Hermann Sprengel’s Pumps

Hermann Sprengel’s Pumps

In 1858, a twenty-four year old man named Hermann Sprengel graduated from the University of Heidelberg. As soon as he could, he abandoned his German homeland and settled in England and becoming a British citizen. After working in a couple of different places in and around London, he settled down as a chemist in Kennington. There, he developed several noteworthy inventions. The most important was a type of explosives which used chemicals that were safe to handle until they were mixed right before detonation. His explosives were used to demolish underwater hazards and clear shipping lanes, like that in the Long Island Sound in 1885.

Sprengel’s most important innovation had nothing to do with blowing things up. It did, however, change the world forever.

During the latter part of the 19th century, there were several people of considerable intelligence working on creating durable, economically feasible electric lighting. There were plenty of applications of electricity that produced light, but all were expensive and labor intensive to maintain, and most were extremely dangerous. Everyone knew that the way to produce a good light would be to find some kind of filament that would glow when electricity was passed through it.

No one could keep a filament lit because the oxygen in the air around the filament would cause it to burn out quickly. Working independently, the English inventor Joseph Swan and the American inventor Thomas Edison would eventually master the incandescent light bulb at just about the same time, and it was Hermann Sprengel who made their work possible.

Sprengel developed a simple but ingenious type of air pump that emptied the air from a container simply by the nature of mercury. You attached the vessel you wanted to empty to a long glass tube. On either end of the tube were simple openings. The bottom drained into a receptacle, but the top was connected to a reservoir containing mercury. When the mercury reservoir was elevated above the tube, drops of mercury would form and descend to the bottom receptacle. Because of the nature of mercury as an extremely heavy liquid, the drops would trap air between them – releasing it from the bottom opening. Since air will always thin out and be spread uniformly through a vessel, the air in the vessel would continue to thin out. Within twenty minutes, a one-liter bottle could be essentially emptied of all air, with a pressure of 1/1,000,000 of atmospheric pressure at sea level.

It was a brilliant piece of work, and it was all but ignored until Swan and Edison independently realized that this type of vacuum would allow a carbon filament to glow for hundreds if not thousands of hours. Without Sprengel, there would be no incandescent light bulbs as we know them. Without incandescent lighting, we would live in a very different world.

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