Solid solutions calorimetry

Solution calorimetry covers the measurement of the energy changes that occur when a compound or a mixture (solid, liquid or gas) is mixed, dissolved or adsorbed in a solvent or a solution. In addition it includes the measurement of the heat capacity of the resultant solution. Solution calorimeters are usually subdivided by the method in which the components are mixed, namely, batch, titration and flow. 

Preliminary work by solution calorimetry (Oriani and Murphy, to be published) shows clearly that the enthalpy of formation of solid Co-Pt alloys is a negative quantity, so that the statement made on p. 125 is not correct. 

Several experimental parameters have been used to describe the conformation of a polymer adsorbed at the solid-solution interface these include the thickness of the adsorbed layer (photon correlation spectroscopy(J ) (p.c.s.), small angle neutron scattering (2) (s.a.n.s.), ellipsometry (3) and force-distance measurements between adsorbed layers (A), and the surface bound fraction (e.s.r. (5), n.m.r. ( 6), calorimetry (7) and i.r. (8)). However, it is very difficult to describe the adsorbed layer with a single parameter and ideally the segment density profile of the adsorbed chain is required. Recently s.a.n.s. (9) has been used to obtain segment density profiles for polyethylene oxide (PEO) and partially hydrolysed polyvinyl alcohol adsorbed on polystyrene latex. For PEO, two types of system were examined one where the chains were terminally-anchored and the other where the polymer was physically adsorbed from solution. The profiles for these two... 

The thermodynamics experiments are subdivided into experiments on calorimetry and heat capacity, Table XVI phase transitions, Table XVII properties of gases, liquids, solids, solutions and mixtures, Table XVIII and finally equilibrium and miscellaneous thermodynamic topics , Table XIX. 

Using differential scanning calorimetry and 2HNMR spectroscopy, it was possible to ascertain that at least 1 wt% of 105 with n = 18-22 is solubilized into the solid phases of C21. Representative results from irradiations of these solid solutions are collected in Table 20. They and other results from irradiations in the solid phases of eicosane (C20) [321] indicate that the highest photoproduct ratios are observed when the alkanone is one carbon atom shorter than the alkane host. As in many other ordered systems, the t/c ratios are probably mechanistically meaningless when the E/C ratios are very large since a very small fraction of the BRs cyclize and those that do may... 

For these experiments it was important to establish that solid solutions were formed, and that the crystals had structures that were isomorphous with that of pure UP. The crystals were shown to be single by examination with a polarizing microscope, and to have lattice constants within 0.1% of pure UP by X-ray diffractometry. The presence of a single melting endotherm upon differential scanning calorimetry showed that the DUP molecules had not segregated into a separate phase. Certain spectroscopic similarities between DUP and UP sites also indicate that the DUP is included within the crystal lattice of UP. 

CaSO 5H20. No gypsum or any other sulfate phase was detected either by x-ray diffraction or scanning differential calorimetry, suggesting that any sulfate produced in the reactor will be present in solid solution with the CaSO t O. 

Knowledge of the concentration of defects and molar disturbance enthalpies would permit calculation of the actual free energy of the solid, and also the chemical potential. These can be measured by using either solution calorimetry or differential scanning calorimetry. An example of the excess energy was given as 20-30 kj mol-i in mechanically activated quartz. Different types of reactions demand different defect types. For example, Boldyrev et al. [25] state a classification and provide examples for solid reactions with different mechanisms and necessary solid alterations. Often, reaction rates in solids depend strongly on the mass transport of matter. Lidi-ard [26] and Schmalzried [27] each provide reviews on transport properties in mechanically treated solids. The increased amount of defects allows a faster transport of ions and atoms in the solid structure. 

Molodetsky, 1, Navrotsky A, Lajavardi M, Brune A (1998) The energetics of cubic zirconia from solution calorimetry of yttria- and calcia-stabilized zirconia. Z Physik Chem 207 59-65 Molodetsky 1, Navrotsky A, Paskowitz MJ, Leppert VJ, Risbud SH (2000) Energetics of X-ray-amorphous zirconia and the role of surface energy in its formation. J Non-Crystalline Solids 262 106-113 Moloy EC, Davila LP, Shackelford JF, Navrotsky A (2001) High-silica zeolites a relationship between energetics and internal surface area. Microporous Mesoporous Materials (submitted)... 

The enthalpies of formation of solid solutions with compositions in the range Tmo sySe-Tm I osSe were determined by Spychiger, Kaldis, and Fritzler [85SPY/KAL] at temperatures around 2400 K using fluorine combustion calorimetry. The phase relationships around the stoichiometric composition are unclear and two phases seem to form at or... 

The standard enthalpy of formation of lithium nitride has been determined by solution calorimetry. The enthalpies of reaction of LigN with water and hydrochloric acid are -581.62 1.42 and -803.50 1.26kJmoL, respectively. These values are combined with auxiliary thermochemical data to derive a weighted mean value of -164.93 1.09 kJ moP for the standard enthalpy of formation of lithium nitride. This value differs by about 8 kcal moP from previous determinations.Lithium nitride reacts in the solid state with M (M = Ca, Th, or Hf) to form MN as intermediate, and with MN to form Li2MN2. These reactions have been studied using d.t.a.and t.g.a. X-ray powder diffraction investigation shows... 

Sodium zirconium triphosphate, NaZr2P30 2, is one of the end members of the NASICON solid solution system (Nai+vZr2SivP3-jtO 2(s) (0thermochemical data determined for this species by Maier et al. [86MAI/WAR], between 1.5 and 810 K using a combination of adiabatic and differential scanning calorimetry, are discussed in Section V.7.2.5. The selected thermochemical data are ... 

After a multicomponent aqueous solution has been freeze-concentrated to the limit and the ice has been sublimed, any residual unfrozen water must be removed from the remaining solid solution by diffusion, desorption and evaporation (transfer to the condenser). This process is termed secondary drying . For an amorphous preparation, the amount of unfrozen water remaining after the removal of ice may be typically 20-30% w/w, but much higher values, even >50% w/w, have been found in some formulations. Attempts are on record to measure the amount of water that remains in the freeze-concentrated solution phase at 7, mainly by differential scanning calorimetry but such... 

This method allows measurement of the local structural environment around species complexed at the solid/solution interface and yields interatomic distances and the coordination number of the nearest neighbors. Calorimetry... 

A detailed account of polymorphism and its relevance in the pharmaceutical industry is given elsewhere in this volume and in the literature [42,46,47]. This section will focus on the use of vibrational spectroscopy as a technique for solid-state analysis. However, it should be noted that these techniques must be used as an integral part of a multidisciplinary approach to solid-state characterisation since various physical analytical techniques offer complimentary information when compared to each other. The most suitable technique will depend on the compound, and the objectives and requirements of the analysis. Techniques commonly used in solid-state analysis include crystallographic methods (single crystal and powder diffraction), thermal methods (e.g. differential scanning calorimetry, thermogravimetry, solution calorimetry) and stmctural methods (IR, Raman and solid-state NMR spectroscopies). Comprehensive reviews on solid-state analysis using a wide variety of techniques are available in the literature [39,42,47-49]. 

Microcalorimetry is an extremely sensitive technique that determines the heat emitted or adsorbed by a sample in a variety of processes. Microcalorimetry can be used to characterize pharmaceutical solids to obtain heats of solution, heats of crystallization, heats of reaction, heats of dilution, and heats of adsorption. Isothermal microcalorimetry has been used to investigate drug-excipient compatibility [82]. Pikal and co-workers have used isothermal microcalorimetry to investigate the enthalpy of relaxation in amorphous material [83]. Isothermal microcalorimetry is useful in determining even small amounts of amorphous content in a sample [84]. Solution calorimetry has also been used to quantitate the crystallinity of a sample [85]. Other aspects of isothermal microcalorimetry may be obtained from a review by Buckton [86]. 

Heats of mixing of solid solutions of CsCl with CsBr, KCl, and RbQ have been obtained by precise aqueous solution calorimetry. Results show evidence for the abrupt stabilization of the NaCl (Fm3m) structiure with respect to the CsQ (Pw3m) structure in the Csi K Cl and Csi- Rb Q systems at molar ratios corresponding to x=0.25 (Csi K,Cl) and x = 0.50 (Csi, Rb,Cl). ... 

This apparatus is used to measure how much heat is liberated when a known amount of solid material, such as a mineral, dissolves. Most minerals are notoriously insoluble in water and so an acid, such as hydrofluoric acid (HF), is used. The method is called solution calorimetry. 

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