ANALYTICAL EDITION
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(20) Rupp and Krauss, Ber., 35 4167-60 (1902) Selivounoff, Ann. chim. anal. chim. appl., 11, 133-5 (1929). Spielmann and Jones, J. SOC.Chem. Ind., 38, 185-7T (1919). Treadwell and Hall, "Analytical Chemistry," 6th ed., Vol. 11, p. 609, Wiley, 1924. Treadwell and Hall, Ibid., p. 610. Weiss, J. IND.ENO.C H ~ M10, . , 1009 (1918).
Vol. 4, No. 1
(26) Zeise, Ann. physik. Chem. (Poggendorff), 35,487-514 (1835). (27) Zeise, Ann. Chem. Pharm., 55, 304-17 (1845); Ann. chim. phys., [3] 17, 338-47 (1846); [3] 20, 128-7 (1847). (28) Zeise, Ann. Chem. Pharm., 62,375-80 (1847). R B C ~ ~ IAugust V ~ D 5 , L931. Published by permission of the Direotor, U. S . Bureau of Mines. (Not subjeot to copyright.)
A Precision Sodium Cutter E. B. HERSHBERG AND E. H. HUNTRESS, Massachusetts Institute of Technology, Cambridge, Mass.
T
HE preparation of small pellets of metallic sodium is usually effected by cutting off fragments from large commercial pieces by means of a Gattermann-style sodium knife (1). This crude method serves for most purposes, but is not well adapted to the preparation of small portions reproducibly uniform in weight.
opening 5 mm. in diameter. To ensure uniform cross section, the approaches to the hole should be well rounded and the opening itself reamed and polished to a mirror surface. The 6- to 8-inch rods may be kept in a stock bottle under dry kerosene and the pellets cut off with the new cutter as may be desired. The details of construction are indicated in the accompanying diagrams. Because of the severe alkaline conditions to which the cutter must necessarily be exposed, acidic alloys such as brass and bronze should not be used. Mild steel has proved entirely satisfactory, and stainless steel or nickel may advantageously be employed. The method of using the cutter is as follows: Holding the cutter in such a manner that the feed tube H (Figure 3) is vertical and the cap D is pressed against the palm of the hand, a length of sodium rod is inserted in tube H and allowed to fall until it comes in contact with the adjustable stop, M . The plunger is then pressed forward, the razor, P , cutting the sodium, and the snap button, E , aiding in the ejection of the pellet. Pressure on the cap is released, the plunger is returned to its normal position by the spring I , and the feed rod of sodium is allowed to fall by gravity or by a slight pressure of the hand until it again strikes the plate M , placing it in position for the cutting of the next pellet. By adjusting the
I.-;--
FIGURE 1. DETAILS OF BARREL
Mulliken and Gabriel (2) have suggested that a slab of sodium of given thickness be prepared, and pellets cut from this by means of a cork borer. Because of the plasticity and great reactivity of the metal, however, it is not easy to prepare slabs of precisely the right thickness. Furthermore, the resultant pellets are difficult to remove smoothly from the borer. In any case, approximately half the slab remains as a perforated plate which must be discarded or worked into wire. I n the course of research in progress in this laboratory, it became necessary to obtain uniform pieces of sodium 0.2 * 0.003 gram in weight, Pellets of sodium of this size are used in organic qualitative analysis in the process of decomposing the organic compound prior to the tests for the elements. Since with large classes of students it is desirable to reduce the handling of sodium to a minimum, a precision cutter has been constructed and successfully employed. This cutter consists essentially of a razor blade arranged so as to be operated by hand pressure in such a manner that uniform lengths of metal are cut from a 6- to 8-inch (15.2to 20.3-cm.) cylindrical rod of sodium, These rods are formed by the usual sodium press (S), using a die with an
@ P U S H ROD
@ CUTTER HEAD FIGURE 2. DETAILS OF PLUNGER
stop M , various lengths of sodium may be obtained. If desired, the feed tube H may have a different internal diameter from that specified in Figure 1. By these two adjustments considerable dimensional variation may be acquired. The list of parts shewn in Figures 1, 2, and 3, is as follows: A , Barrel-mild steel, stainless steel, or nickel. B, Push rod-mild steel; turn 0.002 inch smaller C, Cutter head-same metal as A . D, Cap-same metal as A. E , Snap button and spring collar--'3/16 inch long; collar soldered o n rod after bearing 0 has been slipped on; steel.
January 15, 1932
IIC’DUSTRIAL A N D E N G I N E E R I N G
F , Snap button ~ p r i n g - ~ / ~inch ~ in diameter, 1 inch long; fine steel compression spring. G, Finger rests-make two; bent from S/winch iron rod; ends screwed into barrel.
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back of razor ground to fit groove in cutter head; blade snapped off or ground to proper length ( 7 / ~ inch) after back has been sawed through. The reproducibility of the weights of the sodium pellets obtained is even better than that originally required. For example, with the stop set to cut a 200-mg. pellet, twelve successive units were cut from a freshly pressed rod of sodium 5 mm. in diameter. These were allowed to fall into dry benzene, later individually removed, dried quickly, and weighed on an analytical balance sensitive to 0.1 mg. Of the twelve pellets, eight weighed exactly 200 mg., two weighed 199 mg., one 201 mg., and one 202 mg. When used as described, the operation is so rapid that the amount of oxidation is negligible and the purity of the resultant units is simply the purity of the original metal. Since far more oxidation obviously occurs when the sodium pellet is heated prior to the addition of the organic compound in the test for elements than takes place in its preparation, a more detailed determination of the actual sodium content was deemed unnecessary. ACKNOWLEDGMENT
FIGURE 3. ASSEMBLYOF CUTTER
SODIUM
PI, Sodium feed tube-preferably of stainless steel or of nickel. I , Plunger return spring-steel compression spring, inch in diameter, 23/8 inches long; wire 0.047 inch in diameter.
J,Cap screw--l/q inch in diameter, ‘/e inch long; fillister head. K , Set screws-make two, inch in diameter; flat point. L, Set screw--’/s inch in diameter; flat point. M, 8top--a/le inch in diameter, 8/4 inch long; make fine thread for close adjustment. N , Lock nut-threaded for stop screw M . 0, Snap button upper hearing--a/l~ inch in diameter; cut groove in upper face to aid in screwing in. P , Cutter blade-safety-razor blade of Gem or Eveready type;
The authors wish to thank A. A. Morton, V. F. Harrington, C. L. Gallagher, and I. S. Cliff for invaluable suggestions and criticisms. LITERATURE CITED Gattermann, “Practical Methods of Organic Chemistry,” 3rd American from 11th German ed., pp. 385-6, Macmillan, 1921. (2) Mulliken and Gabriel, 8th. Intern. Cong. Appl. Chem., 6, 208-11 (1)
( 1912). (3) Parke, J. Chem. Education, 4, 918-19 (1927). RECEIVPD June 5 , 1931. Contribution 73 from the Research Laboratory of Organic Chemistry, Massaohusetts Institute of Technology.
Determination of Tetraethyl Lead in Ethyl Gasoline E. L. BALDESCHWIELER, Standard Oil Derelopment Company, Elizabeth, N . J .
A
S MEIiTIOXED by A S I M P L E and reliable gravimetric method PROCEDURE E d g a r and Calingaert for the determination of tetraethyl lead in gasoline The method d e p e n d s upon (2), the various methand other petroleum products is described. the fact that t e t r a e t h y l lead ods published in the literature f o r t h e d e t e r m i n a t i o n of The method has been in for several Years in is completely decomposed by this laboratory and has given complete satisshaking the gasoline s o l u t i o n tetraethyl lead are either too with concentrated nitric acid, tedious or are l a c k i n g in acfaction. It is specially adapted for intermittent curacy. The bromine method work and requires only ordinary laboratory fprming l e a d n i t r a t e . The liquid separates into two layers published by Edgar and technic. Its use in the analysis of other organoand the lower layer, containgaert (2) is rapid and accurate but sometimes troublesome, esmetallic compounds is discussed. ing the acid with most of the lead n i t r a t e , can be drawn pecially with gasolines rich in unsaturated compounds which require the addition of a large off. Since lead nitrate is not very soluble in concentrated amount of bromine. This results in the evolution of much nitric acid, the acid shaking is followed by washing in water hydrobromic acid and, sometimes the formation of gummy in order to remove the last traces of lead nitrate. The reprecipitates which are difficult to handle, and it is the writer’s action takes place without appreciable rise in temperature, experience that unless special precautions are taken, low re- even with gasolines rich in unsaturated compounds, and can therefore be safely carried out in a separatory funnel, sults are obtained. To obviate these inconveniences, the method described using the method described below. Measure 200 cc. of the gasoline into a 500-cc. glass-stopherein has been devised and used in this laboratory for sevpered separatory funnel. Add 20 cc. of concentrated nitric eral years.
