Ketelaar

The crystal structure of NaZn13 and of several homologous compounds AB13 was repotted by Ketelaar and by Zintl Hauke to be based on space group 0 -Fm3c, with 8 Na in 8(a) ... 

Some years ago Ketelaar (1937) reported a tentative structure for NaZn13 and five other AB13 compounds (KZn13, KCd13, CaZn13, SrZn13, and BaZn13). Zintl ... 

Zintl Hauke cited no limits of error, but Ketelaar cited an uncertainty of 0-005 A for a0 and an uncertainty of 0-003 in y and z. From comparisons among the intensities obtained for the five compounds that they investigated, Zintl Hauke concluded that the y and z parameters are substantially the same for all five. 

Table 1 Compound. Parameters obtained in previous work on compounds of type AB13 Ketelaar Zintl Hauke ...

In Fig. 2 conditions (11) and (12) are plotted on a parameter map together with the parameter values reported for NaZn13 by Zintl Hauke, those reported for KCd13 by Ketelaar, and those determined for NaZn13 in the present investigation. The uncertainties are indicated by the radii of circles drawn around the points determined by the parameter values since Zintl Hauke reported no uncertainty value, the uncertainty reported by Ketelaar (0-003) was assumed. It is seen that the parameter values obtained in the present work lie between those of Zintl Hauke and those of Ketelaar, and that they differ considerably from the values required either by a regular icosahedron or by a regular snub cube. 

The brittleness of these intermetallic compounds suggests an electronic structure involving a filled Brillouin zone. It was pointed out by Ketelaar (1937) that the strongest reflection, that of form 531, corresponds to a Brillouin polyhedron for which the inscribed sphere has a volume of 217 electrons per unit cube, which agrees well with the value 216 calculated on the assumption that the sodium atom is univalent and the zinc atoms are bivalent that is, calculated in the usual Hume-Rothery way. It has also been... 

Lagaveen RG, Huisman GW, Preusting H, Ketelaar P, Eggink G, Witholt B (1988) Appl Environ Microbiol 54 2924... 

The rather complex structure of the compound NaZn13 was studied by Ketelaar (1937) and by Zintl and Haucke (1938). Every Na atoms is surrounded by 24 Zn atoms at the same distance. The lattice parameters of several MeZn13 compounds pertaining to this structural type are, in a first approximation, independent of the size of the alkali (or alkaline earth) metal atom. Similar consideration may be made for the MeCd13 compounds. Zintl, therefore, considered the fundamental component of this crystal structure to be a framework of Zn (or Cd) atoms with the alkali (or alkaline earth) metal atoms occupying the holes of the framework. However notice (Nevitt 1967) that in compounds MeX13 radius ratios (rMe/rx) deviating by more than about 15% from the mean value 1.54 are unfavourable for the occurrence of the structure. 

To determine the basicity order, complexes with SOg (Booth et al., 1959) and with I2 (Ketelaar, 1954 Ketelaar et al., 1952 Traynham and Olechowski, 1959) as acceptors have been investigated. 

Since these early X-ray diffraction experiments, several other crystals have been subjected to analysis by X-ray and neutron diffraction and the F bond length has remained virtually unchanged. The location of the proton has been the point at issue. Early ir studies on KHF2 were interpreted as evidence for a double minimum potential well (Ketelaar, 1941 Glocker and Evans, 1942), but later studies questioned this (Pitzer and Westrum, 1947 Cote and Thompson, 1951 Newman and Badger, 1951) and led to a revision of earlier opinions (Ketelaar and Vedder, 1951). 

Chemical/Physical. Tetraethyl pyrophosphate is quickly hydrolyzed by water forming pyrophosphoric acid (NIOSH, 1997). The reported hydrolysis half-life at 25 °C and pH 7 is 7.5 h (Ketelaar and Bloksma, 1948 Coates, 1949). 

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