A SMALL LABORATORY FOR CHEMICAL MICROSCOPY RAYMOND D. COOL SCHOOL O F MEDICINE. UNN-ERSIN OR PENNSYLVANIA, PMLADELPHIA
Instruction i n chemical microscopy is being ignored or neglected in a large proportion of the institutions of higher learning in.:this country. The usual excuse of the large expense involved i n suchinstruction can hardly be justijied. A brief description is given of a smell laboratory jbr instruction i n elementary chemical microscopy. ..~
. . . . . .
The time and labor-saving features of chemical microscopy, its educational value in the training of chemists, and some of its applications have been pointed out by Chamot (I), Chamot and Mason (Z),(3), Lindsley (4, p. 49), Benedict (5), and Mason (6). Willard (7), in a paper presented at the "Symposium on Analytical Chemistry" a t the Atianta meeting (1930) of the American Chemical Society, referred to the importance of microscopic methods and said that particular stress was being laid a t the symposium upon the application of physical and physico-chemical methods because the extent of developments in these methods was not as widely known as it should be. The desirability of training in the use of the microscope was also pointed out in a report by a sub-committee of the Division of Chemistry and Chemical Technology of the National Research Council (8) which announced, "the microscope has come to be so valuable a part of research laboratory equipment that every research chemist should be well trained in its use." , As early as 1899 Chamot (9) wrote, "it.is rather remarkable how slow American chemists have been in realizing the importance of the microscope as an adjunct to every chemical laboratory," and in 1914, in the preface to the first edition of "Elementary Chemical Microscopy" (lo), he again pointed out their reluctance to take advantage of the microscope as an important tool in the solution of their problems. In 1921, in the preface to the second edition of "Elementary Chemical Microscopy" (ll), he noted an increase in their appreciation of the importance of the microscope as a laboratory accessory, and Lindsley [ ( 4 ) ,preface] claimed that a slow but steady growth in instruction in chemical microscopy in American institutions of higher learning had resulted in the establishment of departments in a t least seven of these institutions by 1926. I n spite of the growing recognition of the value of the microscope as a tool for the chemist, and the general admission that its use involves not a new theory but a new technic which can be best learned practically under the direction of one familiar with it, training in chemical microscopy does not seem to have become as widespread as its importance would justify. A search through the catalogs of a number of institutions of higher learning in this country showed that relatively few list courses in 2084
VOL. 9, No. 12 LABORATORY FOR CHEMICAL MICROSCOPY
2085
chemical microscopy, and the fact that some which list such courses do not actually give them makes the number of schools giving instruction in this subject still smaller. The frequent excuse of the large expense involved can hardly be justified. It seems quite possible that on visiting a department so magnificently equipped as that in Baker Laboratory a t Cornell somebody unfamiliar with this work might he overcome with the realization that it would be impossible to reproduce such an outlay of equipment in his own department. He fails to realize that the department a t Cornell is the result of a long period of development, and that it is not necessary to duplicate so great a material equipment, which probably is not equaled anywhere, for instruction in elementary microscopy. While it is true that a microscope costs more than the usual individual pieces of apparatus intrusted to undergraduate students it costs no more than some of the more special apparatus which has come to be regarded as necessary for the instruction of students in thorough courses in chemistry. The actual cost of material consumed in this work is so small that if it is averaged with the initial investment the average cost over a period of years will compare very favorably with the cost of any other laboratory course in chemistry. If the instructor concerned is willing to expend the time and energy much of the equipment can be prepared by him, and if he has at his disposal the services of a skilled mechanic the amount of material which can be produced locally is considerably increased. The apparatus which requires highly specialized expert workmanship must necessarily be purchased, but if the instructor has the co6peration and support bf the administrative head of his department this can be managed without unduE hardship in any but the most indigent departments. The special apparatus required is becoming more readily available in this country, and the amount of reference material in English has been notably increased recently. I n order to indicate what might be accomplished on a small scale a brief description is given of a laboratory which was equipped under the direction of the writer* several years ago. With the sympathetic cooperation and generous support of the head of the department of chemistry, the services of a skilled mechanic, and the expenditure of many hours personally he was able to accumulate, in a relatively small department with limited resources, equipment which though limited in amount was nevertheless of splendid quality and adequate for the work given in elementary microscopy. The laboratory, part of which is shown in the illustrations, was planned to take care ultimately of twelve students, but because of the lack of abundant resources provision was made for the immediate needs of only six students. By making plans in the beginning for the ultimate capacity of the laboratory, plumbing and electrical installations could be arranged in such a 'The writer is indebted to Dr. C. W. Mason of Cornell University for valuable advice in connection with the equipping of the laboratory
2086
JOURNAL OF CHEMICAL EDUCATION
DECEMBER. 1932
manner that they need not be changed in the future but could be added to as the need arose and resources became available. The wall case and microscopy tables were built by a local mill according to specifications furnished by the instructor. The shelving was put up by the departmental mechanic, and the plumbing and electrical installations were taken care of by the university plumbers and electricians, respectively. The tables, 27 inches high, were made slightly lower than the usual table provided for microscopes in the biological sciences so that a worker could
VOL. 9, NO. 12 LABORATORY FOR CHEMICAL MICROSCOPY
2087
sit on a chair of normal height and still use a microscope with comfort. Stenographer's swivel chairs with adjustable backs were used. The tops of the tables measured 60 X 33 inches, and had a "cut-out" space 8 X 22 inches, as recommended by Chamot (12), and Chamot and Mason [(7), Vol. I, p. 1361. This "cut-out" was not in the middle of the table edge but slightly to one side so that a worker could swing from one side to the other on the swivel chair during various manipulations without bumping his knees into the drawer on the left or the cupboard on the right. Each table was provided with a double electrical outlet and a gas cock at its back edge. A reading lamp with flexible arm and containing a frosted blue "daylight" bulb was plugged into one of the outlets and used for ordinary artificial illumination. The other outlet was available for special apparatus which was used only occasionally. Bunsen burners with pilot flame attachment served for general heating purposes. The cupboard part of the table was built so as to offer its contents as much protection from dust as possible. It contained three well-fitting drawers which were covered by a single door. The latch was arranged so that the door was pressed tightly against its frame when the catch was closed, and could be locked with an ordinary laboratory padlock if desired. The lower parts of the tables were finished with a dark oak stain and the tops were painted with a "flat" black paint and lightly waxed to make them water repellent. A chemical laboratory table of the usual type, provided with air, gas, and water, and an outlet for direct current in the wall nearby snpplemented the equipment installed especially'for microscopic work. Each student was provided with a chemical lnicroscope equipped with a triple nosepiece, 32 mm., 16 mm., and 8 mm. achromatic objectives, 5 X , 7.5X or 8X, and 10X cross-hairedeyepieces,a 7.5X or 8 X micrometer eyepiece, a 7.5X or 8 X net-ruled eyepiece, Abbe condenser, analyzer, polarizer, and stage micrometer. Two reagent blocks [Cf. (4).p. 51; ( 3 ) , Vol. 11, p. 22; (13), p. 181, each holding sixty 2-cc. glass-stoppered vials, were provided for each student. One of these blocks contained the materials ordinarily required in the work in general microscopy [(3), Vol. I, p. 4601, while the other held the reagents for microscopical qualitative analysis [Cf. (3), Vol. 11, p. 4011. These reagent blocks were made and stained by the mechanic and treated with molten paraffin by the instrnctor. Empty vials, purchased from a laboratory supply house, were cleaned and filled by the instrnctor. A reagent block holdmg five 1-02. bottles with ground-glass droppers for the common dilute acids and ammonium hydroxide were prepared in a similar manner for each student. A piece of plate glass, 12 X 12 inches, served to protect the table top during manipulations which might disfigure it, and also acted as a cover for the key charts to the vials in the reagent blocks. The students bought certain personal items such as ordinary slides, cover-glasses, dissecting needles, and forceps
2088
JOURNAL OF CHEMICAL EDUCATION
DECEMBER. 1932
from the chemistry storeroom. Drawing cameras and mechanical stages were shared by two students. The more important special apparatus which had to be purchased as single items and shared by the whole class included a Greenough binocular microscope with multiple, revolvingnosepiece, 1.7X, 3.4X, and 6.8X objectives and paired 9 X eyepieces, a quartz wedge, a "first order red" selenite plate, a 4-mm. apochromatic objective with correction collar, a 10X compensating eyepiece with crosshairs, a fluorite oil-immersion objective with iris diaphragm, a comparison eyepiece, a vertical illuminator, a bi-centric dark-field condenser, a special cell for dark-field illumination, a cube of uranium glass, a cover-glass gage, a microscope lamp with short focus condensing lens, iris, and "daylite" glass, a 45" totally reflecting prism for miaoprojection, an automatic arc lamp with rheostat, and a small water cell and "Aklo" glass filter for absorbing heat while using the arc lamp. Although some of the apparatus could not be selected directly from catalogs of the usual stock equipment handled by the manufacturers, and in some instances required special orders, the manufacturers were willing in every case to cooperate in a most commendable manner and furnish material according to specifications and requirements. With the exception of some special reagent bottles [cf. ((3, Vol. I, p. 139, Figure 65; Vol. 11, p. 21, Figure 141 which required a special order, the glassware needed was readily obtainable from the standard stocks of laboratory supply houses. Most of the other apparatus required, Such as sampling rods, crucible holders, cells for determining the refractive indices of liquids, glass crucibles (made from Pyrex test tubes), filtration tubes, and glass rods were made by the mechanic, the instructor, or both. Metal beads and paint films for practice in micrometry were prepared by the instructor who also collected materials such as abrasives, pigments, fillers, and fibers from various sources. The few reagent chemicals which were not already in the department were practically all readily available on the market, and the professor in charge of the class in inorganic preparations kindly cooperated in the preparation of those which were not easily obtainable. In addition to the material mentioned above a number of reference books on general and applied microscopy were collected. Although the planning and equipping of such a laboratory in the manner described above may take a very large part of the instructor's time, including holidays, the writer believes that it is well worth the effort. This phase of the chemist's training has increased in importance until i t should be slighted or ignored no longer, and the work is welcomed with enthusiasm by the student as a departure from the usual routine of analytical iustruction.
VOL.9, NO. 12 LABORATORY FOR CHEMICAL MICROSCOPY
2089
Literature Cited (I)
(2)
(3) (4)
(5)
CHAMOT. "Chemical Microscopy-Time and Labor Saver." Sci. Monthly, 24, 366 (1927). AND MASON,"Chemical Microscopy I. Crystallization Experiments CHAMOT as a n Introduction to Metallography," J. CHEM.EDUC.,5, 9-24 (Jan., 1928); "Chemical Microscopy. 11. Its Value in the Training of Chemists," ibid., 5, 2 5 8 6 8 (Mar., 1928); "Chemical Microscopy. 111. Its Value in the Training of Chemists." Oid., 5, 5 3 6 4 8 (May. 1928). CHAMOT AND MASON,"Handbook of Chemical Microscopy," John Wiley and Sons, Inc , New York City, Vol. I , 1930, Vol. 11, 1931. Lrrrosmv, "Industrial Microscopy." William Byrd Press, Richmond, Virginia, 1929. BENEDICT, "The Polarizing Microscope in Organic Chemistry," Ind. Enf. C h m . . Anal. Ed., 2, 91-2 (Jan., 1930). MASON," M i c r ~ ~ c ~ p Methods i~al in Analytical Chemistry," ibid., 2, 20313 (July, 1930). WILLARD, "Modern Trends in Analytical Chemistry," ibid., 2 , 2 0 1 3 (July, 1930). GEER AND STINE, "Education of the Research Chemist," Ind. Eng. Chem., News Ed., 7, KO.13, 1 (July 10,1929). CHAMOT, "A Microscope for Micro-Chemical Analysis." I. Applied Microscopy, 2, 502 (1899). CHAMOT,"Elementary Chemical Microscopy." John Wiloy and Sons, Inc., New York City. 1915. ibid., 2nd ed., 1921. CHAMOT, CHAMOT, "The Laboratories of Chemical Microscopy a t Cornell University, Ithaca, N. Y., U. S. A,," Mikrochemie, 2, 104 (1924); National Research Council Committee Report, "Laboratory Construction and Equipment," The Chemical Foundation, Inc., New York City, 1930, p. 235. EMICH-SCHNEIDER, "Microchemical Laboratory ~ a n u a l , "John Wiley and Sons, Inc., New York City. 1932.
