Spot-grinding

After finishing the assembly of these two groups, the spot-grinding of the two mold halves on spotting presses follows (Figure 4.26). Here, the two mold halves have to be closely spotted to each other, so that during the subsequent injection process, the material remains bound in the mold cavity. Leakage of material is a defect and needs to be dealt with later. 

In 2005 it became grindingly obvious that there was a certain spot on Seattle s monorail where tram cars trying to simply pass each other by had to stop to take samples of exterior paint from each other. That was traced back to an engineering error they had made back in 1988, when the rails were brought in a little too close Somebody get me a ruler please ... 

Marlies Teichmuller. We have observed dark spots in vitrinites (especially in anthracites) under the electron microscope without impregnating the coal. The technique was to grind the coal in a rocking ball mill, and treat the very fine particles obtained by this process as thin sections, (cf. R. Meldau and M. Teichmuller, Ol Kofde 37, 751 (1961)). 

Providing that care has been taken in the disc preparation the final disc should be slightly opaque due to the presence of the sample (the blank disc should be transparent). Should the disc show a number of white spots, it is probable that the mixture has been unevenly ground. If the disc shows a tendency to flake, then excessive grinding of the powder is indicated. If after being removed from the die the disc becomes cloudy this is indicative of the uptake of water to avoid this difficulty it is necessary to ensure that the die is evacuated for a sufficiently long period and that the removal of the disc from the die is carried out under a radiant heater. 

Ferricyanide Dissolve about 10 mg of sample in 10 mL of water, and place 1 drop of this solution on a spot plate. Add 1 drop of a 1% solution of lead nitrate followed by a few drops of a solution prepared by saturating cold 2 A acetic acid with benzidine. No blue precipitate or blue color appears. Free Moisture Heat 20 g of sample at 105° for 6 h, cool in a desiccator, and weigh. Grind the dried sample rapidly, heat 3 g of the powder to constant weight at 105°, and calculate the total water content (W). Calculate the percent free moisture in the sample by the formula... 

Macerate (grind) one-half cake of yeast or half an envelope of dry yeast in 50 mL of water in a beaker, add 0.35 g of disodium hydrogen phosphate, and transfer this slurry to a 500-mL round-bottomed flask. Add a solution of 51.5 g of sucrose in 150 mL of water, and shake to ensure complete mixing. Fit the flask with a one-hole rubber stopper containing a bent glass tube that dips below the surface of a saturated aqueous solution of calcium hydroxide (limewater) in a 6-in. test tube (Fig. 1). The tube in limewater will act as a seal to prevent air and unwanted enzymes from entering the flask, but will allow gas to escape. Place the assembly in a warm spot in your desk (the optimum temperature for the reaction is 35°C) for one week, at which time the evolution of carbon dioxide will have ceased. What is the precipitate in the limewater ... 

Sample extraction and cleanup procedures for TLC are similar to those for gas chromatography (GC) and HPLC. If the analyte concentration is sufficiently high, pharmaceutical dosage forms can often be simply dissolved in a solvent that will completely solubilize the analyte and leave excipients or extraneous compounds undissolved to yield a test solution that can be directly spotted for TLC analysis. Grinding of the sample and application of heat and/or sonication may be required to assure solubility of the analyte, as well as filtration or centrifugation to remove undissolved excipients. If the analyte is present in low concentration in a complex sample, solvent extraction, cleanup (purification), and concentration procedures usually precede TLC in order to maximize the analyte and minimize interfering extraneous components in the... 

Or, you can grow your own pyrethrum daisies. Pick the blossoms in full bloom (when the concentration of pyrethrin is at its peak) and hang them in a sheltered, dark and dry place. When the flowers are thoroughly dry, store them in a tightly sealed, labeled container in a dark, cool spot. To use, grind the flowers with a mortar and pestle, then mix the powder with a little liquid dish. soap and enough water to make a sprayable solution. You ll have to experiment with proportions, because the concentration of pyrethrin in home-grown flowers is variable. If your spray doesn t seem to kill the pests, try a more concentrated solution the next time. 

AM joints must be continuous solid welded. All welds must be smooth with no porosity holes, high spots, lumps, or pockets. Grinding is required to eliminate porosity, sharp edges, and high spots. 

The earliest systematic studies of mechanically induced chemical reactions in solids were those of Cary-Lea [61] and Parker [62], who showed that the shearing action of grinding was able to bring about a number of doubledecomposition reactions between simple inorganic salts. Moreover, Parker concluded that this was due to local heating at points of contact between crystals, resulting in fusion and subsequent chemical reaction. This point of view was later taken up by Bernal [63], who proposed that energy could be concentrated into localized hot spots by friction. Detailed experimental studies on the initiation of explosion by impact and friction were subsequently carried out by Bowden and Yoffe [64] and Ubbelohde [65,66] and their coworkers. 

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