4816.) ‘during the Year 1815. 31 
globule of mercury was however attracted by it, and was gradually 
converted into an amalgam. Hence it would seem that hydrogen 
has the property of forming an amalgam with mercury. If so, it 
must be a metallic body ; at least if the opinion universally admitted 
at present be true, that mercury amalgamates only with metals. I 
am disposed to admit the truth of this experiment, though I have 
not repeated it, because some years ago 1 remember that Sir H. 
Davy very nearly hit upon it. He exhibited the evolution of oxygen 
gas at the positive pole without the extrication of any gas whatever 
at the negative wire; but the quantity of mercury which he used 
being very considerable, no sensible amalgam was formed; but if 
hydrogen be a metal, we have a simple explanation of the amalgam 
formed by means of ammonia or sal-ammoniac and mercury when 
acted upon by the galvanic battery. The speculations on the pre- 
sence of oxygen in ammonia, as far as they depend upon that ex- 
periment, would be refuted ; while a good deal of the most plausible 
part of the reasoning respecting the composition of azote would 
likewise be destroyed. It becomes, therefore, of the utmost con- 
sequence to verify or refute this fundamental experiment of Dobe- 
reiner. 
2, Charcoal.—As to Dobereiner’s metallization of charcoal, 
mentioned also in the Annals of Philosophy (vol. v. p. 237), I have 
not yet had an opportunity of judging how far his experiments are 
correct. ‘There is an account of these experiments in the first 
volume of Dobereiner’s Chemistry; but as I have not yet seen that 
book, I do not know how they were made, nor what degree of con- 
fidence can be put in them. At present I own I am not disposed to 
admit the trath of the opinion. 
Dobereiner has published a set of experiments in order to show 
that charcoal has the property of purifying air, and of freeing it 
from those offensive fumes with which it is often contaminated. 
Nothing more is necessary than to put the charcoal into the conta- 
minated air, and to allow it to remain for a certain time. It im- 
bibes the noxious fumes, and deprives the air of all smell. In this 
way he freed air from the fumes of tobacco smoke, of asafoetida, 
&c. When water is present at the same time with the charcoal, 
the air is purified the sooner. 
3. Cyanogen.—Gay-Luussac has lately discovered a new gaseous 
substance, to which be has given the name of cyanogen, because it 
constitutes the basis of prussic azid. It is obtained by exposing dry 
prussiate of mercury to heat ina retort. ‘The gas speedily passes 
over, and must be received over mercury. It possesses the following 
properties :— 
It is colourless; has a very pungent, but quite peculiar smell ; its, 
specific gravity is 18011; it burns with a blue flame, requires 
twice its volume of oxygen gas for combustion, and leaves as a re- 
siduum one volume of azotic gas, while two volumes of carbonig: 
acid gas are formed. Hence it is composed of 5 
