ASTM C114:15 pdf free download – Standard Test Methods for Chemical Analysis of Hydraulic Cement.
6.5.2 Thred or Weighed Crucibles—The tare weight of crucibles shall be determined by preheating the empty crucible to constant weight at the same temperature and under the same conditions as shall he used for the final ignition of a residue and cooling in a desiccator for the same period of time used for the crucible containing the residue.
6.5.3 Constancy of Weight of Ignited Residues—To definitely establish the constancy of weight of an ignited residue for referee purposes. the residue shall be ignited at the specified temperature and for the specified time, cooled to room temperature in a desiccator, and weighed. The residue shall then be reheated for at least 30 mm, cooled to room temperature in a desiccator, and reweighed. lithe two weights do not differ by more than 0.2 mg. constant weight is considered to have been attained. If the difference in weights is greater than 0.2 mg, additional ignition periods are required until two consecutive weights agree within the specified limits. For ignition loss, each reheating period shall be 5 mm.
6.5.4 Volarilicarion of Platinum—The possibility of volatilization of platinum or alloying constituents from the crucibles must be considered. On reheating, if the crucible and residue lose the same weight (within 0.2 mg) as the crucible containing the blank, constant weight can be assumed. Crucibles of the same size, composition, and history shall be used for both the sample and the blank.
6.5.5 calculation—In all operations on a set of observed values such as manual multiplication or division, retain the equivalent of at least two more places of figures than in the single observed values. For example, if observed values are read or determined to the nearest 0.1 mg. carry numbers to the nearest 0.001 rng in calculation. When using electronic calculators or computers for calculations, perform no rounding, except in the final reported value.
6.5.6 Rounding Figures—Rounding of figures to the number of significant places required in the report should be done after calculations are completed, in order to keep the final results substantially free of calculation errors. The rounding procedure should follow the principle outlined in Practice E29.6 In assessing analyst- and method-qualification in accordance with Section 4, the individual duplicate results, the difference between them, the average of duplicates on CRMs, and the difference of this average from the certificate value shall be left un-rounded for comparison with the required limits. Round results for reporting as shown in Table 3.
Nori X—The rounding procedure referred to in 6.5.6. in effect, drops all digits beyond the number of places to be retained if the next figure is less than 5. If it is more than 5. or equal to 5 and subsequent places contain a digit other than 0. then the last retained digit is increased by one. When the next digit is equal to 5 and all other subsequent digits are 0. the last digit to be retained is unchanged when it is even and increased by one when it is odd. For example 3.96 (50) remains 3.96 but 3.95 (50) becomes 3.96.