ANALY TIC AL EDITION
300
In use the liquid to be measured is drawn into the delivery tube b y dipping the tip of the latter into the liquid and moving the roller upward. When a sufficient quantity has been drawn into the tube the roller is moved downward until the level of the water in the calibrated tube is at one of the graduations, The solution adhering to the tip of the after which the microburet is delivery tube is touched ready for use* The desired amount of solution is delivered by running the roller downward, the amount of solution de-
Vol. 6, No. 4
LITERATURE CITED (I) Nitchie, C. C., IND.E m CHEM.,Anal. Ed., 1, 1-18 (1929). (2) Nitchie, C. C., and Standen, G. W., Ibid., 4, 182 (1932).
-March 1, 1934. RECEIVBD
1 This is not exactly true, inasmuch as the volume of the air column between the liquid in E and the water in C is not constant but varies with t h e height of the column of liquid retained in E. Calculation ehowe, however, that the error in delivering each 0.1 cc. from a 5-mm. inside diameter delivery tube is only about 0.00005 cc. from this source.
Automatic All-Glass Extractors for the Laboratory W. A. LA LANDE,JR.,AND E. C. WAGNER, University of Pennsylvania, Philadelphia, Pa.
T
HE extractors shown in Figures 1 and 2 are designed
for extractions with immiscible solvents lighter than water. They are self-contained and compact, occupying little table space as they have a minimum of lateral extension. The absence of projecting parts decreases the liability to breakage. Obviously these extractors can be made only by a glass blower, b u t i t may be assumed that apparatus of such permanent usefulness need not be considered an extravagance because it cannot be homemade. The extractors are made wholly of Pyrex glass and may be of any convenient size; those now in service have about 1000 cc. capacity to the overflow at level b. Dimensions of parts can be varied within reasonable limits, depending upon the size of the apparatus; hence no dimensions are indicated in the figures, which are drawn to scale. The liquid to be extracted is poured through G into the main vessel, C, to level a. The solvent is put into the boiling flask, A , and enough is added through G to form a floating layer, ab. The inner tube, B, is of sufficiently large bore to accommodate both the ascending solvent vapor and the overflowing solvent from the upper layer. The solvent vapor passes upward through the ports at D and into the condenser. As the entire path of the vapor is within the extractor, which is thereby kept somewhat warm, there is avoided much of the useless refluxing which occurs when an external tube is used to convey the solvent vapor from boiling flask to condenser. The reflux from the condenser is directed by F so that it passes through the tube E, entering the lower part of the liquid through e, whence it rises through the liquid, eventually overflows through B, and returns to the boiling flask. Tube E must be long enough above the overflow level so that with a light solvent and a heavy liquid a sufficient head of solvent can collect in E to expel it rapidly at e. The extractor shown in Figure 1 has tube E divided into four branches, the refluxed solvent being thus delivered through the perforated bulbs at four points in the lowermost level of the liquid. The apparatus shown in Figure 2 is provided with a mechanical stirrer and liquid seal. The stirrer is so placed that the upper paddle is in the solvent layer, ab, and the other paddles in the lower liquid. Further, the upper paddle and the lower paddles are opposed so that, by operating the stirrer a t moderate speed, the upper solvent layer is pushed downward and the lower liquid upward, the sliding interface and the continuous movement within both layers increasing the rapidity and thoroughness of the extraction. The drainage tube, H , permits the apparatus t o be emptied while assembled. These extractors once started require no attention and can be operated a t a high rate of solvent flow. Those now in use are of substantial construction, and are the work of J. D. Graham, University of Pennsylvania glass blower. RECEIVEDFebruary 6, 1934.
FIGURE 1
FIGURE2
