Anal. Chem. 1900, 8 0 , 1009-1018
-=( dt2
1009
Hexp
The thermal resistance factor, R,, is defined as
l
K
l
_ -- - + - + Rx
RS
(
--
- tmax RTCS
+
)
=
TSH - TS RS
(-410)
In eq A9 and A10, RT = Rs RD. The time derivative of eq A9 yields the rate of catch up of Ts
l RGr
RG
Integration of eq A2 with the boundary condition, eq A4, yields a general equation (eq A5) for the sample response during a melting transition
The rate of catch up of the sample platform temperature, TSH, is given by the time derivative of eq A10
Substitution of eq A l l in eq A12 yields the required expression Use of the energy conservation law (10) in conjunction with the condition dTs/dt = 0 yields eq A6 for the rate of enthalpy change, d h l d t , during melting d h - 1 dTp _ - --t + cs-ddTPt dt R, d t
(A131 gives
The rate expressed by eq A13 decreases exponentially with increasing t and will equal the programmed rate a t t >> t,=.
Note that the above expression is similar to that derived by Gray (IO)with the important difference that the heat leakage effect is explicitly included herein. Another parameter, namely the time derivative of the i.e. dTSH/dtlt>t,,, is sample holder temperature a t t > t, required to simulate the posttransition DSC curve-shape. This is derived from our model as follows. According to Newton's law, a t t > t,,,
(1) Brennan, W. P.; Miller, B.; Whitwell, J. C. I n Analytlcal Calorimetry; Porter, R. S., Ed.; Plenum: New York, 1970; VoI. 2, p 441. (2) Jang, G.-W.; Rajeshwar, K. Anal. Chem. 1086, 58, 416-421 (3) Jang, G.-W.; Segal, R.; Rajeshwar, K. Anal. Chem. 1987, 5 9 , 684-687. (4) Nelder, J. A.; Mead, R. Computer J . 1085, 7 , 308-313. (5) O'Nelll, M. J. Anal. Chem. 1964, 3 6 , 1238-1245. (6) Baxter, R. A. I n ThermalAnalysis;Schwenker, R. F., Jr., Garn, P. D., Eds.; Academlc: New York, 1969; Vol. 1, p 65. (7) O'Neill, M. J. Anal. Chem. 1075, 47. 630-637. (8) Claud)', P.; Commercon, J. C.; Letoffe, J. M. Thermochim. Acta 1083. 68, 305-316. (9) Schonborn, K. H. Thermochlm. Acta 1083, 69, 103-114. (10) Gray, A. P. I n Analyrical Calorimetry; Porter, R. S., Johnson, J. F., Eds.; Plenum: New York, 1972; Vol. 3, p 17. (11) Brennan, W. P. Ph.D. Thesis, Princeton University, 1971. (12) O'Neill, M. J. Anal. Chem. 1986, 38, 1331-1336. (13) Flynn, J. H. NBS Spec. Pub/. (US.)1070, No. 338, 119-136. (14) Van Dooren, A. A.; Muller, B. W. Thermochlm. Acta 1981, 4 9 , 151-161. (15) Van Humbeeck, J.; Bijvvet, M. Thermochim. Acta 1087, 720, 55-61. (16) Morgan, S. L.; Demlng, S. N. J. Chromatogr. 1075, 772,267-285.
Integration of eq A6 between the limits t and 0 and t,, the total enthalpy of fusion, AH, of the sample
LITERATURE CITED
Equation A7 may be solved for t,,,
Hexp
(
t - t,,
--
RTCS
Tp- Ts =-
)
(A9)
RT
RECEIVED for review June 23,1987. Resubmitted November 18, 1987. Accepted January 14, 1988.
The Vinland Map Walter C. McCrone McCrone Research Institute, 2820 South Michigan Avenue, Chicago, Illinois 60616
A recent paper In this journal presents analytical data that caused those authors to dlffer wlth our conclusion published In 1974 that the Vlnland Map Is a modern forgery. A summary of our data pertalning to authenticity Is Included here to sup port our conclusion.
The Vinland Map (VM) was first revealed to the world in 1965 with the appearance of a book, The Vinland Map and the Tartar Relation, by Skelton, Marston, and Painter (1). The map, an unassuming pen and ink rendering, is a world
map on 27.8 X 40 cm parchment folded in two leaves. It is, however, remarkable for its purported date of 1440 in depicting lands to the west of Greenland, their shape, size, and position resembling the Northeastern extensions of North America (Le., Vinland). The lack of a convincing provenance for the VM and "grave doubts" by some scholars and scientists led Yale University, the owners, to discuss with McCrone Associates (MA) an investigation of the map in an effort to evaluate its authenticity. In February 1972, Ken Nesheim of the Yale Beinecke Library brought to Chicago the Vinland Map (VM) which had
0003-2700/88/0360-1009$01.50/00 1988 American Chemical Society
I010
ANALYTICAL CHEMISTRY. VOL. BO, NO. 10. MAY 15. 1988
Figurb 1. Vinland Map. sampling locations are designated by number-letter pairs: Vinland has been hatched
been bound with two manuscripts: the "Tartar Relation" (TR) and the "Speculum Historiale" (SH). These two manuscripts, accepted as authentic 15th and 13th century documents, respectively, had been bound together with the VM as indicated by contiguous worm holes. The two manuscripts and the VM were examined by MA personnel and sampled by Anna Teetsov, MA microscopist. A total of 54 nanogram-to-microgram samples were taken: 29 from VM, 7 from TR, and 18 from SH. T h e sites for the 29 VM samples are indicated on the map (Figure 1)and described in Table I. These were subsequently examined by polarized light microscopy (PLM), X-ray (XRD) and electron diffraction (SAED), and scanning (SEM) and transmission (TEM) electron microscopy and with electron (EMA) and ion (IMA) microprobes in the McCrone Associates laboratory. The McCrone Associatea report covering their investigation was submitted to Yale University in January 1974. A brief paper (2)was presented at a symposium on the map in London in February 1974. In 1976, a further general paper on the map was published in Analytical Chemistry (3). Until now, however, no complete description of the 1972-1974 work at McCrone Associates has appeared.
EXPERIMENTAL DATA Preliminam Examination, Stereo Microscope. Initial examination of the Vinland Map (VM) by stereo microscope disclosed what appeared to be a normal hand-drawn map. The black ink line was bordered along its length hy a yellowish dismloration which was at fmt assumed to he the stain normally resulting from discoloration by ink components having migrated into the fibers over time. During sampling, however, this yellow discoloration was observed to have body, unlike a stain. It could be removed as tiny fragments with a fine-tipped tungsten needle while viewing the map with a stereo microscope at 2RsOx. The black pigment itself existed as a thin shiny hlack layer easily flaked from the yellow line; indeed much of the black line layer had already flaked away in all parts of the map. Examination of the map lines showed that the black line had been carefully drawn over and, more or less, down the middle of a previously drawn yellow line. There was evidence of some
Figure 2. Parchment fragment, about 100 X 200 pm, coated wlth black (right onsthird) and yellow Ink (left two-thirds). transmitted light micrograph. The bar represents 20 fim.
wobble in placement of the black line relative to the yellow line and in, a t least, one area (West Coast of England) the second (black) line applied over the yellow line had "cut corners" and missed its registration with the yellow line. Polarized Light Microscopy (PLM). Figures 2 and 3 show a portion of the same parchment fiber with adherent hlack and yellow ink (taken from the East coast of Vinland itself, sample 10-A). Careful examination of this fiber a t higher magnifications (1000-2500X) showed further details of the small white (hirefringent) spots and smaller dark (pseudo-opaque) particles risible in the center portion of the fiber. A polarized light micrmcopist, especially one trained in pigment identification, would note the high birefringence (An = 0.161) and low refractive indexes (w = 1658.6 = 1.487) of the white particles and assume they are calcite (limestone). Similarly, he would note that the dark particles are suhmicrometer with a very high refractive index (or indices). If such very tiny pigment particles appear dark hy transmitted light and white by reflected light, as these do, they are most likely titanium white (TiO,). The absence of polarization colors then indicates low birefringence and therefore anatase (An = 0.06) rather than rutile (An = 0.28). A similar examination of 19 of
ANALYTICAL CHEMISTRY. VOL. 60, NO. IO. MAY 15. 1988 * 1011
Table 1. Vinland Map Samplen sample
location on map
EA EB ED BE 9-A 9-B 9-C 9-D
inscription on back, yellow inkD inscription on back, yellow ink plus parchment fibers from patch over wormhole, west of British Isles parchment fiber from hack (hair side) of map from map crease. loose black particles plus parchment from background North Atlantic, black particles from Vinland coast, black ink particle with yellow ink from top of 'B" of 'Byarno" in legend 6 6 'Vinlanda Insula...", yellow ink from bottom of 'B" 'Byarno" in legend 6 6 yellow ink from Vinland coast, ink stain from N. African eosst, South of Sardinia, black ink plus yellow ink from Coastline West of 10-B,yellow ink from first "S" in "Tunesis" (Legend 20). black ink plus yellow ink from second 'S" in "Tunesis" (legend 20), yellow ink from Vinland coast, yellow ink from SE edge of wormhole in legend 39 below 'Thule Ultima", black ink particles with adhering yellow ink from "9" in 'Montes" (legend 39). black ink plus yellow
9-E 10-A 10-B 10-C 10-D
IO-E 11-A 11-9
11-C
ink
11-D from river above 'Kemmodi" (legend 31), black particles plus yellow ink 11-E from coast of island below 'Postreme Insula" (legend 58), black ink plus yellow ink 12-A from coast of next island south of 11-E, yellow-brown ink 12-8 from background, Iraq, black particles with yellow ink 12-C from 'P" of 'Postreme" (legend 581, black ink plus yellow ink 12-D from yellow ink from same letter (12-C) 12-E from ocean SE of Africa, fibers 14-A from just off coat marked Ayram. orange lining of wormhole 28-A from just off Vinland coast, parchment 28-B from East coastline of Vinland, black ink DTheyellow ink along both sides of the black ink line appears yellow, orange, or brown depending on thickness and relative percentages of calcite and anatase.
rl
t t i
1
Figure 3. Same parchment fragment in Figure 2 shown here with slightiy uncrossed polars. The small white particles are calcite (limestone): the smaller dark particles are anatase. This is a transmitted light micrograph with slightly uncrossed polars. The bar represents
20 Irm.
the samples that showed at least 8ome portions of yellow ink diedosed that,at least, 16 showed the same two kinds of particles. The high birefringent (limestone?) particles are also associated with other low refractive index particles, probably associated minerals like quartz, clays, feldspars, etc. The black ink areas also showed (by PLM) very tiny, hut truly opaque particles, m i h l y carbon black (soot?) or an iron tannate; they were not magnetic (i.e., not Fe,O,, magnetite). Another important PLM observation was the fact that the samples varied
considerably in the relative amounts of yellow and black ink as well as in the distribution of pigments in the yellow ink. This illustrates the difficulty of mixing very fine particles in a suspension to achieve a uniform dispersion. It also explains why different portions of the same sample analyzed by different techniques sometimes show different compositions. It was not difficult to find small areas, a few square micrometers, of pure components. Two such areas of pure anatase are shown later (Figures 8 and 9) by transmission electron microscope (TEM). A final PLM observation has to do with shapes of the calcite and anatase particles, since this has a strong bearing on the origin of these particles. A regular uniform shape and micrometer particle size of calcite would indicate a man-made precipitated product availablecommercially only in the 19th century and later. The gound mineral limestone, however, has been used for hundreds of years. The calcite in the VM is ground limestone and therefore not helpful in dating this map; moat calcite in modern paintings, etc., is the precipitated mineral. The anatase, on the other hand, is of uniformly small diameter particles averaging about 0.15 pm. The larger anatase particles can be resolved by PLM as rounded crystallineshapes typical of commercial titanium white (4). This product has been produced only since 1911. For a few years after 1917, the color of this anatase (TiOJ pigment was yellow due to traces of iron. The observed color of the yellow ink line may be due to early yellow TiO,. In any case we observed no other yellow particles. Examination of successive VM yellow ink flakes by PLM consistently confiied the above results (Table 11). A t this point, after finding submicrometer anatase in samples 9-C, 9-D, lO-D, 10-E, 11-A, 12-A, and 12-C hy PLM, we were convinced the VM was of recent origin. In fact, the sampling steps showing the presence of an applied yellow ink line simulating the natural staining of ink line boundaries would be sufficient to label the Vinland Map as a forgery. We proceeded, however, to obtain as much confirmation as possible through the use of other ultramicroanalytical instrumentation. Moat of these data are summarized in Table 11. The different area samples are denoted by a figure and a letter (e.g., 10-A); an added third digit signifies a small portion of that sample. These portions often yield different results due to heterogeneity of the nanometer samples. X-Ray Diffraction (XRD). We used a special micro X-ray diffraction camera capable of excellent powder diffraction patterns on subnanogram samples to X-ray a portion (about 7 Irm in average diameter) of yellow ink (sample 9-C) which had been assumed (by PLM) to contain anatase and calcite. The resulting powder diffraction pattern (Table 111) shows about equal amounts of anatase and calcite with a small quantity of quartz thus confirming the PLM identification. Quartz particles are ubiquitous and accompany most quarried or mined materials, e.g., limestone. Titanium is also reasonably ubiquitous, being ninth in order of abundance of the chemical elements. Titanium dioxide as anatase, however, is not so common and in the modern pigment form it has been available only since about 1920. Similar XRD patterns were obtained on other portions of 9-C and 11-A (Table 111). Scanning Electron Microscopy (SEM). As a next step, we examined a small portion of VM yellow ink sample 9-D by using the scanning electron micmscope (SEMI with its energy dispersive detection system (EDS). Figures 4 and 5 show typical yellow ink particles at 11ooOX. The surface asperities are likely due to the small anatase and calcite particles observed by PLM and XRD. This is further indicated by the corresponding energy dispersive X-ray spectra (Figures 6 and I). The 9-D-3 yellow ink particle shows (Figure 6) titanium as its strongest EDS peak, presumably corresponding to anatase; a black ink particle (Figure I, 9-C-2), shows equally strong iron and chromium peaks. Even though it is difficult to he sure each of the two ink samples is not, a t least slightly, cross-contaminated, the two are shown to be very different. Transmission Eleetron Microscopy (TEM). Because of the unique character (size and shape) of modern anatase pigment particles, the size and shape of the observed VM anatase particlea then became crucially important. We turned next, then, to transmission electron microscopy (TEM). Jagged irregular particles with widely varying particle sizes would signify ground mineral anatase; well-formed, although rounded, regular crystal shapes and a narrow submicrometer size range would indicate
1012
ANALYTICAL CHEMISTRY. VOL. 60. NO. 10. MAY 15. 1988
ili
Figure 4. VM yellow ink flake (9-D-2) about 10 r m in maximum dimension. The tiny rounded protuberances may be the pigment panicles anatase and calcite. This is an SEM micrograph taken at IIOOOX. The bar represents 1 r m .
Figure 5. Flake of VM yellow ink (9-D-3)under the same conditions as given in Figure 4. The energy dispersive X-ray panern lor this sample is shown in Figure 6.
Figure 6. Energydispersive X-ray panern lor VM yellow ink sample 9 0 3 (full scale is 10 keV). The cursor is set on the tnanlum peak at 4.51 keV the peaks. left to r!ght, are magneJlum. aluminum. silicon.
gold. calcium. titanium (two peaks). copper, zinc. copper, and gold. a precipitated man-made product. The TEM easily resolves these submicrometer particles, thus making possible size and shape determination, and its selected area electron diffraction (SAED) capability identifies the crystallographic phase and, thereby, the chemical composition. The smallest possible subnanogram portion taken from VM sample 11-A (Vinland,S.E. coast) was crushed between two clean glass surfaces and the flattened residue (amounting to only a few picograms) was mounted on a TEM grid. Figure 8 confirms the size and shape characteristics of the VM anatase (Le., rounded single crystals less than about 0.5 pm in diameter). Figure 9 shows
i,/
< r
1'.
Figure 7. Energy dispersive X-ray panern lor VM black ink samples 9-C-2 showing an expanded portion of the panern from Silicon (1.74 keV) to tungsten (8.40 keV from ow tungsten needle). The two tallest peaks are chromium (5.41 keV) and iron (6.40keV) (full scale is 15.31 keV). modern commercial anatase pigment samples from NL Industries (Titanium Pigments Division). Finally, Figure 10 show the typical shapes of ground mineral anatase. Figures 8 and 10 were taken at 25000X, Figure 9(left)at 50000X, and Figure 9(right) at 2oooOX. Good SAED data for anatase obtained on VM samples 9-D, 11-A, and 12-A are tabulated in Table IV. The observed diffraction patterns show spotty rings as expected with small samples, hut the ring diameters are in good agreement with the lattice parameters previously observed by XRD for anatase. The shapes of the VM anatase particles (Figure 8 ) show them to he characteristic of the commercial pigment, i.e., rounded, reasonably uniformly sized, single, post-1917 crystals (Figure 9). It is impossible for ground mineral anatase (Figure 10) to show the particle shape and size distribution of the commercial product. Particle Size Measurements. One of the additional means chrmen at this point to further characterize the anatase found in the VM was a particle size distribution measured from the TEM images such as those illustrated in Figures 8 and 9. The distribution of sizes based on more than 300 particles for the two commercial samples is shown graphically in Figure 11. The similarity between the particle size distribution curves for VM sample 11-A and NL Industries (Titanium Pigments Division) anatase pigment is obvious as is the size distribution difference between these two precipitated pigments and the ground mineral anatafie in Figure 10. A ground material always shows increasing numbers of smaller and smaller particles with a wide size range and (usually) irregular jagged particles. It is extremely difficult even today to grind any sample to yield all submicrometer particles. Electron Microprobe Analyzer (EMA). This instrument is capable of elemental analyses on samples ranging down to f e m w a m levels (WS g) with a 1-pm beam diameter. Its analysis, however, is produced from about a 100 pm3volume of the sample. It detects and identifies all elements except the four lightest (H, He, Li, and Be). The EMA analyses of 16 yellow VM inks (Table V) show significant amounts of titanium; the single black ink sample (9-C-2) and the parchment sample (28-A) analyzed by electron microprobe show little or no titanium (Table V). Ion Microprobe Analyzer (IMA). The ARL ion microprobe, newly acquired at McCrone Associates in 1971, was also used to analyze several VM ink samples (Table VI). A t that early date, the sensitivity of the IMA for different elements was not well understood-hence accurate quantitation was impossible. It is, however, extremely sensitive for many elements and in subattogram g) quantities. For most elements, it is strictly a qualitative surface analyzer covering areas as small as 5 pm2and a few atom layers deep. Depth profiles at nanometer levels are also possible with IMA. The ink samples analyzed by IMA ranged in size from 4 pm to slightly more than 10 pm in average diameter. The small size accounts, no doubt, for some variations in EMA and IMA data (Table 11) but the sensitivity for different elements also varies greatly from EMA to IMA. There is good agreement for most
ANALYTICAL CHEMISTRY, VOL.BO, NO. IO. MAY 15. t s w
-re
ioia
0. Particles of anatase from the Viniand Map (particle 11-A-5. l e t pariicle 9-D-1. right) viewed at 25000X. TEM. The bars represem
0.15 pm.
d Flgue 9. Precipitated TiO, (anatase). mmples from National Lead Industries (Titanium Pigments Division).viewed at 50000X (len)and 2OOOOX (right) TEM. The bars represent 0.15 pm.
A".
P
Fbun I O . Ground mineral anatase. sample from lhe Smithsonian Institution, the (left) and coarse (right)fractions. viewed at 25000X. E M .
replicate samples by E M A 8-A-I and -2,s-B-1 and -2, 1 l . A - I , -2, -3. and -4, as well as 12-A-I, -3, and -4 ITahle VI. Table VI shows IMA data for 23 different V M samples, including all those that showed any indication of yellow ink. The absence of data for trace elements for samples %I 1 does not mean ahenre of trace elements. We were looking only for major and minor elements at the time they were analyzed. The IMA k very sensitive for alkali and alkaline-earth elements but much less sensitive for transition elements and especially insensitive for the noble metals. Barium was reported as -major" based on our then understanding of the highly sensitive IMA (subattogtam, 10 whereas the EMA. a more quantitative but less sensitive (subferntugram, gl instrument. found only ahnut 1% barium. Titanium is one of the elements for which the IMA is relatively sensitive: hence *major" may he reported for low
pereentages (e.& SB-I). The inhomogeneity of UltramiemSamplea can cause apparent discrepancies. hut these me usually explained by microscopical examination of the sample(s). Sample 12-A, for example, shows variable composition depending on the portion analyzed. Table V shows data for four different portions of this sample. Three agree quite well (12-A-I, -3, and -4) hut 12-A-2 is very different. It was very small (average diameter, 4 wm) and apparently was a tiny patch of anatase similar to those selected for the TEM pictures shown in Figure 8. This illustrates the necessity of understanding the capabilities and limitations of each microanalytical tool. Table I1 summarizes the extent to which each of the ultramicroanalytical instruments was used on the VM ink samples. Comparison of VM,TR,a n d SH I n k Samples. The ion microprobe was also used to compare samples from the "Tartar
1014
ANALYTICAL CHEMISTRY, VOL. 60, NO. 10, MAY 15, 1988
Table 11. Summary of Major Microanalytical Results”
sample*
typec
8-A-1 8-A-2 8-B-1 8-B-2 8-D 8-E 9-C-1 9-C-2 9-D-1 9-D-2 9-D-3 9-D-4 9-E 10-A 10-B 10-c 10-D 10-E
ink, Y ink, Y ink, Y ink, Y fiber fiber ink, Y, B ink, B ink, Y ink, Y ink, Y ink, Y ink, Y ink, Y ink, Y, B ink, Y ink, Y, B ink, Y ink, Y ink, Y ink, Y ink, Y ink, Y ink, Y, B ink, Y ink, Y ink, Y, B ink, Y, B ink, Y
11-A-1 11-A-2
11-A-3 11-A-4
11-A-5 11-B 11-c
11-D 11-E 12-A-1 12-A-2
PLM
XRD
TEM EMA microSEM graph SAED micrograph % Ca % Fe % Ti 15 15 8 15
anatase
anatase
anatase
anatase
anatase
anatase anatase
anatase
anatase
Fe, Cr, S anatase anatase anatase anatase
4 1-2
0.5 1.5 0.8 1.5 0.8
8
Ti, Ba, Ca
Ti, Ba Ca ( 8 4 organic organic 28-35 Ti 8
Ba (8-C) Ca
highd 0
3-5
15-20 Ti, Ba
3-5 3-5
15-20 15-20 Ti, Ba Ti, Ba, Ca Ti, Ca, Ba
anatase
anatase anatase
anatase
anatase
anatase
7-9 4-6 4-5 4-8
1-2
Ti, Ca Ti 15-22 Ca, Ti, Ba 12-16 10-15 5-7 Ca, Ti, Ba Ti, Ca, Ba Ca, Ti Ti
anatase? anatase? anatase anatase
trace
9 4
anatase? anatase anatase anatase anatase anatase anatase
IMA minor
major
7-9
anatase
anatase
12-A-3 ink, Y anatase 12-A-4 ink, Y anatase anatase 12-A-5 ink, Y 12-B ink, Y, B
7-9 7-9
20-28 40-45 Fe, Ca, Si, K
Na, Mg, Al, Ti, Cr
15-20 12-15 Ca, Ti, Fe
Na, Mg, Al, Si,
Ti, Ca, Ba
Na, Mg, Al, Si, K Na, Mg, Al, Si Ca, K, Na, Mg, Al, Si
Cr 12-c
ink, Y,B anatase
12-D 12-E
ink, Y fiber
28-A 28-B
fiber ink, B
Ca, Fe, Ti
anatase anatase
erg, N
S
