uel seems to have figured it out. No, there is no such thing as spherical pressure in physics, unless that expression is being used illogically in some jargon. Any boiling point depends upon the pressure. The easiest pressure to do any experiment to determine the boiling point is with no special pressurization. Then the pressure will be what we experience in normal atmosphere, namely atmospheric pressure. Since it is always better to say at what pressure a phase transition like boiling occurs, the expected phrase would be, "at atmospheric pressure". BW, Nancy