A M M ( 53 ) AM M

monia was used, the appearances were thesame, but a black matter formed in the cavity,apparently carbon.

It then occurred to Sir H. Davy that the strongdeoxydating power of potassium or of sodium,might be made to produce the same effect onthe ammoniacal salt without the interventionof any galvanic apparatus. Accordingly asmall portion of potassium was dropped intothe globule of mercury contained in the moist-ened cavity of the lump of muriat of ammonia,and immediately without any further apparatus,the mercury enlarged as before to six or seventimes its bulk, and the same amalgam wasformed, with this slight difference however, thatit appeared to be more permanent, and to retaina portion of the potassium used.

This ammoniacal amalgam at the tempera-ture of 70* or S(P is of the consistence of butter,at the freezing point it crystallizes into smallundefined brilliant facets. When exposed tothe air it soon becomes covered with a whitecrust of carbonat of ammonia. When throwninto water it produces about half its bulk ofhydrogen, and returns ta the state of runningmercury, the water becoming ammoniacal.When thrown into muriatic acid gas, it instantlybecomes coated with muriat of ammonia, andsome hydrogen is disengaged. In sulphuricacid it becomes coated with sulphat of ammoniaand sulphur.

The physical properties of this amalgam arevery curious. The mercury appears to gainno more than about vs-rnroth of its weight ofnew matter, but is thereby rendered solid, hasits specific gravity diminished from 13.5 to lessthan 3. and retains its metallic colour, lustre,opacity, and conducting power.

Sir H. Davy made many attempts to obtain apeculiar metallic substance from this amalgam,by distillation, out of the contact of air, andthus to exhibit the, supposed basis of ammonia(or Ammonium), in a separate state. Butall these attempts failed, for under every cir-cumstance the amalgam, when heated, gaveout hydrogen and ammonia, and the mercuryreturned to its former state. In the most accu-rate experiments the proportions of these twogasses evolved were two of ammonia and oneof hydrogen.

The nature of this- amalgam is still veryobscure, and much difference of opinion pre-vails on this subject among chemists. As itseems well ascertained that ammonia is re-solvable solely into azote and hydrogen, it foNf Recherches Physico-Chimiques faitcs

lows, that if ammonia is really an oxyd ofsome metallic base, azote and hydrogen, or oneof them, must also be oxyds of Some hithertounknown substance, and this idea has beenadopted by M. Berzelius, in his elaborate ana-lytical researches, who supposes both hydrogenand azote to be oxyds of ammonium in differentproportions. But when the ammoniacal amal-gam is distilled, hydrogen and ammonia bothappear, and the source of the hydrpgen remainsto be accounted for. This Sir II. Davy does,by supposing that as the amalgam is formedfrom moist substances, sufficient water adheresto it to afford oxygen by' its decomposition,whilst its hydrogen unites with the amalgam.Nevertheless an excess of hydrogen is alwaysproduced in the distillation of the amalgam,even where the most scrupulous care is taken,to exclude moisture.

Before we proceed with the other decom-positions of ammonia, we shall relate the expe-riments of Messrs. Gay Lussac and Thenard, fon the ammoniacal amalgam, in which theyhave repeated the experiments of Seebeck andDavy , and have added other interesting facts.They observe that when the amalgam is formedby the agency of galvanic electricity uponmercury in contact with moistened muriated-ammonia, the acid of the salt and the oxygenof the water are carried to the positive pole,round which a dense and suffocating vapour ofoxymuriatic acid collects. On the other hand,little or no gas of any kind escapes at the nega-tive pole; but if the mercury is removed, thenthe effervescence is equally great at this pojaalso ; from which they infer that the mercurysimply absorbs the gas that would otherwisehave escaped, and forms the amalgam..

When this amalgam is well dried and inclosedin a dry bottle of common air, and simply shakenfor a few minutes, it is entirely decomposed,running mercury is produced, and hydrogenand ammoniacal gas are found mixed with theair of the bottle, which is no way altered whenexamined by Volta’s eudiometer. Hence itappears that this amalgam can only exist underthe electric influence, and as soon as this isdestroyed by agitation, it returns to its ele-mentary state. The amalgam made in Davy ’s-method by mercury.,- potassium, and.muriat ofammonia, without the agency of electricity,is more permanent,, and remains in this stateas long as it contains any. potassium, but assoon as this is destroyed the amalgam is sud-denly broken up. A quantity of this amalgam.

par M.M.Gav Inusac and Thenard,