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| All Patents in class 431/171 | |||||
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| Number | Date | Patentee | Title | Type | |
| 825,779 | Jul. 10, 1906 | W.L. Doyle, E.J. Vraalstad | Hydrocarbon Furnace | stationary boilers | |
| 2,314,827 | Mar. 23, 1943 | R.M. Hortvet | Process for extracting pure nitrogen from air | ||