A Challenging Balance

In 1995 an article by Stout [10] on a chemical equation that is difficult or incredibly challenging to balance appeared. This article caused a series of subsequent 

Because essentially everything that can be said has been said, I am declaring a moratorium 

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True sizing from scratch is impractical since a pressure balance on a channel-to-cnannel basis, from channel closest to inlet to furthest, must be achieved and when mixed plate angles are used this is quite a challenge. Computer sizing is not just a benefit, it is a necessity for supplier s selection. Averaging methods are recommended to perform any sizing calculations. 

Reliable mechanistic conclusions require high intrazeolite yields that account for the majority of the substrate mass balance. This can be a challenge because of the small-scale reactions often conducted for mechanistic studies. In addition, rapid removal of the products from the zeolite, and/or low conversions to decrease residence time, is occasionally necessary because of the sensitivity of the reaction products to the zeolite environment.44,45 Intrazeolite products are generally recovered by extractive techniques from either the intact zeolite, or from a mixture formed after mild digestion of the zeolite. Polar solvents such as tetrahydrofuran or acetonitrile coupled with a continuous extraction technique is in particular an effective means to remove polar products with an affinity for the interior of the zeolite.44 Zeolite digestion with mineral acids, in order to liberate the products, must be conducted with care in order to prevent acid catalyzed product decomposition or reaction.46,47... 

How to balance Nafion ionomer contenf and Pf/C loading is a challenge for optimizing CL performance, due to fhe complexity induced by proton and electron conduction, reactant and product mass transport, as well as electrochemical reactions within the CL. The optimization of such a complex system is mainly implemented through multiple components and scale modeling, in combination with experimental validation. 

Take several minutes and try to balance this equation the multitude of elements involved makes it a challenging exercise. 

The generation of an intense, deep-blue flame represents the ultimate challenge to the pyrotechnic chemist. A delicate balance of temperature and molecular behavior is required to obtain a good blue, but it can be done if the conditions are right. 

The production of a vividly-colored flame is a much more challenging problem than creating white light. A delicate balance of factors is required to obtain a satisfactory effect... 

Achieving a balanced presentation in limited space has presented the writer with a challenge. The constructive suggestions of referees has helped to achieve this goal. 

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