 
serious diminution of the strength of the current, so that Bunsen 
writes me that no one who has once used the new battery will 
ever think of again employing the old forms. I had hoped to 
be able to exhibit to the Section this important improvement in 
our means of producing a strong current ; but war has demanded 
the use of other batteries, and Bunsen has been unable to send 
me a set of his new cells. ; 
Amongst the marked points of interest and progress in in- 
organic chemistry during the past year, we have’ to notice the 
preparation of a missing link amongst the oxy-sulphur acids by 
Schiitzenberger. It is the lowest known, and may be called 
Hydro-Sulphurous Acid, H,SO,. The sodium salt, Na H-SO,, 
is obtained by the action of zinc on the bisulphite. As might be 
expected, it possesses very powerful reducing properties, -ancl 
bleaches indigo rapidly. The metallic vanadates have also been 
carefully examined, and the existence of three distinct series of 
salts proved, corresponding to the phosphates, viz. the ortho 
or tribasic vanadates, the pyro or tetra-basic vanadates, and the 
meta or monobasic vanadates. Of these, the ortho-salts are 
most stable at a high temperature, whilst at the ordinary atmo- 
spheric temperature the meta-salts are most stable. Inthe phos- 
phorus series, as is well known, the order of stability is the 
reverse ; and thus the points of analogy and of difference between 
phosphorus and vanadium become gradually apparent. 
As an illustration of the results of modern organic research 
for in viewing the year’s progress in this ever-widening branch of 
chemistry it is impossible to do more than give a few illustra- 
tions—I may quote Baeyer’s remarkable investigations on 
Mellitic Acid. Originally discovered by Klaproth in honey- 
stone or mellite (a substance which yet remains the only source 
of the acid), mellitic was supposed to be a four-carbon acid. 
Baeyer has quite recently shown that the acid contains 12 atoms 
of carbon, or has a molecular weight three times as great as was 
originally supposed. He has shown that mellitic acid is benzo}- 
hexacarbonic acid, C,, Hg O,., or benzol in which the 6 atoms 
of hydrogen are replaced by the monad radical carboxl (C O OH} - 
as benzoic is Benzol Monocarbonic acid, or benzol in which ong 
of hydrogen is replaced by carboxyl. The most interesting por- 
tion of Baeyer’s research, however, lies in the intermediate acids, 
partly new and partly acids already prepared, which he has 
