Content formula

Therefore, on a given level, every substance can be assigned a content formula... 

The granite pictured above may serve as an example for a petrographical content formula ... 

Just giving the type and proportion of the constituents is often not sufficient to describe a substance completely. More characteristics are necessary. In addition, the spatial arrangement of the atoms of the basic substances is important. In chemical formulas this stmcture is often indicated by dashes, brackets, etc., or by a particular grouping of element symbols. The pair made of ammcmium cyanate and urea (carbamide) (Fig. 1.1) is an example. Both of these substances have the same content formula, CH4ON2, but their structural formulas differ. This is called structural isomerism. 

There is a substance appearing in the formulas for metals whose composition carmot be expressed by the chemical elements the electrons e. One must therefore introduce a new basic substance. The most obvious candidate would be the electrons themselves. Consequently, negative ions like chloride ions or phosphate ions would obtain the content formulas... 

The concept of basic substances and material coordinate systems is used for making order of the great multitude of substances. It is only possible to make quantitative descriptions of transformation processes by use of content formulas. 

In Sect. 1.2, we saw that the multitude of substances can be understood as combinations of relatively few basic substances, where the ratio is quantitatively expressed by the content formula. In chemistry, we have seen that chemical elements play the role of basic substances and when indicated, electrons e, if the totality of ions is considered a charged substance. 

Note that the index for B is arbitrary, while the content numbers in the content formulas are well defined. In the case of the variable B, we use another font in order to avoid confusion but also because we use B as well as B for other purposes. 

A symbolic 0 appears on the left that does not actually represent the number 0, but a substance represented by a content formula in which all content numbers disappear. If we consider the substances to be numbered as discussed above, the expression can be written more compactly using the summation operator Y.-... 

As was mentioned earlier, the strength of the inherent tendency to transform, and with it the numerical value of p, fundamentally depends upon the nature of the substance. In this context, we see the nature of a substance being determined by its chemical composition, characterized by its content formula, but also by its state of aggregation, its crystalline stmcture, etc. Hence, liquid water and water vapor as well as diamond and graphite will exhibit different chemical potentials under otherwise identical conditions and therefore need to be treated as different substances. In addition, the strength of the tendency to transform also depends upon the milieu in which the substance is located. By milieu we mean the totality of parameters such as temperature T, pressure p, concentration c, the type of solvent S, type and proportions of constituents of a mixmre, etc., which are necessary to clearly characterize the environment of B. In order to express these relations, we may write... 

N appears two times oti the left as well as on the right side of the conversion formula H, however, appears six times. Therefore, if the chemical potential of a substance is increased by a fixed, although arbitrary summand (say 1,000 kG, as shown above in the third line) for every H appearing in its content formula, this added value cancels when we compute the potential difference and we end up with the same result as in the second line above. The same holds for nitrogen. This means that the reference level for any element could in principle be chosen arbitrarily as mentioned earlier. For the sake of simplicity, the value 0 is assigned to the chemical potential of all elements. 

Processes of this type can be discussed in the same way as chemical reactions. The constituents of the mixture assume the role of elements as basic substances whose amounts are conserved during transformation (see Sect. 1.2). The homogeneous and heterogeneous mixtures themselves, however, correspond to chemical compounds. Therefore, the composition of these mixtures can be given by a content formula but with the peculiarity that the content numbers are not necessarily integer... 

Some tips The element symbols in the content formulas are arranged in the following sequence (with decreasing rank) ... 

Fluorine content Formula weight Hydroxyl number Melting point Moisture content Purity... 

In the following index the compounds are listed by their empirical formulas in the order of increasing carbon content. Formulas of ionic compounds are given in brackets ions as well as components of solvates and adducts are separated by a period. 

Figure 2 shows the flavor notes in the middle of picture that each of the flavors (Formulas) included 5 volatile compounds in the right (with different proportions in Table 2). The customer groups in the left can select the contentment formula that has difference compounds. This model looks like networks that have complex... 

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