A Small Chemical Separation of the Chlorine Isotopes

Abstract

A SMALL chemical separation of the chlorine isotopes has been observed by heating carbon tetra-chloride with sodium amalgam, when the reactionoccurs almost quantitatively¹ and the light isotope reacts preferentially. Carbon tetrachloride (A.R.) was fractionated eight times (twenty-four fractions) and the densities of the middle fractions after drying with purified phosphorus pentoxide were compared by the flotation method, using a cylindrical pyrex float. After four successive fractions the density became constant. The float was controlled by means of a small piece of enclosed soft iron. The ground-stoppered vessel containing the carbon tetrachloride was placed in an outer vessel containing phosphorus pentoxide and supported by brass clamps in a thermostat at 23°. An intermittent Gouy regulator² controlled the temperature, which was read on a Beckmann thermometer by a travelling microscope reading to 0.002 mm., so that 0.00025° could be easily read. The thermometer varied 0.00019° per mm. with change of pressure. The velocity of the float varied linearly with temperature, 0.001° in set point corresponding with a density change of 1.9 × 10⁶ and a velocity change of 0.0024 cm. per sec.