Determination of molecular

Beckmann thermometer A very sensitive mercury thermometer with a small temperature range which can be changed by transferring mercury between the capillary and a bulb reservoir. Used for accurate temperature measurements in the determination of molecular weights by freezing point depression or boiling point elevation. 

Heinz T F, Tom H W K and Shen Y R 1983 Determination of molecular orientation of monolayer adsorbates by optical second-harmonic generation Phys. Rev. A 28 1883-5... 

In practice, each CSF is a Slater determinant of molecular orbitals, which are divided into three types inactive (doubly occupied), virtual (unoccupied), and active (variable occupancy). The active orbitals are used to build up the various CSFs, and so introduce flexibility into the wave function by including configurations that can describe different situations. Approximate electronic-state wave functions are then provided by the eigenfunctions of the electronic Flamiltonian in the CSF basis. This contrasts to standard FIF theory in which only a single determinant is used, without active orbitals. The use of CSFs, gives the MCSCF wave function a structure that can be interpreted using chemical pictures of electronic configurations [229]. An interpretation in terms of valence bond sti uctures has also been developed, which is very useful for description of a chemical process (see the appendix in [230] and references cited therein). 

Molecular Weight Determinatioos. Details of the determination of molecular weights on a semi-micro scale by the Freezing-point method are given on p. 436, and by the Boiling-point method on p. 440. 

DETERMINATION OF MOLECULAR DEPRESSION CONSTANT OF CAMPHOR, using Solute of Known Molecular Weight (Naphthalene, Ck,Hj). 

DETERMINATION OF MOLECULAR WEIGHT OF A GIVEN SUBSTANCE, e.g., ACETANILIDE, using the above Molecular Depression Constant of Camphor. 

A. Hinchliff, Ah Initio Determination of Molecular Properties Adam Hilger, Bristol (1987). 

A double-focusing mass spectrometer can mea.sure mass accurately to several decimal places, thus enabling the determination of molecular formulae and elemental compositions of fragment ions. 

It is not the purpose of this book to discuss in detail the contributions of NMR spectroscopy to the determination of molecular structure. This is a specialized field in itself and a great deal has been written on the subject. In this section we shall consider only the application of NMR to the elucidation of stereoregularity in polymers. Numerous other applications of this powerful technique have also been made in polymer chemistry, including the study of positional and geometrical isomerism (Sec. 1.6), copolymers (Sec. 7.7), and helix-coil transitions (Sec. 1.11). We shall also make no attempt to compare the NMR spectra of various different polymers instead, we shall examine only the NMR spectra of different poly (methyl methacrylate) preparations to illustrate the capabilities of the method, using the first system that was investigated by this technique as the example. 

Before doing this, however, it is informative to compare the sensitivity of the four colligative properties in the determination of molecular weight. In the following example this is done by making the appropriate numerical calculations. 

These results show more clearly than Fq. (8.126)-of which they are special cases-the effect of charge and indifferent electrolyte concentration on the osmotic pressure of the solution. In terms of the determination of molecular weight of a polyelectrolyte by osmometry. ... 

In the chapter on vibrational spectroscopy (Chapter 6) 1 have expanded the discussions of inversion, ring-puckering and torsional vibrations, including some model potential functions. These types of vibration are very important in the determination of molecular structure. 

Whereas correlation energies can be included, in practice it is even more time-consuming to use them in the determination of molecular geometries (ie, n P and determining the correct basis set to use can be difficult. 

Polarimetric analysis of sorbitol and mannitol in the presence of each other and of sugars is possible because of their enhanced optical rotation when molybdate complexes are formed and the higher rotation of the mannitol molybdate complex under conditions of low acidity (194). The concentration of a pure solution of sorbitol may be determined by means of the refractometer (195). Mass spectra of trimethylsilyl ethers of sugar alcohols provide unambiguous identification of tetritols, pentitols, and hexitols and permit determination of molecular weight (196). 

Analysis. Many analytical procedures calling for determination of molecular stmcture are aided by crystallization or requite that the unknown compound be crystalline. Methodologies coupling crystalliza tion and analytical procedures will not be covered here (see X-RAY TECHNOLOGY)... 

NEW APPROACH TO INCREASING OF ROBUSTNESS FOR METHOD OF DETERMINATION OF MOLECULAR WEIGHT DISTRIBUTION IN DEXTRANS... 

The main problem of determination of molecular weight distribution (MWD) of dextrans (polysachaiides which ai e used as active substances for infusion medicines) is low robustness of the existing method. It means that obtained results are strongly dependent on controlled and uncontrolled pai ameters of chromatographic system standai d substances for calibration loading on columns etc. It has been shoved on practical examples. 

Polarization effects are another feature of Raman spectroscopy that improves the assignment of bands and enables the determination of molecular orientation. Analysis of the polarized and non-polarized bands of isotropic phases enables determination of the symmetry of the respective vibrations. For aligned molecules in crystals or at surfaces it is possible to measure the dependence of up to six independent Raman spectra on the polarization and direction of propagation of incident and scattered light relative to the molecular or crystal axes. 

The determination of molecular structure by microwave spectroscopy (Section VII,A), the measurement of acid-base equilibria by ICR (Section VII,F), and theoretical calculations, especially accurate for the gas phase, are the main novelties of this section. 

The highly detailed results obtained for the neat ionic liquid [BMIM][PFg] clearly demonstrate the potential of this method for determination of molecular reorienta-tional dynamics in ionic liquids. Further studies should combine the results for the reorientational dynamics with viscosity data in order to compare experimental correlation times with correlation times calculated from hydrodynamic models (cf [14]). It should thus be possible to draw conclusions about the intermolecular structure and interactions in ionic liquids and about the molecular basis of specific properties of ionic liquids. 

None of Einstein s first four papers published between 1901 and 1904 foreshadowed his explosive creativity of 1905, his annus mirabilis, in which he produced in March, his proposal of the existence of light quanta and the photoelectric effect, work for which in 1922 he received the Nobel Prize in April, a paper on the determination of molecular dimensions, which earned him his Ph.D. m Zurich m May, his theory of special relativity in September, a sequel to the preceding paper containing the relation E = mc. Any one of these papers would have made him greatly renowned their totality made him immortal. 

Diethyl dithioacetal derivatives of carbohydrates are generally crystalline compounds which are easily prepared from sugars in the combined or free form. In contrast to the mass spectra of the carbohydrate derivatives discussed above, the mass spectra of diethyl dithioacetals allow direct determination of molecular weight from molecular-ion peaks of... 

Regularities observed in the behavior of gases have contributed much to our understanding of the structure of matter. One of the most important regularities is Avogadro s Hypothesis Equal volumes of gases contain equal numbers of particles (at the same pressure and temperature). This relationship is valuable in the determination of molecular formulas—these formulas must be known before we can understand chemical bonding. 

This returns us to the problem of the determination of molecular weight. Avogadro s Hypothesis provides one of the convenient ways of measuring molecular weight if the substance can be vaporized. 

Lennard-Jones, J., Proc. Roy. Soc. London) A198, 1, The molecular orbital theory of chemical valency. I. The determination of molecular orbitals."... 

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