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| Patents for John C. Douglas | |||||
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| Number | Date | Patentee | Title | Type | |
| 6,623X | Jul. 20, 1831 | J.C. Douglas | Safety Steam Boiler | stationary boilers | |
| 6,915X | Jan. 30, 1832 | J.C. Douglas | Piston safety valve | steam safety valves | |
| 7,431X | Feb. 19, 1833 | J.C. Douglas | Evaporating vessels to carry caloric from No.1 to any number upwards, purifying sugar, extracting acids therefrom | evaporating apparatus | |