Sample Consideration

Surface phases have low Debye temperatures. As a result, the recoil-free fraction may be low at room temperature (see Fig. 5.2). Thus, measuring at cryogenic temperatures will increase the Mossbauer intensity of such samples considerably. But there can also be other circumstances which call for low temperature experiments. 

In point source sampling, consideration of the topography, in this case (Figure 7.6) the slope and soil type, will be important. Discussion of soil types and sampling is presented in the next section. 

Wages SA, Church WH, Justice JB Jr. 1986. Sampling considerations for lin-line microbore liquid chromatography of brain dialysate. Anal Chem 58 1649-1654. 

As to the method of preparing our catalyst samples, considerable work was devoted to the various methods of preparation by which the ferroferrioxide (Fea04) can be obtained from metallic iron, in view of the... 

APPENDIX III SAMPLING CONSIDERATIONS AND TOOLS Homogenous Systems... 

IR spectra were recorded with a Beckman Acculab 6 spectrophotometer. Pellets were prepared by torque pressing a finely ground mixture composed of 1-2 mg of sample and 100-500 mg of spectroanalytical KBr. The pellets were translucent brown and showed good dispersion of the sample. Considerable attention was given to prevent moisture interference. The spectrum of a polystyrene film was recorded prior to the sample for QA purposes. 

Amides have a very strong tendency to self-associate by hydrogen bonding, and the appearance of the spectrum is very much dependent on the physical state of the sample. Considerable shifts in band positions can occur on passing from a dilute solution to a solid, thus N—H and C=0 stretching bands show a marked shift to lower frequency while the N—H bending (amide II) band moves to higher frequency. 

As above mentioned, the presence of CMI units within the PMMA chain backbone makes the sample considerably more brittle. Such an effect is already reflected in the type of deformation micromechanisms more and more crazes when the CMI content increases. 

Figure 18.2 shows the scanning electron microphotograph of the fractured surface of the sample. Considerable featureless material, possibly amorphous or microcrystalline, is visible. Due to the very fine starter powders used in this material, it is likely that the resulting crystals of magnesium potassium phosphate are also very fine and, hence, are not easily visible in the micrograph. The elongated crystals of calcium silicates are embedded in this amorphous mass. Also notice the crack due to fracture of the material, which is diverted by... 

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