The Problems of Measurement

Metallurgists are included in the category for chemist in the 1970 Census. Since no separate estimate of the number of metallurgists in 1970 is available, the figures and the text discussion employ the composite total for chemists, assayers, and metallurgists for that year. In Appendix A, an attempt is made to eliminate metallurgists from the 1970 Census tabulation. 

On high school and university chemistry teachers, see the note to Table 2.1. 

To check the reliability of the findings, a variety of refinements or adjustments have been made wherever feasible. To the Census data for chemists in the labor force, for example, available estimates were added for chemistry faculty and for chemical engineers. The result of such changes is the more complex graph discussed in Appendix A.2. This Appendix reveals how efficacious the indicators approach can be, since the trends evident in the homogeneous time series are rarely altered significantly by such adjustments. 

Relative size of an occupational group is only one measure of the group s power and importance in society, but it is a significant measure. The growth curve for chemistry as occupation carries important implications for the chemical profession, for the social and economic resources available to sustain the intellectual work of chemistry as a scientific discipline, and for the meaning of chemistry as an instrument of socialization into, and as a facet of, American culture. 

85-124, and II, Harnett, 1975, 439-475, offer readable introductions to time series analysis, while II, Croxton et c/., 1967, 214-342, is a vade mecum of the art. For techniques of nonlinear least-squares estimation, only highly technical texts (such as II, Bard, 1974) are available. Derek de Solla Price has discussed the implications of exponential and logistic growth for the scientific enterprise in II, Price, 1963, esp. 20-32. For a stimulating apphcation of these concepts to the description of social change in general, see II, Hamblin et al, 1913. 

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Thus we are challenged by the problem of measuring a small signal against the background of one much stronger. The problem is usually solved by one of two means (a) lock-in-amplifier detection and (b) a boxcar type of detection (to some extent we can include double-input optical multichannel detection in this category). 

At this point, the problem of measurement of rancidity would appear to be relatively simple, in that one would merely determine the peroxide value at arbitrary intervals, and at a given point the sample would be considered rancid. This paper points out some of the difficulties involved in such a procedure from the standpoint of obtaining useful data. 

Thomas Edison was faced with the problem of measuring the electricity that each of his customers had used. His first solution was to use a zinc coulometer, an electrolytic cell in which the quantity of electricity is determined by measuring the mass of zinc deposited. Only some of the current used by the customer passed through the coulometer. (a) What mass of zinc would be deposited in 1 month (of 31 days) if... 

Few positive ion methods are generally applicable to the investigation of triradicals because of the problem of measuring ionization energies for di- and triradicals and... 

The problem of measuring small concentration of oxygen in a buffer gas can be solved by using the semiconductor sensor with a sensitive element consisting of a zinc oxide film immersed in a polar or, better, a protodonor liquid (see Section 3.4). 

Chapter 1 provided a general research area, where the problem of measuring safety pro-actively was identified in literature and in practice. This was done by sketching a recent accident and discussing how safety was measured in the past and currently. Moreover, it highlighted that the pro-active measurement of safety is still a problem in the chemical process industry. The development of substantially more understanding of how to pro-actively indicate accidents in the chemical process industry, was finally derived as the scope of this study and will be discussed in the remaining Chapters of this thesis. 

In this chapter, the data reconciliation problem for dynamic/quasi-steady-state evolving processes is considered. The problem of measurement bias is extended to consider dynamic situations. Finally in this chapter, an alternative approach for nonlinear dynamic data reconciliation using nonlinear programming techniques will be discussed. 

The problem of measuring the thermodynamic properties of aqueous transition metal ions above 100 C has also received some attention with studies on Fe + complexing with Cl (46), Br (47) and SO - (48) up to 150°C and the formation of anionic hydroxy complexes of Pb2+ up to 300°C (49). 

In order to properly address the problem of measuring intensities with minimum dynamical dififaction contributions we used the technique where the electron beam is precessed by means of beam tilt coils in the TEM. These coils are situated before the sample in combination with a similar precession of the ED pattern via deflection coils below the sample. ... 

Calorimetry requires large areas of interface, which virtually demands powdered solids. We have not considered (yet) the problem of measuring 0 and dd/dT for powders. Solids that are available as large specimens with smooth surfaces (suitable,... 

Later in this chapter we shall consider the experimental methods of detecting reactions like 3.11 and 3.12 and the problem of measurement of their equilibrium constants. 

Acid-base reactions have long served as a starting point for consideration of the effects of changes in a structure on the course of chemical reactions. Table 3.2 summarizes solution data for a variety of Bronsted acids and bases because of the problems of measurement, any such table necessarily contains a fair amount of uncertainty. The pKa values that fall between 2 and 10 may be used with considerable confidence, since they are based on accurate measurements in dilute aqueous solutions the values outside this range must be regarded with a certain amount of skepticism. As we have noted in the two previous sections, uncertainties... 

Considering that the current in a typical laboratory cell is in the mA-to-A range and that the resistance in non-aqueous solvents may easily amount to several hundred ohms, the iRs drop can reach several volts it follows that A V cannot be directly related to A E. However, we are usually concerned only with the potential of the electrode at which the conversion of interest takes place, i.e. the anode in oxidations and the cathode in reductions. This electrode is referred to as the working electrode and the other as the counter electrode. The solution to the problem of measuring the potential of the working electrode is to introduce a third electrode, a reference electrode, and then measure the potential of the working electrode relative to that of the reference electrode in a separate measurement in which very little or no current flows (see Section 6.4.5). 

The symposium upon which this book is based was organized by the Pesticide Chemistry Division to address the problem of exposure to pesticides. The choice of location of the symposium was the ACS National Meeting initially planned for San Francisco, California in August 1980, which was appropriate in view of the considerable agricultural interest within the state. The major concerns were the problems of measurement, monitoring, and safety in relation to the question of worker exposure and its many implications. 

In the previous chapter, the fact that stoichiometric and apparent constants have been widely used in seawater systems was discussed. Berner (1976) reviewed the problems of measuring calcite solubility in seawater, and it is these problems, in part, that have led to the use of apparent constants for calcite and aragonite. The most difficult problem is that while the solubility of pure calcite is sought in experimental seawater solutions, extensive magnesium coprecipitation can occur producing a magnesian calcite. The magnesian calcite should have a solubility different from that of pure calcite. Thus, it is not possible to measure pure calcite solubility directly in seawater. 

Example 10 illustrates how thermochemical data for aqueous ions may be obtained from measurements in electrochemical cells. The problem of measuring cell potentials in the standard state, which is a hypothetical state, will be discussed in section 10.12. The temperature variation of the voltage of such cells would provide AHJ of aqueous ions, through the use of Eq. (48). 

By introducing another electrochemical interface, it would seem that the problem of measurement has been doubled. In fact, if the additional interface is at thermodynamic equilibrium, then the practical problem of measurement is solved. By maintaining a reaction in equilibrium at the interface, the potential across it is constant (and calculable). Thus any changes in the measurement of the potential between the two interfaces can be attributed to the electrode of interest (typically referred to as the working electrode). 

The Problems of Measuring Hydrogen-Bond Lengths and Angles... 

Approaching the problem of measurement of high temperature in a gas from the statistical standpoint, we can calculate theoretically several temperatures (where temperature is defined as a measure of broadness of a distribution) depending upon how the energy is distributed in the gas. The energy modes available in a molecular gas are translational, rotational, vibrational, and electron-excitational, and before attempting a description of temperature measurements, it will be necessary to define, and point out the interrelations between these energies. 

The capillary format of SFC is attractive because of the potential of interfacing with a wide array of detectors available when carbon dioxide is used as the mobile phase. Several advances, beyond the issue of mobile-phase polarity, are, however, required prior to the technique becoming viable for pharmaceutical analyses. Capillary SFC instrumentation has lacked the requisite analytical performance for pharmaceutical analyses, and difficulties are encountered due to the acidic nature of fused silica and the problem of measuring impurities while, at the same time, not overloading the stationary phase with the main component. ... 

The quantum efficiency (p defined as the ratio of the number of electrons transferred across the interface, and of the number of photons absorbed by the adsorbed dye layer, is not easy to determine. This is on account of the problems of measuring the light absorption by one monolayer or separating it from the absorption by the dye solution. Therefore, many scientists prefer to give values of a quantum yield, defined as the number of injected electrons per incident photons which is easy to measure. These two quantum yields are related by the equation... 

The calculation of the absorption factor in practice demands use of a computer with a sophisticated program and requires also accurate knowledge of the shape and dimensions of the crystal specimen. The problem of measuring the shape and dimensions of an object as small as a diffraction specimen with sufficient accuracy is by no means trivial, and some workers prefer to retain the simple parallelepipedal habit possessed by some specimens naturally, rather than to grind the crystal to a somewhat rough sphere with a somewhat ill-defined radius. The problem of measurement is especially severe for chips or fragments... 

The problem of measuring the emf produced by centrifugal action was first successfully solved by Tolman (loc at) The success depended essentially upon the mechanical arrangements whereby very high rotation frequency could be realised without undue introduction of extraneous effects which would influence the observations For the details of the expenmental arrangement the original paper must be consulted. It is proposed only to summarise here the results... 

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