Roozeboom

As already remarked in the introduction, the formulation of the laws governing heterogeneous equilibria by Bakhuis Roozeboom1 was partly based on his studies on gas hydrates. Although the general laws he derived are certainly correct, and have marked an important step in the development of physical chemistry, Roozeboom and his contempories were mistaken in the nature of the phase diagram of gas hydrates gas hydrates are not stoichiometric... 

If a heterogeneous equilibrium is such that the pressure of the system depends on the temperature alone, and is unchanged when the phases alter in relative amount, it is called a completely heterogeneous equilibrium (Roozeboom), or an indifferent equilibrium (Duhem). 

Inside ABCD, the crystalline solid is stable, above ABC the liquid, whilst to the right of CD the stable form is the amorphous glass. Roozeboom, however, holds a different opinion as to the latter part of the curve Heterogene Gleichge-u ichte, vol. I.). 

Then from (4), (6), (11), and (12) we find Theorem II. Ij an isopiestic p + dp is drawn to cut the three curves of transition (or their prolongations) meeting at a triple point, the central point of section corresponds u-ith the transition involving the greatest change of entropy. This theorem is due to Roozeboom (1901). 

The triple point divides each of the curves of transition passing through it into two parts, one of which corresponds with a stable system, and the other with an unstable system. The discrimination between these is effected by means of two theorems due to Roozeboom (1887), which are analogous to the theorems of Moutier and of Robin, for two-phase systems ( 105). 

Roozeboom, 1901) that the system of two phases which corresponds with the transformation invoicing the greatest change of entropy is in stable equilibrium under pressures lying on one side of the triple point, while the other two systems are in stable equilibrium under pressures lying on the other side of the triple jwint. 

B. Roozeboom Heterogen. Gleichgewichte, I., 1901 P. Saurel, Journ. Phys. Chem, 1902 P. Duhem, Zeitschr. physik. Client., 8, 867, 1891 Gibbs, Scientif. Papers, I.)... 

The general theory was worked out by Roozeboom (Zeitschr. physik. Chem., 1899) from the standpoint of the theory of thermodynamic potential. The equations (2a, h), (3a, h) of the preceding section apply equally well to the present case, and details need not be given here. The liquid solidifies at a constant temperature when it has the same composition as the solid deposited— the so-called eutectic point. 

The curves of the hydrates of ferric chloride, investigated by Roozeboom, afford an excellent illustration of this type. 

From the shape of the maximum, some information can be obtained as to the extent of dissociation of the compound in the liquid state thus the maximum on the freezing-point curve of CaCl2 and H20 is very broad and flat, an indication of the almost complete dissociation of the compound CaCl2. 6HaO in the fused condition (Roozeboom and Aten, 1905 Kremann, 1906). 

Rajeshwar, K. Roozeboom, F. 2007. Gordon Moore and his legacy four decades and counting. Electrochem. Soc. Interface Spring ll-14. 

Figure la. Roozeboom s classification for the distribution of the ionic compounds AX and BX over the solid phase and the aqueous phase. 

Figure 2 compares the experimental data (8) with the provisional equilibrium compositions on a conventional Roozeboom diagram. It appears that equilibrium is most closely approached in the mid-range compositions, but compositions closer to the end-members KC1 and KBr deviate... 

Figure 2. Roozeboom diagram comparing experimental and provisional equilibrium compositions in the KCl-KBr-I O system at 25°C.

---