136 
NATURE 
| Fune 16, 1870 
eee 
doubt, has assisted in giving currency to the notion that hydro- 
gen isametal. Except for it, perhaps the crudity, hydrogenium, 
would not have been inflicted upon us. Of course it has occupied 
a conspicuous place in chemical literature ; scoresof papers, and 
at least two books, have been printed about it. The name am- 
monium amalgam expresses the supposed constitution of the 
substance ; the radical ammonium is represented as dissolved in 
or united with mercury, The ammonium is, moreover, conceded 
to be a solid or a liquid, and to have a truly metallic character. 
Thus the latest and best authorities present the case. It is de- 
scribed, in nearly all treatises on chemistry, as if its constitution 
was as certainly ascertained as that of common salt. There have 
been from the beginning, however, those who doubted the pre- 
vailing ideas, and some (see Daniel’s ‘‘ Chemical Philosophy,” 
p- 520, and Dr. Wetherill on Ammonium Amalgam, in Sidi 
man’s Fournal, vol. x., p. 160) boldly objected to them, but 
the reasons they alleged had not sufficient weight. Ammonium 
amalgam has always been a pet with chemists ; it has always 
been ready for the service of one theory or another. The am- 
monium theory, the radical theory, the nitrogen and hydrogenium 
theories, have each in their turn been of too much importance to 
permit any of their props to be withdrawn. : 
The author considers the so-called ammonium amalgam to be 
a mechanical or physical mixture of liquid mercury with the 
gases ammonia and hydrogen, and that its semi-solid consistence 
is due to the mixture having the nature of a froth. | When 
sodium-amalgam is brought into a solution of sal-ammoniac (the 
ordinary method of preparing ammonium amalgam) the chlorine 
combines with the sodium, and the residue (NH, + H) of the sal- 
ammoniac is set free all over the surface of the mercury. The 
particles of the mixed gases adhere tothe mercury, and by reason 
of the movement bringing to the surface fresh mercury, they 
become enfilmed and carried inward, until the mixture becomes 
a homogeneous froth. The principal considerations by which 
this view of the constitution of ammonium amalgam has been 
reached, are as follows :— 
1. The volume of ammonium amalgam is inexplicable in 
any other way ; it is utterly inconsistent with the well-established 
laws of combinations by volume. There is no case of a liquid 
or solid chemical compound, or amalgam, which has any analogy 
to it. 
2. Mercury has a mirror-like surface, while ammonium 
amalgam has comparatively a whiter and more dead surface; it 
approaches in appearance to matt silver. Such changes are 
characteristic of froths. 
3. Ifammonium amalgam be subjected to varying pressure, 
its volume changes apparently in accordance with Mariotte’s law 
of gaseous volume. To illustrate this important fact, a glass tube 
one-third inch in diameter, twenty inches long, and fitted with a 
plunger, was employed. Mercury containing a little sodium was 
poured into the tube to one-third of an inch in depth, and upon 
this was poured a strong solution of chloride of ammonium, occu- 
pying about two inches in length of the tube. The ammonium 
amalgam was completely formed in a few minutes, and occupied 
several inches of the tube. On adjusting and depressing the 
plunger, the volume of the amalgam progressively diminished till 
it closely approached the original volume of the amalgam. Also 
it was notable that the amalgam progressively gained fluidity 
and the mirror surface; till at the greatest pressure it appeared 
like mereury. On withdrawing the pressure the original volume 
and appearance of the compound were resumed, and on reducing 
the pressure below that of the air, the amalgam still expanded, 
until it rose above the surface of the liquid in the tube. If the 
great pressure be maintained, more ammonium amalgam will be 
formed, the mass expanding progressively, apparently in accord- 
ance with the fact that the absorption or adhesion of gases to 
liquids is favoured by pressure. By means of the simple appa- 
ratus used a pressure of ten atmospheres, or a good vacuum, is 
easily and at once attainable, and the experiments with it are very 
striking. : 
The so-called ammonium amalgam is therefore not an amalgam 
at all; ammonium is not proved to bea metal, and if it be admit- 
ted that the monatomic radical really exists in ammonium amal- 
gam, it is neither a solid nora liquid, but a gas. 
The considerations regarding ammonium amalgam are evidently 
equally applicable to Loew’s hydrogenium amalgam ; both are 
only metallic froths. The expansion of palladium observed by 
Graham, on its absorption of hydrogen, is probably analogous to 
the case in question. In both cases the gases concerned are con- 
densed by reason of their attraction to the metal; and if the 
molecules of palladium were made free to move, as those of 
mercury, it is probable that Graham’s hydrogenium alloy would 
become a palladic froth, more remarkable than the corresponding 
mercuric froth. Many have erroneously supposed that hydrogen 
was conspicuous in its capability of being absorbed by metals, 
and thus have more readily been infused with the hydrogeninm 
theory. Oxygen has an eminence over hydrogen in that property, 
and yet no one has a theory of oxygenium. Iron absorbs car- 
bonic oxide, but,no one is bold enough to suggest that carbonic 
oxide is a metal, 
DIARY 
THURSDAY, June 16. 
Royat Society, at 8.30.—Papers to be read by Dr. Hofmann, F.R.S. } 
Dr. H. E. Armstrong, Dr. Alex. Rattray, Prof. Macalister, C. Tomlin- 
son, F.R.S., W. Huggins, F.R.S., Sir Award Sabine, P.R.S., the Earl 
of Rosse, F.R.S., Dr. Stenhouse, F.R.S., G. Busk, F.R.S., the Hon. J. 
W. Strutt, Mr. J. Broughton, Mr. A. Le Sueur, and W. H. L. Russel 1, 
F.R.S. 
Royat Society or ANTIQUARIES, at 8.30.—On Heydon Church, Yorkshire : 
Mr. G. E. Street. 
Linnean Society, at 8.—On two Species of Serapias which oceasionally 
present semi-labelliform lateral sepals: Mr. J. T. Moggridge. 
Cuemicat Soctery, at 8. 
Numismatic Socrery, at 7—Anniversary Meeting. 
SUNDAY, June 19. 
Sunpay Lecture Society, at 8.—On Volcanoes: Mr. D. Forbes. 
MONDAY, Jvne 20. 
Lonpvon InstiTuTion, at 4.—Botany: Prof. Bentley. 
TUESDAY, June 21. 
STatisticaL Socrery, at 8.—On Free Libraries: Mr. W. B. A. Axon. 
ETHNoLoGicaL Society, at 8.30 (at the Royal United Service Institution, 
Whitehall Yard).—On the Aymara Indians of Bolivia and Peru : Mr. D. 
Forbes. 
WEDNESDAY, June 22. 
GEoLoGIcAL Society, at 8. 
THURSDAY, June 23. 
ZooLocicat Society, at 8.30.—On the Walrus: Dr. J. Muriz.—Catalogue 
of the Mammals of South China and Formosa: Mr. R. Swinnoz.—On 
a Collection of Birds from the Island of Trinidad :; Dr. O. Finscu. 
BOOKS RECEIVED 
ENGiisuH.—On Diamagnetism and Magne-Crystallic Action : Prof. Tyndall 
(Longmans and Co.).—Notes on Light : Prof. Tyndall (Longmans and Co.). 
—Grave-mounds and their Contents: L. Jewitt (Groombridge and Sons).— 
Gymnastics for Ladies: Madame Brenner.—First Principles of Chemical 
Philosophy : J. P. Cooke, jun. (Macmillans). 
Foreicn.—(Through Williams and Norgate).—Annales de Chimie et de 
Physique: Chevreul et Dumas, Tome xx.—Zeitschrift fiir Ethnologie, 1870, 
Hett [1.—Ueber die Entstehung der Welt: C. S. Cornelius.—Lehrbuch der 
Chemie: A. Genther.—Histoire des Poissons: Aug Duméril. Tome 1i, et 
Atlas.—Charles Darwin et ses précurseurs francais: A. de Quatrefages, ’ 
CONTENTS 
Tue ScienTiFic EpvCaTion of WoMEN. . . . . . 1 ss a 6 
Natura History Cottections. By P. L. SceaTer,F.R.S.. . . 
Fosst. MAmMaALs 1N Nortu America. By W. Boyp Dawkins, 
NAuMANN ON THERMO-Cuemistry. By Dr. E. J. Mts .. . . 
Our Boox SHELF. 0°35. SGA eres Ss OF ee 
LETTERS TO THE EpDITOR:— 
The Apparent Size of the Moon.—W. T. Raprorp. . . . 4 4 
Occurrence of the Little Egret —W. S. M. D'UrBAN . . . 4. 
Pinkish Colour of the Sun.—A.S. HerscHEL. . . . 1. se 
La_ Petite Culture en Belgique. (Wth Idiustrations.}—N. A. 
The Rapes ‘of the Meeting of the British Association for the Ad- 
vancementionmbeente, 6 <s . 1 3 & ss woe. eC 
TERRESTRIAL MAGNETISM. By Rev. S. J. Perry . . ee 
Corres, By J. R. Jackson, Curator of the Royal Museum, Kew. 
(With Tiustrations) 6 6 ww ee ek 
Notes. Wort ss 8 80a. Speed cack om ae 
Etuno.ocy: THE MEENAS OF CENTRALINDIA . . 4. ww eG 
CRYSTALLOGRAPHY : CRYSTALS OF PoTassic RACEMATE . 4... 
Zoo.ocy: DeveLopMENT OF MorGuta TuBULosA . . . 4... 
ScrenTIRIG SBRIALE. 2. 6 4 tt se wt 
SocigTIgSs AND ACADEMIES 4. 4 6 + 6 6 6 Ce oN Be yey 
Diary AnD Books ReckilveD ...... + 
Pace 
117 
a8 
