**3.4. Summary**

*3.3.7. Liquid alcanes*

methane to eicosane by the formula

of hydrogen atoms with one atom of carbon.

126 Solar Cells - New Approaches and Reviews

must be calculated by the formula

molecule and hydrogen environment of the carbon atom.

We calculate the density of a standard amount of substance in a series of liquid alkanes from

**Figure 6.** A change of density of amount of matter in series of liquid alkanes from methane to eicosane as a function of reciprocal mass of mole of molecules. The lower curve corresponds to the specification of the structural element of a liquid substance in the form of molecule, straight lines and points 1, 2 correspond to the specification in form of groups

σ0=ρ/ M<sup>0</sup>

where ρ is the density of the fluid, M<sup>0</sup> is the mass of the mole of molecules. The dependence of the density of the amount of liquid alkanes on chemical composition is presented in Fig. 6 as a function σ<sup>0</sup> from the reciprocal mass of mole of molecules M0. It is seen that σ0 decreases in a series of alkanes from methane to eicosane, and the nonlinearity of the function is explained by the different densities of alkanes, which depends on the length of the carbon chain of the

Remember that on the Butlerov's theory properties of organic compounds are sufficiently determined by the number and spatial position of carbon atoms in the chain of the molecule. So we give up on the structural element of liquid alkanes in the form of molecules and choose the structural element of a liquid substance in a series of alkanes in the form of groups of hydrogen atoms with one atom of carbon. In this case, the density of the amount of substance

σn= nρ/ M0,

where n is the number of carbon atoms in the molecule. Function σ n-1/ M0 is also presented in Fig. 6. In this case this function is linear and is explained by features of building a carbon The diversity of the aggregate state and structural bodies are shown in the diagrams called "state diagrams" for one-, two-, and three-component systems. Phase boundaries are depicted graphically in the coordinates of temperature and pressure, temperature and composition. We have shown above that the intersection of the phase boundaries is accompanied by changes in the amount of substance under given mass of this substance. Therefore, the authors of this Chapter argue that *the amount of substance is a function of temperature, pressure and composition.*

Presented here and previously received the knowledge of the amount of substance [42, 43, 51] corresponds to the resolution of XXIV the General conference on weights and measures, which proposes in future to link determinations of theamount and mass of the substance [22].
