Bureau Circular Volume a - 3

Bureau Circular Volume a - 3

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1918 edition. Excerpt: ...purchase of complete sets of standards if this must be done, as is often the case, at the expense of quality. Probably the best denominations for reference standards for most scientific laboratories are one Too g or 50 g weight, one i g weight, and one 10 mg weight.8 The i g weight should be of platinum, as it is used as the starting point for the calibration of the fractions of a gram, which are usually of platinum. 1. WEIGHING (a) Zero Reading and Equilibrium Point.--The phrase "zero point" is often used to designate the center of the scale over which the pointer of a balance moves, or, in general, the place at which the pointer should come to rest without load if the instrument were perfectly constructed and balanced. It is sometimes used to designate the rest point when there is no load on the pans, whether this point is at the center of the scale or not, but this idea is better expressed by the phrase "zero reading." 8 It is often advisable to add a smaller weight, generally i or 7 ms. for determining the sensitiveness of the balance, or even a small set, from 5 to i mi, which will also serve to measure any large difference that may exist among the larger weights. The phrase "rest point" or "equilibrium point" is then used to indicate the point on the scale at which the pointer would come to rest in any particular case. In very rough testing this may be found by waiting until the pointer comes to rest and then noting the reading, but it is seldom advisable to adopt this method. In careful work the rest point must be calculated from the extreme positions to which the pointer swings on each side of this point. The number of readings taken when the rest point is to be calculated will depend upon the...
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Product details

  • Paperback | 28 pages
  • 189 x 246 x 2mm | 68g
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236539273
  • 9781236539274