- v = 0.42.
- vʹ = -0.18.
- t = 27.9.
- tʹ = 213.1.
- n = 5.
| n-1 | |||
| ∑ | Θr = Θ₁ + Θ₂ + Θ₃ + Θ₄ + | Θ₂ - Θ₁ | = 667. |
| 1 | 9 | ||
Substituting these values in the formula of Regnault-Pfaundler, the value of the correction for the influence of the external air is
| ∑ Δt = | [ | 0.42 - (-0.18) | ( | 677 + | 214 + 29 | - (5 × 27.9) | ) | - (4 × 0.42) | ] | = 0.45, |
| 213.1 - 27.9 | 2 |
which is to be added to the end temperature (Θₙ = 214.0).
The computation is then made from the following data:
| Corrected end temperature (Θₙ + 0.45) | 214.45 | = | 15°.3699 |
| Beginning temperature (Θ₁) | 28.90 | = | 12°.8406 |
| Increase in temperature | 185.55 | = | 2°.5293 |
| Total calories 2.5293 × 25000 | = | 6323.3 | |
| Of which there were due to iron burned | 9.1 | ||
| ” ” ” ” nitric acid dissolved | 8.2 | ||
| Total calories due to one gram of substance | 5893.5 | ||
The thermometric readings are given in the divisions of the thermometer which in this case are so adjusted as to have the number 28.90 correspond to 12°.8406, and each division is nearly equivalent to 0°.014 thermometric degree.
The number of calories above given is the proper one when the computation is made to refer to constant volume. By reason of the consumption of oxygen and the change of temperature, although mutually compensatory, the pressure may be changed at the end of the operation. The conversion of the data obtained at constant volume referred to constant pressure may be made by the following formula, in which [Q] represents the calories from constant volume and Q the desired data for constant pressure, O the number of oxygen atoms, H the number of hydrogen atoms in a molecule of the substance, and 0.291 a constant for a temperature of about 18°, at which the observations should be made.