True solute rejection

We always had to use additional criteria. As we observed, it is a better criterion to estimate the quality of a fit by the human eye, than by the -value. By inspecting the fits we can usually reject some phase combinations for their poor correspondence with the experimental intensity, the number depending on the quality of the intensity measurement. In order to find out the true solution out of the remaining phase combinations, the following methods seem to be useful ... 

From the list of space groups in Table 24 it follows that hexahelicene crystals are apparently chiral. This is also true for crystals of hexahelicene grown from racemic solutions. However, dissolved single crystals of [6] display optical rotations which show only about 2 % enantiomeric excess instead of 100 %. Solid solutions are unlikely in this case (m.p. racemate 231-233°, optically pure [6] 265-267 °C) and ordinary twinning can also be rejected. 

We would most earnestly advise the student to bend his mind first toward the solution of Sulphur, for it is less veiled, and much more clearly expounded than Mercury and once IT is discovered, it becomes a most valuable key, being, of course, invaluable in the work of the Stone. If you try common sulphur, you will find it insoluble, and it might as well be rejected first as last, for it is really NOT true Sulphur at all, but only a crude mineral to which the blundering chemists of the early centuries attached the name of "sulphur," which it has borne ever since. It is not our "divine catholic water," our "Holy Water" from the Virgin Spring, which alone is rich in pure sulphur or sun-fire. 

Scaled membranes exhibit lower productivity and lower salt rejection. This lower salt rejection is a function of the concentration polarization phenomenon (see Chapter 3.4). When membranes are scaled, the surface of the membrane has a higher concentration of solutes than in the bulk solution. Since the membrane rejects when the membrane "sees," the passage of salts will be higher, even though the absolute or true rejection stays constant. 

Prior knowledge is available before the experiment. There is almost always some information available about chemical data. An example is that a true spectrum will always be positive we can reject statistical solutions that result in negative intensities. Sometimes much more detailed information such as lineshapes or compound concentrations is known. 

Brandt classed mercury, antimony, bismuth, cobalt, arsenic and zinc as semi-metals, rejecting cinnabar, vitriols, etc., from this class. He considered that true metals solidify from fusion with a convex surface. The semi-metals have a metallic appearance but are brittle under the hammer. He describes metallic zinc spiauter, conterfeth) from the East Indies, Rammelsberg, and Dalecarlia and Rattwick in Sweden, as a semi-metal. Blende is an ore of zinc and white vitriol is a compound of zinc, since it can be prepared by dissolving zinc in sulphuric acid, and if the solution of white vitriol is precipitated with alkali and the precipitate (zinc carbonate) heated with copper and charcoal, brass is produced. 

This relation is identical to equation (6.3.142b) however, if the ratio [Cip/Cub] is greater than 1, as is true here (which is exacdy the reverse of what happens in RO and UF, where the solute is rejected by the membrane), we have severe concentration polarization when ka vz -For example, suppose vz /ku) l, and the membrane is such that (Cip/C i) is, say, 1000. Then, rewriting equation (6.3.190c) as... 

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