Inexpensive Applications
George A. Scherer and Richard s. Sakurail Western College for Women Oxford, Ohio 45056
of Polaroid Film
The photographic detection of radiation is useful in laboratory experiments at several levels in the undergraduate chemistry-physics curriculum. The traditional procedure has been to use ordinary film which must be developed in a dark room. A more recent development has been the use of Polaroid Land film which does not require a darkroom, but this film requires special cameras or holders which are expensive. To overcome this difficulty,a simple inexpensive homemade holder for Polaroid 4 X 5 Land Film Packet Type 57 (Fig. 1) has been developed, and a simple hand roller (or a toy rolling pin) is used to carry out the developing.
Figure 1. type:57.
Homemade Rim holder for Polaroid 4 Hand roller for developing Polamid Rlm.
X 5
Land Film Pocket
The film holder is made from two 5l/. , - in. X 5 I / a in. pieces of '/a in. masonite, one of which has an ooknina 33/r in. x 43/4 in. cut in it. The two pieces a& held apart by wooden shims in. wide which are the thickness of the film and serve as guides for it. The two oarts of the holder are hinged along one edge ., and closed with a simple clasp at the opposite edge. One-fourth inch black velvet ribbon is cemented around the opening to keep out stray light. A #57 film packet is placed in the holder so that the active side is toward the ooeninz and the metal strin of the packet is along one edie of the holder. When thk holder is in place for exposure, the blackpaper fdm cover is pulled out the distance, the eiPo-sure is made, and the film cover pushed back over the exposed film. The exposed film is then removed from the holder readv for develooina. ., The develooina . is accomolished the film on a table top and running roller by (made from a toy rolling pin) over the developing pod
a
Presented before the Division of Chemical Education a t the National Meeting of the American Chemical Society, Chicago, Illinok, September 11, 1967. 'Present address: Webster College, Webster Groves, Missouri. 'SCHOENBECK, RALPH,AND TABBUTT,FREDERICK,D., J. CHEM. EDCC. 40,452 (1963). Hxnn~s,J., AND AHLOREN, A., P h v ~ mTeacher, 4,321 (1966).
134 / Journal of Chemical Educafion
in the film. At the end of 10 sec the print can be removed and viewed on the spot. This technique is used to detect the following three kinds of radiation: emission spectra from a grating spectrograph, X-rays diffracted by crystals, and radioactivity from I4Ci n plant materials. Emission Spectra
Schoenbeck and Tabbutt,%describe the construction of an inexpensive ($80) spectrograph of moderately high resolution which can be used wit,h this polaroid film holder. The spectrograph is built in a 3/4 in. plywood box 36 in. X 15 in. X G iu. Two razor blades form the entrance slit,. The light beam from the slit is reflected by a spherical mirror to a plane reflecting grating (2 in. X 2 in., 15,000 lines/in.) which can be rotated. The light from the grating is reflected by another spherical mirror to the opening where the film holder is mounted. Using this instrument, mercury and hydrogen at,omic spectra have been studied. Figure 2 shows these spectra and the apparatus. The
C %, I
1 1
duel
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7
Figure 2.
5/61
4340
I
I 5021
InexpenGve spectrograph (top off).
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MERCURY
Em\srion spectra (mercury
Ond
relative distances between the lines can be accurately measured by projection using an opaque projecto:. The 5790, 5770, 5461, 5025, 4355, 4075, and 4047 A lines of the mercury spectrum are readily identified. the hydrogen atomic spectrum the 4861 and 4340 A lines of the Balmer series can easily be located. Harris and Ahlgren3 describe how essentially the
Crystal Patterns
Hiltou4 describes an inexpensive set-up for taking Laue photographs of crystal structure. It uses obsolete medical X-ray equipment. The collimatirlg slits for the X-rays are in. holes in lead sheets about 10 cm apart. The crystd is placed about 2 cm in front of the second slit and the film 5-10 cm in front of the crystal. With such a set-up, photographs of sodium chloride and calcite patterns have beeu made on #57 Polaroid film (Fig. 3). I n this application the holder can be dispensed with since the black paper cover does not have to he removed from the film during exposure with X-rays. Radioactivity
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1 X-my Diffraction unit from obsolete medical equipment lthowr mounting ofcrystal). Calcite Loue structure. Figure 3.
Figure 4. leaf.
C o ~ b a n - 1 4pattern
in
radioactivity in plants and ulant materials. For example plants can be grown in a bell jar containing an atmosphere of a carbon-14 dioxide made by treating Nad4COTwith HCL5 Dried and messed leaves from such plants show a pattern when placed on #57 film for several days (Fig. 4). In the same way one can see where the 14C goes in paper chromatography of ma-
terial from such plants. The techniques described are inexpensive, use homemade equipment, and are far more convenient than the conventional darkroom wet-process methods. Exposure time is shortened since this film is approximately eight times faster than standard film. A finished positive print is produced for viewing on the spot after only 10 sec of development at a cost of approximately s.75.
same experiment can be done without a spectrograph hut their method must be carried out in a darkroom and requires a Polaroid camera. HILTON, WALLACE A,, School Sn'. Math., 51,717 (1951). H E ~ M I AAND S JOECILE,"Radioactivity Fundamentals and Experiments," H o l t , Rinehart & Winaton, Inc., N. Y., 1963, Experiment 51. 4
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Volume 45, Number 2, Februory 1968
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