Melting Point of Adsorbed Liquids

Brown, Marjorie J.; Foster, A. Graham

doi:10.1038/169037b0

Cited by 4 publications

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“…These investigations included dilatometry of water adsorbed on hydrogels like alumina, ferric oxide and silica [33,34], vapour pressure measurements of benzene adsorbed on charcoal [35], dilatometry of water in egg white, silica gel and hydrated ferric oxide [36] as well as vapour pressure measurements of iodine on silica gel [37] and water on silica gel [38]. Studies were carried out with 1, 2-diaminoethane capillary condensed in 2.5 nm pore-size silica gel [39], and it was shown that dioxan adsorbed on ferric oxide gel (r ∼ 10 nm) melts 6 • C below T m , and that water on silica gel of r ∼ 1.1 nm remains liquid at −65 • C [4]. The first calorimetric study [40] found a sizeable freezing-point depression for water, naphthalene, benzene and p-nitrotoluene adsorbed on silica gel.…”

Section: Early Studies Of Porous Mediamentioning

confidence: 99%

Confinement effects on freezing and melting

Christenson¹

2001

J. Phys.: Condens. Matter

574

594

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A review of experimental work on freezing and melting in confinement is presented. A range of systems, from metal oxide gels to porous glasses to novel nanoporous materials, is discussed. Features such as melting-point depression, hysteresis between freezing and melting, modifications to bulk solid structure and solid-solid transitions are reviewed for substances such as helium, organic fluids, water and metals. Recent work with well characterized assemblies of cylindrical pores like MCM-41 and graphitic microfibres with slit pores has suggested that the macroscopic picture of melting and freezing breaks down in pores of molecular dimensions. Applications of the surface force apparatus to the study of freezing and melting phenomena in confinement are discussed in some detail. This instrument is unique in allowing the study of conditions in a single pore, without the complications of pore blockage and connectivity effects. The results have confirmed the classical picture of melting-point depression in larger pores, and allowed the direct observation of capillary condensation of solid from vapour. Other results include the measurement of solvation forces across apparently fluid films below the bulk melting point and a solid-like response to shear of films above the bulk melting point. These somewhat contradictory findings highlight the difficulty of using bulk concepts to define the phase state of a substance confined to nanoscale pores.

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Section: Early Studies Of Porous Mediamentioning

confidence: 99%

Confinement effects on freezing and melting

Christenson¹

2001

J. Phys.: Condens. Matter

574

594

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Über eine Schmelzpunktserniedrigung organischer Substanzen in dünnen Schichten. III. Mitteilung

Karagounis¹

1954

Helvetica Chimica Acta

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Volumen XXXVII, Fasciculus 1 1 1 (1954) -No. 100. 805 100. 'Uber eine Schmelzpunktserniedrigung organischer Substanzen i n diinnen Schichten. 111. Mitteilung') von Georg Karagounis. (1. 111. 54.)Vor einiger Zeit berichteten wir2) uber die Feststellung einer kritischen Belegungsdichte bei der Ausbreitung von polaren organischen Substanzen uber Metalle, Metalloxyde, Salze und allgemein uber feste Substsnzen mit grosser Oberflachenenergie. Diese kritische Belegungsdichte, welche wir mit Br bezeichneten und die Anzahl der Gramme der Substanz bedeutet, welche uber die innere Oberflache von einem Gramm der fein verteilten, festen Unterlage ausgebreitet sind, stellt sich bei der Vervollstandigung der ersten monomolekularen und dem Reginn der Bildung der zweiten Schicht ein. Sie ist durch eine Reihe besonderer Eigenschaften charakterisiert, unter welchen ihre FLhigkeit, als Wachstumskeim in der unterkiihlten Schmelze zu wirken und somit die Kristallisation derselben auszulosen, hervorsticht. E s is t somit moglich, die B i l d u n g einer monomolekularen S c h i c h t d u r c h eine F a l l u n g s r e a k t i o n s i c h t b a r zu m a c h e n . Die Dicke, welche dieser Belegungsdichte entspricht, wurde zu 6,9 d ermittelt, was c = 8,69 A, Z = 2. Anthracen: a = 8,58 A, b = 6,02 A, c = 11J8 A, Z = 2. l) 11. Mitteilung, Helv. 36, 1681 (1953. z, Geory Kuragounis, Helv. 36, 282 (1953).

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Phase Transitions in Multimolecular Layers of Adsorbed Nitrogen

Morrison¹,

Drain²,

Dugdale³

1952

Can. J. Chem.

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ABSTRACT?'lie heat capacity of nitrogen adsorbed on titanium dioxide has bee11 measured for amounts adsorbed corresponding to 2.2,3.1,4.0, and 4.8 molecular layers in the temperat~~re range 14' to 75'IC. Thc occurrence in the adsorbed films of nielting and of the transition in the solid phase of nitrogen is shown by maxima in the heat capacity. The m e l t i~~g process is completely reversible and takes place a t temperatures below the normal meltina point. The solid phase transition does not occur reversibly, the magnitude of the anomaly in the heat capacity depending upon the extent to which the system has been cooled prior to the measurement of the heat capacity. The experimental results are discussed in terms of current thern~oclynamic treatments of phase transitions in adsorbed films.A number of instances of melting in adsorbed filnls have been described in the li terati~re. Patrick and ICemper (20) have discussed the rnelting of water, naphthalene, benzene, and p-nitrotoluene adsorbed on silica gel. Other evidence for melting of substances adsorbed on silica gel has been given by Higuti (8), by Brown and Foster (3), and by Iwakami (11). In addition, Batchelor and Foster .(I) have found that the melting point of dioxane adsorbed on ferric oxide gel occurred. below that of the bulk substance. Several attempts have been made to calculate the lowering of the melting point in the adsorbed phase with the assumption that the effect ~v a s due to adsorption in capillary spaces (1,21,9). This hypothesis is reasonable enough for porous solids. On the other hand, experiments which have recently been made with argon adsorbed on crystalline titanium dioxide (19) s h~~\ a similar lowering of the melting point. It seems ~~nliliely that in this system capillary condensation plays any important part.Also of interest is the occurrence of the A-point in films of heli~lnl adsorbed on nonporous solids, the experime~ltal evidence conling from heat capacity rneasurements (6, 14), and from flow experiments (12, 13, 2).In this paper the behavior of the phase transitions in nitrogen adsorbed on I-utile is described and discussed with special reference to the possible coexistence of t11.0 surface phases, as has been proposed by Meyer and Long (15).* Besides the results to be given here, additional values of the thermodynamic functions of nitrogen adsorbed at co~lccntrations corresponding to less than about two layers have been obtained, but these do not sho\v phase transitions and will bc discussed else~vhere. Brief mention is made of some results for argon adsorbed on rutile, not given previously. EXPERI MENT.'\LThe cnlol-imeter assembly used for the experiments and the calculation of the ilIa?rzrscript received J~i l y 7 , 1952.

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Melting Point of Adsorbed Liquids

Cited by 4 publications

References 0 publications

Confinement effects on freezing and melting

Confinement effects on freezing and melting

Über eine Schmelzpunktserniedrigung organischer Substanzen in dünnen Schichten. III. Mitteilung

Phase Transitions in Multimolecular Layers of Adsorbed Nitrogen

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