AN IMPROVED FORM OF THE COTTRELL BOILING POINT APPARATUS V. T. JACKSON University af Florida, Gainesville, Florida NEARLY every one who has used the original Cottrell boiling p i n t apparatus for the determination of molecular weights has experienced difficulty in keeping a constant flow of liquid over the bulb of the Beckmann thermometer. The apparatus in the illustration eliminates this difficulty. The condenser, A, is 30 cm. b its greatest length. It is sufficientlylong to insure a minimum loss of solvent. Theouter tube, C, with the side neck for the condenser, is 24 cm. long and 5 ern. in diameter. The overall length of the inner tube, opposite C, is 12 cm. It is not attached to C, but rests on the bottom of C. . The hemispherical bottom is 4 cm. in diameter and 2 cm. high. A 6-mm. opening is provided a t the union of it with the upright part of the tube. Four tips are pressed into the tube, one cm. from its top. These keep the Beckmann thermometer in the center. Four holes, 6 mm. in diameter, are made, 5 cm. from the top of the tube. These allow an overilow of the boiling solution. No difficulty is experienced in keeping the temperature constant if the tube, C, is surrounded with an air bath (not shown in sketch) of galvanized sheet iron, and heated with a Bunsen burner. The bath is 20 cm. high and 10 cm. in diameter. The bottom of the bath is closed with an asbestos disc. An opening, 2 cm. in diameter, is made in the asbestos disc.
