Crystalline state percent crystallinity

The pentahalides of phosphorus, PX, in the gas phase exhibit varying tendencies to dissociate into trihaUde and halogen. InstabiUty increases with increasing ionic radius of the halogen. The pentafluoride appears to be thermally stable. Dissociation of the pentachloride, a few percent at 100°C and 101.3 kPa (1 atm), is essentially completed at 300°C (36). The pentabromide is partially dissociated in the Hquid state and totally dissociated above ca 35°C (39). Pentaiodide does not exist. The molecules of PF and PCl in the vapor phase are trigonal bipyramids. In the crystalline state, both pentachloride and pentabromide have ionic stmctures, ie, [PClJ IPClg] and [PBr4]" PBrJ , respectively. The PX" 4 cations are tetrahedral and the PX anion is octahedral (36,37). 

H is the heat given off by that part of the polymer sample which was already in the crystalline state before the polymer was heated above T. With this number H it is possible to figure out the percent crystallinity it is divided by the specific heat of melting, H, which is the amount of heat given off by a certain amount of the polymer. So the mass of crystalline material, m, follows as ... 

D-Mannose. —In contrast to the arabinoses and D-erythrose, the alkaline condensation reaction mixture of D-mannose and nitromethane in methanol remains heterogeneous throughout. However, visual inspection shows a moderately rapid replacement of the crystalline sugar in the insoluble phase by the amorphous sodium ocz-nitroalcohols. Both epimeric nitroalcohols are obtained in the crystalline state in a combined yield of approximately 55 percent. The separation of 1-nitro-... 

Molecules are never motionless. They are performing vibrations all the time. In addition, the gaseous molecules, and also the molecules in liquids, are performing rotational and translational motion as well. Molecular vibrations constitute relative displacements of the atomic nuclei with respect to their equilibrium positions and occur in all phases, including the crystalline state, and even at the lowest possible temperatures. The magnitude of molecular vibrations is relatively large, amounting to several percent of the intemuclear distances. Typically, there are about 1012-1014 vibrations per second. 

In the supercooled liquid state, BMGs have very high yield strength and a high elastic-strain limit (often exceeding 2 percent, compared with crystalline materials that are almost always less than 1 percent), which makes them very springy. However,... 

An alloy in the region ADBj such as that represented by the point P, at 35 atomic percent lead and 400° C, lies in a two-phase region, and the variance is accordingly stated by the phase rule to be two. The pressure and the temperature are the two variables the phase rule hence states that it is not possible to vary the composition of the phases present in the alloy. The phases are crystalline arsenic, represented by the point P directly to the left of P, and the molten alloy, with the composition P" directly to the right of P. The composition of the molten alloy in equilibrium with crystalline arsenic at 400° C and 1 atm pressure is definitely fixed at P" it cannot be varied. 

Ammonium sulfate (uh-MOH-ni-um SUL-fate) is an odorless, colorless to white crystalline solid that occurs in nature as the mineral mascagnite. In 2004, 2.6 million metric tons (2.9 million short tons) of the compound were produced in the United States, placing it in 21st place among chemicals made in that year. More than 95 percent of the ammonium sulfate produced is used in the production of fertilizers. 

Another use of Raman spectroscopy for quantitative analysis is the determination of percent crystallinity in polymers. Both the frequency and intensity of peaks can shift on going from the amorphous to the semicrystalline state for polymers. The percent crystallinity can be calculated with the help of chemometrics software. 

---