on the new method for the estimation of Nitrogen, §c. 295 
The experiments of Faraday show with the greatest accuracy 
that the ammonia was not only not formed, but that it either 
existed already in the material employed, or received it from 
the air by exposure. The quantities obtained were so ex~ 
tremely small that he could not estimate them. 
In the foregoing experiments I have not only confirmed, but 
at the same time demonstrated the correctness of Faraday’s 
statement, that the nitrogen of the atmosphere does not in any 
way possess the property of forming ammonia with hydrogen at 
the moment of its separation from any combination. If this 
were the case, a quantity of ammonia capable of being esti- 
mated, and in proportion to the duration of the experiment or 
the quantity of the material, would have been obtained in the 
experiments with tin, iron and sugar, in which, by the gradual 
heating of the substance with an alkali in a continued current 
of air or of nitrogen, the conditions for the formation of am- 
monia were as favourable as possible throughout the whole 
combustion; but this did not occur, and by proper care we are 
even in a condition to avoid every trace of ammonia, although 
nascent hydrogen may come in contact with nitrogen gas. 
If we consider that ammonia forms a never-failing consti- 
tuent of our atmosphere, that further, it is a body which is easily 
absorbed by liquid and porous substances, particularly when 
these latter possess at the same time the properties of an acid, 
we must at once perceive that, being in possession of an exceed- 
ingly delicate test of the presence of ammonia, that volatilealkali 
must be found in all, or nearly all substances exposed to the air. 
It is quite evident from this why Faraday did not obtain 
ammonia with fresh hydrate of potash which had been previous- 
ly melted, nor with resin which is not a porous body, although 
resin, like other organic bodies, was decomposed with the disen- 
gagement of hydrogen gas by fusion with the hydrate. A small 
quantity of nitrogen contained in the body as a constituent 
may be in part or altogether the cause of the disengagement 
of ammonia in many cases where Faraday observed it. The 
fact that the flocculent black residue always obtained by the 
solution of zinc in sulphuric acid after being well washed dis- 
engages a pretty considerable quantity of ammonia, accounts 
very easily for the [presence of nitrogen in commercial zinc. 
Cast iron, according to Schafhaeutl, also contains nitrogen. 
The statements contained in most treatises on chemistry, 
that iron by its change into oxide under the combined in- 
fluence of moisture and air containing carbonic acid affords the 
nitrogen of the latter the conditions necessary to form am- 
monia, agree exactly with the above cases of its supposed 
formation. ‘This production of ammonia, if it actually took 
place, presupposes that iron is capable of decomposing water 
