Boxing procedure

As computer programs evolve they become easier to use. Modem programs often communicate with the user in terms of a graphical interface, and many methods have become essential black box procedures if you can draw the molecule, you can also do the calculation. This effectively means that you no longer have to be a highly trained theoretician to run even quite sophisticated calculations. 

Dry-box procedures are often simpler than vacuum-line techniques. 

The all-dry box procedures resulted in another interesting visual effect. By controlling the solvent removal step that is, how long a vacuum was applied to the polymerization vessel, the location of the polyacetylene within the membrane structure could be regulated. For example, sandwich structures could be created by immediately applying a vacuum to a membrane sample wet with catalyst solution. This technique caused the solution to move into the center of the membrane s cross section thus polyacetylene formed only in the center of the cross section as well. The presence of polyacetylene, then, was hidden by the membrane s surface. Consequently, the surface of the membrane appeared almost white when dry (opaque) but instantly turned very dark when wet with solvent (transparent - polyacetylene then could be seen). Upon drying, the membrane again turned white. The phenomenon could be observed countless times with the same sample. 

Clearly the DIM approach will become increasingly important for the calculation of potential surfaces, especially those for chemical reactions. However, it must be used with caution quantitative features are certainly very sensitive to poor input data. On the other hand, the use of experimental diatomic potentials does not ensure qualitatively correct surfaces if sufficiently careful analysis of the nature of the bonding and of the important structures has not been performed. The use of DIM as a black-box procedure is certainly not to be recommended. 

The major concern in the preparation and study of alkalides and electrides is their extreme sensitivity to air, moisture, and especially elevated temperatures. Thus, ordinary glove box procedures do not suffice without provision to keep the samples cold (below about — 40°C) at all times during and after synthesis. It should be noted. 

Furthermore, since impurities in the monomer feed can limit molecular weight, monomers must be highly pure and great care must be taken to use dry glassware and glove box procedures when setting up a polymerization run. Additionally, the formed crude polymer, especially poly(p-dioxanone) and its copolymers, will contain unreacted monomer in amounts typically greater than 1 %. Vacuum or other extraction techniques must be utilized to remove residual monomer and catalyst in order to obtain polymers with optimized properties. 

M. Guerra,/. Phys. Chem., 94, 8542-8547 (1990). Boxing Procedure for Estimating Shape Resonance Energies from Stabilization Graphs with the MSXa Method. 

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