Uses of Cl


An example of such recychng in a parallel reaction system is in the Oxo process for the production of C4 alcohols. Propylene and synthesis gas (a mixture of carbon monoxide and hydrogen) are first reacted to ra- and isobutyraldehydes using a cobalt-based catalyst. Two parallel reactions occur  [c.38]

Fajans method The titration of Cl" with Ag using fluorescein as an adsorption indicator. At the end point the precipitate becomes red.  [c.172]

We present state-to-state transition probabilities on the ground adiabatic state where calculations were performed by using the extended BO equation for the N = 3 case and a time-dependent wave-packet approach. We have already discussed this approach in the N = 2 case. Here, we have shown results at four energies and all of them are far below the point of Cl, that is, E = 3.0 eV.  [c.71]

The CSP method involves approximations that separate the different modes, and treats each mode as moving in the average field of all the other modes. The effective single-mode potentials are determined from independent classical Molecular Dynamics simulations carried out at the outset, and then used in the quantum calculation. The CI-CSP extension goes beyond the separability approximation by expanding the multidimensional time-dependent wavepacket into a sum of separable terms with variationally determined coefficients. The choice of the Cl terms is guided by the individual classical trajectories. In this way, the number of Cl terms is grossly reduced and due to a favorable (non-exponential) scaling with the number o degrees of freedom the method is applicable to large polyatomic systems. The applications that will be mentioned in the present paper are all for cluster systems. This seems to us a natural choice In trying to develop simulation methods ultimately applicable to condensed phase problems, large clusters offer physical properties similar to these phases, while still retaining the simplicity of finite systems.  [c.367]

There are two types of Cl calculations implemented in Hyper-Chem — singly excited Cl and microstate CL The singly excited Cl which is available for both ab initio and semi-empirical calculations may be used to generate UV spectra and the microstate Cl available only for the semi-empirical methods in HyperChem is used to improve the wave function and energies including the electronic correlation. Only single point calculations can be performed in HyperChem using CL  [c.39]

Using Cl may not necessarily improve the calculation of ground state energies. Parameters for the MINDO/3, MNDO, AMI, and PM3 methods already include the effects of CL Cl calculations require more computing time.  [c.40]

The energies, and Ep of the initial and final states of transitions in equations (178) and (179) are determined by the Cl eigenvalues and the transition dipole moment is obtained by using the Cl eigenvectors, that is.  [c.331]

Since equimolar concentrations of analyte and interferent were used (Ca = Cl), we have  [c.42]

Fragmentation under El conditions yields structural information, but Cl yields little or none because it gives few fragment ions. Thus, Cl is used mostly for molecular mass information and is frequently used with El as a complement. Because there is little structural information, in contrast to El, there are no extensive libraries of Cl spectra. Cl spectra are apparent also in atmospheric-pressure ionization systems (see Chapters 9 and 11). Cl is often called a soft ionization method because little excess energy is put into the molecules (M) when they are ionized. Therefore, substances that might not otherwise give mass spectra containing molecular ions will give molecular mass information under Cl conditions.  [c.4]

Sa.tura.tion Index. Materials of constmction used in pools are subject to the corrosive effects of water, eg, iron and copper equipment can corrode whereas concrete and plaster can undergo dissolution, ie, etching. The corrosion rate of metallic surfaces has been shown to be a function of the concentrations of Cl ,, dissolved O2, alkalinity, and Ca hardness as well as buffer intensity, time, and the calcium carbonate saturation index (35).  [c.300]

Chlorination of Cl—G3 Hydrocarbons or Partially Chlorinated Derivatives. Tetrachloroethylene and carbon tetrachloride are produced with or without a catalyst at high temperatures (550—700°C) from light hydrocarbon feedstocks or thek partially chlorinated derivatives. This is one of the most versatile processes, allowing for a wide range of mixed chlorinated hydrocarbon wastes from other processes to be used as feedstocks. However, the large quantities of HCl produced requkes integration with other HCl consuming processes. As with the previous process, product distribution is controlled by controlling feedstock ratios, and partially chlorinated by-products are recycled to the chlorinator. As examples, reaction of EDC or propane are shown in the following.  [c.28]

The BMS deviation is a measure of the spread of values for c around the mean. A large value of O indicates that wide variations in c occur. The probability that the controlled variable hes between the values of Cl and C9 is given by the area under the distribution between Ci and Cg (histogram). If the histogram follows a normal probabihty distribution, then 99.7 percent of aU observations should lie with 3o of the mean (between the lower and upper control limits). These Emits are used to determine the quality of control.  [c.735]

A number of gravimetric methods, such as the determination of Cl in a soluble salt, have been part of the standard repertoire of experiments for introductory courses in analytical chemistry. Listed here are additional experiments that may he used to provide practical examples of gravimetry.  [c.266]

As with the saturated calomel electrode, the potential of the Ag/AgCl electrode is determined by the concentration of Cl used in its preparation.  [c.473]

Applications of CL to the analysis of electron beam-sensitive materials and to depth-resolved analysis of metal-semiconductor interfaces by using low electron-beam energies (on the order of 1 keV) will be extended to other materials and structures.  [c.159]

Neutron activation also has been combined with accelerator mass spectrometry and has been demonstrated to have part-per-billion sensitivities fer bulk nitrogen analysis in silicon. This combination was also used to obtain depth profile of Cl in silicon semiconductors.  [c.678]

We ll compute the first four excited states using the Cl-Singles method and then compare their character to Mulliken s findings as well as with experimental determinations of the excitation energies.  [c.214]

Typical analysis of light Arabian vacuum resid before and after solvent treatment using once C4 and another C5 hydrocarbon solvent  [c.54]

The first step involves dehydrogenation of the butanes to a mixture of butenes which are then separated, recycled, and converted to butadiene. Figure 3-16 is the Lummus fixed-bed dehydrogenation of C4 mixture to butadiene. The process may also be used for the dehydrogenation of mixed amylenes to isoprene. In the process, the hot reactor effluent is quenched, compressed, and cooled. The product mixture is extracted unreacted butanes are separated and recycled, and butadiene is recovered.  [c.103]

Using Cl may not necessarily improve the calculation of ground slate cn crgics. Pararn eters for th e MINDO/3, MNDO,. AM I, and PM3 methods already iricltide the effects of Cl. Cl calculation s retjuire m ore corn pii ting time.  [c.40]

As described up to now, the PPP-SCF procedure using a single determinant overestimates electronic repulsion because all electrons are assumed to be locked into the ground state. This enor can be diminished by use of multiple-determinant wave functions. Quantum mechanically, occupation of any state has some nonzero probability, although the ground state predominates. Each single-determinant wave function has some unoccupied orbitals called virtual orbitals. Replacing a filled orbital with a virtual orbital (promoting electrons to an excited state) gives a new basis function for the linear combination that is to generate the multiple-determinant wave function. More than one substitution of virtual for occupied orbitals can be made (Cl doubles, triples, etc.), approaching the full configuration interaction solution called a full Cl solution. The degree of Cl substitution chosen is a trade-off between accuracy required and computer time allowed because Cl methods approaching full Cl interactions are ver y time consuming. Antisymme-tr ization and Cl substitution will be treated in more detail in Chapters 9 and 10.  [c.256]

Description of the Method. The chlorination of public water supplies results in the formation of several chlorine-containing species, the combined concentration of which is called the total chlorine residual. Chlorine may be present in a variety of states including free residual chlorine, consisting of CI2, HOCI, and OCI , and combined chlorine residual, consisting of NH2CI, NHCI2, and NCI3. The total chlorine residual is determined by using the oxidizing power of chlorine to convert 1 to 13 . The amount of 13 formed is then determined by a redox titration using 8203 as a titrant and starch as an indicator. Regardless of its form, the total chlorine residual is calculated as if all the chlorine were available as CI2, and is reported as parts per million of Cl.  [c.340]

A common mistake for beginners in mass spectrometry is to confuse average atomic mass and isotopic mass. For example, the average atomic mass for chlorine is close to 35.45, but this average is of the numbers and masses of Cl and Cl isotopes. This average must be used for instruments that cannot differentiate isotopes (for example, gravimetric balances). Mass spectrometers do differentiate isotopes by mass, so it is important in mass spectrometry that isotopic masses be used  [c.348]

Miscellaneous Uses of Fats, Oils, and their Derivatives. Fatty-derived materials have been important ia a wide variety of iadustrial apphcatioas for many years, although they have beea supplanted ia some areas with less expeasive petroleum-based compouads. Fats, oils, fatty acids, and their derivatives remain ia use ia iadustrial areas where their unique stmcture produces a functional effect. Drying oils for protective coatings depend on oxidation of multiple double bonds. Aldehydes derived from oil oxidation react with coUagen in the process of leather tanning. Fatty acids, present in low concentration in oils, allow the formation of thin films on metal parts, providing useful lubricating oils. Wax esters are useful plasticizers because they have a critical balance of alkyl chains and polar functionafity. As fossil fuels become more critically managed in the future, renewable fats and oils are likely to cl aim an additional share in many iadustrial appfications.  [c.136]

Permethrin [52645-53-1] (3-phenoxyphenyl)methyl-3-(2,2-dichloroethenyl)(+)-i7j ,/n7 j -2,2-dimethylcyclopropanecarboxylate (14), R = X = H (mp 35°C, vp 45 //g/Pa at 25°C) is a mixture of four isomers of 70% ( )-trans and 30% ( )-cis esters. It is soluble in water to 0.2 mg/L. The rat oral LD qS are 1500 and 2000 mg/kg. The incorporation of Cl atoms for the dimethyl vinyl group substantially increases persistence. Thus permethrin is a broad-spectmm, persistent insecticide widely used for pests of cotton, com, and other important crops. Cypermethrin [52315-07-8]  [c.273]

All l Monolayers on Silicon. Robust monolayers can be prepared where the alkyl chains are covalentiy bound to a siUcon substrate mainly by C—Si bonds (332,333). In the first experiments hydrogen-terrninated siUcon, H—Si(lll) and H—Si(lOO), were used with diacetylperoxide (332). These monolayers, although exhibiting thickness, wettabiUty, and methylene-stretching frequencies indicative of highly packed chains, lost - 30% of the chains when exposed to boiling water. The apparent conclusion was that hydroly2able acyloxy groups are removed, leaving the robust alkyl chains bound to the surface by the C—Si bonds. In an attempt to reduce the fraction of surface acyloxy groups, a mixture of alkene and diacetylperoxide was used (333). Reaction of alkynes also yielded robust, closely packed monolayers, and chlorine-terminated olefins gave monolayers having wettabiUty indicative of Cl-terminated alkyl chains. The resulting monolayers are - 90% olefin-based, as shown by deuterium labeling experiments. The introduction of olefin molecules can be explained by a radical reaction. The surface radical (dangling bond ( )) reacts with the double-bond to yield a secondary carbon radical  [c.543]

Liquid/hquid reactions of industrial importance are fairly numerous. A hst of 26 classes of reactions with 61 references has been compiled by Doraiswamy and Sharma Heterogeneou.s Reactions, Wiley, 1984). They also indicate the kind of reactor normally used in each case. The reactions range from such prosaic examples as making soap with alkali, nitration of aromatics to make explosives, and alkylation of C4S with sulfuric acid to make improved gasoline, to some much less familiar operations.  [c.2116]

This article describes conditions for using a household microwave oven to dry precipitates for the determination of CL as AgCl, the determination of S04 as BaS04, and the determination of Ca as CaC204 H2O.  [c.266]

The preferred method for calculating AGf is to use DFT, for the reasons just described. The difference is significant for the [IFe] analog in vacuum, because the DFT calculation gives a value of 1.79 eV whereas the HE calculation gives a value of 2.13 eV. The HE calculation is clearly sensitive to the lack of Cl, because calculations using an effective core potential on the Fe give values of 0.251 and 1.18 eV at the HE and MP2 (second-order Mpller-Plesset) levels, respectively. The values are also sensitive to the use of geometric optimization, lowering AGf by 0.150-0.130 eV for the [2Fe-2S] site relative to geometries of the oxidized and reduced species [11]. Assuming a single geometry for both oxidation states can lead to considerable errors in AGf , because AGf is about 0.5 eV in the HE calculation of the [IFe] site. The effects of the environment on AGf alone are variable, less than 0.1 eV in the Mn-SOD site but 0.2-0.3 eV in the [2Fe-2S] clusters.  [c.400]

All the methods, with the exception of CL, provide elemental composition. The most widely used is X-ray emission. If EDS is used the package can be quite inexpensive ( 25,000 and up), and can be routinely fitted to SEMs, TEMs, and STEMs. In addition EDS is one of the two detection schemes in EPMA (the other is WDS). Its great advantt e is its ability to routinely provide rapid multi element analysis for Z>11, with a detection limit of about 200 ppm for elements with resolved peaks. Its major disadvantages are very poor energy resolution, so that peaks are often overlapped a detector problem that adversely affects detection limits and the fact that the detector must remain cooled by liquid nitrogen or risk being destroyed. All these shortcomings of the EDS detector can be overcome by using the other detection scheme, WDS. The disadvantages of this scheme are that it is more expensive and cumbersome experimentally and does not have simultaneous multi element detection capability. For these reasons it is not so much used in conjunction with an SEM, TEM, or STEM, but is the heart of the electron microprobe, which is designed to combine WDS and EDS in the most effective analytical way.  [c.118]

Cathodoluminescence (CL), i.e., the emission of light as the result of electron-beam bombardment, was first reported in the middle of the nineteenth century in experiments in evacuated glass tubes. The tubes were found to emit light when an electron beam (cathode ray) struck the glass, and subsequendy this phenomenon led to the discovery of the electron. Currendy, cathodoluminescence is widely used in cathode-ray tube-based (CRT) instruments (e.g., oscilloscopes, television and computer terminals) and in electron microscope fluorescent screens. With the developments of electron microscopy techniques (see the articles on SEM, STEM and TEM) in the last several decades, CL microscopy and spectroscopy have emerged as powerfirl tools for the microcharacterization of the electronic propenies of luminescent materials, attaining spatial resolutions on the order of 1 pm and less. Major applications of CL analysis techniques include  [c.149]

Two general categories of CL analysis systems are wavelength nondispersive-versus-dispersive, and ambient-versus-cryogenic temperature designs. The first categorj essentially leads to two basic CL analysis methods, microscopyand spectroscopy. In the former case, an electron microscope (SEM or STEM) is equipped with various CL detecting attachments, and thus CL images or maps of regions of interest can be displayed on the CRT. In the latter case an energy-resolved spectrum corresponding to a selected area of the sample can be obtained. CL detector designs differ in the combination of components used. Although most of these are designed as SEM attachments, several CL collection systems were developed in dedicated STEMs. The collection efficiencies of the CL detector systems vary from several percent for photomultipliers equipped with light guides, to close to 90% for systems incorporating ellipsoidal or parabolic mirrors coupled direedy to a monochromator. A relatively simple and inexpensive, but powerful, CL detector using an  [c.153]

An example of CL depth-resolved analysis of subsurface metal-semiconductor interfaces, using an ultrahigh-vacuum CL system," is shown in Figure 5. This figure presents CL spectra of ultrahigh vacuum-cleaved CdS before and after 50-A Cu deposition and pulsed laser annealing." The deposition of Cu produces a weak peak at about 1.27 eV, in addition to the CdS band-edge emission at 2.42 eV. Pulsed laser annealing with an energy density of 0.1 J/cm increases the intensity of this peak, which is related to Cu2S compound formation." This specific example clearly indicates that low-energy CL spectroscopy can be used effectively in the analysis of chemical interactions at buried metal-semiconductor interfaces.  [c.157]

The beauty of using photons is that their absorption is easily understood and exacdy calculable, so that structural analysis can be based on comparisons of experimental data and calculated spectra. Statistical confidence limits can easily be computed, although the systematic errors will often be much greater than the random errors. An example of data analysis by curve fitting is depicted in Figure 4 for the system of % monolayer of Cl on Ag (111). The nearest neighbor Cl—Ag (2.70 A) and Cl-Cl (2.89 A) shells are so close in distance that they cannot be separated in a Fourier transform approach, but they are easily detected here by the fact that their atomic backscattering factors vary differently with energy, thus influencing the overall shape of the spectrum.  [c.233]

The field butanes splitter serves to concentrate the isobutane in this stream most of the normal butane is removed in the splitter bottoms for use in gasoline blending. The isobutane rich overhead is joined by a similar stream from the deisobutanizer tower in the Fractionation Section. The combined stream is cooled and dried and then is mixed with H2SO4 acid catalyst recycled from the settler before proceeding to the reactor.The reaction occurs at 35-60 F in a series of vigorously agitated mixing compartments through which the isobutane rich acid emulsion moves in series flow. The exothermic heat of reaction is removed by autorefrigeration resulting from vaporization of a portion of the reaction mixture. The reactor effluent emulsion is broken in the settler, providing a product hydrocarbon stream for fractionation and an acid stream for recycle to the reactor. Compression in the refrigeration sections permits heat removal from the system to be accomplished by cooling water. A portion of the iC4 rich refrigerant is sent to a purge depropanizer to avoid excessive buildup of C3 in the system. The settled reactor hydrocarbon is caustic and water washed before proceeding to the deisobutanizer where iC4 is taken overhead for recycle to the reactors. Additional removal of C4 from alkylate is accomplished in the debutanizer before the alkylate is cut to the desired end point in the rerun tower. The rerun alkylate is usually caustic and water washed before going to blending. Debutanizer overhead can be recycled back to the splitter tower to recover additional isobutane, thus reducing field butane requirements. Light olefins can be polymerized to products in the gasoline boiling range by passage over a phosphoric acid catalyst at 400 to 500 F. and 500 to 1000 psig. In one type of process, the phosphoric acid is supported on kieselguhr clay pellets. The catalyst becomes carbonized or softens and crumbles as a run progresses and has to be replaced when the pressure drop through a reactor becomes excessive, and/or catalyst activity has been lost. The first type of process is the "selective" operation for the production of aviation gasoline base stock. In this operation, isobutylene alone or a mixture of butylenes is polymerized at about 300 - 350 F to form some multiple of C4. The selective polymer is then hydrogenated to form a high ASTM octane number branched paraffin (2,2,4-trimethyl pentane 2,2,3-trimethyl pentane, etc.).The more common type of catalytic polymerization is the "non-selective" operation which is a high conversion process aimed at the production of motor gasoline by polymerizing either propylene, mixed butenes, or both. Since they are practically pure mono-olefins, narrow fractions of the polymer product are often valuable chemical raw materials. Examples are C7 and C9 cuts for Oxo alcohol manufacture, and C12 (propylene tetramer), which is used in the production of detergent alkylate. In a typical non-selective polymerization plant, the feed to the plant is a mixed C3 - C4 stream from a catalytic light ends plant debutanizer. The products are a C3 stream which is fed to the LPG plant a C 4 stream for blending purposes the polymer gasoline product and heavy polymer which goes to refinery slop. The usual poly plant consists of three sections feed preparation, reaction, and product fractionation. An example of such a plant is shown by the flowsheet in Figure 27,  [c.225]

The diammine [Hg(NH3)2Cl2], descriptively known as fusible white precipitate , can be isolated by maintaining a high concentration of NH4+, since reactions (2) and (3) are thereby inhibited, or better still by using non-polar solvents. It is made up of a cubic lattice of Cl ions with linear H3N-Hg-NH3 groups inserted so as to give the common, distorted octahedral coordination about Hg (Hg N = 203 pm, Hg-Cl = 287 pm) (Fig. 29.4a).  [c.1219]

Cl methods determine the energy by a variational procedure, and the energy is consequently an upper bound to the exact energy. There is no such guarantee for perturbation methods it is possible that the energy will be lower than the exact energy. This is rarely a problem. Limitations in the basis set often mean that the error in total energy is several a.u. (thousands of kcal/mol) anyway. Furthermore, the interest is normally not in total energies, but in energy differences. Having a variational upper bound for two energies does not give any bound for the difference between these two numbers. The main interest is therefore in the error remaining relatively constant for different systems. The lack of size extensivity of Cl methods is disadvantageous in this respect. The MP perturbation method k size extensive, but other forms of MBPT are not. It is now generally recognized that size extensivity is an important property, and the MP form of MBPT is used almost exclusively. Combined with the low cost relative to Cl methods this often makes MP calculations a good method for including electron correlation.  [c.129]

Symmetry ean sometimes be used to facilitate the loeation of TSs. For some reaetions, especially those where the reaetant and product are identieal, tlie TS will have a symmetry different from the reaetant/produet. The reaction vector will belong to one of the non-totally symmetric representations in the point group. The TS therefore ean be loeated by eonstraining the geometry to a eertain symmetry, and minimizing the energy. Consider for example the S 2 reaction of Cl with CH3CI. The reactant and products have Cj,v symmetry, but the TS has D-ni symmetry. Minimizing the energy under the eonstraint that the geometry should have >3 synunetry will produce the lowest energy strueture within this synunetry, which is the TS.  [c.337]

Both of these substitution pathways in MeCN solution have been simulated using the Onsager model (Tables IV and V). Whereas pathway b is favored in the gas phase, inclusion of solvent effects in the calculations causes pathway a to be energetically favored. Substitution of Cl via pathway a is now 1.6 kcal/mol more favorable. In addition, TS(X)/TS(Pyr) calculations (Scheme 15) for the OMe (40) and OSiMes (41) cations have been performed. TS(X) of both 40 and 41 remain significantly disfavored (+66.9 kcal/mol and +46.6 kcakmol, respectively), thus indicating that pathway b should be preferred in MeCN.Tliese calculations are in complete agreement with experimental observations.  [c.198]


See pages that mention the term Uses of Cl : [c.326]    [c.375]    [c.39]    [c.236]    [c.204]    [c.340]    [c.613]    [c.322]    [c.690]    [c.803]    [c.18]   
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Mass Spectrometry Basics  -> Uses of Cl