Stackelberg

P. Halbach, G. Friedrich, and U. von Stackelberg, eds.. The Manganese Nodule Belt of the Pacific Ocean, Stuttgart, Ferdinand Enke Vedag, 1988. 

For a detailed account of the work on gas hydrates and references prior to 1925 the reader is referred to Schrdder s historical account of this subject,40 while later references are given in von Stackelberg s papers.4 49... 

The mechanism responsible for the formation of gas hydrates became clear when von Stackelberg and his school 42 49 in Bonn succeeded in determining the x-ray diffraction patterns of a number of gas hydrates and Claussen6 helped to formulate structural arrays fitting these patterns. Almost simultaneously Pauling and Marsh26 determined the crystal structure of chlorine hydrate. 

The unit cell of Structure I is illustrated in Fig. 2, taken from the paper by von Stackelberg and Muller.48 It contains 46 water molecules which enclose two types of cavities. The smaller cavities are... 

Fig. 2. Unit cell of a gas hydrate of Structure I according to von Stackelberg and Muller.48 For the sake of clarity only the elements lying in the nearer half of the unit cell have been drawn. The smaller dots indicate the tetrahedrally surrounded water molecules, the larger dots represent the centers of the two types of cavities.

The data in the table have been copied from the papers by von Stackelberg and Muller8, and von Stackelberg and Jahns,b except when otherwise indicated.)... 

According to von Stackelberg and Muller,48 the hydrates tabulated in the top section of Table I all crystallize in Structure I. 

From the condition 21a it immediately follows that if the clathrate is formed in the presence of a number of compounds which are potential solutes, i.e., sufficiently small to have 0 for some i, all these compounds contribute to its stability. As has already been pointed out by Barrer and Stuart4 this at once explains the stabilizing influence of "Hilfsgase" such as air, C02, or H2S on the formation of gas hydrates discussed by Villard49 and von Stackelberg and Meinhold.47 If there is only one solute, Eq. 21a with the = sign determines the minimum vapor pressure fiA necessary to make the clathrate stable relative to Qa. Since all cavities contribute to the stabilization, one cannot say that this minimum pressure is controlled by a specific type of cavity. 

Fig. 8. The system CHCla-HaS-HaO. The univariant equilibria of the single-component systems have been indicated by dotted lines, those of the binary systems by thin lines, and those of the ternary system by heavy lines. The latter are approximate only, except for the lower half of the four-phase line HnLxL%G measured by von Stackelberg and Friihbuss.4 ...

Figure 9 represents the system CC14-H2S-H20, where no hydrates occur in the binary system CC14-H20. In the ternary system von Stackelberg and Fruhbuss again determined the lower half of the four-phase line As the binary quadruple point... 

The difference in behavior reported by Von Stackelberg is not thought to be an essential one. Whether decomposition of a hydrate containing two solutes by removal of its vapor through pumping will be a univariant process depends on the number and compositions of the phases formed. In the system of Fig. 10, for instance, a mixed HtS-propane hydrate will exhibit a constant decomposition pressure on pumping at — 3°C if it contains HaS and propane in the azeotropic" ratio of approximately 3 1. 

The quantitative relations have been tested by Braun, by Stackelberg (1896), and by Cohen, Inouye, and Euwen (1911). 

All of the observed reflections could be indexed on the basis of a cubic unit cell with Oo = 11.82 A the estimated probable error is 0.01 A. The only systematic absences were hhl with l odd this is characteristic of the space group 0 -PmP>n, which also was reported by von Stackelberg from his single-crystal work on sulfur dioxide hydrate. For 46 H20 and 6 Cl2 in the unit cell the calculated density is 1.26 densities reported by various observers range from 1.23 to 1.29. 

In column IV there are listed the G2 values calculated from the parameters proposed by von Stackelberg. As an approximation to the configuration of the chlorine molecules spherical shells of uniform density were placed at the centers of the eight cavities formed by the oxygen atoms. It is seen that the calculated values are not compatible with... 

In June, 1951, a brief description of the present structure was communicated by letter to Prof. W. H. Rodebush and Dr. W. F. Claussen. The structure was then independently constructed by Dr. Claussen, who has published a note on it (J. Chem. Phys., 19, 1425 (1951)). Dr. Claussen has kindly informed us that the structure has also been discovered by H. R. Muller and M. v. Stackelberg,... 

Sta von Stackelberg, M. Polarographische Arbeitsmethoden, Berlin Walter de Gruyter Co., 1960. 

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