What is the maximum acheivable amount of vacuum in inches?

The maximum “inches of vacuum” would be roughly equal to the barometric pressure outside, around 29.92 inches for a typical day (1 atmosphere here on Earth). This would be, for example, how far the mercury would rise if you pull air out of the top of a tube whose lower end is in a pool of mercury.

Another way which is commonly used in science and engineering is to measure in “inches of mercury” or “mm of mercury” (torr). In this case, you pull a near perfect vacuum inside the tube (by sealing the end, filling it with mercury and flipping it over) and see how high the mercury is when it stops draining out. A perfect vacuum in this case would be zero inches. It all depends on whether you’re measuring the vacuum inside the tube or outside!

Maximum Vacuum Pressure

One atmosphere supports 30 inches of mercury in a mercury barometer. In a perfect vacuum (inside a bell jar?) there would be zero inches of mercury (but mercury vapor would exist above the mercury column and well). Radio vacuum tubes of course contain a near perfect vacuum and also often employ “getters” to capture trace amounts of gas. Outer space is a near-perfect vacuum being constantly traversed by mass-less photons of energy. A vacuum chamber (on earth) must withstand the pressure of the outside atmosphere caused by the bombardment of billions of gas atoms and molecules on its surface every second with little or no gas molecules bombarding the inside surface to balance the force. That imbalanced force could crush a weak chamber like seawater can crush a weak submarine. You can’t get a “stronger” vacuum than just removing all the air.

<<H. The getter

We want a good, hard vacuum inside a tube, or it will not work properly. And we want that vacuum to last as long as possible. Sometimes, very small leaks can appear in a tube envelope (often around the electrical connections in the bottom). Or, the tube may not have been fully “degassed” on the vacuum pump at the factory, so there may be some stray air inside. The “getter” is designed to remove some stray gas.

The getter in most glass tubes is a small cup or holder, containing a bit of a metal that reacts with oxygen strongly and absorbs it. (In most modern glass tubes, the getter metal is barium, which oxidizes VERY easily when it is pure.) When the tube is pumped out and sealed, the last step in processing is to “fire” the getter, producing a “getter flash” inside the tube envelope. That is the silvery patch you see on the inside of a glass tube. It is a guarantee that the tube has good vacuum. If the seal on the tube fails, the getter flash will turn white (because it turns into barium oxide).>>

What Is A Perfect Vacuum

No inches. It’s about 0.00000 inches of mercury with an ordinary roughing pump and fairly easy to put more 0’s on with more sophisticated pumps, temperature control and adsorbtion.

Why ?

I don’t understand your unit (inches??)

But I can say you that the best vacuum is reached with a turbomolecular pump (10 ^ -15 torr or more)

Didn’t you think about space before asking this question. Sapce has infinite size vacuum

it would only be limited by the strength of the container and the pump.

too much vacuum and the chamber would collapse.

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