Pressure measurement, powder

Diammino-stannous Iodide, [Sn(NH3)2]I2, is obtained as a yellow powder by passing dry ammonia gas over anhydrous stannous iodide.2 By dissolving stannous iodide in liquid ammonia at a temperature of —78° C. a white crystalline substance separates containing ten molecules of ammonia. This, however, is not regarded as a definite compound, and from dissociation-pressure measurements it seems probable that pentammino-stannous iodide is the highest ammino-derivative which definitely exists. Diammino-stannous iodide, [Sn(NH3)2]I2, and monammino - stannous iodide, [Sn(NI-I3)]I2, arc coloured, the former yellow, the latter brown. The other ammines arc white. 

Fig. 2. Powder profile of solid C q at atmospheric pressure, measured on a diffractometer equipped with a position-sensitive detector (8) and a 1.5-kW sealed Cu source monochromatized by the (002) reflection of graphite (k = 1.54 A). The powder sample was containol in a Lindemann capillary tube (0.7 mm in diameter). Dots are the measured points (2 hours accumulation), and the solid curve is a least-squares fit to an fee lattice of uniform spherical shells. The best-fit parameters are a = 14.11 A and shell radius Rq = 3.5 A. This sample exhibits much less intensity in the low-angle shoulder of the (111) reflection.

The essential parts of a volumetric apparatus are a closed system of known volume, a source of adsorbate and a pressure measuring device. This type of apparatus is more commonly used for the determination of adsorption isotherms, but kinetics can be measured provided that the adsorbent surface is large and the response of the pressure measuring device is much faster than the rate of adsorption. These criteria are usually only satisfied by powders or films which show activated adsorptions. Bond has discussed the phenomenon of activated adsorption. Although the results may often be ascribed to contamination or incorporation into the bulk of the material, in other instances a genuine activated chemisorption is found. 

Powder neutron-diffraction data for BiF3 show eight-fold co-ordination for bismuth (Bi—F 2.217—2.502 A), but from a comparison with the isostructural YF3 it is clear that the lone pair is stereochemically active and occupies a ninth co-ordination position.778 New vapour-pressure measurements are now available for BiCl3 over the temperature range 151— 437 °C.779... 

N. N. Thadhani, R. A. Graham, T. Royal, E. Dunbar, M. U. Anderson, and G. T. Holman, Shock-induced chemical reactions in titanium-silicon powder mixtures of different morphologies time-resolved pressure measurements and materials analysis. J. Appl. Phys. 1997, 82, 1113-1128. 

Muller CR, Davidson JF, Dennis JS, Fennell PS, Gladden LF Oscillations in gas-fluidized beds ultra-fast magnetic resonance imaging and pressure sensor measurements. Powder Technol 177 87-98, 2007. 

As noted above, a combination of high pressure diamond anvil techniques, all utilizing the ruby fluorescence method of pressure measurement, were used to carry out these experiments. These include (1) Fourier transform infrared (FTIR) spectroscopy for the kinetic measurements [9-11], (2) energy dispersive x-ray powder diffraction for crystallographic identification of the observed polymorphic forms and also compression measurements [12], (3) optical polarizing microscopy... 

Where and Hp are the pressure measured in the manometers as shown. It should be noted that in the above equation there is no need to know the value of the viscosity of the fluid nor the exact value of the acceleration due to gravity in the laboratory where the experiments are being carried out. For a given flow meter and for a specific powder, the above equation reduces to the form... 

If the solid in question is available only as a finely divided powder, it may be compressed into a porous plug so that the capillary pressure required to pass a nonwetting liquid can be measured [117]. If the porous plug can be regarded as a bundle of capillaries of average radius r, then from the Laplace equation (II-7) it follows that... 

Microcapsules are used in several film coatings other than carbonless paper. Encapsulated Hquid crystal formulations coated on polyester film are used to produce a variety of display products including thermometers. Polyester film coated with capsules loaded with leuco dyes analogous to those used in carbonless copy paper is used as a means of measuring line and force pressures (79). Encapsulated deodorants that release their core contents as a function of moisture developed because of sweating represent another commercial appHcation. Microcapsules are incorporated in several cosmetic creams, powders, and cleansing products (80). 

In the static method the powder is isolated under high vacuum and surface gases driven off by heating the container. The container is next immersed in hquid nitrogen and known amounts of nitrogen vapor are admitted into the container at measured increasing pressures in the relative pressure range 0.05 to 0.35. 

In the dynamic method the powder is flushed with an inert gas during degassing, nitrogen is then adsorbed on the powder in a carrier of helium gas at known relative pressure while the powder is in a container surrounded by hquid nitrogen. The changing concentration of nitrogen is measured by a cahbrated conductivity cell so that the amount adsorbed can be determined. 

A powder s strength increases significantly with increasing previous compaction. The relationship between the unconfined yield stress/, or a powder s strength, and compaction pressure is described by the powder s flow function FE The flow function is the paramount characterization of powder strength and flow properties, and it is calculated from the yield loci determined from shear cell measurements. [Jenike, Storage and Flow of Solids, Univ. of Utah, Eng. Exp. Station Bulletin, no. 123, November (1964). See also Sec. 21 on storage bins, silos, and hoppers.]... 

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