Size of Spacer Disks
Free mace requireh, cc.
Diameter, cm.
5
4.24 3.54 2.66 2.09
10
15 17.5
slits, 90" apart and 1 mm. deep, are cut with a scalpel as shown. The bottom diaphragm disk (Figure 1) has large
slots cut and is trimmed to seat smoothly on the bottom of the glass tube. Operation. After the compartments are filled, pressure is applied t o the system with valves B and E closed and the rubber hose clamp, D, open. D is then closed and B opened. The needle valve, C, acts as a temporary vent if necessary and the flow through the whole system is controlled by the column valve, E. ACKNOWLEDGMENT
Appreciation is expressed for the tech-
nical assistance of R. C. Verney. The financial assistance of the National Research Council of Canada is gratefully acknowledged. LITERATURE CITED
(1) Harpur, R. P., Can. J. Biochem. and Physiol. 36? 707 (1958). (2) Harpur, R. P., J. Chem. Educ. 36, 149 (1959). ( 3 ) Roberts, E. J., hlason, A., ANAL. CHEM.28, 1063 (1956).
Modified Absorption Cell and Cell Compartment Cover for the Beckman Model DU Spectrophotometer Samuel R. Henderson and Louis J. Snyder, Research and Development Department, Ethyl Corp., Baton Rouge 1,La.
TOtions
the number of manipulaand improve the over-all accuracy of the determination of heavy metal ions (lead, bismuth, copper, mercury, zinc, etc.) by the colorimetric dithizone method, a special absorption cell was developed. Its use eliminates indeterminate errors arising from leaky, plugged, or frozen stopcocks, emulsions due to temperature changes in immiscible solvents, contamination during filtration or excessive handling, and increase in concentration of metal dithizonates due to evaporation of volatile solvents during transfers. The cell permits the analyst to carry out the color development, extraction, and photometric measurement rapidly and accurately in a single container. I t is a modification of a color comparator tube previously described [Snyder, L. J., Barnes, W. R., Tokos, J. V., AKAL.CHEM.20, 772 (1948); Griffing, M. E., Rozek, A., Snyder, L. J., Henderson, S. R., Ibid., 29, 190 (1957)l for visual estimations. Its wide application to other accurate photometric measurements employing different photometers makes it a valuable laboratory tool. The cell (Figure 1) may be fabricated by attaching a square precision (borosilicate glass) absorption cell (10.0 X 10.0 X 95 mm.) to the upper part of a globe-shaped 200-ml. separatory funnel. A shorter cell (10.0 X 10.0 X 48 mm.) REDUCE
i , i t . Figure 1. tion cell
u
I
I
Modified absorp-
*Absorption cell and glass bulb fabricated from borosilicate glass or comparable material
may be used, but requires the insertion of a piece of borosilicate glass tubing (11 mm. in outside diameter X 48 mm.) between the cell and the glass bulb. The dimensions given here are for a cell to fit either the Bcckman Model DU spectrophotometer or the Leitz Rouy photometer. This modified absorption cell is now available on special order from E. Leitz, Inc., 304 Hudson St.,NewYork14, N . Y . Otherphotometers may require slight changes in the dimensions. The Hellige Chromatron requires a 13 X 13 X 88 mm. cell. A special cell compartment cover
Figure 2. Cell compartment cover for Beckman Model DU spectrophotometer
(Figure 2) is required for the Beckmnn Model DU spectrophotometer. This cell has been found to have great usefulness in all types of photometric measurements: determination of lead, bismuth, mercury, copper, zinc, etc., by dithizone techniques; aluminum by extraction of the oxinate with chloroform; chlorine in organic solvents by extraction with aqueous o-tolidine reagent; and iron in organic solvents by extraction with o-phenanthroline reagent. In any case, the colored phase is obtained 2s the lower layer by adjusting the density of the organic solution by diluting with a more dense solvent (chloroform) or a less dense solvent (hexane) as the case may require.
VOL. 31, NO. 12, DECEMBER 1959
21 13
