Calorimetric determination of the half-life of polonium

Abstract

The hea t s of radioa ctivity of four samples of polonium have been measured with a B unsen ice calorimet er over a period of about seven months. With sa mples rangin g in initial powers from 0.17 to 1.4 watts, t h e ha lf-life values calcul ated from these measure ments were fo und to agree within 0.1 per cent, or t he equivalen t of 0.0003 watt, whichever was t h e larger. The result s with th e sa mple with t he largest p ower gave a ha lf-life value of 138.39 days, with an un cert ainty of 0. 1 per cent (0.14 day) . This is in agreement with the value of 138.3 d ays ( ± 0.1 p ercen t ) reported b y Beamer an d Easton, who used a differen t calorimetric met hod.

Excess molar volumes and excess molar heat capacities of (dimethyl carbonate, or diethyl carbonate +n-heptane) at several temperatures

“…(15) The excess molar volumes V E m of table 2 were fitted to the following expression: where T 0 = 278.15 K, T is the temperature, and x is the mole fraction of dialkyl carbonate. The fitting coefficients A i j were obtained by using Marquardt's optimization method.…”