PHOTOGRAPHY of CHEMILUMINESCENCE EVANS W. COTTMAN Madison. Indiana
I
N THE May, 1937 issue of THISJOURNAL the pres-
ent writer named and described several substances which emit cold light upon proper oxidation. Since then a number of attempts have been made in our laboratory to photograph this chemiluminescence. The four photographs here presented are among our best. Chemiluminescent photography presents the following problems: 1. Light production. 2. Maintenance of the light. 3. Selection and adjustment of camera. 4. Selection of film. 5. Length of exposure.
PRODUCTION To produce chemiluminescence, the following substances must be present in suitable concentration: (a) A chemiluminescent compound.-This is usually some unsaturated ring compound, capable of emitting visible radiation upon disruption of the ring. (b) An oxidizing agent.4odium hypochlorite, potassium ferricyanide, blood, and perchromic acid were found among the most satisfactory. (c) A perode.-A three per cent. solution of hydrogen peroxide, diluted to the proper strength, may be used for most purposes. (d) An alkali.-Either sodium hydroxide or potassium hydroxide may he used. The degree of alkalinity LIGHT
required, will depend upon what other solutions are used. (e) Proper sol~ent.Some chemiluminescent reactions require water medium; others, alcohol. MAINTENANCE OF THE LIGHT
Chemiluminescence is of low intensity. Therefore, long photographic exposures are required. When the solutions described above, are poured together, the flash of light usually lasts only a few seconds. There-
thirty inches from the reaction tube, facing i t directly. A portrait attachment lens (Eastman #5) is placed on the camera, and the camera is focused on the reaction tube, using a ground glass. The camera and reaction tube are then both clamped firmly in place, the film is inserted into the camera, and the room is darkened. After the apparatus is working smoothly, and a steady light is being emitted, the camera shutter is opened and the exposure is begun. SELECTION OF FILM
A very high-speed film, particularly sensitive to the central portion of the visible spectrum, should be em-
played. In these experiments Eastman's Super X USED IN MAMTAMING LUMINESFIGURE 1.-APPARATUS A , B, C, THE SOLUTIONS WHICHWILL PRODUCE film was used. It has been recommended that hyperWHEN MIXEDTOGETHER. D. BLOCKUPON WHICH sensitization with mercury vapor might prove helpful TKE CONT~OLLINQ PINCHCOCKS ARE MOUNTED. E, REACTION TUBE I N WHICH THE LUMINESCENCE WILL TAKE PLACE. in lessening the necessary exposure time. This has not been tried in any of these experiments, however. F, OVERPLOW TUBE CENCE. LIGHT
LENGTH OP EXPOSURE
The required length of exposure may be determined fore, in order to obtain the necessary exposure, the duration of this light must be indefinitely prolonged. roughly by the visibility of a watch dial, illuminated by This is accomplished by passing the various solutions through separate mbber tubes, into a reaction tube, where they mix, producing the luminescence. Figure 1 shows a diagram of the apparatus. The rate a t which the various solutions enter the reaction tube, E, is controlled by the pinchcocks shown a t D. The used solutions pass from the reaction tube through the outlet tube, F. In some of the photographs the luminous outlet tube is plainly visible. SELECTION AND ADJUSTMENT OF CANERA
In order to reduce the necessary time for exposure, a camera having a very high-speed lens should be selected. In making the accompanying photographs, an Eastman Kodak Bantam Speaal was used. The lens of this camera has an aperture of f :2. The camera should be placed a t a distance of from twenty-four to
FIGURE ~.-LIGHI.P R O M LOPHINE
the light emitted from the reaction tube. First, the eyes are thoroughly adapted to the dark, and are then brought up to within six inches from the watch. If the light is so faint that one cannot tell time when the watch is held up next to the tube, the exposure should be something over fifteen hours. If the time is just visible when the watch is held one foot from the light and six inches from the eyes, the exposure should be from one to three hours. If the light is of sufficient intensity to enable the observer to tell time when the watch is three feet from the light, the exposure should be from seven to twenty minutes. These exposure lengths
solution contains sufficient material to last about two hours, hut when i t is about half gone the intensity of the luminescence in the reaction tube will begin to wane, due to the decomposition of the peroxide. This can he restored by adding another 100 cc. of the peroxide to Solution C. Figure 3 shows the light emitted when lophine is oxidized. The exposure was one hour and twenty
FIGURE 5.-LIGHT
FROM
CHEMGLO
minutes. The light from lophine is yellow. Solution A was a one-half saturated solution of lophine in methyl alcohol. Solution B contained 200 cc. of three per cent. hydrogen peroxide in 1800 cc. of methyl alcohol. Solution C was composed of 400 cc. of Clorox (sodium are given only for the experimental conditions de- hypochlorite commercial cleaning fluid), 200 cc. of scribed above. A camera of different aperture, or a forty per cent. aqueous sodium hydroxide solution. different type of film would cause a change in the re- and 1400 cc. of water. quired length of exposure. In Figure 4 is shown the light emitted from the oxidation of luminol (3-aminophthalhydrazide). The exEXPERIMENTAL posure time was fifteen minutes. The light is blue. The accompanying photographs were taken under Solntion A was made by dissolving one gram of luminol the following experimental conditions, all but Figure 5 in 160 cc. of five per cent. aqueous sodium hydroxide using the apparatus sketched in Figure 1. solution and diluting this to 2000 cc. Solution B conFigure 2 is a photograph of the light emitted by urine tained 40 cc. of three per cent. hydrogen peroxide soluwhen oxidized by blood in alcoholic alkaline peroxide tion diluted to 2000 cc. Solution C was a 1:10 mixmedium. The exposure was sixteen hours. Solution A ture of Clorox and water. was one part defihrinated cow blood to fifty parts water. Figure 5 is a photograph of the chemiluminescence Solntion B was urine. Solution C was made by dis- emitted when chemglo was dissolved in a bowl of water. solving 200 cc. of forty per cent. aqueous sodium Chemglo is a dry powder preparation which emits a hydroxide solution in 1800 cc. of methyl alcohol and greenish light when dissolved in water. The water was adding 200 cc. of three per cent. hydrogen peroxide kept agitated and more chemglo was added, a spoonful solution. This solution deteriorates rapidly and a t a time as needed, to keep the light a t its maximum should be used immediately after making up. Such a brilliance. This photograph was exposed ten minutes.
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The lesson to be derivedfrom the whok of this strange hisfory is one which n e e h to be continually revived a n d set i n the new light of modern discovery and invention. The Lesson is simply that until men 6egan to observe and interrogate Nature for the sake of learning her ways, and without concentrating their attention on the expectation of w c f u l applications of such knowledge, little or no progress was made. I n other worh, until a suficienf,foundafion of pure science hm 6een succesJfuUy /aid there can be no applied science. Real progress comesfrom the purTILDEN suit of knowkdgefor its own sake.-%^ WILLIAM
