A CONVENIENT SAND BATH* The conversion of sodium bicarbonate to sodium carbonate bas always given the student considerable difficulty, especially if he used a direct flame to the porcelain crucible containing the bicarbonate salt instead of performing the operation on a hot air b g h . The temperature, nine times out of ten, would exceed 300' with the consequent formation of sodium oxide, which, naturally, means erroneous results if it is used for standard acids. As a consequence of this, it was decided to try a sand bath, which gave very satisfactory results. The bath used was a 50-cc. iron crncible (E & A, No. 21272). A 30-cc. porcelain crucible (E & A, No. 21242), containing the sodium bicarbonate, was inserted and surrounded on all sides with sand. After the apparatus had been set up, and the thermometer had been inserted into the bicarbonate and held in place in such manner that the bulb is totally immersed but does not come in contact with the bottom or sides of the crucible, a Tirrill burner was placed under the iron crucible. The heating process continued until the temperature of the salt was 200°, and then the burner was withdrawn. By stirring the salt and keeping the bulb of the thermometer covered at all times, it was observed that the temperature of the salt rose rapidly, then slowly, and finally stopped between 270' and 300" C. By using a flame about one inch and a half high, it was found a simple matter t o keep the temperature between 270" and :700°, a condition which was very difficult to obtain otherwise. G. J. C .
* From The Hormone, 3 , 3 0
(March, 1929).
