Technique and Applications of Industrial Microradiography G. L. CLARK AND S. T. GROSS, University of Illinois, Urbana, Ill.
.
Because of w idespread interest in the possibilities of the technique of microradiography as an industrial testing and research method, this paper presents details of the best equipment, procedures, and applications de%elopeda t present. Since i t is impossible to magnify x-ray images i n the same sense that optical images are magnified by suitable lenses, i t is necessary to register the x-ray image on a photographic plate and then enlarge the photographic image. By use of the Lipmann emulsion with extremely fine grain size for the silver halide, a magnification up to 300 may be made without loss of detail from graininess. Successful radiography also depends upon the choice of x-ray wave lengths which will give a suitable differentiation between constituents in a specimen, such as aluminum arid copper i n an alloy used in the construction of aircraft. A new technique employing two or more characteristic radiations to bring out details of polycomponent metal systems is presented and illustrated with a variety of alloys such as copper-
berjllium, aluminum-magnesium, aluminunicopper, bronze, leaded iron, rolled beryllium, silicon steel, graphitic steel, season-cracked brass, and lead-antimony type metal. Instead of employing \cry soft x-rays generated with special equipment at a few thousand volts and applicable to a \cry limited number of materials, and without yacuum cameras, jery successful results were obtained w i t h characteristic Kn-rays of molybdenum, copper, iron, cobalt, chromium, etc., as produced in ordinary diffraction apparatus. It is demonstrated t h a t microradiography supplements the microscope in metallurgical and other industrial applications, with the advantages t h a t i t gi\es a three-dimensional view of the specimen; does not depend upon differential action of etchants b u t only on the variations i n absorbing power of constituents, including internal voids and cracks; requires no special polishing of the specimen; and is directly and incontrovertibly interpreted. A few striking biological applications, especially in wood technology, are illustrated.
T
HE most familiar branch of x-ray science is termed radiography. This depends essentially upon the differential absorbing power of different materials for x-rays as they penetrate through a given specimen to produce the resulting ‘[shadowgraph” which delineates the gross structural details of any heterogeneous material. Thus medical diagnostic radiographs show very clearly the shadows and gross structural details of bones or foreign bodies in contrast with soft tissues. In industrial applications cracks, blow holes, and other defects may be shown in metal castings and welds, foreign bodies in packages of breakfast food or candy, slate in coal, and in general the internal structure of any material. Similarly in the field of art, old paintings may be tested for retouching, hidden pictures, and characteristic technique of masters. A logical extension of the practical uses of this property of x-rays is to the examination under high magnification of the gross structure of various types of small specimens as revealed by means of x-rays, analogous to the familiar science of photomicrography, in which the microscopically enlarged image of a surface can be examined and photographed in visible light. However, one very serious obstacle presents itself -namely, the aksence of any lenses for the enlargement of x-ray images corresponding to those which form the essential optical systern of a microscope. Thus all radiographs are representations of the exact size of the object irradiated by the beam from an x-ray tube, since the object is in direct contact with the photographic film. The science of microradiography must, therefore, depend upon the exact registration on a photographic film and the subsequent microscopic enlargement of the image recorded in the developed silver emulsion of the film. Because of the present extraordinary interest in the possibilities of the technique of microradiography in research and testing of a variety of important defense materials, this paper outlines details of the best procedures which have been de-
veloped, and illustrates applications to metallurgical and biological specimens.
Historical Microradiography grew out of the desire to obtain and view radiographic images of heterogeneous objects of small size. 9 s early as 1913, Goby ( b ) , using x-ray radiation of very long wave length and working in a vacuum, obtained radiographs of fossils and minerals. These radiographs were then enlarged to such an extent that they could be viewed with the unaided eye. In 1930, Dauvillier (S), using a technique similar to that employed by Goby, obtained radiographs of vegetable cells, such &s those of elder pith. He used voltages as low as 8 kilovolts. The sample and photographic plate were both mounted in a vacuum connected directly with the x-ray tube in order to prevent absorption by the air of the very soft radiation used. Lamarque and associates ( 7 ) in 1936, using 5000 volts and currents as high as 100 milliamperes, studied plant and animal cells. The method was found very useful for studying the differences in densities of the various cell components. Stereoscopic microradiography was suggested by Goby (6) in 1925 and Yoshida and Tanaka (9) in 1934. The use of very soft x-rays on grenz-rays to differentiate inorganic and organic constituents in a sample has been rather common. For example, Schupp and Boller (8) in 1938 studied the sodium silicate bonds in corrugated fiberboard with low-voltage rays; but the maximum enlargement used for any radiograph was only 15 diameters, so that the technique could scarcely be classed as microradiography. In 1938 the senior author had the privilege of witnessing attempts to adapt microradiography with x-rays of very long wave lengths to aircraft light alloys in the French Air Ministry in Paris. Very intense x-ray beams from special tubes were generated at 4000 volts and passed through very thin specimens in vacuum cameras. Some success was achieved, as reported by Fournier (4). However, it was evident from all previous work that, because of the special requirements of apparatus and technique and the limitation to so few types of specimens consequent upon the use of very soft radiation, there was little hope of practical use of the method in industry. Successful results with metal specimens were reported in 1939 by Clark (1) and Clark and Shafer ( 2 ) ,with a technique involving the use of ordinary x-ray diffrac676
August
15, 1942
ANALYTICAL EDITION
tion tubes operating at 30,000 or 40,000 volts and the elimination of all vacuum cameras.
Experimental Technique The principal features of the practical microradiographic technique which has been developed and tested are: 1. Preparation of the sample in the form of a small piece with a thickness of 0.1 mm. or less for metals or other dense materials, or considerably greater if necessary for biological specimens. 2 . Registration of the radiograph by a very simple technique involving a special photographic emulsion. 3. Enlargement of the radiograph to a suitable size.
The two chief essentials are: (1) a photographic emulsion of sufficiently small grain size to stand enlargements of 100 to 300 diameters n ithout loss of definition from graininess; and (2) the selection of x-radiation of suitable wave length and intensity. PHOTOGRAPHIC EIIIULSIOKS. Tests on microradiographs and electron microscope photographs at 60,000 diameters magnification have demonstrated that the Lipmann photographic emulsion alone is sufficiently fine-grained so that enlargements may be made of the radiograph up to 300 diameters without serious loss in definition. To physicists this transparent emulsion is generally familiar. It has been rather widely used in aerial photography when great enlargement is desired. The first work on microradiography in this laboratory in 1938 u as carried out with Belgian Gevaert film. Khen this supply was cut off by the war, Eastman Type 548-0 spectrographic plates with Lipmann emulsion became available and have proved entirely satisfactory. There is some advantage in the film, since it may be cut into small circles for each exposure. Multiple exposures, however, may be made on a plate by a simple translation after each exposure. The plate has the further advantage of no shrinkage or warping. The Lipmann emulsion has a resolving power of 2 microns or 500 lines per millimeter. The limit may be approached for sufficiently thin sections. As expected, the Li mann emulsion is very slow in comparison with the usual type ofx-ray films. As a matter of fact, it may be developed in any light safe for ordinary chloride photographic papers. The contrast of the developed films or plates, as measured by the slope of the density os. log exposure curve, is used to determine the effect of various times of development in Eastman regular x-ray developer a t 18 . The densities of the steps were determined with the aid of a Leeds & Xorthrup microphotometer and plotted against log E . The values of y graphically determined were as follows: Development Time Min. 0.5 1.0 2.0
4.0 8.0
Y
0.93 1.07
1.48 1.80
2.05
The thin emulsions may be considered fully developed in 1 minute, but it is actually advantageous to develop 5 minutes. Eastman developer D-8 as recommended by the company develops the Eastman 548-0 plates satisfactorily in 1.5 minutes. A number of fine-grained developers have been tried but no advantage was observed; in fact, they tended to increase fogging. Attempts have been made to increase the sensitivity of the Lipmann emulsion by prefogging and by treatment with mercury, ammonia, and ammoniacal silver tungstate. The last named does increase the sensitivity very markedly but the treatment is so difficult to control and the possibilities of introducing artifacts are so great that it is not recommended until further investigations are carried out.
PREPARATIOS OF THE S - m P L E . The thickness of the sample is dependent upon the intensity of the available radiation and upon the linear absorption coefficient of the material being investigated. Using commercial diffraction x-ray tubes as radiation source, it has been found advisable for best results to take steel samples down to about 0.075 mm. (0.003
677
inch) in thickness; copper alloys are usually suitable up to 0.125 mm. (0.005 inch) in thickness, magnesium up to 0.25 mm. (0.010 inch) thick. Khen the sample is too thick, the microradiograph will show ordinarily only diffuse resolution of detail rather than well-defined structural effects. The metal sample may be cut to approximate size by any method, and the only finishing necessary is a final treatment uith 2(0) emery paper, moistened with oil to remove pits and tool marks. RADIOGRAPHIC TECHSIQUE. Cameras may easily be made for holding the sample and film, or the assembly can be improvised by binding the sample against the fine-grained film or plate with a piece of black paper 2nd .imply exposing to the s-ray beam.
I I/
FIGURE1. >~ICRORADIOGRAPHIC CAMERADESIGNED TO FITAS INSET IN COLLIMATING SYSTEMS OF COMMERCIAL X-RAYEQUIPMENT 1. Fine-grain film.
2. Sample.
3.
Black paper.
In this laboratory, it has been convenient to make small cylindrical cameras (Figure 1) which will fit in the collimating tube system of the regular x-ray diffraction equipments. This particular method employs a cup of the proper dimensions to fit the collimating system, which holds the film. A close-fitting cylinder, with the sample fastened on one end, is then slipped into place, bringing the sample in contact with the film emulsion. The x-radiation passes down the cylinder and impinges on the sample, It is essential that the sample be as close to the emulsion of the film as possible; otherwise there is an appreciable decrease in definition. The radiation employed does not have to be collimated with any especial care. If the sample and film are about 12.5 to 15 em. (5 to 6 inches) from the target of the x-ray tube, no collimation is really required, although it is preferred to use a 0.15- to 0.31-cm. (1/16 to inch) opening near the window of the x-ray tube to define the beam. The close contact of sample and film makes this use of essentially noncollimated radiation possible and also permits comparatively rapid exposures. Clark and Shafer ( 2 ) described a microradiographic camera adapted from a flat diffraction cassette holder in which a circular disk cut from film can be rotated for making multiple exposures. When Eastman plates are used, small pieces are cut and wrapped tightly with black paper or aluminum foil on which the specimen is placed, preferably inside in close contact with the emulsion. A camera is now being designed in which the specimen is directly against the plate emulsion without intervening paper or foil layers, and in which the plate may be moved laterally for multiple exposurec. The period of exposure required is dependent upon the nature of the sample, its thickness, and the intensity of the xray beam, and no generalizations can be made. This subject is discussed in a quantitative sense in the follolving section.
CHARACTERISTIC RADIATION us. SOFTGENERAL RADIATION FOR METALMICRORADIOGRAPHIC EXAMINATION; MICRORADlOGRAPHS O F S P E C I F I C ELEMENTS I N -4 POLYCOMPONENT
METALSECTION.I n all earlier work on microradiography, as outlined above, very soft general x-radiation produced at voltages as low as 4000 volts was used simply because there
678
INDUSTRIAL AND ENGINEERING CHEMISTRY
I
o
N
w
-
o
m
m
mercial Machlett cobalt-target diffraction tube operating a t 15 milliamperes and 40,000 volts, with the Kal characteristic ray of c2balt with a wave length of 1.785A. predominating. Copper or iron characteristic radiations are as suitable. Clark and Shafer (2) first demonstrated the successful use of the a-rays of molybdenum for a variety of alloys. In Figure 2 are plotted the linear absorption coefficients for the elements usually found in brass and bronze. The light vertical lines correspond to various specific radiations obtained with commercial x-ray diffraction tubes. The heavy lines represent the linear absorption coefficients ; therefore, the vertical distance between any two lines is related to the maximum intensity ratio obtainable on the microradiograph by the relation :
:i I / I
,
c
a
Y)
Vol. 14, No. 8
d
k iI o v o l t s
FIGCRE2. LISEARABSORPTIONCURVES FOR METALLIC ELEMENTS IN THE ALLOYBROXZE
IJIb
=
e-(:Po
-@ Pb pb
T h e vertical light lines represent t h e critical voltage above which the characteristic K a - r a y s from t h e various x-ray t u b e targets are generated.
1.
where z is the sample thickness in centimeters, pm/pmis the mass absorption coefficient, and pm is the density of the metal. The greater the vertical distance between any two curves on the graph, the greater the sensitivity of the microradiographic method for the detection of inhomogeneities, etc. Another factor t o be considered is that the required exposure to the x-ray beam is fixed by the height of the curves above the base line. This height is the linear absorption coefficient p (also listed in Table I) and is related to the proper exposure by the formula on the next page.
is the greatest differential in absorbing power of different constituents a t these long wave lengths. However, the technique n-as a failure from the standpoint of practical use because of the extraordinary precautions required in making extremely thin specimens and in the necessity of working in vacuum t o avoid scattering effects of air. Hence, there was no success whatever nith metals and only a very limited number of biological specimens showed any promise. Where x-ray diffraction equipment is available, its use should not be ignored for microradiography, since the “characteristic” radiation obtained from such B s g b equipment is present in very considerable intensity, far greater than that usually obtained with low voltage and general radiation; furthermore, these characteristic radiations may be considered as essentially monochromatic, mhile radiation obtained at low voltages is always spread over a considerable band of wave lengths, even when filters are employed. The microradiography of such a system as / / I I magnesium-aluminum is ordinarily considered to require general radiation, but the print shown in Figure 5 for an alloy containing 10 per cent aluminum, 0.2 per cent manganese, with the balance magnesium, is from a mikilovolts croradiograph obtained in 15 minutes from a comFIGURE 3. LISEARA4BSORPTION C U R V E S FOR METALLIC ELEMENTS I K SICKEL-CHROMIUM
/
N1
/
STEEL
August 15, 1942
FIG-
4.
679
ANALYTICAL EDITION
B A ALLOY.MADE WITH CHARACTEEISTIC COPPER MICRORADIOGRAPRS SHOWN AS NEQATIVE PRINTS OF (:OPPER-BERYLLIUM RADIATION ~~
Magnifications ( A ) x80. ( B ) x300 (enlargement
Of
area indicated in A ) . Copper-rich phase light. beryllium dark
Time of exposure = Ke”= where 2:is the thickness of the sample in centimeters, II. is the linear absorption coefficient for the material predominant in the sample, e is the base of natural logarithms, and K is a constant for any given source of x-radiation. K varies inversely &s the intensity of the x-ray beam.
For a partial illustration of the possible use of such a graph as that given above, we may consider a bronze with the composition about 80 per cent copper, 10 per cent lead, 10 per cent tin, andO.75per cent phosphorus. Examination of the graph shows that molybdenum radiation would tend to show the distribution of the lead in the sample; but that use of copper radiation would show not only the lead but also the tin distribution. Therefore, if two microradiographs were taken, such as those shown in Figure 6, using the same metal section, and successively with molybdenum and copper radiation, it is possible to learn considerably more from the sample than has previously been indicated. The above method of using characteristic radiations for the purpose of identifying the material present may be employed generally for any favorable case. For example, a more complicated alloy might be considered-a steel containing iron, chromium, nickel, and silicon. Examination of the graph of linear absorption coefficients for these materials (Rgure 3) shows that we could expect the radiographs listed below: Expoanre
F I G ~5. E MICROUDIOGRAPH (NEGATIVE ALLOY PRINT) OF MAGNESIUM-ALUMINUM MADE WITH CHARACTERISTIC COBALT RADIATION sample thickness 0.010 inch, exposure time 15 minutes. magmfioatmn XSO. C o p ~ e r light. magnesium dark.
Light Regions on Negative
Dark Regions
Short
Mdvhdenum chluaoteristia radiation Elements of high atomio numbm--e.g.! Mo.. eto.--oIvery dense regions
Short
Cobalt oharaoteristic radintion Chromium also the effects observed ’kith molybdenum radiation
Long
Copper oharaoteristic radiation As with molybdenum Large amounts of chromium. nickel. silicon
.. . . .... ....... ,
It is apparent that the use of several characteristic radiations can be of considerable value in the interpretation of the enlargements obtained; this is rather generally true for practically any polycomponent system of metals.
nscea in me oraer 01 meir aosorpnon 101' me various nnear absorption values foiP given characteristic radiation values. The linear absorptio n value, estimated by taking the hest, values of mass absorrition coefficientsfrom the literature and multiplying them by reasonable density values for the elementary materials, irj given along with the atomic symbol. Table I may, therefore, be used to ascertain whether these particular characteristic radiations are suitable for the examination of any particular binary system of metals. Thus, nickel and cobalt may be easily differentiated with characteristic copper radiation although a rather thin sample would probably be required; however, iron or molybdenum radiation would not he suitable. Beryllium and magnesium are well differentiated by iron radiation, and even better by the characteristic chromium radiation. Lead and iron could not be distingnished by copper radiation, but molybdenum radiation (Figure 7 A ) would furnish an exceedingly sensitive
muinpnea ac iennn on me simple principle ma& me sensitieti for differentiation is greater, (he greater the: difference in linear absorption.
Metallurgical E x a m p l e s Figure 4 illustrates the remarkable results obtained with a copper-beryllium alloy which now has such great industrial importance. The microradiograph a t 80 diameters enlargement shows three distinct phases--essentially beryllium in black, copper in white, and an intermediate phase in gray showing a peculiar beaded structure of the matrix. The area enclosed with ink lines is shown in beautiful detail a t 300 diameters in Figure 4B. Figure 5 for a magnesium-aluminum alloy has been discussed above. The more highly absorbing aluminum phase is shown as needlelike crystals.
c s (NEGATWE PRINTS) iation. Magnifiestion XQO. Lead light, iron dark reteristio ohromium radiation. Magnification X 100 radiation. Xsenifioation X I O O . Aluminum dark. copper lignr
August
681
YTICAL EDITION
N
1942
B
A
C
FIGURE 8.
MICRORlDIOGRAPHS (NEGATIVE PRlh-TS) A . Silicon steel with inelusions (dark) made with,ohsraoteriatip qopper radiation. Magnification X200. B . Graphitic steel showing dirk, made -7th $haraotenst?e molybdenvm, radiation. Magnification X100, C. Season-cracked brass s i t h cracks black snd lead rhitc, made with ehsracteristse molybdenum radiation. Magmfiohtion X 100
T ~ B L I. E RADIATIOK Copper Radiation
Be
Mg
6:
2.96 11.4
;:: 182
228 41s
427 454 95s 659
79s :I24
Iron Radiation
Be
Mg
.41
Si
S ?e
Be
266
s
5n
346 560 785
: u
797 868
vi
ri V
Jn :r
SO9
Ig
!57S :1S6 i397
Pb W
Xhlybdenum Radiation
5.64 135 252
1771 2612 3422 2460 4253 4854 5790
AMlg Si Ti Mo
Cr Sn
A&. Fe
co
Zn Ni
cu Pb W
0.58
15.2 19.8 109 203
221 248 289 303 383 421 427 455 1537 2007
Figure 6 for a bronze has also been discussed in connection with the technique of two or more characteristic radiations in showing the marked difference in using molybdenum and copper K a rays for diagnostic purposes. Reference to Figure 2 demonstrates that with the former radiation the tin should not appear (Figure 6A) but will be disclosed with copper Ka rays (Figure 6B). The two figures correspond exactly and any chosen area may he compared to show the effect of tin on the general structure. Actually in Figure 6A, some slight evidence of the tin areas appears in gray, from which we might conclude that there is some solid solution of the tin in lead or that it is in the form of an intermetallic compound. Figure 7A, represents the difficult case of leaded iron (lead being introduced for improved machinability without otherwise affecting physical properties), The specimen is cold-rolled in fabrication, so that the lead appears as extended white streaks parallel with the rolling direction. The microradiographic technique has been successfully used in perfecting the prooess of rolling beryllium into foil for use as windows in Machlett x-ray diffraction tubes. Because of the very great transparency of this element of atomic number 4 it presents perhaps the most difficult possible case. Furthermore, it is almost impossible to prepare satisfactory optioal photomicrographs for this metal. The sample in question was found unsatisfactory in maintaining a high Coolidge vacuum. The microradiograph in Figure 7B, with
characteristic chromium Ka radiation (2.285 %.) shows clearly the streaks of inclusions responsible for the microporosity. Figure 7C, is a typical microradiograph for aircraft agehardening aluminum alloy. Copper, supposedly in solid solution, actually appears, as white streaks a t grain bonndaries, and in this case in lamellar layers. This alloy was unsatisfactory in performance. Figure SA, illustrates inelusions which were missed entirely on photomicrographs in very large grains of silicon steel for high-duty electrical use. This is an excellent example of the value of the three-dimensional information of the microradiograph in contrast with the two-dimensional view of a polished surface in the photomicrograph. Figure SF, illustrates t,he distribution of graphite (black)
FIGURE 9. MlCRORADIOGRAPH (P\TEGATIVE Parm) OF TYPEMETAL (LEAD-ANTIMONY CRYSTALS DARK), MADEWITH CHARACTERISTIC MOLYBDENUM RADIATION. MAGNIFUXTION
x200
A.
r"..*,*r y,.y"
"L
*Ilr
"L
LI
".,"%?""
"yLIIIIy*~,I~LL"
B. Negative print of the smallest bone in the foot of
B
y"pyc.
LIIYILI*IYII.
and plastics, bone structures especially in cases of lead poisoning, soil and clay sections, fillers in peper, foreign particles in insulators, and many other materials have been subjected successfully to this technique.
in some of the new graphitic steels now being widely used for mchining operations. Figure SC,is typical of season-cracked cartridge brass, a long recognized and dreaded failure. Numerous cases have been found similar to this of the incipient formation of cracks and other failures in metals as a result of fatigue or temperature conditions. Figure 9 is a striking example of magnification a t 200 diameters of intermetallic crystals in type metal (essentially leadantimony) which serve to preserve the type against deform* tion of the soft lead of the matrix. In similar fashion a wide variety of alloys, metals such as tungsten which are very difficultto use in photomicrography, ceramic materials, minerals, powder mixtures, fillers in rubber
A OF SECTIONS OF FIGWEE 11. MICRORADIOGRAPHS
II.ycL.LI"II
very small frog taken through tfk web. made with characteristic copperradiation. Mapnifioalion XJO
Biological Microradiography An extended account of this application by Clark and Bicek will appear in an appropriate journal, but a few of the choicest photographs are illustrated here. For the most part a successful radiograph for very small biological specimens depends very largely on a difference in density of a given material such as cellulose, chitin, protein, etc., where oxygen is ordinarily the heaviest element present in the compound. I n such cases there is no segregation of different chemical ele-
B WHITE O A K WOOD,-MADE WITH CHAFCACTERISTIC COPPER
CATIONS
x5u
:ction ehowini: i n white row8 calcium oxdate mystals ?section ("ole :fibers in large ohannel opemws) a1 section
RADIATION.MAGSIFI-
ANALYTICAL EDITION
August 15, 1942
ments or phases as in alloys, unless, for example, a tissue is injected with thorotrast or some other heavily absorbing snbstance. The photographs here were made with the cbaracteristic K a radiation of copper exactly as with metals. Very soft general radiation generated at low voltages is useful for this type of specimen depending upon very slight differences in thickness of the same material in adjacent areas. Figure 10.4, shows in amazing detail the eye of an ordinary house fly; Figure 10B,is the microradiograph of the smallest bones in the foot of a very small frog, taken through the web of the foot; Figure 11 illustrates the striking structures of white oak wood taken through radial, transverse, and tangential sections. The three photogaphs are highly characteristic of each type of wood at different ages, conditions of growth, drying, impregnation, and other treatments to which wood may be subjected. It is evident that very accurate measurements can be made even of cell-wall thicknesses.
Acknowledgments The authors gratefully acknowledge the assistance of former students in the X-Ray Laboratory of the University
683
of Illinois, in the preparation of specimens and photographs illustrated in this paper: specimen of Figure 4, W. J. Craig and E. C. Lauck; specimen and photograph of Figure 7 A , J. Hino; Figures 7B, SA, 10, and 11, E. J. Bicek; Figures 7C, 8B, 8C, and 9, W. M.Shafer.
Li
ited
(1) Clark,G.L.,Photo TechnZque, 1, NO. 12 (Deo. 1939). (2) Clark, G. L..and Shafer, W. M,, Tram. Am. SOC.Metals, 13. 732 (1941). (3) Daulillier, A,. C m p t . rend., 191, 1287 (1930). (4) Fournier, M. F.,Reo. mdt. 35, 349 (1938). (5) Goby, P.,Compt. ?end., 156,686 (1913). (6) Zbid., 180, 735 (1925). (7) Lamarque, P.,et al.. Ibid., 202, 684 (1936): Radiology, 27, 563 (1936): Compt. vend. soc. biol.. 123. 1051 (1936): Bull. histol. appl. physiol. path. tech. micioscop.. 14, 5 (1937); Aroh. soe. sCi. m4d. biol. Montpellier et Languedoc, 18,27 (1937); J . Rad.. 20,6 (1936). (8) Schupp, 0. E.,and Boiler, E. R., IND. END. Cam&.. 30, 603 (1938). (9) Yoshida. U., m d Tanaka, H., M a . Coil. Sci. Kyoto Imp. Univ., AI^, 401 (1934).
Identification of Sugars By Microscopic Appearance of Crystalline Osazones W. Z . HASSID AND R. M. McCREADY Division of Plant Nutrition, University of California, Berkeley, C
vm,caraonyutaws as a group form a number of chemical and give a variety of reactions greater perhaps than any other class of chemical compounds. However, because of the close similarity in properties of the various sugars, the identification of the different members is often
... .
.
identihuuSvLL yu.u uUbY.s L ... "..".. -"-.-..-envatlves is the microscope. The identification of pure sugars and certain sugar mixtures has been accomplished by crystallizing the sugar from saturated aqueous solutions upon the addition of precipitating agents . . (4, f%). . . . .The,- sugar -, is then . . identified . uAJ
I
