Dati11g Iro11-Base lnlr Writings on Documents * N. K. Sen, D.Sc.** and P. C. Ghosh, M.Sc. ** Introduction As a part of a study on the changes in ink writings with time ( 1, 2) , experiments were conducted regarding the TLC patterns of the extracts from ink strokes on documents written with iron-base inks. Iron-gall ink undergoes a series of progressive physical and chemical changes on drying. These changes are primarily due to oxidation of iron salts which bring about the darkening of ink and simultaneous oxidative changes of the provisional coloring matter-the blue dye that is added to the ink. Signifi~ cant difference in color appears with lapse of time. After a number of years the ink begins to turn brown and final1y yellow, like rusty iron, as an indication of old age. Various methods, both physical and chemical, have been described in the literature for establishing the age of writing, with differing degrees of success (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14). Hence, an investigation was undertaken to asce1¡tain to what extent it would be possible to measure the progressive changes in iron-base ink strokes on paper in an exact and reproducible manner by TLC examination of the blue dye and iron content. The method employed was photodensitometric evaluation of the size and intensity of the spots of blue dye and red fer~ ric thiocyanate directly on the chromatograms obtained from the writings on a number of personal diaries of known ages ranging from January 1942 to December 1969. These were written with
* Received for publication September 3, 1971. Accepted for publication September 26, 1971. ** State Forensic Science Laboratory, Calcutta Medical College, Calcutta 12, India. Vol. 16 • No. 4
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the same type of ink on almost the same kind of paper and were stored under similar conditions. Present Study The type of the ink used in writing the personal diaries was determined by certain classic tests (15, 16), on the excised fragments of ink strokes of known ages collected at random from the diaries. By these tests the ink was found to be of the iron-gall type and the presence of iron and blue dye was confirmed in the fragments of ink strokes of all the writings removed from the pages of the diaries of different years. Materials and Experimental .Techniques Reagents: 1. 2. 3. 4. 5. 6. 7.
Silica gel G (E. Merclt). Methanol, reagent grade. n-Butanol, reagent grade. Acetic acid, reagent grade. Hydrochloric acid (reag-ent grade) solution (50% v/v). Ammonium thiocyanate (reagent grade) solution (20% w/v). Amyl alcohol, reagent grade.
Equipment: 1. Photodensitometer of Impex International Co., Model TNE-65, equipped with sliding carriage for scanning and the slit-width of 1 X 5mm. 2. Local made applicator according to Stahl (17). 3. 10 ,ul and 25 ,ul pipets having deviations of volumes of delivery of Âą 2 toÂą 4%.
Procedure: For chromatographic examination small fragments from the ink strokes we1¡e punched out of the paper by the method proposed by Harrison (18). A suitable punch was made by grinding the point off a hypodermic needle at right angle to its length and sharpening the blunt end. The page of the diary containing ink strokes to be examined was placed on a she&t of thick rubber and tiny discs, having approximately the same color intensity, were cut out of the paper from the center of the ink strokes by pressing the sharpened end of the needle on the paper and turning it around. With this simple method of removing extremely small :fragments numerous tiny and neat discs were collected for examination without impairing in any way the legibility, characteristics of the handwriting, or life of the documents (Figs. 1 and 2).
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Fig. 1-The removal of tiny paper discs from the ink lines does not reduce the legibility of the writings.
a. Estimation of the blue dye in the ink st'roke: A number of tiny discs punched out of the paper from the ink strokes on a page of known age were moistened with methanol and ltept in a refrigerator overnight and then extracted several times with fresh quantities of the solvent and the dye solution concentrated. The final volume of the extract was made to 0.5 ml for quantitative thin layer chromatography.
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Fig. 2-Positions of the tiny paper discs on the back side of the document. TLC plates (20 X 4 em) were prepared by spreading a homogenous slurry of pure silica gel G (E. Merck) and distilled water, 1:2, to obtain layers of 0.215 mm thickness. The plates were allowed to set in air for 10 minutes and then baked at 105째C for 45 minutes. The plates were then washed with the developing solvent by the ascending technique and then activated by heating for 30 minutes at 105째0 before spotting. The extracted dye solution in methanol from the ink stroke was spotted on the TLC plate with a 25 ~1 capillary pipet.
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TECHNICAL SECTION After drying with hot-air blower fo1• 1 minute, the plates were developed for about 90 minutes using a solvent system of n-butanol-acetic acid-water ( 45:10:45) and the ascending technique. After developing and drying for 20 minutes at room temperature each plate was viewed under UV light and the Rr values of the spot or spots were recorded. No chnl'acteristic fluot·escence was found in the chromatograms. The chromatograms consistently showed the presence of deep blue spots of Rr values lying between 0.1 and 0.14. These blue spots, with almost of equal Rt values 1 were :found to he the major constituents of the organic coloring matter in the ink strokes. The total area of these blue spots was scanned by means of the photodensitometer (19).
b. Estimation of the i?'on content of the inlc strokes: The tiny discs of paper from the ink strokes, after separation of the dyestuffs by solvent, were dried and ignited at a low temperature until the carbon was completely burnt off. The ash was dissolved by digesting- with 2 ml of 50% HCl at near the boiling point for 15 minutes and the solution cooled and transferred to a glass-stoppered cylinde1·. To the solution, 1 ml each of 20 per cent ammonium thiocyanate and of amyl alcohol were added and shaken thoroughly. The colored layer of amyl alcohol was removed with a pipet and made up to a known volume. An aliquot of the solution was then spotted on the TLC plate with a 10 ,ul pipet and the spot a1•ea was evaluated photodensitometrically. Blank tests were carried out on unstained portions of the plates with a mixture of hydrochloric acid solution (50%), ammonium thiocyanate solution (20 per cent), and amyl alcohol treated as described above.
Results: The chromatograms and the results have been summarized (Table I and Fig. 3). The table shows the solvent system used, number of spots in the plates, color and Rt values. The integrated spot area of the major blue spot has been plotted against time. The result is a decreasing linear plot (Fig. 4). The conditions for experjments have been kept as constant as were feasible. The number of the ink fragments in samples compared have to be chosen so as to contain the same amount of ink. This can he done by calculation based upon the iron content ,(see b in the previous section).
n
Discussion A preliminary note (2) describes the results of earlier experiments with different brands of iron-base ink writings. It was noticed that the· generaJ. appearance of chromatograms of the iron-base ink strokes varied considerably with age. Further study has. shown the -evolutionary patterns of these chromatograms yield information sufficient in details for determination of the age of the documents written with ironbase ink. Vol. 16 • No. 4
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Year and date 1969 31.12.69 1968 5.6.68 1964 27.7.64
1962 1.7.62 1960 26.8.60 1959 12.11.59 1957 12.2.57 1955 19.2.56 1963 2.1.53 1950 13.9.50 1947 9.5.47 1942 27.1.42 I
Rr X 100 NumMajor Minor her of spots spots Solvent system spots 10 (deep blue) I n-Butanol Acetic Acid Water 4 30 (light blue) ' 55 (pink) 10ml 45 ml 45ml 70 (yellow) F 35 (light blue) n-Butanol Acetic Acid Water 4 12 (deep blue) 58 (pink) 45ml 10ml 45ml 73 (yellow) F 33 (light blue) n-Butanol Acetic Acid Water 4 12 (deep blue) 56 (pink) 45ml 10ml 45ml 75 (yellow) r.路 35 (light blue) n-Butanol Acetic Acid Water 3 12 (deep blue) 55 (pinl{) lOml 45ml 45ml n-Butanol Acetic Acid Wate1路 35 (light blue) 3 13 (deep blue) lOml 45 ml 57 (pink) 45ml n-Butanol Acetic Acid Water 34 (light blue) 3 13 (deep blue) 45 ml lOml 60 (pink) 45 ml 3 12 (deep blue) n-Butanol Acetic Acid Water 30 (light blue) 45ml 45ml 54 (pink) lOml n-Butanol Acetic Acid Water 34 (light blue) 3 13 (deep blue) 45ml 45ml lOml 58 (pink) n-Butanol Acetic Acid Water 3 14 (deep blue) 30 (light blue) 45ml lOml 45ml 58 (pink) n-Butanol Acetic Acid Water 3 13 (deep blue) 35 (light blue) 45 ml lOml 45ml 60 (pink) n-Butanol Acetic Acid Water 3 10 (deep blue) 35 (light blue) 45ml 45 ml lOml 57 (pink) n-Butanol Acetic Acid Water 3 11 (deep blue) 36 (light bhie) 45ml lOml 45ml 58 (pink)
Colors of the major and minor spots are given in parentheses.
F Faintly visible.
The chromatograms indicate four types of spots : 1. Yellow 路spots of Rt values ranging from 0.70-0.75 (Table I). The spots are not noticeable with fresh ink. When the writings are about three months old (2), the spots are quite distinct. However, these spots disappear when the documents are around 9 years old, though even after
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7 years the yellow spots can be distinctly noticed. It is believed that a precise study of these yellow spots would enable a specification of the age of the documents less than 7 years old, to within a few months, however, a much more detailed investigation of these spots for the initial years is necessary ( 2) • 2. Pink spots of R.t values ranging from 0.55-0.60. These spots are noticeable even with fresh ink writings. The spots are distinct up to about 21 years and very faint at about 28 years. 3. Light blue spots of Rt values ranging from 0.30 to 0.36. These have not been studied in the present investigation because of their faint color, however, they persist through~ out the period studied. 4. Deep blue spots of Rt value ranging from 0.1-0.14. These spots have been the main subj eet of the present study. It has been shown that within the period studied, the plot of the total intensity of these spots against time
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JOURNAL OF FORENSIC SCIENCES 30 28 26 24
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~
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Log of integrated Spot area..Fig路. 4-Plot of log路 of integrated blue spot areas vs. time.
shows a linear decrease (Fig. 4). The behaviour of the deep blue spot alone is sufficient to specify the age of the document within ;a few years. As indicated, it is believed that a more detailed study of all these spots may permit a specification of the age within a few months in the initial stages, and within a year, after a longer period of time. The transient nature of the yellow spots appears to be of considerable forensic importance. The spots are perhaps due to an oxidation product of a dye component, however, this has not been established.
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Summary A new method for TLC evaluation of progressive changes of the blue dye and iron content in the ink strokes on documents of known ages written with iron-base inks has been described. This method may prove to be of forensic importance in determination of the age of documents bearing such ink. Acknowledgments: The work was supported by grants from the Council of Scientific and Industrial Research, government of India. Thanks are due to Professor Asima Chatterjee, head of the Department of Chemistry, University College of Science and Technology, Calcutta, and to Dr. S. Chowdhuri, director, State Forensic Science Laboratory, West Bengal, for encouragement to the work. The authors a1·e also indebted to the director, Central Food Laboratory, Calcutta, for kindly pet·mitting one of us (P.C.G.) to use their photodensitometer for the wor1{ and to Dr. Ranjit Sengupta, reader in chemistry, University of Kalyani, West Bengal, for his keen interest and helpful suggestions in this work.
REFERENCES 1. Sen, N. K. and P. C. Ghosh. Differentiation and Identification of Ink Writing of Different B1·ands of Iron-Base on Documents by T. L. C.
2. 3. 4. 5. 6. 7. 8. 9. 10.
11.
and Spectrochemical Analysis. J. Indian Acad. Forensic Sci. 9, 54-59 (1970). Sen, N. K. and P. C. Ghosh. The Change in the Thin-layer Chromatographic Patterns in the Ink Stroke Extracts with Time (in press). Casey, R. Writing Ink. Chem. Industr. 58, 246-249 (1946). Mitchell, C. A. Estimation of the Age o:f Ink Writing. Analyst 45, 247-258 (esp.253) (1920). Rhodes, H. T. F. F01·ensic Chemistry. Chern. Pnb., 101-102. New York City, N.Y. (1940). Osborn, A. S. Questioned Documents, 471-476 (2nd Ed.). Boyd Printing Co., Albany, New York (1929). Rhodes, H. T. F. The Oxidation of Ferrous Il·on in Iron-Gall Ink. Chern. and Industr. 59, 143-145 ( 1940). Mezger, 0., RaU, H. and W. Heess. New Methods for Examining Inks. Z. Angew. Chem. 44, 645-651 (1931). Heess, W. Sulphate Pictures as a Means of Identifying Inks and Estimating the Relative Age of Writing. Arch. f. Krim. 96, 13-17 (1935) ; see also Analyst 60, 388 (1935). Heess, W. A New Procedure for the Determination of Identity and Age of Ink Writing III. Hist01•ical Review and Systematic Guide for Judging the Age of Iron Gall Writing. Arch. f. Krim. 107, 7-37 (1937}. Cornish, R. E., Finn, J. and W. Mclaughlin. Age of Inks as Determined by the Chloride Test. Ind. Eng. Chern., News Ed. 12, 316-316 (1934).
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JOURNAL OF FORENSIC SCIENCES 12. Finn, J. and R. E. Cornish. Determination of Age of Ink by the Chloride Method. Ind. Eng. Chern., Anal. Ed. 10, 624-525 (1938). 13. Waters, C. E. Blue Dye as Evidence of the Age of Writing. Chern. Industr. 25, 1034-1035 (1933). 14. Waters, C. E. Ink. Circular C 426, 24. Bureau of Standards, United States Dept. of Commerce (1940). 15. Ward, T. J. Microchemical Identification of Ink Handwriting. Analyst 59, 621-2 (1934). 16. O'Hara, C. E. and J. W. Osterburg. An Introduction to Criminalistics, MacMillan and Company, New York City, N.Y. (1949). 17. Stahl, E. Thin Layer Chromatography, A Laboratory Hand Book, 6. Academic Press, Inc., London, England (1965). 18. Harrison, W. R. Suspect Documents, Their Scientific Examination, 118. Sweet and Maxwell, London, England (1966). 19. Klaus, R. Einige kritische Betrachtungen zur photometrischen Auswertung von Diinnschichtplatten. J. Chromatogr. 16, 311-326 (1964). Nirala 22/3H, Sreenath Mukhe1•jee Lane Calcutta SO, India
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