748
INDUSTRIAL AND ENGINEERING CHEMISTRY
agitate gently, and again allow the layers to separate. This time the separation should be complete in a couple of hours. The wax is now practically completely in the chloroform layer. It is probably desirable to wash the chloroform solution of extracted wax a t least once with water. Therefore drain the separatory funnel and discard the spent alcohol-water solution, which also contains the sugars and other alcohol-soluble, nonwaxy substances. Without washing the funnel, pour the chloroform solution of wax back; add about 100 ml. of distilled water, shake carefully, and allow the two layers to separate. When separation is complete, draw off the chloroform layer, receiving it into the same Erlenmeyer flask from whence i t was last taken. Now add two 5-ml. portions of fresh chloroform successively to the separatory funnel, shake well, allow to separate, and draw off each in turn into the Erlenmeyer flask containing the main body of chloroform solution. This should complete the transfer of the wax back into this flask. Remove the chloroform from the wax by evaporating in tared 100-ml. beakers on a steam bath. The beakers should not be f i l l 4 more than half way a t a time, because of the tendency for the chloroform t o superheat and boil up slightly a t times as well as to leave a deposit of wax above the solvent on the sides of the beaker. After the wax residue appears to be dry, cool and weigh the beakers, then heat them on the steam bath 30 minutes more, and again cool and weigh. If the weights are not constant, repeat reheating until two successive weighings agree within 0.1% of the residue weight.
A
Vol. 16, No. 12
ACKNOWLEDGMENT
The assistance of Meyer D. Silverman and James H. Kettering in obtaining the data herein reported is gratefully acknowledged. LITERATURE CITED
(1) Ahmad, N., and Sen, D. L., Indian Central Cotton Committee Technological Laboratory, Tech. BUZZ.Series B, No. 18 (1933). (2) Bloor. W. R.. Chem. Reaiews. 2 . 243-300 (1925-26). (3) Clifford, P. H., Higginbotham, L., and Fargher, R. G., J. Teztileznst., 15 (3), T120-37 (1924). (4) Clifford, P. H., and Probert, M. E., Shirley Inst. Mem., 3, 16981 (1924). ( 5 ) Conrad, C. M., and Neely, J. W., J. Agr. Research, 66 (S), 30712 (1943). (6) Fargher, R. G., and Higginbotham, L., J . Textile Inst., 15, T419-33 (1924). (7) Fargher, R. G., and Probert, M. E., Ibid., 15, T337-46 (1924). (8) Hess, K., “Die Chemie der Zellulose und ihren Begleiter”, Leipzig, Akademische Verlagsgesellschsft, 1928. (9) Maclean,H., and Maclean, I. S., “Lecithin and Allied Substances. The Lipids”, London, Longmans, Green and Co., 1927. (10) Thor, C. J. B., personal communications. (11) Thor, C. J. B., and Smith, C. L., J . Agr. Research, 50, 97-121 (1935).
Fractionating Column
For Continuous Production of Distilled W a t e r of
High
Purity
FREDERIC E. HOLMES A e r o Medical Laboratory, A r m y Air Forces, Wright Field, Dayton, O h i o
THE
entire apparatus shown in Figures 1 and 2, the fractionating column of which is of primary interest here, was used to prepare redistilled water of high purity from a laboratory supply of rather poor quality. Long single tubes of small inside diameter and concentric glass tubes, in which the reflux is distributed on the walls of the tubes have been found to give an efficiency of up to the equivalent of more than 85 theoretical plates in a length of less than 150 cm. (5 feet) ( 2 ) . The present apparatus may be regarded as two such columns in series, but arranged concentrically to prevent loss of heat and to reduce the over-all height. Accessories shown serve to make the operation of the apparatus continuous and automatic. The constant-level device for controlling the input is a more sturdy modification of one previously reported (I). To maintain an easily controlled uniform flow of cooling water through the condenser, an obvious device was used (constant head, Figure 2). Present circumstances do not justify a careful study of the heat exchange and otlier details of performance of the apparatus. Instead, certain seemingly valid assumptions were made, and the final effectiveness of the column was tested by a simple electrometric measurement of the conductivity of the distillate (water).
It is assumed that the greater part of any higher-boiling frac-
tions are condensed in the outer space between the outer aircooled shell and the middle concentric tube and are refluxed back into the boiling flask, and that, a t least in the case of water, any heavier fractions which pass over the top in more than negligible traces are substances that will readily distill with steam and will be carried with the steam to the top of the condenser. T h e amount and composition of the first reflux (above) will, of course, depend on temperature and rate of flow of the vapors, temperature of the surrounding air, and other factors. The marrow space between the centra1 and middle concentric tubes serves to conduct the remaining vapors to the bottom of the central space and to maintain or slightly increasc their temperature toward the bottom of the space. These vapors then ascend
through the central space to the condenser, which is maintained by slow flow of cooling water a t near the temperature of condensation of water, As the condensate flows down the walls of the central tube, it is continually in contact with hot vapor flowin upward. Any lighter fractions which may have condensed and any gases redissolved in the water are assumed to be driven off again and returned to the top of the column. Gases and lowerboiling fractions are eventually driven out with a small portion of steam from the top of the condenser. On several occasions the performance of the still was tested by measuring the conductivity of the distillate in a Barnstead purity meter in terms of an electrometrically equivalent concentration of sodium chloride in solution in pure water. The results are given in Table I. From these data it is evident that the first 150 to 200 ml. should be discarded, that the still is then clean and
Table
1. Conductivity of Distillate (Water) Delivered et 3 to 4 Liters Per Day
Run
Sample, Portion of Run, Condition of Stili, etc.
Tenip.
F. 1
2
3
NaCl Equivalent P.p.m.
Water in rerervoir 80 First distillate taken, read when taken 130 First distillate taken, after 30 min. 105 Probable solution of electrolyte from glass Beginning of dny, first 150 ml. discarded ... First Rample, barely in zero range 95 End of day, far into zero range 132 End of 2-liter run, last portion from reservoir in flask, far in zero range 132
A considerable arc on the meter below 0.1 is marked “zero range”.
5.8
0.3 0.5
co:1
