Crystalline definition

Cu9ln4 and Cu2Se. They performed electrodeposition potentiostatically at room temperature on Ti or Ni rotating disk electrodes from acidic, citrate-buffered solutions. It was shown that the formation of crystalline definite compounds is correlated with a slow surface process, which induced a plateau on the polarization curves. The use of citrate ions was found to shift the copper deposition potential in the negative direction, lower the plateau current, and slow down the interfacial reactions. 

Degree of ciystallinity of polymer films (a volume fraction of the crystal ordered areas in a material) in this research was defined by diffractograms Fig. 5.3 for a series of samples only semiquantitative (more/less). The essence of the method of crystallinity definition consists in analytical division of a diffractogram profile on the Bragg peaks from crystal areas and diffusion peak of an amorphous phase [20], as is shown in Fig. 5.4. 

The traditional definition of a zeolite refers to microporous, crystalline, hydrated aluminosilicates with a tliree-dimensional framework consisting of comer-linked SiO or AlO tetrahedra, although today the definition is used in a much broader sense, comprising microporous crystalline solids containing a variety of elements as tetrahedral building units. The aluminosilicate-based zeolites are represented by the empirical fonmila... 

For tire purjDoses of tliis review, a nanocrystal is defined as a crystalline solid, witli feature sizes less tlian 50 nm, recovered as a purified powder from a chemical syntliesis and subsequently dissolved as isolated particles in an appropriate solvent. In many ways, tliis definition shares many features witli tliat of colloids , defined broadly as a particle tliat has some linear dimension between 1 and 1000 nm [1] tire study of nanocrystals may be drought of as a new kind of colloid science [2]. Much of die early work on colloidal metal and semiconductor particles stemmed from die photophysics and applications to electrochemistry. (See, for example, die excellent review by Henglein [3].) However, the definition of a colloid does not include any specification of die internal stmcture of die particle. Therein lies die cmcial distinction in nanocrystals, die interior crystalline stmcture is of overwhelming importance. Nanocrystals must tmly be little solids (figure C2.17.1), widi internal stmctures equivalent (or nearly equivalent) to drat of bulk materials. This is a necessary condition if size-dependent studies of nanometre-sized objects are to offer any insight into die behaviour of bulk solids. 

It is a white, deliquescent solid, very powdery, which exhibits polymorphism on heating, several different crystalline forms appear over definite ranges of temperature -ultimately, the P4O10 unit in the crystal disappears and a polymerised glass is obtained, which melts to a clear liquid. 

The problems already mentioned at the solvent/vacuum boundary, which always exists regardless of the size of the box of water molecules, led to the definition of so-called periodic boundaries. They can be compared with the unit cell definition of a crystalline system. The unit cell also forms an "endless system without boundaries" when repeated in the three directions of space. Unfortunately, when simulating hquids the situation is not as simple as for a regular crystal, because molecules can diffuse and are in principle able to leave the unit cell. 

Pyrophosphoric (diphosphoric) acid, H4P2O2, is the only condensed phosphoric acid definitely obtainable ia crystalline form. It has a theoretical P2O5 content of 79.8%. However, Hquid polyphosphoric acid of such content shows by analysis only 42.5% the remainder is phosphoric acid and... 

Bismuth trioxide may be prepared by the following methods (/) the oxidation of bismuth metal by oxygen at temperatures between 750 and 800°C (2) the thermal decomposition of compounds such as the basic carbonate, the carbonate, or the nitrate (700—800°C) (J) precipitation of hydrated bismuth trioxide upon addition of an alkah metal hydroxide to a solution of a bismuth salt and removal of the water by ignition. The gelatinous precipitate initially formed becomes crystalline on standing it has been represented by the formula Bi(OH)2 and called bismuth hydroxide [10361 -43-0]. However, no definite compound has been isolated. 

The polyions postulated in solution all have known structural analogues in crystalline borate salts. Investigations of the Raman (66) and B nmr (67) spectra of borate solutions have confirmed the presence of three of these species the triborate (3), B202(0H) 4, tetraborate (4), [B40 (0H) 4], and pentaborate (5) B O (OH) 4, polyanions. Skeletal stmctures were assigned based on coincidences between the solution spectra and those soHd borates for which definitive stmctural data are available (52). These same ions have been postulated to be present in alkah metal borate glasses as well. 

Isobutyhdene diurea [6104-30-9] is a nonhygroscopic white crystalline soHd available in fine (0.5—1.0 mm), coarse (0.7—2.5 mm), and chunk (2.0—3.0 mm) particle sizes. The AAPFCO official definition requires a minimum nitrogen content of 30% with 90% of the nitrogen in water-insoluble form prior to grinding (3). 

There has been considerable discussion about the extent of hydration of the proton and the hydroxide ion in aqueous solution. There is little doubt that this is variable (as for many other ions) and the hydration number derived depends both on the precise definition adopted for this quantity and on the experimental method used to determine it. H30" has definitely been detected by vibration spectroscopy, and by O nmr spectroscopy on a solution of HF/SbFs/Ha O in SO2 a quartet was observed at —15° which collapsed to a singlet on proton decoupling, 7( 0- H) 106 Hz. In crystalline hydrates there are a growing number of well-characterized hydrates of the series H3O+, H5O2+, H7O3+, H9O4+ and H13O6+, i.e. [H(0H2) ]+ n = 1-4, Thus... 

Scammel proposed its separation by means of a definite crystalline compound with phosphoric acid. This body has the composition CioHjgO. H3PO4. The use of phosphoric acid is the basis of the British Pharmacopoeial test for cineol in essential oils. 

The direct synthetic process is described in U.S. Patent 2,772,280. A solution of 73.3 g (0.332 mol) of (3-aminoxyalanine ethyl ester dihydrochloride in 100 ml of water was stirred in a 500 ml 3-necked round-bottomed flask cooled in an ice-bath. To the above solution was added over a 30-minute period 65.6 g (1.17 mols) of potassium hydroxide dissolved in 100 ml of water. While the pH of the reaction mixture was 7 to 10.5, a red color appeared which disappeared when the pH reached 11 to 11.5. The light yellow solution was allowed to stand at room temperature for 14 hour and then added to 1,800 ml of 1 1 ethanol-isopropanol. The reaction flask was washed twice with 10 ml portions of water and the washings added to the alcohol solution. The precipitated salts were filtered out of the alcohol solution and the filtrate cooled to 5°C in a 5 liter 3-necked round-bottomed flask. To the cold, well-stirred solution was added dropwise over a 35-minute period sufficient glacial acetic acid to bring the pH of the alcohol solution to 6.0. When the pH of the solution had reached 7 to 7.5, the solution was seeded and no further acetic acid added until Crystallization of the oil already precipitated had definitely begun. The crystalline precipitate was collected on a filter, washed twice with 1 1 ethanol-isopropanol and twice with ether. The yield of 4-amino-3-isoxazolidone was 22.7 g. 

In electrochemistry it is customary to multiply each of those quantities by Avogadro s constant and, when a few additional ions enter the already saturated solution, to speak of the entropy of solution per mole. Let the entropy of one mole of the crystalline solid be denoted by Scr and let Si and S2 denote, respectively, the entropy of the solution before, and after, the entry of the additional solute, both expressed in calories per mole. The total initial entropy is obviously (S + Si) and the final entropy is St. The difference between the final and the initial entropy is by definition AS,at. 

As part of a. basic study on M-8 proplnt, Revere (Ref 2lj using TEM, discovered that proplnt stored at —20° and —40° for 12 hour periods became wrinkled and exhibited definite parallel cracking and changes in crystalline structure, which was reflected in erratic burning... 

A distinction between a solid and liquid is often made in terms of the presence of a crystalline or noncrystalline state. Crystals have definite lines of cleavage and an orderly geometric structure. Thus, diamond is crystalline and solid, while glass is not. The hardness of the substance does not determine the physical state. Soft crystals such as sodium metal, naphthalene, and ice are solid while supercooled glycerine or supercooled quartz are not crystalline and are better considered to be supercooled liquids. Intermediate between the solid and liquid are liquid crystals, which have orderly structures in one or two dimensions,4 but not all three. These demonstrate that science is never as simple as we try to make it through our classification schemes. We will see that thermodynamics handles such exceptions with ease. 

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