Cautioning

Optimisation on charges is not implemented in the standard version. It may be wanted when optimising a PEP which includes charge parameters. In this case there is one more type of observables for each molecule look into subroutine RDEXP or consult us. As for the standard version, all lines must be there. 

A dipole moment not known, or known to be zero by symmetry, is specified with a line containing only NOK. (Symmetry must emerge in a more fundamental way than by imposing zero dipole moment.) 

Similarly for charges, if they cannot be estimated from photoelectron spectra or ab initio calculations. (Do not use estimates from CNDO, PCILO, they are usually unreasonably low for a monopole model of charge distribution.) 

Users are strongly advised to acquire much experience in minimisation and some in normal coordinate analysis before adventuring into optimisation. 

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Appendix C presents the best set of constants for Equation (2). Also shown are the temperature limits of the real experimental data. Users must exercise caution when using the correlation outside the range of real data such use should, in general, be avoided. 

However, a note of caution should be added. In many multiphase reaction systems, rates of mass transfer between different phases can be just as important or more important than reaction kinetics in determining the reactor volume. Mass transfer rates are generally higher in gas-phase than liquid-phase systems. In such situations, it is not so easy to judge whether gas or liquid phase is preferred. 

At low temperatures, using the original function/(T ) could lead to greater error. In Tables 4.11 and 4.12, the results obtained by the Soave method are compared with fitted curves published by the DIPPR for hexane and hexadecane. Note that the differences are less than 5% between the normal boiling point and the critical point but that they are greater at low temperature. The original form of the Soave equation should be used with caution when the vapor pressure of the components is less than 0.1 bar. In these conditions, it leads to underestimating the values for equilibrium coefficients for these components. 

The model is predictive and uses a method of contributing groups to determine the parameters of interaction with water. It is generally used by simulation programs such as HYSIM or PR02. Nevertheless the accuracy of the model is limited and the average error is about 40%. Use the results with caution. 

Caution is required in the use of the simple cashflow indicators, since they fail to take account of changing general price levels or the cost of capital (discussed in Section 13.4). It is always recommended that the definition of the indicators is quoted for clarity of understanding. 

Barnes cautions about using the appropriate units (molecular area with mole fraction, or area per unit mass with mass fraction) when analyzing area data [244]. 

The effect is more than just a matter of pH. As shown in Fig. XV-14, phospholipid monolayers can be expanded at low pH values by the presence of phosphotungstate ions [123], which disrupt the stmctival order in the lipid film [124]. Uranyl ions, by contrast, contract the low-pH expanded phase presumably because of a type of counterion condensation [123]. These effects caution against using these ions as stains in electron microscopy. Clearly the nature of the counterion is very important. It is dramatically so with fatty acids that form an insoluble salt with the ion here quite low concentrations (10 M) of divalent ions lead to the formation of the metal salt unless the pH is quite low. Such films are much more condensed than the fatty-acid monolayers themselves [125-127]. 

In conclusion, any observation of slowness in attainment of physical adsorption equilibrium should be analyzed with caution and in detail. When this has been done, the phenomenon has either been found to be due to trivial causes or else some unsuspected and interesting other effects were operative. 

It should be cautioned that the correctness of the factors involving z has not really been verified experimentally and that the algebraic forms involved are modelistic. Additional analyses have been made by Ruckenstein and Dadybur-jor[lll]. 

As a word of caution, the Bom-Oppenlieimer assumption is not universally valid. There are many reactions in which. 

The molecular phase effects are especially important when the system has some type of synnnetry. Nevertheless, the typical treatment of non-adiabatic effects ignores the adiabatic phase, although, as cautioned, this is a problematic step. 

All the azides are potentially dangerous, and liable to detonate on heating, but those of the alkali and alkaline earth metals can be heated with caution if pure they then evolve pure nitrogen. 

Caution is required in both methods. In the second case, in particular, gentle heating only is essential once the reaction starts. 

Any solid mercury compound when fused with sodium carbonate yields a grey deposit of mercury. (Caution mercury vapour is formed.)... 

Caution If you arc new Lo com pn taLion al chemisLry. do not use Unilcd ALoms for AMBER calciilalions. This TlypcrCh cm oplion is available for researchers who warn lo alter aiom types aiul parameters for this force field. 

Caution C omparing the shifted constant dielectric to a constant dielectric function without a cutoff shows that the sh ifted dielectric, iin like a switch in g fun ction, perturbs the en tire electrostatic energy curve, not only the region near the cnioff. 

Caution Geometry optimi/ation s of large molecules may take Ion ger Ih an you expect. Th e n um her of com pii tin g cycles req iiired for a con jugate gradien t calculation is approximately proportional... 

Be cautions when projecting the resuIts of calculations in one solvent to those using a different environment. 

Caution During a sininlation, solvent temperature may increase wh ile th e so In te cools. This is particii larly true of sm all solven t molecules, such as water, that can acquire high translational and rotational energies. In contrast, a macromolecule, such as a peptide, retains most of its kinetic energy in vibrational modes. This problem rem ains un solved, an d this n ote of cau tion is provided to advise you to give special care to simulations using solvent. 

Caution Restrain ts may sign ificantly affect the property yon are observing. When using restrain is, ch cck th eir effects on measured values. 

Caution For ion ic reaction s in solution, solven t effects can play a sign ificari I roic. fhesc, of course, arc neglected in calculation s on a single molecule. You can obtain an indication of solvent effects from sem i-eni pirical calculations by carefully adding water molecules to th e solute m olectile. 

This simplification must be used with caution, of course, making sure that the specification of the problem does not determine the magnitude of the pressure gradient, but it is very useful in the important case of a coarsely porous catalyst pellet. 

HC0N(CH3)2, also possess exceptional solvent properties. The alkyl-glycols, dioxan and dimethyl-formamide should be used with caution, however, as their hot vapours are poisonous. 

Caution.—If the ethanol used to extract the methylamine hydrochloride is not absolute, i.e., if it contains traces of water, considerably less than the above suggested quantity will be required for the extraction, because the solubility of the hydrochloride will be markedly increased by the water present. The recrystallised material will now, however, contain traces of ammonium chloride. 

CAUTION. The vapour of selenium dioxide is poisonous, and all operations involving the hot material, alone or in solution, should be performed in a fume-cupboard. If lumps of selenium dioxide have to be powdered in a mortar, the latter should also be in a fume-cupboard, with the window lowered as far as possible, to avoid inhaling the fine dust. (cf. p. 191)... 

CAUTION. Sodium must be handled with great care and under no circumstances may the metal be allowed to come into contact with water as a dangerous explosion may result. Sodium is stored under solvent naphtha or xylene it should not be handled with the fingers but with tongs or pincers. Waste or scrap pieces of sodium should be placed in a bottle provided for the purpose and containing solvent naphtha or xylene they should never be thrown into the sink or into the waste box. If it is desired to destroy the scrap sodium, it should be added in small portions to rather a large quantity of methylated spirit. 

In practice, it is best to purify a quantity, say one Winchester quart bottle, of technical 0 720 ether to cover the requirements of a group of students. The Winchester quart of ether is divided into two approximately equal volumes, and each is shaken vigorously in a large separatory funnel with 10-20 ml. of the above ferrous solution diluted with 100 ml. of water. The latter is removed, the ether transferred to the Winchester bottle, and 150-200 g. of anhydrous calcium chloride is added. The mixture is allowed to stand for at least 24 hours with occasional shaking. Both the water and the alcohol present are thus largely removed. The ether is then filtered through a large fluted filter paper into another clean dry Winchester bottle (CAUTION all flames in the vicinity must be... 

Method 2. Mix 1 0 g. of 3 5-dinitrobenzoic acid with 1 5 g. of phosphorus pentachloride in a small, dry test-tube. Warm the mixture gently over a small smoky fiame to start the reaction when the reaction has subsided (but not before), boil for 1-2 minutes or until the solid matter has dissolved. Pour the mixture while still liquid on a dry watch glass (CAUTION the fumes are irritating to the eyes). When the product has solidified, remove the liquid by-product (phosphorus oxychloride) by transferring the pasty mixture to a pad of several thicknesses of filter paper or to a small piece of porous tile. Spread the material until the liquid has been absorbed and the residual solid is dry. Transfer the 3 5 dinitrobenzoyl chloride to a test-tube, add 0-5-1 ml. of the alcohol, and continue as in Method 1. 

CAUTION. Bromine must be handled with great care and in the fume cupboard. The liquid produces painful bums and the vapour is unpleasant. Bromine bums should be treated immediately with a liberal quantity of glycerine. If the vapour is inhaled, relief may be obtained by soaking a handkerchief in alcohol and holding it near the nose. 

CAUTION Alkyl fluorides are said to he highly toxic. Great care should be taken not to inhale the vapours. 

Diethyl sulphate, b.p. 210° (decomp.), does not ordinarily react so vigor ously as dimethyl sulphate, but is nevertheless of great value for ethylations. It is somewhat leas poisonous than the methyl analogue, but the same pre cautions should be taken. Both sulphates should be stored in glass stoppered bottles sealed with paraffin wax, for they attack cork. 

CAUTION. Ethers that have been stored for long periods, particularly in partly-filled bottles, frequently contain small quantities of highly explosive peroxides. The presence of peroxides may be detected either by the per-chromic acid test of qualitative inorganic analysis (addition of an acidified solution of potassium dichromate) or by the liberation of iodine from acidified potassium iodide solution (compare Section 11,47,7). The peroxides are nonvolatile and may accumulate in the flask during the distillation of the ether the residue is explosive and may detonate, when distilled, with sufficient violence to shatter the apparatus and cause serious personal injury. If peroxides are found, they must first be removed by treatment with acidified ferrous sulphate solution (Section 11,47,7) or with sodium sulphite solution or with stannous chloride solution (Section VI, 12). The common extraction solvents diethyl ether and di-tso-propyl ether are particularly prone to the formation of peroxides. 

CAUTION. Acetals, like ethers, may contain explosive peroxides which must be removed before distillation is attempted. The procedure to be adopted is similar to that described under Ethers (see Section 111,60). 

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