INDUSTRIAL AND ENGINEERING CHEMISTRY
218
Verdino, A,, Mikrochemie, 9, 123 (1931). Vetter, F., Ibid., 12, 102 (1932). Vieboeok, F.,Be?., 65, 493 (1932); 63, 3207 (1930). Wasitzky, A,, Mikrochemie, 11, 1 (1932). Weygand, C., “Quantitative analytische Mikromethoden der organischen Chemie in vergleichender Darstellung,” Leipzig, Akademiache Verlagsgesellschaft, 1931. (144) Whitmore, W. F., and Schneider, F.,IND. ENQ. CHEM.,ilnal. Ed., 2, 173 (1930); Mikrochemie, 8, 293 (1930). (139) (140) (141) (142) (143)
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Wiesenberger, E., Ibid., 10, 10 (1931). Willard and Smith, J . Am. Chem. Soc., 44, 2028 (1916). Wormley, “Microchemistry of Poisons,” Philadelphia, 1867. Zacherl and Krainich, Mikrochmie, 11, 61 (1932). RECEIVED May 26, 1936. Presented before the Division of Physical and Inorganic Chemistry, Symposium on Recent Advances in Microchemical Analysis, at the 89th Meeting of the American Chemical Society, New York, N. Y., April 22 to 26, 1935.
The Role of Analytical Chemistry in Industrial Research 11. Microanalysis BEVERLY L. CLARKE
AND H.
W. HERMANCE, Bell Telephone Laboratories, 463 West St., New York, N. Y.
The application of microtechnic to industrial chemical N T H E FIRST paper (3) of this series a general descripproblems is a recent development in the United States. A tion was given of the analytical organization evolved number of papers, such as those of Grassner (7), Niessner a t Bell Telephone Laboratories. The present paper (11), and Goubau ( B ) , have described the use of this technic is concerned with the unit of the organization that was termed in European laboratories. in the first paper “microchemical analysis.” The word Kirner (Q),in a recent paper, has discussed the applica“micrurgy” was coined by Pet6rfi ( l a ) to describe biological tion of the standard Pregl methods of organic microanalysis microdissection and later expanded by Titus and Gray (13) to a specific industrial problem-research on coal a t the Coal to include dissection and examination under the microscope Research Laboratory a t Pittsburgh. So far as the writers of nonbiological material. Since the term, by its pure know, however, no description has appeared of an American Greek derivation, means “operations on a small scale or laboratory designed to handle general problems in the exwork with minute quantities,” it can logically be used as a amination of materials by micrurgical technic. general term to include microchemistry, microanalysis, and Such a laboratory has been evolved a t Bell Telephone chemical microscopy, as well as such special technics as those Laboratories (8). A number of industrial concerns, hearing developed in the authors’ laboratory and presently to be deof its work, have sent their chemists to inspect the laboratory, scribed. It is here so used, and is suggested for general adoption. with a view to setting up similar facilities; others have Moser (IO) has emphasized the fact that until recent years written to the authors. The present paper is intended to analysis has not been a specialized branch of chemistry. make generally available a record of experience in this field. This is true as to both apparatus and personnel. The classical methods of analysis evolved largely through the application of such reactions as were readily conceived on the basis Province of Micrurgy of nonspecialized chemical knowledge. Comparatively little Materials analyzed or examined by the Analytical Division search was made for new reactions having specific advanfall into the following broad tages for analysis. Very classes : few special pieces of apparatus were d e v e l o p e d , and 1. Electrical conductors even today the glassware 2. Materials used as elecand other equipment seen trical insulators or dielectrics in most analytical labora3. Magnetic materials 4. Protective and finishtories do not mark them off ing materials from laboratories devoted 5. Structural materials to other kinds of chemical 6. Transformation prodwork. Among the other ucts 7. Miscellaneous shortcomings and disadvantages of classical analytical By “transformation prodc h e m i s t r y are: frequent ucts” are meant materials disproportionality between used in telephone apparatus the q u a n t i t i e s of the eleand in the plant, that have ments sought and the size undergone some deterioraof the apparatus, causing tive change with use. Chief large inherent errors; and, among them are corrosion as Kirner (9) has pointed and tarnish products proper; out, time-consumption, exalso included are deterioplosion hazards, and costlirated rubber, insulating and ness of reagents in macrol u b r i c a t i n g oils, paper, FIGURE 1. PLAN OF LABORATORY scale operations.
I
JULY 1.511935 ,
ANALYTICAL EDITION
impregnating compounds, etc. Tests made on such materials are usually of a diagnostic nature: There has been a service failure, and the samples submitted are the material evidence firom which it is desired to gather information as to fundamental causes and a t the same time to deduce the proper preventive or palliative measures. When a request for an analysis is accompanied hy an adequate sample, and when the work to be done calls for standard procedures, the analysis is carried out in the General Analytical ]Laboratory by macromethods. Fre,quently, however, because of the delicacy of the necessary sampling or preparative operations, of the small size of sample, or of the complex character of the tests to be made, a requested analysis cannot be performed efficiently by a standard procedure. In these cases the use of micrurgical technic is indicated,
Ilescription of Laboratory
219
FIGURE 2. VIEWOF HOOD Center, steam bath for microapparatus; right, air jets for aiding evaporation of liquids on hot plate.
The objective was to design laboratory space suitable for general micrurgical work in which three or four men could work comfortably. Owing to the extreme dustiness of the air in lower Manhattan, it was immediately apparent not only that a special room must be provided but that some system o f air filtration must be employed. While air filtration may not be necessary in localities where the air is cleaner, it is the authors’ conviction that a special room is a prime requirement for good results. Similarly, the materials used to cover the walls, floor, and laboratory furniture should be chosen with the object of eliminating, so far as possible, dust sources within the room. Some of the work benches are covered with “battleship linoleum,” a heavy grade of blacksurfaced linoleum. Once a month the surface is refinished with beeswax. This material, besides its advantages from the dust standpoint, tends to reduce breakage; and the black background is desirable. Since, however, heating equipment would injure linoleum, benchtops carrying such apparatus are of stone. The laboratory floor is covered with “asphaltasbestos tile.” Figure 1 is a plan of the laboratory. There is a general division of the space into four sections: for macropreparative opera-
FIGURE3. MICRURGICAL SECTION Left, one of reagent blocks, partly lifted out of its well.
tions, A ; for quantitative microanalysis, B; for qualitative microanalysis, C; and for microscopic and general micrurgical work, D. The hood has three removable partitions, so that operations can be segregated when desirable. A micro-Kjeldahl digestion stand is permanently placed in the hood. Into the back wall is built an assembly for treatment with hydrogen sulfide, supplied from a small tank of the “lecture bottle” type. An arrangement is provided whereby the gas can be passed with the same facility into a large beakerful of solution or a single drop on a microscope slide. The hood contains a steam bath, shown in Figure 2, with provisions for the steam-evaporation of liquids in microcentrifugetubes of various sizes, microbeakers, etc. Capillary air-jets are used to aid evaporationboth on the steam bath and on hot-plates. A Becker microbalance having a rated sensitivity of 0.001 mg. 7 is used. In order to minimize the effect on the balance of changes in temperature and humidity caused by the presence of the operator, the balance compartment is so constructed as to allow free circulation of air and yet to prevent sudden drafts. Me- ; chanical insulation is effected in the following manner: The ’: balance table consists of a slate slab on metal pipe legs which are 1 insulated from the floor by rubber pads. A second slate slab rests on the table, supported by rubber stoppers. On this the balance case stands, its feet protected by Sartorius shock absorbers. A hood over the balance protects it from dust and air currents. A carefully centered light housing is built into the hood about 45 cm. (1.5 ft.) above the balance. A 1.25-cm. (0.5-inch) glass plate, ground on both sides, is interposed to absorb most of the heat. No trouble from unequal heating of the balance arms has been experienced with the particular balance in use. To avoid accidental jarring of the balance by the operator, a table top and apron are built around the balance on a level with the balance floor. These are attached to the partition and have no physical connection with the balance supporting structure. ~
A corner of the room, D, is equipped for the performance of general m i c r u r g i c a l operations. It is desirable to have available within a conveniently small working space facilities for applying the greatest possible variety of physical and chemical agencies to microscopic specimens. The d e t e r m i n a t i o n of physical and optical properties, the study of s t r u c t u r e , the mechanical separation and isolation of minute amounts of material, as well as such general operations as ignition, fusion, digestion, filtration, electrolysis, etc., may all be performed under the microscope with the special accessorieshere provided.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
For chemical microscopy a Leitz petrographic instrument is used. It has been found to be a great convenience to have the microscope supported below the table in a well, K , of such depth that the stage is at bench level. Access to substage adjustments is through a sliding door at the front end of the well. When it is desired to use the microscope a t bench level, a cover plate fits in the recessed edges of the well. The substage light is supported below the well, light being admitted to the microscope through a hole in the well floor. The substage light may be slid away and an arc l i g h t beam s u b s t i t u t e d when more intense illumination i s desired. T h e a r c l i g h t assembly is mounted horizontally on a rack near the floor, and may be slid to the back of t h e bench when n o t i n use. T h e beam is b e n t vertically upward by a 45” mirror placed in line with the hole in the bottom of the well. Incident light is f u r n i s h e d b y a Busch “punktlight” (tungsten arc bulb) supported on a ball FIGURE 4. MICROMANIPULATOR AND joint above the well. EUSCOPE IN USE When the microscope is used a t bench level this may also be used for more powerful transmitted light, particularly when the image is to be projected on a screen. Close to the microscope a Reichert micromanipulator unit is mounted on a sliding base. The particular model was selected for its ruggedness of construction, a necessary requirement when relatively hard materials are studied. A viewing screen (Bausch & Lomb Euscope) is also available for attachment to a permanently mounted adjustable supporting rod, so that both the micromanipulator and the illuminating devices may be used without change in the arrangements. This is useful for demonstration purposes and is particularly desirable where observations continued over a long period, as in dust counts, micrometry, etc., might otherwise result in eye fatigue. It also permits simultaneous observation of image and object being manipulated when more difficult operations are performed. Solid reagents in 5-gram vials are kept in wooden blocks, stored in wells, G, in the table top where they are immediately available on removing the flush cover plates. This arrangement makes for neatness and compactness and reduces contamination from dust. Three wells are provided, one for inorganic solids, one for organic reagents, and a third for refractive index liquids. The two smaller wells shown in Figure 1 are for storing miscellaneous small equipment. To avoid waste of time in setting up special equipment, a number of accessories have been installed permanently in the micrurgical section. A transite panel, H , set into the table top contains electrically heated aluminum blocks, a warm air jet universally inclinable for evaporation of liquids on microscope slides, and a quartz-lined muffle furnace of dimensions suitable for the ignition of microscopic specimens. The slides may be supported during preparation in the rubber-faced jaws of a spring clamp supported in turn on a ball joint. The slide may thus be inclined in any direction, a facility of considerable value in the decantation of drops and in evaporation with the air jet. A group of flashlight cells controlled by a multipoint switch and a rheostat provides the small current necessary for carrying out electrolyses under the microscope, particularly with the cell described by Brenneis ( 2 ) . Electrical controls for the various illuminators, heating devices and other equipment, and meters for the microelectrolytic circuit, are centralized on a switch panel a t the back of the table. A small high-speed centrifuge, L, with interchangeable heads for microtubes and capillaries is also conveniently available on the table. In order to avoid the deteriorating effects of acid
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fumes on delicate equipment, a miniature hood is provided, the draft through a hole in the window pane being maintained from the positive pressure of the air in the room. A sink of small dimensions, F , is provided by a Buchner funnel fitting into a circular opening with its edge level with the table top. A dental motor with flexible shaft and a complete set of drills, burrs, stones, and cutting wheels is of invaluable service in procuring microsamples and in systematically reducing complex structures under the microscope. Dissecting tools are kept within easy reach in a wooden containing block. A Zeiss binocular dissection microscope is useful here. Its large stage permits the attachment of various accessory tools, clam s etc., while the increased depth of focus and stereoscopic ,$e& aid materially in carrying out manual operations. Besides the microscopes mentioned above, a Zeiss researchtype instrument is used for micrometric measurements and photography, while a portable-type Zeiss stand is available for field work where lightness and compactness are important. On a bench in the east side of the room, back of the analytical balances, a group of small duralumin heating blocks designed for various purposes is permanently installed (Figure 6). Duralumin is preferable t o other metals for this purpose owing to its high heat capacity and its nonoxidizability at elevated tem-. peratures. On this same bench a ground-glass plate, sunk flush with the table top, contains a number of perforations each fitted with a flanged hard-rubber orifice and connected through its own valve under the table to the suction line. By placing a bell-jar with a filtering system inserted in its top over any of these suction outlets, a set-up for suction filtration is instantly available. An International clinical-type centrifuge, E, stands permanently in the southeast corner of the room. Bench BI is mainly used for. microelectroanalysis, and cells of special design (4)are set up. there. At the north end of the bench is a control panel on which are mounted switches, meters, etc., providing four circuits which can be simultaneously used. Concealed wiring leads to the. four electroanalytic cell stations, M , on bench BI. Figure 1 does not show the outlets for water, gas, pressure,. and vacuum, which are conveniently placed. Storage space is provided by cabinets and shelves above and under the benches. and on the walls. In an effort to conserve bench space and eliminate cumbersome equipment, the ordinary ring stand supports have been replaced by steel rods which fit into tapering. bores of flush sockets, several of which are installed on each bench. Bunsen burners are permanently mounted below t h e table top in the hood, 6-cm. (4-inch) holes, J,with removable flush. cover plates providing access to the flame and support for clay chimneys, triangles, etc. Tripods and stands are thus eliminated.
In micrurgical work especially the apparatus is usually built around the job. It is therefore essential that facilities. for working in wood and metals, as well as for glass-blowing,. be available. The authors employ for this purpose a room adjoining the micrurgical laboratory. Here also is installed equipment for grinding and polishing specimens.
FIGURE 5. SOUTHEAST ENDOF ROOM
JULY 15, 1935
AXALYTICAL EDITION
In addition to the apparatus and equipment mentioned, and to other standard microchemical equipment, the following items, for the most part original with the authors and to be described in separate papers, are used in the micrurgical laboratory: Sublimation apparatus Stage furnace Magnetic stage Hot wire for use under microscope Sedimentation devices Steam-jacketed wells for evaporation of drops Dilatometer for gasometric microanalysis Microdistillationapparatus Microextraction apparatus A unit containing a quartz microfurnace,in which small specimens msy be treated with various gases and the gaseous products analyzed Leitz colorimeter and nephelometer Apparatus for dust collection and analysis
221
ings being retained by a drop of oil from which they are subsequently recovered by centrifuging and washing with a suitable oil solvent. The quantitative analysis of such minute samples employs specially designed microapparatus, such as weighed microbeaker and inverted filter units or centrifuge tubes, and the microcolorimeter. The micrurgical laboratory is frequently called upon to diagnose cases of high contact resistance. Some of these were found to be caused by the entrapment of foreign particles, as of dust, between the points. This led to an elaborate study of the nature and origin of dust in central office air, involving nearly the whole range of micrurgical technic.
Examples of Use of Micrurgical Technic The examinations carried out in the micrurgical laboratory are of the most varied nature, as to both the materials studied and the technics employed. By contrast with most microchemica,l laboratories the authors deal little with the elementary analysis of pure organic compounds. The following is one method of classifying micrurgical technic: GENERAL TECHNICS 1. Identifications by reactions carried out under the microscope. 2. Identifications by “spot tests,” using specific color reactions and indicator papers. 3. Quantitative analysis of organic and inorganic materials in which. usual analytical operationsare reduced to microscale. 4. Identification of organic compounds facilitated by micromet hoda . 5. Quantitative organic analysis by Pregl methods. 6. Diagnostic studies and chemical differentiation of microstructure in complex materials. 7. Identification of materials based on recognition of microstructural features. 8. Studies of grain and crystal forms of powders, precipitates, etc. 9. Micrometric studies. 10. Preparation of small amounts of substances either too rare or too dangerous to be handled on larger scale. SPECIAL TECHNICS AND APPLICATIONS 1. Diagnosis of corrosion causes. 2. Identification of surface contaminants, such as tarnish films, compacted deposits, efflorescent products, etc. 3. Composition studies made on thin layers or localized areas t o determine degree of nonhomogeneity of materials. 4. Dust analysis. 5. Analysis of air for gaseous impurities. 6. Identification of foreign inclusions and segregations. 7. Application of improved methods for determining impurities. 8. Transformations in materials best observed on a microscale. Two examples, taken from the authors’ laboratory records, will illustrate the types of problems in which micrurgical methods are effective. Contact points of various metals and alloys are widely used in telephone apparatus, as in relays and switches. Rapid qualitative analyses are frequently required to identify the alloy. Usually only a single contact is available and this must n.ot be destroyed. Sufficient sample is obtained by drawing the metal across a roughened spot on a microscope slide. The resulting streak is dissolved in acid, transferred t o a clear glass slide, and evaporated. Identification of this residue is made by reactions carried out under the microscope. If a quantitative analysis is desired, samples may still be removed without destroying all of the contact point by means of the dental engine using a tiny rounded burr. The operation is carried out under the microscope, the drill-
FIGURE6. DURALUMIN HEATING BLOCKS When tarnish films or corrosion products are found to cause the trouble, an attempt is made, by considering the method of manufacture of the apparatus and its service environment, to determine the primary cause. In one case welded silver contacts developed high resistance. An extremely thin tarnish film was detected on the silver. Sulfide was demonstrated by the sodium azide catalytic reaction of Feigl, and confirmed by the formation of cadmium sulfide with cyanide solution containing cadmium. The presence of copper was made strikingly evident by pressing the contact points on ammoniacal diethyldithiocarbamic acid test paper. The weight of the tarnish film on one of these contacts was not more than a few ten-thousandths of a milligram. The copper contamination probably came from the welding electrode. The other example is the analytical examination of lead cable sheath. Because of the large amount of this material used by the Bell System, and of its essential protective function in the telephone plant, constant effort is made to develop improved alloys, to perfect manufacturing methods, and to reduce cable losses caused by corrosion of the sheath. Micrurgical methods of analysis are of great service in all this work, but particularly in diagnosing cases of cable sheath failure. When the sheath is corroded it is necessary to distinguish between the different types of chemical and electrolytic corrosion, and, in seeking the cause, to examine the environment. Lead peroxide, chlorides (anodic products), and free alkali (cathodic), in abnormally high concentration, are indicative of electrolytic corrosion. Such substances are quickly and graphically detected by specific indicator papers. The flattened specimen is pressed against moistened phenolphthalein, silver chromate, and benzidine acetate papers in the order named. Photographs of the original specimen and the corresponding prints provide a permanent record of the examination. The structure of the different zones and layers of the specimen, revealed by dissection with the micromanipulator and analytical study, gives information that aids in reconstructing the mechanism of the corrosion process.
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Discussion
Literature Cited
The purpose of special analytical technics is to increase the economy of analysis. Emich (6) has enunciated this as a general principle:
(1) Benedetti-Pichler,A., 2.anal. Chem., 73, 257 (1928). (2) Brenneis, H., Mikrochmie, 9,385 (1931). (3) Clarke, B. L., IND. ENG.CHEM.,23, 1301 (1931). (4) Clarke, B. L., and Hermance, H. W., J.Am. C h m . SOC.,54, 877 (1932). (5) Emich, F., “Lehrbuch der Mikrochemie,” 2nd ed., Munich, J. F. Bergmann, 1926. (6) Goubau, R., Chimie & industrie, 17,170 (1927). (7) Grassner, Mikrochemie (2), 4,255 (1931). (8) Hermance, H. W., Bell. Lab. Record, 13,81(November, 1934). (9) Kirner, W. R., IND.ENG.CHEM.,Anal. Ed., 5,363 (1933). (10) Moser, L., Mikrochemie, 1,l (1923). (11) Niessner, W., Ibid., (2), 4, 271 (1931). (12) PetBrfi, Naturwissenschaften,6 , 8 1 (February, 1923). (13) Titus and Gray, IXD. ENG.CHEM.,Anal. Ed., 2,368 (1930).
Auf allen Gebieten menschlichen Schaff ens kommt dem Prinzip der Okonomie die grosste Bedeutung au. Dieses Prinaip verlangt bekanntlich, dass man sich bemiihen muss, ein gegebenes Ziel mit einem Minimum von Material- und Energieaufwand, von Zeit und von Denkarbeit zu erreichen.
Perhaps the most characteristic feature of micrurgy is its employment of direct observation instead of inferential deductions from indirect observations. The organic chemist, wishing to determine the position of a substituent, is not able to make direct microscopic observation but must rely on circumstantial evidence. Similarly, a paper chemist, if limited to macroanalytical methods, might conclude from analyzing the ash of two condenser papers that the one with the higher iron content would be functionally the poorer. But micrurgical examination of the papers might disclose that the one with lower iron contained actual metallic particles, greatly reducing the breakdown resistance, while the iron in the other was evenly dispersed as the relatively innocuous iron oxide. Again, a lead-cable-sheath corrosion product, examined by “test tube” methods, might show no active ion, and the analyst would be a t a loss to diagnose the corrosion cause. Under the microscope, however, tiny pockets might be found which contained a high chloride concentration, easily detected micrurgically because the test is made in situ and not after dilution below the sensitivity of the test. Many other similar instances could be given where analytical data are useless or even misleading when the factor of distribution is not taken into account. Many materials are made up of minute structural elements, upon the nature and interrelation of which depend most of their gross mechanical properties. In such cases micrurgical methods are necessary no matter how large the available sample. Petrographers and metallographers preceded analytical chemists in recognizing the importance of this in analysis.
Conclusions 1. Directors of analytical laboratories should strive to provide a t least some facilities for the use of all analytical technics, so as to allow some freedom of choice in a given problem. 2. The natural tendency is to use samples and apparatus of a size convenient to handle. The principle should be inculcated that following this tendency is often the way of inefficiencyand sometimes results in gross error. The analyst should shape the apparatus and methods to the job, not to his hands. While the authors cannot fully agree with Benedetti-Pichler (1) that no special skill is necessary for the use of micrurgical methods, it is certainly true that much good micrurgical work can be done by any conscientious, welltrained analyst. 3. Teachers of microanalysis should impress upon their students that the operations of sampling and preparation in industrial micrurgy frequently require more time and skill than microchemical tests proper. 4. Finally, the authors would urge manufacturing engineers and research directors to adopt a more critical attitude towards analytical results. They will thus come to appreciate both the possibilities and the limitations of chemical analysis, and will be able properly to appraise the value of analysis to manufacturing and research. The prestige of the profession of analytical chemistry will not suffer from this appraisal.
RECEIVEDMay 3, 1936. Presented before the Division of Physical and Inorganic Chemistry, Symposium on Recent Advances in Microchemical Analysis, a t the 89th Meeting of the American Chemical Society, New York, N. Y., April 22 to 26, 1935.
An Efficient Vacuum Pump Check Valve ROY L. MOBLEY Lacto-Yeast Co., Inc., Baton Rouge, La.
IN
MANY instances the laboratorian is not aware of the availability of mechanical devices of professions associated with his, and their most efficient adaptability to his purposes. Such an instance is evident in the use of the water-operated vacuum pump. Of the valves used for this purpose, none have ever consistently filled the requirements over any period of time. The writer, constantly working with this type of laboratory apparatus, desired a perfected valve, which was easily had by using simple pipe and fittings with a ballcheck valve. The materials required include one 0.125-inch brass ballcheck valve, one 0.125 X 3 inch brass nipple, one 0.125 X 8 inch brass nipple, and two 0.125-inch brass street ells. Determine the direction of flow through the valve and start the street ells in either end. Then insert the shorter nipple in the exit ell and the longer in the entrance, so that the longer of the two will be placed in the trap bottle and the shorter will lead t o the pump. Tighten the joints well with a wrench, being sure to leave the valve in its upright position and horizontally in the assembly, otherwise it will not work. Then insert in the stopper of the trap bottle and connect to the pump by means of tubing. The trap serves as a further safety device, should the valve leak a bit. Such a valve has given very satisfactory service when used on a pump maintaining from one to three funnels under a vacuum of 10 to 20 inches of mercury. RECEIVED May 10, 1936.
