FEBRUARY. 1950
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AN IMPROVED APPARATUS FOR OBTAINING BOILING POINTS OF LIQUID MIXTURES --
LAWRENCE P. EBLIN Ohio University, Athens, Ohio
THEapparatus described by Mack and France1 for the study of minimum boiling mixtures has been used in our physical chemistry laboratory. Although this apparatus has the commendable feature of simplicity it is sometimes difficult to obtain a steady thermometer reading. To overcome this di5culty a modified apparatus was designed wherein a constant temperature reading is assured by essentially the same means as in the Cottrell type of hoiling point elevation apparatus described by Mack and F r a n ~ e . ~ The modified apparatus is shown in the figure. The flask, C, is a 38-mm. X 200-mm. test tube to which has been attached, as a side arm, a short length of 25-mm. test tube. The flask is the proper size to accommodate the vapor lift pump, D, heretofore used in our boiling point elevation apparatus. A few boiling beads, E, are placed in the bottom of the flask to prevent bumping. As the solution is carefully heated to boiling, bubbles of vapor rise into the pump and carry with them small volumes of the boiling solution. The continued squirting of boilingliquid onto the bulb of the thermometer, B, ensures a constant thermometer reading. As soon as the constant boiling point is reached the flame is removed, and the condenser, A, is turned through an angle of 180' --
1 MACK,EDWARD, JR., AND WESLEYG. FRANCE,"A Laboratory Manual of Elementary Physical Chemistry," 2nd ed., D. Van Nostrand Co., Ino., New York, 1934, p. 127. 2 MACK, EDWARD, JR., AND WESLEYG. FRANCE,ibid., p. 143.
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Boilin9 Point Appuatu.
so that the little cup a t the end of the condenser tube will be filled with reflux liquid. Then the thermometer is removed and a sample for refractometric analysis is withdrawn from the cup by a pipet. Immediately, a similar sample is taken from the liquid in the flask.
