Chimp_Logic wrote on Nov 17^th, 2013 at 8:44pm:


Isn't that basically what I already said?  You can look at it as a submicroscopic water layer if you prefer? You do realise what temperatures we're talking about? Have a read:

http://icestories.exploratorium.edu/dispatches/big-ideas/dry-valleys/

Anyway, This is not exactly theoretical. There's a bloody great glacier that flows into and terminates in an Antarctic Dry Valley.  There is no water involved because it's too cold.

It's a really good place to find meteorites too, because as the ice sublimates it leaves behind anything that dropped into it.   

Sorry about my chauvinistic comment Mrs Chimp. Men and Women do think differently. It wasn't unreasonable.

Chimp_Logic wrote on Nov 17^th, 2013 at 9:23pm:


Soren, for all his faults, will have a field day with this, and he'll be right. My life experience helps me tell the difference. There are distinctive personality differences. Don't get me wrong though. They are subtle differences that make very little difference in practice. I'm not claiming significant advantages (but you are....hmmm. )

I also think that you're trying to applying phase diagrams inappropriately - In other words in non-equilibrium cases. In the Antarctic situation, there are all sorts of complex dynamic effects at play. Surface effects, non laminar flow, Venturi effects etc.  We have katabatic winds at speeds in excess of 200km/hr. It's not a neat quasi-equilibrium laboratory experiment where everything  fits neatly into boxes. You're not making allowances for kinetics and fluid dynamics. 

Do that. She would know about the McMurdo Dry Valleys I suspect.

Think of it in similar terms to water. At the boiling point, the partial pressure of water vapour is equal to the atmospheric pressure. However as we approach boiling point there is still a significant volume of water vapour given off. It's not actually boiling. It's evaporating.

In the same way, you could say that ice is evaporating, but as it's going from solid to liquid, the term used is sublimating.  There is no practical distinction in terminology  made between ice vaporising below the triple point or above the triple point pressure, although we know that the Sublimation Point is defined for given pressures.  At the Sublimation/Deposition point itself, there is a phase transition.  As long as enough heat is applied/ removed to maintain the Sublimation/deposition temperature, then the process will rapidly go to completion.

I know exactly where you're coming from though.

Chimp - read my last post on this thread and please stop taking up two threads on the same subject.

# and Chimp:

1. Boiling is the rapid change of state from liquid to gas ok? It occurs at the Boiling Point.

2. Evaporation is the slow change of state from liquid to gas. It occurs below the boiling Point. It's a consequence of the vapour pressure of water even below the Boiling Point.

3. Sublimation is the rapid change of state from Solid to gas ok? It occurs at the Sublimation Point. (Refer to your phase diagram)

4. The slow change of state that occurs because of ice evaporating (even above the triple point pressure) is also called sublimation. That's common nomenclature. It's an entirely different process from case 3, but it still involves the transition from solid to gas (at a much slower rate). This rate of "sublimation" is dependent on the rate at which the water vapour in the gas phase is removed (Le Chateliers principle).

This has been much more interesting that arguing with denialist dead heads, but let's move on. OK? 

I'm telling you both  enough already 

Maybe I could have expanded on Point 3 and said that a "Sublimation Point" is only possible for pressures below 0.006 atmospheres, and that the Sublimation Point is not constant but varies with pressure. (The stem of the Y is not vertical).

I said above instead of below. Is that what you mean?

No. That was intentional.

Chimp_Logic wrote on Nov 19^th, 2013 at 3:45pm:


Here's another one for you.