Early concepts

The problem of how to determine the mass fraction of salts (S ) in seawater quickly and with sufficient accuracy (10 kg/m for derived density) has occupied oceanographers over the last century and led to three definitions of saUnity (5) that approximate Sa These have been reviewed thoroughly by Lewis (1980) and by Fofonoff (1985), and will be briefly outlined in this and the next section. 

Based on the relatively constant comjxjsition of the bulk of seasalts, Knudsen and co-workers Forch et al, 1902) suggested salinity, S%o, to be determined from the titration of chlorinity with silver nitrate using Mohr s (1856) method as 

To derive Eq. (3-1), Knudsen and co-workers mainly used samples from the Baltic and from the Mediterranean and the Red Sea. The offset of 0.03 in Eq. (3-1) reflects that the salt composition especially in the Baltic Sea is not exactly constant (Millero and Kremling, 1976) and thus contradicts the basic assumption of constancy that led to Eq. (3-1). However, the proposed titration method also had advantages it could be performed in reasonable time onboard a ship, and for salinity measurements in open ocean areas where S is close to 35 %o, the error induced by the non-constancy is less than that from titration (0.02 %o in salinity). Therefore, the so-called Mohr-Knudsen titration method (Mohr, 1856 see Chapter 11) and the Knudsen formula (3-1) served oceanographers for more than 60 years to determine salinity from chlorinity. 

To achieve the accuracy of 0.02 %o in salinity for a single determination with the above method, and also to make salinity determinations from different institutions comparable, Knudsen required frequent comparison with an internationally accepted standard of known chlorinity. On behalf of the International Council for the Exploration of the Sea (ICES), standard seawater (SSW), later often called Copenhagen Water as it was prepared in Copenhagen for a long time, served this purpose. Each batch was numbered and distributed to oceanographers in sealed ampoules with the chlorinity indicated. For a detailed description of the history of standard seawater see Culkin and Smed (1979). 

In the early 1960s, bench salinometers were developed that allowed measurement of the electrical conductivity of a seawater sample relative to that of a standard with high precision. Cox et al. (1967) had related chlorinity and conductivity ratios of seawater to standard seawater at temperatures higher than 10 °C and tabulated their results (UNESCO, 1966). Following their work, the responsible international oceanographic organizations adopted a redefinition of salinity (Wooster et al, 1969). Firstly, it was assumed that salinity was proportional to chlorinity, to be consistent with the assumed constancy of the ionic composition. The constant was chosen so that for 5=35 %o, both the Knudsen formula (3-1) and the new relationship 

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The early concept was that these were values which must not be exceeded in other words, they were truly maximum values. As the understanding of limits and the development of the philosophy for such limits grew, it was realized that short-term exposures to somewhat higher concentrations could be permitted without undue harm if the total exposure during the day was sufficiently below the maximum limit. This led to the development of the concept of Threshold Limit Values (TLV s) by the ACGIH. 

Early concepts of the composition of mixed acids were described in Section II. More recent concepts are best summarized by the following equilibria ... 

An early concept of the cycle of thermodynamic processes as relating to steam engine heat-energy performance. 

Tea oxidation is generally referred to as fermentation because of the erroneous early conception of black tea production as a microbial process.66 Not until 1901 was there recognition of the process as one dependent on an enzymically catalyzed oxidation.67 This step and further reactions result in the conversion of the colorless flavanols to a complex mixture of orange-yellow to red-brown substances and an increase in the amount and variety of volatile compounds. Extract of oxidized leaf is amber-colored and less astringent than the light yellow-green extract of fresh leaf and the flavor profile is considerably more complex. 

In recent years, the utility of in vitro inhibition data to predict in vivo DDI was demonstrated. The underlying principles for this approach had been known for many years [99], but demonstration that these early concepts could be used practically in the prediction of clinical DDI was only obtained over the past few years. The principles can be applied for new compounds as the potential perpetrator of an interaction as well as the potential victim. The equation described by Rowland and Matin [99] forms the basis of this approach ... 

Early Concepts for Micro Structured Reactor Plant Design... 

We have given kinetic insight into a number of experimental features of the Soai reaction. It was shown that chiral amplification and mirror-symmetry breaking are driven by a reaction network that contains enantioselective autocatalysis and mutual inhibition as the essential ingredients. In this sense, the Soai reaction moves the early concepts of Frank forward into experimental reality. Taking into account the formation of isopropylzinc alkoxide dimers, an evaluation of the parameter space in which amplification and symmetrybreaking are observed indicates that the heterochiral dimers display a higher thermodynamic stability and have to be formed faster than the homochiral ones. The necessity of such sensitive interplay may explain why such reactions systems are so scarce. 

Which of the following is generally credited with developing the early concept of the dose-response relationship ... 

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