Rule of Constant Proportions

This constancy in relative ion concentration was first postulated by Alexander Marcet in 1819 and, hence, is known as Marcet s Principle or the Rule of Constant Proportions. Formally stated, it says that regardless of how the salinity may vary from place to place, the ratios between the amounts of the major ions in the waters of the open ocean are nearly constant. ... 

As noted earlier and shown in Table 3.9, small deviations in the proportions of the major ions have been observed particularly in coastal and pore waters. Reasons for these exceptions to the rule of constant proportions are described briefly next and addressed at length in later chapters. 

Small amounts of salt are commonly occluded in sea ice. Not all of the ions are incorporated to the same degree. This alters the ion ratios in the remaining brine, leading to deviations from the Rule of Constant Proportions during freezing. Likewise, meltwater from sea ice can contain ions in ratios that deviate from average open ocean water. 

The precipitation sequence presented in Figure 17.1 is a function of temperature and the extent to which equilibriiun is maintained with the increasingly saltier brine. Each of these precipitations alters the ion ratios in the remaining seawater. Since the rule of constant proportions is violated, density, rather than salinity, is used to monitor the increasing saltiness of the brine. 

Rule of Constant Proportions The relative abundances of the six major cations (Na, K, Ca, Mg CF, and SO ) is constant regardless of the salinity of seawater. 

The relative constancy of major (and many minor) elements in seawater is referred to as the rule of constant proportions or Marcet s principle. These elements are considered to be conservative elements, whereby changes in their concentrations reflect the addition or loss of water through physical processes. The remaining elements in seawater are termed nonconservative because they remain in constant proportion due to biological or chemical processes. 

Rule of constant proportions constituents of seawater are found in relatively constant proportions in the oceans, indicating that the residence times of these elements are long (thousand to millions of years)—highly indicative of nonreactive behavior. This is the same as Marcet s principle... 

Berthollet s theory actually challenged Proust s basic rule of definite proportion, which was the cause of the debate, but the empirical evidence of both sides was inadequate to resolve the dispute. The controversy was more important by what it suggested than by what it accomplished. Henceforth, it became imperative to seek a clear understanding of the causes underlying the apparent fact of constant proportions. ... 

On this view, the most basic laws are those that state the existence of particular substances and their properties, that is the reproducible identification and synthesis of substances and the reproducible measurement of their properties. The well-known laws of chemistry are impacked in terms of a mix of following rules or norms. Proust s experiments in support of the law of constant proportions already presuppose this law [Psarros, 1994]. In order for a transformation to qualify as a chemical reaction, the mass of the reaction products must equal the mass of the raw materials. It must be possible to isolate the products of a transformation as pure chemical substances with constant composition. These norms regulate practice, somewhat similarly to the way conservation laws regulate physical practice. If practice seems to go against the norm, it is assumed that something has been overlooked or should be fitted in elsewhere (as happened with radioactivity). 

Generally, it can be said that the damaging effect of a shockwave produced by a detonation is proportional to its impulse (impulse = mass x velocity of the gaseous explosion products) and its maximum pressure, with the impulse being the most influential factor at smaller distances and the pressure being most important at larger distances. As a rule of thumb , the distance D, which offers a chance of survival, is proportional to the cube route of the mass w of an explosive, while for typical secondary explosives at larger distances, the proportionality constant is approximately 2 ... 

As a rule of thumb, the product water flow with constant net applied pressure will increase about 3% for each degree centigrade increase in feedwater temperature. Salt flux through the membrane is also directly proportional to temperature and the ratio of salt flux to water flux is essentially constant at different temperatures. This results in little or no change in rejection as a function of... 

The basis of chemistry as it grew up in the nineteenth century is Dalton s atomic theory. In this the intuitive idea of ultimate particles is applied to explain definite quantitative laws of chemical composition, those, namely, of constant, multiple, and reciprocal proportions. These rules could only have emerged after a long empirical study... 

The amount of free moisture in a substance greatly affects its dielectric constant since water has a high dielectric constant, approximately 78 at room temperature that of base materials is of the order of 2. Thus, with a larger percentage of water, the dielectric constant generally increases, usually proportionally. It should be emphasized that very complex phenomena occur when different dielectrics are mixed. However, a few rules of thumb may be applied ... 

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