Page:Journal of the American Society of Mechanical Engineers, Volume 33.pdf/669

1336 charts as shown in Table 2 and Fig. 9. This shows that it is permissible $$ \frac {1} {2800 - 1.2 t'}$$ as the coefficient instead of $$ \frac {1} {2803 - 1.329 t'}$$, giving

This formula will give values of e for all wet and dry-bulb temperatures and all barometric pressures with an error of less than 0.5 per cent, assuming the chosen value of $$C_{pa}$$ to be correct.