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
-------------------------------------------------------------------
Which results show that it would be impossible to check the flame
anywhere short of the extreme tip (where complete combustion is
approximately taking place), without liberating deleterious products.
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