Eötvös rule

Eötvös rule

The Eötvös rule, named after the Hungarian physicist Loránd (Roland) Eötvös (1848-1919) enables the prediction of the surface tension of an arbitrary liquid pure substance at all temperatures. The density, molar mass and the critical temperature of the liquid have to be known. At the critical point the surface tension is zero.

The first assumption of the Eötvös rule is:

1. The surface tension is a linear function of the temperature.:This assumption is approximately fulfilled for most known liquids. When plotting the surface tension versus the temperature a fairly straight line can be seen which has a surface tension of zero at the critical temperature.

The Eötvös rule also gives a relation of the surface tension behaviour of different liquids in respect to each other:

2. The temperature dependence of the surface tension can be plotted for all liquids in a way that the data collapses to a single master curve. To do so either the molar mass, the density, or the molar volume of the corresponding liquid has to be known.

The Eötvös rule

If "V" is the molar volume and "T"c the critical temperature of a liquid the surface tension γ is given bycite web|url=http://www.nikhef.nl/~h73/kn1c/praktikum/phywe/LEP/Experim/1_4_05.pdf|title=Surface Tension by the Ring Method (Du Nouy Method)|accessdate=2007-09-08|publisher=PHYWE|format=pdf] :gamma V^{2/3} = k(T_c - T),where "k" is a constant valid for all liquids. The Eötvös constant has a value of 2.1×10−7 J/K mol−2/3.

More precise values can be gained when considering that the line normally passes the temperature axis 6 K before the critical point:

:gamma V^{2/3} = k(T_c - 6 K - T),

The molar volume "V" is given by the molar mass "M" and the density ρ

:V = M / ho,

The term gamma V^{2/3} is also referred to as the "molar surface tension" γmol ::gamma_{mol} = gamma V^{2/3},

A useful representation that prevents the use of the unit mol−2/3 is given by the Avogadro constant NA ::gamma = k' left( frac{M}{ ho N_A} ight)^{-2/3}(T_c - 6 K - T) = k' left( frac{N_A}{V} ight)^{2/3}(T_c - 6 K - T)

As John Lennard-Jones and Corner showed in 1940 by means of the statistical mechanics the constant k' is nearly equal to the Boltzmann constant.

Water

For water following equation applies:gamma = 0.07275 mathrm{ N/m} cdot (1-0.002 cdot (T - 291 K))

Historical

As student Eötvös started to research surface tension and developed a new method for its determination. The Eötvös rule was first found phenomenological and published in 1886. In 1893 William Ramsay and Shields showed an improved version considering that the line normally passes the temperature axis 6 K before the critical point. John Lennard-Jones and Corner published (1940) a derivation of the equation by means of statistical mechanics. In 1945 E. A. Guggenheim gave a further improved variant of the equation.

References


Wikimedia Foundation. 2010.

Игры ⚽ Нужен реферат?

Look at other dictionaries:

  • Eötvös — is an old spelling of the Hungarian word ötvös, meaning gold silversmith . Eötvös Family name Pronunciation Hungarian: [ˈøtvøʃ] Meaning silversmith, goldsmith, etc …   Wikipedia

  • Eotvos — Eötvös can refer to one of several Hungarian people: * József Eötvös, a Hungarian statesman and author * Loránd Eötvös, a Hungarian physicist * Peter Eötvös, composer and conductor * József Eötvös (musician), a Hungarian guitar player * Zoltán… …   Wikipedia

  • Loránd Eötvös — Infobox Scientist name = PAGENAME box width = image width =150px caption = PAGENAME birth date = July 27, 1848 birth place = death date = April 8, 1919 death place = residence = citizenship = nationality = Hungarian ethnicity = field = physics… …   Wikipedia

  • Surface tension — For the work of fiction, see Surface Tension (short story). Surface tension is a property of the surface of a liquid that causes it to behave as an elastic sheet. It allows insects, such as the water strider (pond skater, UK), to walk on water.… …   Wikipedia

  • Поверхностное натяжение — Монета, лежащая на воде благодаря силе поверхностного натяжения …   Википедия

  • Hungary — /hung geuh ree/, n. a republic in central Europe. 9,935,774; 35,926 sq. mi. (93,050 sq. km). Cap.: Budapest. Hungarian, Magyarország. * * * Hungary Introduction Hungary Background: Hungary was part of the polyglot Austro Hungarian Empire, which… …   Universalium

  • Hungary — This article is about the European country. For other uses, see Hungary (disambiguation). Republic of Hungary Magyar Köztársaság …   Wikipedia

  • Inertial frame of reference — In physics, an inertial frame of reference is a frame of reference which belongs to a set of frames in which physical laws hold in the same and simplest form. According to the first postulate of special relativity, all physical laws take their… …   Wikipedia

  • Nobility in the Kingdom of Hungary — The front page of the Tripartitum, the law book summarizing the privileges of the nobility in the kingdom The origin of the nobility in the Kingdom of Hungary can be traced to the Magyar conquest of Pannonia in the 9th century, and it developed… …   Wikipedia

  • Coriolis effect — For the psychophysical perception effect, see Coriolis effect (perception). Classical mechanics Newton s Second Law …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”