Percent experimental atom

The measure used to designate the pyrrhotites observed in coal liquefaction residues is com monly the atom percent iron. Pollack and Spitler (4) have described the adaptation of the well-established x-ray diffraction method of determining atom percent iron in natural pyrrhotites to coal liquefaction residues. The atom percent iron was estimated by this technique to 0.1 atom percent. The atom percent iron values observed in liquefaction residues, and in natural pyrrhotites, range from about 46 to 50. The latter would be the essentially stoichiometric FeS, troilite (high pyrrhotite). Experimentally, substances with all compositions from 43 to 50 atom percent iron have been prepared (2). The pyrrhotites found in nature manifest atom percent iron values clustered around 46.67 (Fe Sg ... 

Recently, many experiments have been performed on the structure and dynamics of liquids in porous glasses [175-190]. These studies are difficult to interpret because of the inhomogeneity of the sample. Simulations of water in a cylindrical cavity inside a block of hydrophilic Vycor glass have recently been performed [24,191,192] to facilitate the analysis of experimental results. Water molecules interact with Vycor atoms, using an empirical potential model which consists of (12-6) Lennard-Jones and Coulomb interactions. All atoms in the Vycor block are immobile. For details see Ref. 191. We have simulated samples at room temperature, which are filled with water to between 19 and 96 percent of the maximum possible amount. Because of the hydrophilicity of the glass, water molecules cover the surface already in nearly empty pores no molecules are found in the pore center in this case, although the density distribution is rather wide. When the amount of water increases, the center of the pore fills. Only in the case of 96 percent filling, a continuous aqueous phase without a cavity in the center of the pore is observed. 

The Atomic Energy Act of 1946 represented the interests of American scientists who wished to see nuclear energy developed for nonniilitai y purposes. It called for the establishment of a five-member civilian Atomic Energy Commission (AEC), which could deliver weapons to the military only on presidential order. But the militaiy tensions ot the early Cold War delayed civilian nuclear power development until 1948, at which time 80 percent of the AEC s budget went to militaiy ends. In 1951, U.S. civilian nuclear power development consisted of only a small experimental government (liquid metal) reactor in Idaho. 

When the effective atomic number becomes a little greater than the value for iron, however, the stable atomic orbitals are occupied by one electron per orbital, and further electrons can enter this set of orbitals only by becoming paired accordingly, the magnetic moment begins to fall, as is indicated by the experimental data. The magnetic moment drops to the value 1.7 for cobalt and 0.6 for nickel, and to zero at a point 60 percent of the way between nickel and copper. 

In connection with a discussion of alloys of aluminum and zinc (Pauling, 1949) it was pointed out that an element present in very small quantity in solid solution in another element would have a tendency to assume the valence of the second element. The upper straight line in Fig. 2 is drawn between the value of the lattice constant for pure lead and that calculated for thallium with valence 2-14, equal to that of lead in the state of the pure element. It is seen that it passes through the experimental values of aQ for the alloys with 4-9 and 11-2 atomic percent thallium, thus supporting the suggestion that in these dilute alloys thallium has assumed the same valence as its solvent, lead. 

When a combustible substance is mixed with air, the mixture will explode only when it is neither too rich nor too lean. The lower explosion limit (LEL) is the minimum volume percent of the substance in air with flammability, which is separated from the upper explosion limit (UEL) by the explosive concentration range. The tabulations in handbooks are based on experimental data, and sometimes derived from estimation methods based on the elemental composition of the fuel as CmEtxOy. Figure 6.11 shows the LEL for the series of normal paraffins and of 1-alcohols versus the number of carbon atoms. There are two ways to plot the results, which show that, for paraffins, the volume percent shows a steeply declining trend, but the weight percent shows a mildly increasing trend. One may conclude that a smaller volume percent of higher paraffin... 

Figure 5.2 AMI and AMl-SRP parameters (eV) optimized to reproduce the C-H bond dissociation energy of methanol, the H-H bond dissociation energy of hydrogen, and the experimental energy for the illustrated hydrogen-atom transfer (kcal moL ). Note that in all cases but one, the magnitude of the parameter change on going from AMI to AMl-SRP is less than 10 percent...

In this way there is obtained an interaction-energy curve (the lower full curve in Figure 1-7) that shows a pronounced minimum, corresponding to the formation of a stable molecule. The energy of formation of the molecule from separated atoms as calculated by Heitler, London, and Sugiura is about 67 percent of the experimental value of 102.6 kcal/mole, and the calculated equilibrium distance between the nuclei is 0.05 A larger than the observed value 0.74 A. 

A few years ago experimental values were available for Q, S, /, and Z), but not for E the procedure adopted in testing the equation was to use the equation with calculated values of Uq (Equation 13-5) to find E, and as a test of the method to examine the constancy of E for a series of alkali halogenides containing the same halogen. The values obtained in this way were found to be constant to within about 3 kcal/mole. However, later experimental determinations of the values of the electron affinities of the halogen atoms by direct methods have shown that Equation 13-5 for the crystal energy is in general reliable only to about 2 percent. 

The separation (A) of the hyperfine lines in the ESR spectra of metal-amine, and metal-ether solutions represents a direct measure of the average s-electron (spin) density of the unpaired electron at the particular metal nucleus (12,156). When this splitting is compared to that of the free (gas-phase) atom, we obtain a measure of the "percent atomic character of the paramagnetic species. The percent atomic character in all these fluid systems increases markedly with temperature, and under certain circumstances the paramagnetic species almost takes on "atomic characteristics (43, 53, 160). Figure 9 shows the experimental data for fluid solutions of K, Rb, and Cs in various amines and ethers, and also for frozen solutions (solid data points) of these metals in HMPA (17). The fluid solution spectra have coupling con-... 

Fig. 9. Temperature dependence of the (metal) hyperfine coupling constant, expressed as percent atomic character, as a function of temperature for solutions of (a) potassium (MK), (b) rubidium ( "Rb), and (c) cesium (,J Cs) in amines, ethers, and HMPA. The experimental data are from a variety of sources, and outlined elsewhere (.16). Open symbols denote parameters from fluid solution studies shaded symbols are from frozen solutions in HMPA. Solvent identification as in Figure 8, and BuA = butylamine, i-PA and n-PA are isopropylamine and n-propylamine. 

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