Parr Instrument 6725 - Manual (Page 51)

6725
Semi-micro Calorimeter Instruction Manual
6-3
reasonably constant sulfur content. Any value set-up as a fixed correction will be
automatically applied and the controller will not prompt the user for this value.
Definitions
Total acid is the amount of base required to titrate the bomb washings
(milliliters).
Nitric acid is that portion of the total acid in the bomb washings that result when
the nitrogen in the air that is trapped in the bomb is burned at high
pressure. Since this nitric acid does not result from the sample, and
the combustion conditions are reasonably constant from test to test,
the amount of nitric acid formed is also constant.
Acid multiplier is multiplied by the user entered acid value to arrive at the
number of milliequivalents of acid. This value is normally the
concentration (normality) of the base in equivalents per liter (N).
Percent sulfur is the concentration of sulfur in the sample (weight %).
Molecular weight of sulfur is 32.06.
Equivalent weight of sulfur in H
2
SO
4
is 16.03 (one half of the molecular
weight).
Heat of formation of nitric acid is 14.1 calories / milliequivalent.
Heat of formation of sulfuric acid (from SO
2
) is 36.1 calories / milliequivalent.
Sample mass is the mass of sample burned in the bomb (grams).
Sulfur multiplier is multiplied by the product of the user entered sulfur value and
the sample mass to arrive at the number of milliequivalents of sulfuric
acid in the bomb washings.