Organic 2 Review Problem 481

Organic 2 Review Problem 481 - Q UANTITATIVE ANALYSIS...

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QUANTITATIVE ANALYSIS 465 SECTION B SEMI-MICROANALYSIS The Balance* and Weighing. Precautions. Undoubtedly the most important factor in carrying out semi-micro determinations effectively is to have a balance that is sufficiently accurate. For such determinations it is necessary to weigh to not less than the nearest o-i mg. An ordinary analytical balance of good quality can often be adjusted to such a sensitivity but it is necessary to keep the case and pans scrupulously clean, to shield the balance from draughts, vibration and direct sunlight and to operate the balance with considerable care. A true semi-micro balance is certainly less likely to give trouble but is not essential; a prismatic recording ring-rider balance is almost ideal for the purpose, particularly for rapidity of weighing, but it is expensive. Provided that the balance is functioning correctly, the main source of error is in the weights themselves; these should be calibrated by one of the standard methods so that their relative values are known, and they
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This note was uploaded on 09/19/2011 for the course CHM 2211 taught by Professor Castalleano during the Fall '06 term at University of Florida.

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