INDUSTRIAL AND ENGINEERING CHEMISTRY
60
TABLE Iv. PnR SO,
1
,
3 4
CENT PURITY OF HYDRAZINE SULFATE
Hydrazine Sulfate Gram
0,09858 .\‘ Ceric Sulfate Ml,
0.1055 0,1072 0.1020 01021
3 % .85
33.39 31.75 31.77
13y ceric sulfate
% 99.85 99.88 99.82 99.78 A V . 99.84
Purity By iodatethiosulfate c;
99.81 119.85 99.80 99.88 99 83
Vol. 14, No. 1
point of the titration cannot easily be seen. Ferricyanide should not be added beyond the point at which i t just begins t’o cause a reddish-brown colora,tion. The solution during the final titration should be not more than 1.8M in hydrochloric acid. The method, when properly carried out, is capable of giving results reproducible within less than 0.1 per cent, with a percentage error of about 0.02 to 0.11 per cent compared wit)h the iodate-thiosulfate method (4).
Literature Cited
Summary A new titrimetric method for the determination of hydrazine, in R-hich ceric sulfate is the standard oxidant, gives results which check very closely with those obtained by the but it is much more Bray-Cuy iodate-thiosulfate method (4, rapid and the cost of reagents per determination is less than a third as much. The titration is much more easily carried out than the titration in the Jamieson iodate method (7), in which the end point is dependent upon the disappearance of the purple iodine color in the chloroform layer. This necessitates closing the titration flask and shaking vigorously after the addition of each drop of iodate solution near the end point, a slow, tedious process. The main disadvantage of the method lies in the regulation of the amount of ferricyanide to be used. If the excess over the theoretical amount is too small, the reaction with hydrazine will be incomplete, and if the excess is too great, the end
(1) Atanasiu, J. A , , and Stefanescu,V. Be?., 61, 1343 (1928). (2) Benrath, V. A . , and Ruland, K., Z . anorg. allgem. Chem., 114, 226 (1920). (3) Berry, A. J., Analyst, 54, 461 (1929). (4) Bray, W. C., and Cuy, E. J., J . Am. Chern. SOC.,46, 858 (1924). (5) Cuy, E. J., and Bray, W.C., Ibid., 46, 1786 (1924). (6) Furman, N.H., and Evans, 0. M., Ibid., 51, 1128 (1929). (7) Jamieson, G . S.; Am. J . Sci., 33, 352 (1912). (8) Lang, R., “Newer Methods of Volumetric Analysis”, p. 85, New York, D. Van Nostrand Co., 1938. (9) Oesper, K. E., “Kewer Methods of Volumetric Analysis”, p p . 27-52, New York, D. Van Nostrand Co., 1938. (10) Ray, P. R., and Sen, H. K., Z. anorg. Chem., 76, 380 (1912). (11) Smith, G. F., Sullivan, V. R., and Frank, G., IND. ENG.CHEM., ANAL.ED.,8, 449 (1936). (12) Someya, V. K., Z. anorg. allgem. Chem., 181, 183 (1929). (13) Willard, H. H., and Young, P., J . .Im. Chem. SOC.,55, 3260 (1933). .IBSTR.ACTED from a thesis submitted by C. J. Dernbach t o t h e Graduate School of Oregon State College in partial fulfillment of t h e requirements far the degree of doctor of philosophy.
A Sodium-Hydrogen Geissler Tube FRANK &I. GOYAN College of Pharmacy, University of California, Medical Center, Sail Francisco, Calif.
r HE
need for special glass, preheated electrodes, and a r v a c u u m jacket places the construction of the common sodium vapor arcs (1) beyond the resources of the average worker. Such a n arc requires a separate installation in addition to the equipment needed for the operation of Geissler tubes. In connection with the problem of supplying a suitable light source for a Pulfrich refractometer a very satisfactory Geissler tube was developed in this laboratory. It gives a good sodium line as seen through the telescope of the instrument and, under certain conditions, permits focusing on the C and F lines of hydrogen. Since these three spectral lines are frequently encountered in tabulations of refractive index ( 3 ), this tube serves as a valuable addition to the Geissler tubes used with the refractometer. The design of the tube is such that i t may be constructed a t a nominal cost by anyone who has mastered the a r t of making a small ring seal. Pyrex glass is used and no elaborate technique is required in introducing the sodium because of the presence of a n inner shield which effectively prevents surface impurities on the metal from reaching the glass walls that must maintain a pressure difference. T h e introduction of a stopcock permits the tube to be used while i t is undergoing preliminary pressure fluctuations, thus eliminating the need for extreme care in the initial construction.
Construction of Tube Figure 1shows the tube with the sodium electrodes, S a n d S’, in place With the exception of these electrodes, the glass-wo?l plugs, G, and the rod, D.the diagram represents the tube as it
leaves the glass-blowing table. A mercury manometer (not shown) was also included as an integral part of several of the tubes studied. The glass blowing involved is simple. Each arm of the tube was made as a separate unit, the tungsten electrodes, W and W’, being introduced after the ring seals required to secure the shields, F and F’, were finished. The tungsten wire was prepared by a method suggested by W. D. Kumler. I t was outgassed by heating to a high temperature in the oxygen-gas flame. cleaned by applying a film of sodium nitrite to the hot wire, and washed with water. The bright wire ivas re-oxidized in the Bunsen flame before fusing the sleeve of Pyrex tubing around it t o give the characteristic orange-colored seal. The two completed arms were then connected with a short length of approximately 1-mm. capillary RS shown, and the stopcock and manometer were added.
Charging and Filling The sodium electrodes, S and S‘, are prepared by forcing commercial metallic sodium into lengths of Pyrex tubing. This operation is most conveniently carried out by pressing one end of the tubing, lubricated with a drop of kerosene, into a freshly cut surface of a’large piece of sodium. The completed electrode is immediately lowered into place with the aid of the glass rod, D,which is prepared for this purpose. The point of the rod is so shaped that it, will hold the sodium cylinder but will not break the small tubing when pressure is exerted to force the other end of the sodium cylinder over the tungsten wire. The rod is removed by twisting while pulling very gently. TheTupper Pyrex-wool plugs, G, are added and the tubes, E and E‘, sealed off in the glassblowing torch under ordinary conditions. The tube is evacuated, gently flamed, and filled with hydrogen several times before use. The h drogen inlet is designed to permit displacement of air in tube by passing hydrogen through the capillary, B, before the rubber tubing, C, is forced into place and the stopcock opened. Commercial electrolytic hydrogen was drawn from a tank equipped with a reductmionvalve.
ANALYTICAL EDITION
January 15, 1942
Operation The tubes were operated from the secondary of a transformer capable of delivering 23 milliamperes at 10,000 volts. A current between 15 and 20 milliamperes has been found to give satisfactory intensity of sodium light. Control is accomplished by inserting a variable resistor in the primary circuit or one or two 100,000. ohm, 50-watt resistors in series with the tube in the secondary circuit, or by choosing a working pressure of hydrogen that produces a good light intensity without serious overheating. If the tubes are to be used only as a source of sodium light they will operate successfully a t any pressure between 2 and 50 mm. of mercury. However, to make use of the C and F lines of hydrogen as well as the sodium D line, a low pressure of hydrogen (2 to 5 mm. of mercury) must be established and the current controlled by means of resistors. The exact values of the current or pressure are not critical factors, except that the current must produce sufficient light intensity without dangerous overheating, and the pressure must be low if the hydrogen lines are wanted.
I 1 I
ABC 1
I
-D
,
'
- -E
61
tabulated in the literature (2) arid with ieadiiigr, taken when a commercial sodium arc was used as the light source. The agreement was well within the accuracy of the instrument and indicates that the red C line of hydrogen (6563 A,), the yellow D lineoof sodium (5893 A), and the blue F line of hydrogen (4861 A.) are produced. Other lines in the green and orange and a continuous spectrum in the violet are too faint to cause confusion. The intensity of the sodium line developed in seasoned tubes after 2 or 3 minutes of operation is equal t o or greater than that of hydrogen lines observed. in ordinary Geissler tubes. Although the useful life of these tubes is not so long as that of ordinary Geissler tubes, one tube containing 10 mg. of sodium operated continuously as a source of the sodium line for 50 hours. The capillary was badly etched a t the end of this period but again emitted sodium light for a few minutes after the deposit inside the tube had been heated in a gas flame, indicating that failure had been due, not to the condition of the glass, b u t to the loss of sodium from the electrode region. The'condition of the glass is of greater importance when the hydrogen lines are sought. Because of this fact, and also because tubes operating a t low pressures tend to overheat if allowed to carry normal current continuously, the life of a tube as a simultaneous source of hydrogen and sodium lines is short unless the current is turned off and the tube allowed to cool a t frequent intervals.
Discussion
-F -
-s
-W FIGURE 1
A new tube is filled to a pressure between 10 and 20 mm. of mercury and operated with a current of about 20 mm. for 30 minutes, or until the discharge in the capillary takes on the color of the sodium D line. The tube is then evacuated and refilled with hydrogen to whatever pressure seems to be indicated by the previous behavior or by the type of discharge desired. After the preliminary heating has once produced a strong sodium light in the capillary, the characteristics of the tube change. The same current that produced the first sodium light in 20 or, 30 minutes will accomplish the same result in one tenth of the time. A deposit gradually forms on the cooler surfaces, and the glass of the inner shield darkens and shows signs of erosion. This change does not affect the usefulness of the tube if the glass-wool.plugs are well packed; the inner shields are not required to maintain a vacuum, and the light intensity is sufficient to permit focusing on the side of the capillary. During the early life of the tube the pressure fluctuates to such an extent that it is often necessary to evacuate the tube and refill it with hydrogen. Later, however, the pressure becomes constant, and, after several hours of stable operation with maximum current the stopcock may be removed with the torch to avoid the possibility of slow leaks. Tubes built to the specifications given above have been used in this laboratory for several years as a light source for the Pulfrich refractometer. T h e identity of the three bright lines observed in tubes operating at low pressures has been established b y measuring t h e refractive index of distilled water at 20' C. and comparing the results with the values
Aside from the mechanical design which permits the use of sodium that has been briefly exposed to ordinary air, the successful operation of the tube is associated with the action of hydrogen on sodium at high temperatures (4, 5 ) . The observed facts which support this conclusion are: The time required for a satisfactory emission of the sodium line is much less on the second and subsequent heatings than on the first; a deposit forms on the cooler portions of the tube; under certain conditions there is a sharp decrease in pressure inside the tube during the first few hours of operation; when the tube is operated at low pressures the deposit may consist of bands of different colors, principally blue, gray, black, and orange and sometimes metallic, but, with careful heating a t higher pressures of hydrogen, a gray or white nonmetallic deposit is observed; this nonmetallic substance may be sublimed from one portion of the tube to another without discoloring the glass; and when the tube is broken open and water added this deposit dissolves with the evolution of a gas. It is concluded that sodium hydride forms during operation of the tube and t h a t this substance is responsible for the rapid development of the sodium line after the tube is lighted.
Summary A Geissler tube of Pyrex glass capable of emitting a strong sodium D line is easily constructed and charged with commercial metallic sodium and tank hydrogen and, under controlled conditions, emits the C and F lines of hydrogen and the D line of sodium simultaneously. As a source of the sodium line the tube operates efficiently over a wide pressure range, has a long life, and, after the first few hours of operation, requires no more care than any other Geissler tube.
Literature Cited (1) Buttolph, L. J., Trans. Electrochem. SOC.,65, 143 (1934). (2) ChBneveau, C., International Critical Tables, Vol. VII, p. 13 New York, McGraw-Hill Book Co., 1930. (3) Dixon, A . L., and West, C. J., Ibid., p. 34. (4) Keyes, F. G., J . Am. Chem. SOC.,34, 779 (1912). (5) Mellor, J. W., "A Comprehensive Treatise on Inorganic and Theoretical Chemistry", 1'01. 11, p. 481, London, Longmans, Green and Co., 1922.
