triple point

(redirected from triple points)
Also found in: Dictionary, Medical.

triple point

Chem the temperature and pressure at which the three phases of a substance are in equilibrium. The triple point of water, 273.16 K at a pressure of 611.2 Pa, is the basis of the definition of the kelvin
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Triple Point

 

in thermodynamics, the point on a phase diagram at which three different phases of a substance can coexist in equilibrium.

It follows from the phase rule that there cannot be more than three phases in equilibrium in a substance consisting of one chemical element or compound, that is, a one-component system. The three phases may be, for example, the solid, liquid, and gas phases or, as in the case of sulfur, the liquid phase and two al-lotropes of the crystalline phase. The phases can coexist only for specific values of temperature T and pressure p, which determine the coordinates of the triple point on the p-T diagram.

For example, for carbon dioxide the triple-point temperature Ttp = 216.6°K, and the triple-point pressure ptp = 5.12 atmospheres. At the triple point of water, which is the fundamental fixed point of the absolute thermodynamic temperature scale, Ttp = 273.16°K (exactly), and ptp = 4.58 mm Hg.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

triple point

[′trip·əl ′pȯint]
(physical chemistry)
A particular temperature and pressure at which three different phases of one substance can coexist in equilibrium.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
As a new Amtrak Guest Rewards partner, Enterprise is kicking off the partnership by offering members triple points, which equals 150 points per day on qualifying Enterprise Rent-A-Car rentals through June 30 at more than 5,000 locations in North America.
We now prove more specialized results, adapted to our situation of counting pencils with two triple points:
Triple points for swear words in Scrabble may well be funny at the time, but it isn't funny when you're standing on stage on the first night wondering where the last three months have gone.
Four cells are used for realizing the triple points of Ar (20 [cm.sup.3]), [O.sub.2] (20 [cm.sup.3]), Ne (3 [cm.sup.3]) and e-[H.sub.2] (3 [cm.sup.3]).
A Safeway spokeswoman said the double and triple points' promotion had always been scheduled to last for only six months.
My Millennium members are eligible to earn double points when booked under this offer for a minimum of two nights and triple points when booked for a minimum of three nights.
Propel World cardholders can also earn triple points on airline purchases and double points on hotel purchases, take advantage of special offers, amenities and upgrades at luxury hotels around the world and be supported by 24/7 premium concierge services.
With our Triple Points offer, we further strengthen our unique features for planners of meetings, events, and conventions", said John Kennedy, vice president marketing & CRM at the Carlson Rezidor Hotel Group.
Hertz launches "Triple Points" promotion in 9 European countries The Hertz Corporation has launched a new "Triple Points" promotion for Gold Plus Rewards Members in 9 European countries until December 15, 2012, as well as offering free membership to new participants.
Travel Business Review-January 12, 2011--Choice Hotels Offers Triple Points for Choice Privileges Members(C)2011] ENPublishing - http://www.enpublishing.co.uk
Members can choose from 26 airline frequent flyer programmes and will start earning triple points after their second Marriott stay from 1 February though to 30 April 2011.
Under the new scheme, shoppers spending upwards of pounds 160 a month at Safeway would be entitled to double points on their "ABC" loyalty card and those spending more than pounds 240 in a month would qualify for triple points the following month.