T H E CHE?\IILV!PIIINESCESCEO F SOLID SODIUSI BY ROBERT 111. BOWIE
As long ago as the time of Davy, it was known that freshly cut surfaces of sodium or potassium in open air, when viewed in the dark, give off a faint light. G. Rebaul in 1910 correctly stated that this effect \yas due to the formation of the hydroxide upon reacting with the moisture in the air. I n this article, eighteen reactions are described which were used to determine the nature of the reaction which produces the luminescence. I t was found that the liberation of hydrogen always accompanied the production of light, but its production did not always accompany the liberation of hydrogen. In no reaction in which a halide was formed, was luminescence produced. The luminescence seemed to be associated with the breaking of a hydrogenoxygen bond (or bond to some element resembling oxygen, as sulfur) of a vaporous, polar molecule. The spectrum of this chemiluminescence consisted of a narrow band with a maximum at about j ~ m,u. o Sodium metal when freshly cut and viewed in the dark, gives off a faint greenish light. This fact was probably noticed first' by Davy as indicated by G. Rebaull in his article. Linneman? also noted the fact in 1858,correctly stating its color, and gave an idea as t o its intensity. He found that at about 60" or 70°, sodium produced a light as bright as phosphorus. G. RebauP in 1910 worked with a sodium-potassium alloy. He showed quite conclusively that, although the phenomenon always accompanied the rupturing of the surface, it could not be ascribed to triboluminescence, since with dry air, the rupturing of the surface went on but no light was produced. From this he concluded correctly that it was the formation of the hydroxide from the moisture in the air which produced the light. Spectrographically, it has been found that the chemiluminescence consists of a narrow band with a maximum a t about j ~ o *%". o It was the purpose of this investigation t o determine the nature of the reaction which acconipanied or produced the luminescence. The Investigation I n order to conduct these experiments, it was necessary to have a means of producing a new surface of metal in a controlled atmosphere. I n order to do this, the metal was placed in a small pressure gun having a cylinder five inches long with a bore 518 inches in diameter. The piston was forced down by a threaded rod turned by a handle. The metal was forced through a S o . G. Rebaul: Compt. rend., 168, 119j(1910).
*E.Linneman: J. prfikt. Chem., 75, 128 (18j81. G.Rebaul: Cornpt. rend., 168, 1193 (1910).
2965
THE CHEYTLCJIIPiESCEXCE O F SOLID SODIL31
60 mire gauge hole in the end of the "gun" into R pyrex glass tube having two side arms. The controlled atmosphere was admitted through one and drawn out through the other. I n operation, the gas was first passed through the necessary drying or humidification trains and then into the tube for a period of half an hour in order t o sweep out all other gases. About an inch or two of sodium wire was then exuded and the rate of reaction noted and compared roughly with the rzte of reaction vith moist air. The v:ilues obciiried appear in column 3 in Table I. The light was then turned out and, after a sufficient time h:id elapsed, another few inches of fresh wire were exuded. At the same time, a piece of metal outside of the tube in the moist air of the dark room, as placed hack of the tube so that it rvas vievvtd through the ! U ~ J C . In this !my, the light emitted by the metal wire in the controlled atmosphere was compared roughly with that produced by moist air. T-alues thus obtained appeclr in column .+ of Table I. The reacting suhstmces are given in column I .
TABLE I Table of C'oniparatire Reactivity and Luminescence of Various Renction LIixtures upon Solid Sodium duhst:ince Reacting 0 2 0 2
€1 €I2
c'o:!
0, 1102
Relative Reactivity Moist mr = I
.4dmixetl
C:lS
+
+ 4-
0 . 2
H?!) H,O
I120
Lurninesceriric Relative t o
Moist :air = I 0
I
I
0
0
I
I
0
0
I
;.
1.2
1
I
('12
0 0
0
nr2
0,s
0
I? II
