Volume molecular, table

The differences in polystyrene-equivalent and absolute molecular weight for the LB and MA polymers are represented by the k values in Table 11 they demonstrate dissimilarities in hydrodynamic volume/molecular weight which are conferred by monomeric composition and polymeric backbone structure. The decrease in k from ca. 1.0-1.3 for LB materials to about 0.5 for the corresponding MA reflects the much higher... 

Hentschke [45] and DuPre and Yang [46] compared Kubo and Ogino s data with Lee s theory [53] extended to a (monodisperse) wormlike chain system by using ct(N) (cf. Sect. 2.3). Hentschke took d to be 1.6 nm, which is consistent with the value estimated from the partial specific volume (cf. Table 2). Though good for the middle and highest molecular weight samples in the... 

A quite different approach to the molecular size of solvents is the estimation of its molecular surface area and volume from the van der Waals radii of the constituent atoms and the manner and geometry of their mutual bonding (Bondi 1964). The necessary calculations are quite involved, and the values shown in Table 3.4 have been taken from a single source (DIPPR 1997), in order to be consistent. The reported molar van der Waals surface areas, Ayiw, are in 104 m2 mol 1 and the molar van der Waals volumes, Fvdw, are in cm3 mol 1, the latter in order to be comparable with the molar volumes (in Table 3.1) and the intrinsic volumes, defined below, also reported in Table 3.4. 

Table 9.2 Molecular volumes, molecular weights and densities.

Powder X-ray profiles of silicalite-1 prepared by various research workers, during their preparation of molecular sieves by isomorphously substituting the T element by titanium, tin, zirconium, vanadium, chromium, molybdenum, differ in their crystallinity (80-95%) and their unit cell volume values (Table 1). It is obvious from the Table that whenever a metal ion is being substituted, a metal free all silica polymorph should also be prepared for deciphering the unit cell expansion. The variation in the unit cell volume obtained by various workers is an indication of the inherent problems in synthesising zeolites and molecular sieves with repeatable metal substitution in the framework. 

The volumes eluted with these systems aie close to but smaller than the expected volumes (see Table 3). Maybe / -xylene and toluene are too rigid molecules and do not fit well the supercages, so these latters can not be totally filled up with that molecule. Therefore, a better molecular probe for die determination of the total porous volume would be an alkane, which could better fit the supercages because of its higher flexibility compared to aromatic molecules (experiments to be carried out). 

In operating a continuous stirred tank reactor, maintaining a desired polymerization temperature is often the most important objective. It is because the polymerization rate and many of the polymer properties are strongly dependent on temperature. For example, polymer molecular weight decreases as the reaction temperature is increased. If the reaction heat is not properly removed, excessive pressure buildup and/or thermal runaway may occur. In a jacketed reactor, the removal of reaction heat becomes increasingly difficult as the reactor volume increases because of the reduced heat transfer area/reactor volume ratio. Table 1 illustrates the jacket surface areas... 

The elution volume, F/, and therefore the partition coefficient, is a function of the size of solute molecule, ie, hydrodynamic radius, and the porosity characteristics of the size-exclusion media. A protein of higher molecular weight is not necessarily larger than one of lower molecular weight. The hydrodynamic radii can be similar, as shown in Table 4 for ovalbumin and a-lactalbumin. The molecular weights of these proteins differ by 317% their radii differ by only 121% (53). 

The limitations of SIMS - some inherent in secondary ion formation, some because of the physics of ion beams, and some because of the nature of sputtering - have been mentioned in Sect. 3.1. Sputtering produces predominantly neutral atoms for most of the elements in the periodic table the typical secondary ion yield is between 10 and 10 . This leads to a serious sensitivity limitation when extremely small volumes must be probed, or when high lateral and depth resolution analyses are needed. Another problem arises because the secondary ion yield can vary by many orders of magnitude as a function of surface contamination and matrix composition this hampers quantification. Quantification can also be hampered by interferences from molecules, molecular fragments, and isotopes of other elements with the same mass as the analyte. Very high mass-resolution can reject such interferences but only at the expense of detection sensitivity. 

The above values are based on the assumption that argon is combined with nitrogen, adjusting the molecular weight to 28.16. Other gases present in the atmosphere air are normally ignored, as these represent less than 0.003% (by volume, 27.99 ppm). Table 4.5 provides some basic information on these trace gases. 

Each SynChropak column is tested chromatographically to assure that it has been packed according to specifications. For SynChropak GPC columns, a mixture of a high molecular weight DNA and glycyltyrosine, a dipeptide, is used to evaluate internal volume and efficiency. The mobile phase used for the test is 0.1 M potassium phosphate, pH 7, and the flow rate is 0.5 ml/min for 4.6-mm i.d. columns. Minimum plate count values and operational flow rates are listed in Table 10.4 for 4.6-mm i.d. columns of all supports and the various diameters of the SynChropak GPC 100 columns. 

The weight average molecular weights (M ) and molecular weights at peak evolution volume (Mp) of the PEO standards provided by the suppliers are shown in Table 17.1. All four sets of PEO standards cover a similar molecular weight range, about 10,000 to 1,000,000. 

Va, Vb = molecular volumes of gases, obtained by Kopp s law of additive volumes, cm /gm mol at normal boiling point. See Table 9-44. 

Va = 26.7 for NHg from Table 9-44 (molecular volume) Note The value of Va is from Ref. 63. Molecular volume values vary between references. 

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