Rhombic-pyramidal

Succinic acid is absorbed from aqueous solutions by anion-exchange resins or active carbon (9—11). Succinic anhydride forms rhombic pyramidal or bipyramidal crystals. It is relatively insoluble in ether, but soluble in boiling chloroform and ethyl acetate. Succinic anhydride reacts with water and alcohols, giving the acid and monoesters, respectively. 

Intermediate spin occurs mainly for square- and rhombic-pyramidal five-coordinate iron complexes and also for planar four-coordinate and for asymmetric six-coordinate... 

Basic Tellurium Nitrate, Te203(0H)N03, which has already been mentioned (p. 379), is formed when a solution of tellurium or tellurium dioxide in nitric acid is evaporated without excessive heating.6 It crystallises in rhombic pyramidal crystals (a b c=0-590 1 0-607).7... 

Figure 2-32. Two crystals from Groth s Chemische Kristallographie [38], (a) Centrosymmetric rhombic bipyramidal acetanilide (b) Noncentrosymmetric rhombic pyramidal p-chloroacetanilide.

Tin trimethyl suiphate crystallises in brilliant rhombic pyramids, for which a b c =0-8872 1 l-OSSS. ... 

Figure 2-42. Crystals rn)tii Groth s Chemisclw Krishillograp/iie 2-3.1 (al Conirosyinmccric rhonihit bipyramiital acetanilide (b) noncentrosyminetrie rhombic pyramidal p-ehioro-acelanilide.

Wiede, K. A. Hofmann and H. Hiendlmaier, E. H. Eiesenfeld and co-workers, A. Werner, and A. Wesch prepared chromium triamminotetroxide, Cr04.3NH3, as previously indicated. The salt appears in brown, doubly refracting prisms when rapidly cooled, the hot soln. furnishes rectangular plates. 0. Wiede reported the axial ratios of the rhombic, pyramidal crystals to be a h c=l 0076 1 1 308. 

For structural materials, the hardness is coimected with the wear and abrasion resistance, which is why it might be useful for research and lab testing. Rockwell and Brinell hardness values are not used for the characterization of ceramics. The hardness values, determined by Vickers (square pyramid), Knoop (rhombic pyramid), and Berkovich (triangle pyramid) indenters, which have physical values, have a dimension of gigapascals (GPa) and may be used for the characterization of ceramics and refractories. 

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