Developments in Applications of Chemical Microscopy A Sgmposium of Eight Papers
Presented before the Division of Analltical and Micro Chemistrg at the 114th Meeting o f the AMERICAN CEEMICAL SOCIETY, S t . Louis, Mo. I
The Microscopist in the Technical Organization CLYDE W. MASON Cornel1 University, Ithaca, N . Y . Emphasis is placed on the problems of the industrial microscopist in establishing and maintaining the proper relationship to the organization, in which he can function best only when his work is understood and his conclusions lead to collaboration with others. The justification for a microscopical laboratory, training, and equipment, is discussed. The microscopist must learn process and materials, establish contact, and seek problems. His work must be collaborative, and carry on past the initial report on microstructure. His strategic position allows him to help solve many problems if he can get close enough to the plant and to the sales service. Education-of his customers within the organization is one of his important duties.
T
H E past twenty years have witnessed a great multiplication of the number of laboratories in which microscopical work is being done and the number of publications in which microscopical studies play an important part. This is the best evidence of the value of microscopy in research and technology. There is every justification for the professional chemist’s being concerned, either in his academic training or by later self-education, with the smallscale aspects of the multitude of substances, phenomena, and processes that are encountered by the chemist and the chemical engineer. We have all learned our chemistry through glass, and it is hard to imagine how much we would have been handicapped without direct visual observations. Taking a close-up look is “the natural way” of studying substances and their behavior; the earlier it is done, and the more it is continued during the course of an investigation, the greater the return. One of the greatest advantages of microscopical experience is the fact that it’s so unforgettable. Even if one rarely uses a microscope, he may visualize and reason on the basis of what he once observed, and will be more likely to consider physical factors before he gets too deep in gathering chemical data. The possibility of dealing with minute samples by means of the microscope is a spectacular but usually relatively uncommon benefit. When a speck of impurity or a limited quantity of a’ new synthetic product has to be characterized, the application is ob-
430
vious. But more important is the possibility of studying in place variations in quality or composition so localized as to prevent ordinary sampling. In most technical applications of microscopy, however, the methods are used not because of any limitations in the amount of sample but because of the time and labor they save and the information that is unobtainable otherwise. SCOPE OF MICROSCOPY
Probably few industries have hired a microscopist with any very definite realization of what he might do for them. Probably many industries fail to hire a microscopist because they foresee only a few limited problems, and feel they could not continue to keep him busy. There are two solutions: one is to hire a man who knows something about microscopy, and let him work a t it part time, functioning as an ordinary chemist meanwhile. In many instances microscopists have had to start in a small way, and have struggled through to proper recognition, but given opportunity, it is rarely the case that full-time microscopical work does not become justified. The alternative solution is to establish a microscopical laboratory and give the microscopist as much opportunity as any other investigator to develop usefulness. This may seem like a gamble, because it involves hiring a specialist who does not fit in any of the ordinary categories, and purchasing rather extensive
V O L U M E 21, NO. 4, A P R I L 1949 equipment. I t has paid off where it has been tried, and an adequate start means a quicker return. How to decide whether microscopy is essential in a technical organization? The answer usually comes only after t>hemicroscopist has been on the job for some time, rand largely because he makes his work essential, in ways that even he may not have seen a t first. Obviously, the organization wants to get the most out of this iprcialist it has hired, and the microscopist will be enough of an enthusiast to want the same thing. Rut both should realize that he has a lot to learn-in part, what any new member of a staff has to learn, in adapting and supplementing his training for the zpecific demands of the job, in developing and testing methods that will not be found ready in the A.S.T.11. standards, but most of all in acquiring a background of information on the mat,erials, operations, and products of the company, and their ultimate application and performance. The niicroscopist should not ha.ve been hired as a mere technician. If he is to contribute, in the light of his habitual “closeup” way of looking a t things, he must have a chance to snoop sround the plant, and the rrst of the laboratory, and the salesJervicr division-to explore the territory where he will operate and tu meet the people whom lie will really be working for (and eventually with). Perhaps the microscopist will be doiiig relatively routine examinations at first, or tackling problems that have been saved up for him, but the earlier he learns what is hack of his samples or how these problems fit in the research or testing program, the rarlier will he be prepared to report intelligently and to function cooperatively. Sooner or later he is going to have to tell sonirone “these samples do not prove a thing,” or “they prove what they should uot,” or ‘‘we shall have to have a whole new series of samples,” or “we ought to make up a hatch in a different way,” or maybe even “the microscope is not going to ansLver your question,” and some previous diplomatic contacts are a big help in the kind of discussion ivith nonmicroscopi.qts that should be an important p,rt of his job. If he is smart, the microscopist n.ill be carrying on a subtle educational campaign while he is getting oriented. He will be looking a t many samples, but he will try to let other people have a look a t them too, and he will explain something of the tlasis of his methods and his conclusions, so his colleague “customers” will feel that he has his feet on the ground. If he has to do particle-size work, he will try to get across the idea that an ordinary inspection or an arithmetical average may be meaningless, looking ahead to the time when he may need to “go to bat” on the basis of a wobble in a size-frequency curve. A certain amount of discrete “advertising” of microscopy within the organization is in order-not just so visitors .ail1 be guided to the special room with the impressive shiny instrument,s and the display of photomicrographs, but to make it generally known that microscopy is available and what it can do. One of the hardest jobs of a microscopist dropped in the midst of a research organization is to get himself new business, when he knows he ought to have it, and often a little publicity through the company magazine or the sales literature will reach people better than “through channels.” He should accumulate an exhibit of photomicrographs illlistrating raw materials, treatments, products, grades, defects, applications, and competing materials. These will help others (even plant operators) to visualize the things they work with, and will be particularly attractive to the sales department (which can never be ignored and which always should be impressed). He should dress up his reports with illustrations that prove something to others as well as to himself; they may make hi:3 work known even to the upper levels of administration, where the proverb “one picture is worth a thousand words” still applies, although pages of tabular data or graphs may be skimmed over.
At thih stage in his development, the microscopist needs freedom-to study, to ask questions, to argue, to find out which of his colleagues ran give him advice and background, to try out methods and apparatus, and to cult,ivate the mechanician and the photographer a little. His specialization makes his job a lonely one, and he may tend to become too much of a “fusser” if he cannot get his eyes and his brain away from the microscope occasionally. He must give much thought to what key questions should be asked of the microscope, how they should be put, and horT the different possible answers should be interpreted or used as a basis for further questions. On the other hand, if he is snowed under with samples, if he is told nothing of their history or of the use to which his observations may be put, if he has reason to believe his conclusions are misinterpreted, and if his suggestions for further studies are ignored, he will have a right to feel that he is not doing what he might for the organization, however busy he may be. Lundell once made a very apt distinction between “determinators” and true “analysts,” and one might similarly emphasize the value of analytical microscopy, not just as a substitute for largerscale chemical methods to determine sample composition, but as a way of attacking the problem from which the sample originates. Certainly the microscopist has a right to know the goal of any studies he is asked to make on a sample; this may, in the light of his knowledge, be somewhat different from the immediate reason given him by his customer. He has a right to decide whether the sample is suitable for the real purpose, and to choost, the methods of examination most appropriate to the problem. (“The highest possible magnificat>ion,”so often requested, is not always the most revealing.) These points are only proper, for economy of his own and others’ time and thought. But even more important is his right to have a voice in the interpretation and application of his result’s. He should not be confined to purely objective reports, for if these are of any use, they must be evaluated by someone, and why not with his cooperation? Any intelligent microscopist hates to work in the dark, or to feel that microscopical evidence may be missed or perverted, and thus be worse than useless. He likes to hope that negative results need not give a black eye to microscopy any more than to other methods, and that his customers will appreciate that it has limitations as well as spectacular advantages. There is a tendency to regard the microscopist as one who “just looks at things,” and perhaps t o consider his results as inferior to quantitative analyses, where three or four “significant” figures are reported. But in terms of their ultimate use, the microscopical data may be of far greater significance, and usually reveal valuable unsought information. Microstructure may prove quality or explain performance without any numerical results being involved. The microscopist ought to be an “idea man” as well as an observer of iine structures. His ideas properly should be of particular value, because they are based on direct observations-often on information entirely independent of what is available by ordinary methods, and not to be discounted by juggling constants or introducing mathematical factors. The “different slant” that he contributes because of his background may be useful even if it extends outside microscopy. Obviously, he needs a considerable knowledge of physical chemistry as well as analytical chemistry, with organic and inorganic chemistry as the problems demand, if he is to t,alk the language of the different kinds of people he works with, and is to stand up to them in argument. A mere technician, however skillful, is not so likely to grow up to this level of scientific interchange, so the value of strong training of microscopists in chemistry and physics is obvious. The microscopist is in a peculiarly strategic position to learn the problems of the plant, the laboratory, and the technical service division, and if he makes the most of this opportunity, he can offer valuable contributions to them and can acquire a broad understanding of their relationships.
ANALYTICAL CHEMISTRY
432 All this experience should lead to the microscopist’s developing into more than a specialist in microscopy. He should become able, and should be allowed, to carry his problems beyond the boundaries of his laboratory, working in the best cooperation with other members of the staff. This may mean the establishment of new standards or test methods, the modification of production practice, and the pursuit of more or less pure research, in addition to all sorta of high grade trouble-shooting. One of his chief obligations should be to convince his associates that microscopy is not’ a last resort,, to be tried when all other approaches seem fruitless, or the sample is too small, but rather a primary exploratory method to help shape the course of investigations and to keep in touch with their advance. Whether microscopy is officially part of the analytical, control, research, physics, or other division of the organization is less important than that it should be permitted to go beyond the boundaries of these, wherever its usefulness may lead. Unofficially, the microscopist serves best when he has a roving commission. EQUIPMENT
One of the problems as microscopy takes root is that of equipment. Any good microscopist should be ingenious enough to “make do” with limited apparatus and facilities for a while, and to improvise and adapt apparatus beyond its conventional uses. But there comes a time when more equipment is needed, and here
it is his obligation to justify the expenditure, not necessarily on B strict cost-accounting basis, but in terms of possible future uses. The apparatus of microscopy is inherently versatile, but it hardly pays t o try t o do everything with one or two instruments, when time is lost in rearranging special setups, or in riaiting their release for temporary problems. In times 1%hen plant instrumentation is increased so readily, there should not be reluctance t o invest in equipment to save manpower in the microscopy laboratory. Similarly, the microscopist will find that although his earlier experience has properly been in large part manipulative, and concerned with studies of methods and materials, this knowledge can best bear fruit if he is relieved of much of the noR- routine procedures. He should not have to spend his time doing ordinary preparations, measurements, or photography, if assistants under his supervision and following the methods he has worked out can relieve him for more fundamental or collaborative work. A really valuable microscopist should spend a relatively small portion of his time looking in a microscope. After all, the most important apparatus in microscopy is borne on the shoulders of the microscopist, and it functions day and night, whether above the instrument or elsewhere. This apparatus cannot be purchased; it must be created, and both the administration and the microscopist are responsible for its fullest attainment of usefulness. RECEIVED September 15, 1848.
@ chemical microecopg egmpoe2um
MICROSCOPE OPTICS L. V. FOSTER Bausch & Lomb Optical Co., Rochester, N. Y . Work in the ultraviolet region of the spectrum is being advanced by the use of achromatic microscope objectives. There are all-refracting systems which use synthetic or natural crystals having high transmission in the ultraviolet, allreflecting systems having no optical material through which the ultraviolet light must pass, and the combination of both. A great deal of work remains to be done to improve the lamps and to control the radiations used. Phase contrast will probably be added to ultraviolet systems. The use of electronic image tubes is extending use of the microscope into the near ultraviolet and the infrared.
D
URIKG the past fen. years considerable emphasis has been put on the development of the microscope for use in the ultraviolet and infrared portions of the spectrum. About 1904, Koehler (8) of the Carl Zeiss Works developed a series of quartz monochromatic objectives for use in ultraviolet light. These objectives were designed and used primarily to increase the resolving power of the microscope. The present purpose in working in the ultraviolet region of the spectrum is not only to increase resolving power but to bring out differential absorption characteristics in material. This paper describes recent developments in this field and points out the difficulties that still exist in connection with the work. In many respects work in the ultraviolet region of the spectrum is difficult. Becaus: the eye is not sensitive to wave lengths shorter than 4000 A., a conversion from the image formed by these short radiations to the longer visible rays is either through photography or by fluorescen$e, Glass does not transmit radiations much shorter than 3500 A.; if microscopy in the short ultraviolet (3500 to 2000 A,) is required, all optical parts from the source to the final image must be made from material such as
quartz, fluorite, or lithium fluoride, which transmit these rays. The amount of chromatic aberration inherent in lens systems increases as wave length decreases and, as a consequence, images lack contrast and good definition unless strictly monochromatic light is employed. This mean3 that the light source should emit only a narrow band of ultraviolet. I t is probably for this reason that Koehler designed monochromats and :sed spark sources (9) such H-,S cadmium for illuminating at 2730 A . and magnesium a t 2800 A. There are some advantages to be gained in monochromatic illumination, and others in the use of broad band illumination. Both methods have their own problems. OBJECTIVES USED A T 36501.
I n 1931 the writer and Trivelli (13) showed how 2bjectives could be corrected for the mercury green 5461 and 3650 A. The ordinary glasses used in microscope optics have sufficiently high transmission a t 3650 d. to permit making photographs in this part of the ultraviolet spectrum. These lenses were corrected for chromatic aberration to bring the two wave lengths,
