Some results are given in Table I. K i t h a furnace temperature of 670” + 2 ” C. and less than 30 pmoles of sample, complete combustion took place n-ithin 2 hours. At this temperature the equilibrium pressure of oxygen over cupric oside is mm. (6); however, equilibrium is reached very slowly, as shown by blank determinations. Samples greater than 30 pmoles needed a longer contact time and the results were
less accurate. Ethane may be determined in the absence of methane at slightly loner furnace temperatures.
ACKNOWLEDGMENT
the cost of apparatus.
LITERATURE CITED
(1) a4raki,s.,J a p a n dnaZyst2,365 (1953). (2) Bruckner, H., Schick, R., Gas u. Wasserfach. 82, 189 (1939). (3) Camubell. J. R.. Grav. T..’ J . SOC. ‘ Chem. lnd. 49,447 (1930): ’ ( 4 ) McElcheran, D. E., Wijnen, M.H. J., Steacie, E. W. R . , Can. J . Chem. 36,
’
C h e k S h . 42, 2603 (1920).
‘
Simple and Inexpensive Polarograph Cell J. L. Monkman, Department of National Health and Welfare, Ottawa, Canada quantitative work of a repetitive F nature, tlie analyst requires a polarograph cell which is rugged, easily OR
cleaned, simple, and inexpensive. With a large number of such cells on hand, the maximum daily output may be obtained from a polarograph. Large numbers of samples can be processed quickly only if a large number of clean cells are available. The cell described has given satisfactory service in every detail for over a year. An earlier design, used for 12 years, was identical, except for a plain end a t A .
as concentrations of 1 y of lead per 1 ml. of cell solution can be determined accurately and consistently. This may be partly due to the fact that a polarogram requires 3 minutes or less. The cells are constructed of borosilicate glass throughout. Only el:mentary glass blon ing experience is necessary to construct conipletrly satisfactory cells. hIercury is added to a level slightly below the connection to the side tube, B. It rises in the capillary arm, C, where the anode connection e mm.
A
Th? total capacity is of the order of 5 nil. The masimum working capacity is about 3 ml. Sample volumes of 1.0 ml. or less are commonly used. The cell cross section was chosen to be 1 sq. em., as recommended b y Majer (1). Because, in routine analysis of known systems, voltage scale calibration is not too necessary, no provision was made for use of the saturated calomel electrode with this cell. Lead, for example, is determined in dilute hydrochloric acid electrolyte; the lead wave occurs entirely reproducibly, and very close to the “normal” voltage position ( 1 , a). The solution is not blanketed with nitrogen during a run in $his cell. There is, however, no apparent interference from dissolved oxygen,
is made by inserting the wire lead into this arm. The 7 j l S/B joint is connected to a fixed nitrogen manifold having matching joints with a spring clamp (available from Arthur H. Thomas Co., Philadelphia, Pa., catalog Xo. 3241). This clamp may, however, be instantly attached or detached. Nitrogen is passed through the side a r m in the direction A to B for the appropriate degassing time. It is convenient to use this cell m-ith a nitrogen manifold having four, five. or six openings, with stopcocks and outer S/B joints. Thus a group of samples may be degassed simultaneously. After the initial sample has been degassed for the necessary time, it is only a question of adding a new cell and sample to the manifold each time a samnle is taken off to be run on the pola&graph. Cells may be cleaned by soaking in chromic acid cleaning solution. The shal-e lends itself readily to cleaning by inversion over a steam jet. Cost of joints for 12 such cells is about $13. Fifteen to 20 analyses of prepared samples may be carried out in 1 hour. LITERATURE CITED
(1) blajrr, I-.> Collection Crechoslov. Chem. Commirns. 7, 146, 215 (1033). ( 2 ) Ibid.,9, 360 (1937.
Modified 4,7-Diphenyl-1 ,lo-phenanthroline Method Sensitive to 1 P.P.B. of Iron in High Purity Water William G. Knapp, Argonne National Laboratory, Lemont, 111.
method of Smith, McCurdy, anti Diehl [Analyst 77, 418-22 (1952)l has been modified t o provide a simple, highly sensitive procedure for the determination of iron in high purity water. The original sensitivity to 10 p.p.b. has been extended t o 1 p.p.b,, and the time per determination has been reduced to less than 5 minutes when sis or more samples are run simultaneously. This modified method has been in routine laboratory use in testing of high purity water from corrosion test loops THE
for several months n-ith completely satisfactory results. Reagents. T h e color-forming complexing reagent, 4,7 - diphenyl - 1 , l O phenanthroline (Bathophenthanthroline), a n d 10% hydroxylamine are retained from t h e original method, though after extensive tests t h e use of sodium acetate as a buffer was discontinued. Of t h e two extraction solvents suggested-isoamyl alcohol and n-hexyl alcohol-only t h e latter is suitable where iron concentrations are less than 10 p.p.b. Technical grade n-
hexyl alcohol contains a trace of iron which interferes with evaluation of samples and standards. Redistillation of the alcohol and elimination of sources of contamination (dust, etc.) are necessary. Standards made with known quantities of ferrous iron stock solution (0.1 y of iron per ml.) are very stable in the absence of impurities or contamination. They gradually darkened where such contamination was encountered. Use of carefully purified reagents made possible the preparation of water-white blanks and progressively VOL. 31, NO. 8, AUGUST 1959
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