Hydrogen | 3.55 | 0.47 | 2.08 | Nil. +-----------+-----------+-------------+---------- | 100.00 | 100.00 | 100.00 | 100.00

These figures are of the greatest interest, as they show conclusively that the extreme top of the Bunsen flame is the only portion of the flame which can be used for heating a solid substance without liberating deleterious gases; and this corroborates the previous experiment on the gases in the outer zone of a flame, which showed that the outer zone of a Bunsen flame is the only place where complete combustion is approached.

Moreover, this sets at rest a question which has been over and over again under discussion, and that is whether it is better to use a luminous or a non-luminous flame for heating purposes.  Using a luminous flame, it is impossible to prevent a deposit of carbon, which is kept by the flame at a red heat on its outer surface, and the carbon dioxide formed by the complete combustion of the carbon already burned up in flame is reduced by this back to carbon monoxide, so that even in the extreme tip of a luminous flame it is impossible to heat a cool body without giving rise to carbon monoxide, although acetylene being absent, gas stoves, in which small flat flame burners are used, have not that subtile and penetrating odor which marks the ordinary atmospheric burner stove, with the combustion checked just at the right spot for the formation of the greatest volume of noxious products.

It is the contact of the body to be heated with the flame before combustion is complete which gives rise to the greatest mischief; any cooling of the flame extinguishes a portion of the flame, and the gases present in the flame at the moment of extinction creep along the cooled surface and escape combustion.

Dr. Blochmann has shown the composition of the gases in various parts of the Bunsen flame to be as follows: 

Height above tube. |In tube. |1 inch. |2 inch. |3 inch. |Complete
|         |        |        |        |combustion
------------------------------------------------------------

-------
Air with 100 vols. |         |        |        |        |
gas              | 253.9   | 284.7  | 284.5  | 484.3  | 608.8
Hydrogen           |  48.6   |  36.4  |  17.7  |  16.1  |  Nil. 
Marsh gas          |  39.0   |  40.1  |  28.0  |   5.7  |  Nil. 
Carbon monoxide    |   2.9   |   2.2  |  19.9  |  12.7  |  Nil. 
Olefiant gas       |   4.0   |   3.4  |   2.2  |  Nil.  |  Nil. 
Buteylene          |   3.0   |   2.5  |   1.6  |  Nil.  |  Nil. 
Oxygen             |  52.7   |  52.0  |  21.7  |  Nil.  |  Nil. 
Nitrogen           | 199.1   | 223.8  | 225.9  | 382.4  | 482.3
Carbon dioxide     |   0.8   |   3.5  |  13.0  |  41.7  |  62.4
Water vapor        |   3.1   |  11.8  |  45.8  | 116.1  | 141.2
------------------------------------------------------------

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Which results show that it would be impossible to check the flame anywhere short of the extreme tip