146 - REPORT—1845. 
tial constituent of furnace-gases. The absence of this important ingre- 
dient from Ebelmen’s analyses might be explained on the supposition that 
the gases upon which he operated were collected from a part without the 
column of charcoal, and between it and the lining of the furnace. However, 
we cannot reproach Ebelmen with drawing a theory of the mutual action of 
the gaseous and solid products of the furnace from a mixture of gas which 
had only partially been subjected to this action, because the presence of 7 per 
cent. of hydrogen indicated by his analyses would be still more inexplicable 
on this supposition. Hence we must look to another source for the errors in 
his analyses, and it will be found to lie in the incompleteness of the methods 
used by him. His method of determining the nature and composition of the 
combustible gases, was to pass them over red-hot oxide of copper, collecting 
the products of combustion in the usual way, and forming an opinion of the 
presence or absence of carburetted hydrogen by the loss in weight of the 
combustion-tube. In order to show the degree of inaccuracy of this method, 
it will be best to choose a special case as an example, and as such we select 
the first analysis of the gases of Clerval. The volume of gas used in his ex- 
periments, 1500 cubie centimetres*, contained 87:3 cubic centimetres of 
hydrogen and 352°65 cubic centimetres of carbonic oxide gas. In order to 
burn this quantity, the combustion-tube suffered a loss in weight of 0°3160 
gramme. If we supposed the whole of the hydrogen to be present as car- 
buretted hydrogen, taking its carbon from a corresponding quantity of car- 
bonic oxide, the 1500 cubic centimetres of gas must have contained 43°65 
carburetted hydrogen and 309-0 carbonic oxide ; and, on this supposition, the 
combustion-tube must have diminished in weight 0°3473 gramme, instead of 
0°3150 gramme. It will be seen from this calculation, that the question as 
to whether the mixture of gases contains 5°82 per cent. hydrogen, or instead 
of that quantity, 3°09 light carburetted hydrogen, is entirely dependent upon 
a difference in weight of not more than 0°0323 gramme. Let us assume 
that the weight of the combustion-tube and its contents was 80 grammes, 
then an error of ,,4,, in the weighing would cause a change in the results 
from the composition, as found by Ebelmen, to that placed beside it calculated 
on this supposition :— 
On the supposition that he 
According to was liable to an error of only 
Ebelmen. zoGos in weighing. 
Nitrogen «see eae S779 61°36 
Carbonic acid ....... 12:88 13°68 
Carbonic oxide ...... 23°55 21°87 
Carburetted hydrogen .. 0:00 3°09 
Hydrogen sss esses . BZ 0°00 
100°00 100°00 
Such uncertainties as these are never to be feared in a eudiometric ana- 
lysis conducted with proper precautions; for they would imply errors in 
measurement which could not take place without the most gross negligence. 
Now when we consider the circumstances which would tend to diminish the 
loss in weight of the combustion-tube in Ebelmen’s experiments, and con- 
* Tn the details of our analyses we always employ the French weights and measures, now 
universally used on the continent, and by most of our eminent chemists in this country. 
Their convenience is very great, and as science is universal and not local, English memoirs 
are more readily adopted on the continent when the translators have not the trouble of re- 
ducing our weights and measures. Where the numbers are absolute and not relative, we 
employ English measures. 
