Crystal tests

The crystallization test consists of measuring the evolution of hardness at a specified temperature over several weeks. This method is of special interest for those polymers that can slowly crystallize at service temperatures. 

The supersatxiration caused by compression of the melt was supposed to spread uniformly throughout the melt, and homogeneous crystallization was expected. But in these crystallization tests. 

SODIUM BORATE, PUREST CRYSTALS tests op lritrn... 

Mean Knoop hardness values UK (loading 1961 mN) of synthetic corundum crystals tested in different directions in relation to optical axis C... 

Boyarskaya (1972) carried out comparative tests to determine hardness anisotropy by indentation with a Vickers pyramid and by scratch in a number of minerals and crystals (Table 7.7, Figs. 7.4, 7.5). It is seen from the table that for most of the crystals tested the results for scratch hardness are clearer. Interesting is her finding that where K,1V is lowest, KIiR is highest. This appears to be due to a more legible test, which no doubt facilitates correct hardness measurement. 

Haase and co-workers investigated electro-optic and dielectric properties of ferroelectric liquid crystals doped with chiral CNTs [495, 496]. The performance of the doped liquid crystal mixture was greatly affected even by a small concentration of CNTs. The experimental results were explained by two effects (1) the spontaneous polarization of the ferroelectric liquid crystal is screened by the 7t-electron system of the CNT and (2) the CNT 7i-electrons trap ionic impurities, resulting in a significant modification of the internal electric field within liquid crystal test cells. 

The total number of crystals tested, N, is calculated from the initial mass, m0, and the initial mean diameter, dp0, as... 

Chromatographic techniques are the main methods that have been used to separate, detect, and identify organic components of FDR.152 162 Other methods considered include molecular luminescence,163 infrared spectroscopy,164 Raman spectroscopy,165 electron spin response spectrometry,166 microchemical crystal tests,167 168 ultraviolet spectroscopy/nuclear magnetic resonance/polarography.169... 

Ish was experimentally well known for her ability to coax more-or-less pure crystals of a new substance from tiny amounts of solution of an unlikely looking, gluey reaction product. It was rumoured that her success was the beneficiary of traces of her cigarette ash that provided nuclei in the crystallization test tube to help initiate the crystallization process aided by temperature changes and by scratching the side of the tube with a glass rod.25... 

Experiment 115. — Prepare one or all of the following acetates — a) Sodimn acetate. Dissolve 20 gm. of sodium carbonate in 10 cc. of water in a large porcelain or agate dish, and slowly add 30 cc. of commercial acetic acid, with constant stirring. If the solution is not acid, add a little more acetic acid. Filter the solution, if not clear. Evaporate to crystallization. When the crystals have formed, remove and dry them. Describe the crystals. Prove that they contain water of crystallization. Test the acetate as follows (i) Dissolve a little in water, add a few drops of concentrated sulphuric acid, and boil. What does the odor show is present What other acids have been similarly prepared (2) Dissolve as in (i), add a few drops of alcohol and of sulphuric acid, and boil. What does the odor conclusively prove Preserve the crystals, finally, in a glass-stoppered bottle, or in one having a cork covered with paraffine. 

S. Hess, D. Frenkel and M. P. Allen, On the anisotropy of diffusion in nematic liquid crystals - test of a modified affine transformation model via molecular dynamics. Mol. Phys., 74 (1991) 765-774. 

Newer methods of chemical analysis led to the isolation of the major alkaloids from crude drug preparations. By 1833, aconitine, atropine, codeine, hyoscyamine, morphine, nicotine, and strychnine had been isolated from plants. Color tests for alkaloids were developed between 1861 and 1882 by 1890 quantitative analysis methods became available. Physiological tests for alkaloids, particularly strychnine, first used in 1856, were employed well into the twentieth century. Tests for alcohol, devised by Lieben (iodoform crystal test, 1870) and others, were later perfected for the quantitative analysis of alcohol in body fluids and tissues. Qualitative tests for carbon monoxide in the blood were developed about this time and in 1880, Fodor developed a palladium chloride reduction method to quantitate carbon monoxide in blood. 

Scaringelli separated cocaine and a number of other "caines" (Procaine, Tetracaine, Benzocaine) on a 2 feet long silicone rubber column (10 %) at 220-225°C, and with temperature programming, starting at 75°C. He collected the separated compounds and identified them by their special crystal tests. Estimation of cocaine was obtained by using benzocaine as an internal standard. 

In the case of semiconductors, it was first shown in this laboratory that the arrangements of the atoms in the surface monolayers of (100) and (111) germanium and silicon are not the same as those for these planes in the bulk (25). The altered arrangements were revealed by the presence of fractional order beams for the surface gratings in certain azimuths. This was later found to be the case for all crystals tested which have a diamond-type lattice, including semiconducting diamond and several of the intermetallic compounds. The surface structure of silicon was observed to be much more complex than that of germanium. In some azimuths, several fractional orders less than one-half were observed. 

Once the alkaloid has been isolated, it must be identified. The methods available are (1) the classic color and crystal tests, (2) chromatography,... 

Until about 20 years ago the only way in which an alkaloid isolated from cadaveric material could be identified was by means of color and crystal tests. Both of these date back for well over a century, the color test being the older of the two. It has the great advantage of speed and simplicity and is ideally suited to rapid screening procedures. It has recently secured a new lease on life owing to the way in which it may be used for locating compounds on paper and thin-layer chromatograms. 

FIGURE 17.1 Stress-strain curves for KBr and MgO crystals tested in bending. 

Muhlhausen, C. and Gordon, R.G. (1981) Electron gas theory of ionic crystals, including many-body effects P/jyr. Rev. B23, 900-923 Muhlhausen, C. and Gordon, R.G. (1981) Density-functional theory for the energy of crystals test of the ionic model Phys. Rev. B24, 2147-2160. 

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