Hole-size rule

If the notion that 15-crown-5 is selective for Na" " is correct, then Ks for the interaction 15-crown-5 Na+ should be greater than the interaction 15-crown-5 K+. We see from Table I that log Ks for the sodium interaction is 3.24 (1,740) compared to 3.43 (2,690) for potassium. An alternate definition of Na+-selectivity might be that 15-crown-5 binds Na" " more strongly than 18-crown-6 binds Na" ". The log Ks values for this pair of interactions is, respectively, 3.24 (1,740) vs. 4.35 (22,400). Clearly, 15-crown-5 is not selective for Na" " and the simple "hole-size rule does not correctly account for the results. 

It is essential to ensure that the following criteria are met otherwise errors will result. First, the mouth of the hole inside the duct must be smooth and flush with the duct inner surface. No burrs or other irregularities must be on the surface in the vicinity of the hole. Second, the hole must be perpendicular to the tube axis. The size of the hole has an effect on the measured pressure as well. A general rule is, the smaller the hole the better. Very small holes do, however, slow down the response of the instrument. Usually the hole diameter is a few millimeters. Note also that the smaller the hole, the greater the risk of blockage. Further information on the effect of the hole size can be found, e.g., in Ower and Pankhurst. 

Veitch and Radoslovich [1963] postulate that there should be two distinct octahedral hole sizes for most layer silicates and that octahedral ordering should exist as a general rule. This is only partly true for the chlorites whose structures are known. The llb-2 prochlorite shows cation ordering within both octahedral sheets. The la-4 kammererite and llb-4 corundophilite structures are ordered within the interlayer only. 

Astronomical observations of star movements support the existence of black holes. For example, from movements of stars close to our galactic center, it is believed that a black hole is located at SgrA in the center of the Milky Way, with a mass > 3 x 10 Mq. The radius of such a hole would be of the same size as that of our sun. The density of matter in the hole would be several million times the density of our sun (average value for the sun is about 1400 kg/m ). Obviously matter cannot be in the same atomic state (i.e. nuclei surrounded by electrons) as we know on earth. Instead we must assume that the electron shells are partly crushed we refer to this as degenerate matter, because the electron quantum rules. Tables 11.1 -11.2, cannot be upheld. For completely crushed atoms, matter will mainly consist of compact nuclei. For example, for calcium the nuclear density is -2.5x10 7 kg/m (cf. Fig. 3.4). 

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