Ignorance, learning from pressure

Learning from Ignorance A Brief History of Pressure Vessel Integrity and Failures... 

Let us summarize what we have learned about gases. Any sample of gas can be described in terms of its pressure, temperature (in kelvins), volume, and the number of moles, n, present. Any three of these variables determine the fourth. The gas laws we have studied give several relationships among these variables. An ideal gas is one that exactly obeys these gas laws. Many real gases show slight deviations from ideality, but at normal temperatures and pressures the deviations are usually small enough to be ignored. We will do so for the present and discuss deviations later. 

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