Mixing and Grinding

Infrared spectra for solid organic compounds are frequently obtained by mixing and grinding a small sample of the material with specially dry and pure potassi um bromide (the carrier), then compressing the powder in a special metal die under a pressure of 15 30 tonnes to produce a transparent potassium bromide disc. As the potassium bromide has virtually no absorption in the middle-infrared region, a very well-resolved spectrum of the organic compound is obtained when the disc is placed in the path of the infrared beam. 

Spontaneous ignition occurring dining the early stages of mixing and grinding the components was traced to individual grades of lead oxide and the presence of undispersed lumps in the mixture. 

When a mixture of the powdered ketones and a ten-fold molar amount of NaBH4 was kept in a dry box at room temperature with occasional mixing and grinding using an agate mortar and pestle for 5 days, the corresponding alcohols were obtained in good yields. 

Experiment 64. — a) Mix and grind together in a mortar a little ammonium chloride and lime (calcium oxide). What product is revealed by the odor ... 

Experiment 122.—Mix and grind together in a mortar three or four crystals of potassium iodide and an equal quantity of manganese dioxide. Put the mixture in a 250 cc. Erlenmeyer flask, add about 8 cc. of water, and about 5 cc. of concentrated sulphuric acid, drop by drop. Invert a dry funnel upon the flask, as shown in Fig. 77, and stand the flask on a sand bath. Heat with a low, steady flame. Too much heat will vaporize the water, or crack the flask — perhaps both. The vapor of iodine will fill the flask, and crystals of iodine will collect on the sides of the funnel. Regulate the heat so that the flask is filled with vapor, but so that little or none escapes from the funnel. If vapor escapes from the funnel, plug the stem with cotton or soft paper. If crystals of iodine collect on the upper... 

Although the discussion in this section is qualitative, it must be concluded that the mixing and grinding procedures in preparation of powder mixtures for catalyst synthesis via solid/solid wetting and spreading undoubtedly play an important role and must be carried out carefully and under controlled and reproducible conditions. 

ZnO-ZSM-5 was prepared by thoroughly mixing and grinding requisite quantities of NH4ZSM-5 and Zn-oxalate. The mixture is then calcined at 823 K for 7 hrs. 

Operations heating, distillation, other separation procedures, drying, mixing and grinding, and operations involving reactions at temperatures and pressures above and below ambient conditions. 

Antral contractions (3 per min) are responsible for mixing and grinding of a solid meal into smaller particles (<5 mm) that can pass onto the duodenum. These antral contractions can easily be seen at ultrasonography. The contractions can be occlusive or non lumen-occlusive. An antral contraction is defined as an indentation of the gastric wall greater than one antral wall thickness, which is not due to respiration, pulsation transmitted from the aorta or heart, or to movements of adjacent intestine. 

Table 4.2 Ease of complex formation only by mixing and grinding the component crystals in a mortaC...

Table 4.3 Ratio of complex formation obatined by mixing and grinding the component crystals of aromatic compounds with heteroatoms and the cationic surfactants. The ratios were calculated using the peak heights of the low-angle diffractions of their X-ray powder patterns...

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