THE ANALYST. ENGLISH INKS : THEIR COMPOSITION AND DIFFERENTIATION IN HANDWRITING. BY C. A. MITCHELL, B.A., F.I.C. (Beat7 at the Meeting, Febwary 5, 1908.) IN the following paper I have dealt chiefly with the differentiation of inks, more especially when forming the dried pigment in handwriting; and as I wished to describe characteristic reactions given by the products of the manufacturers whoiu I have named, I have purposely refrained from drawing conclusions as to the relative merits of the various preparations. I n the old type of iron-gall inks-those in which partial oxidation was made to take place before bottling-there could not have been very marked differences, except such as would result from the use of varying proportions of galls, ferrous sulphate, or gum; Hence, as a rule, it would have been practically impossible to distinguish with any degree of certainty between the characters made by two such inks.This old type o€ ink is now rarely met with, having been all but sbperseded by the modern unoxidised inks, in which a ‘‘ provisional ” colouring matter is intro- duced to give some colour to the writing, pending the formation of the black insoluble tannate within the fibres of the paper. I t is true that added dye-stuffs were sometimes employed to improve the colour of inks of the old type, and the use of indigo for this purpose is mentioned by Eisler (1770); and of logwood by Lewis (1763) ; but the inks themselves were still more or less oxidised before use, and it was not until early in the nineteenth century that indigo or logwood was used for their modern purpose of rendering the writing immediately visible.Alizarine was also employed as a provisional colouring matter in Germany, and although it soon gave place to indigo, the unoxidised inks into which it was introduced have retained their original name of ‘( alizarine inks ” to the present day. The discovery of the aniline dye-stuffs added largely to the provisional colouring matters at the disposal of the ink-manufacturer, and such dyes are now found in most of the blue-black inks of to-day. There is a considerable variation in the proportion of solid matter and of iron to organic matter in commercial writing fluids, as will be seen in the following table, giving the results of partial analyses made during the past twelve months of the best-known preparations.Most of these are iron-gall inks, but the list also includes samples of chrome-logwood and aniline inks. I take this opportunity of thanking those manufacturers who have kindly placed specimens of their preparations at my di apo s a1 .THE ANALYST. ~.-COMPOSITION OF ENGLISH WRITING INKS. 81 Ink. Arnold’s Blue-black ... Blackwood’s Blue-black . . . . . . Day and Martin’s Biue -black Draper’s ( ( Dichroic ” ... Faher’s Blue-black . . . ), Black ... ... Field’s ‘‘ Non-corrosive ” . . . Halsey’s Blue-black ... Lyon’s Blue-black . . . . . . Rlordtln’s “ Azuryte” ... ?, Blue-black ... “ Jet-black ” ... 11or;ell’s Blue-black ... Paul’s Blue-black . . . ... Black ... ... Prihge’s Blue-black . . . StephenR’ Blue-black * . . T’icker’s Penwing ” ... Walkden’s Blue-black .. . ,) Black ... ... ‘‘ Record ” Carr’iblue-black . . . ... Black ... ... ... ,, Black ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... Specifie Gravity a t 15” C. 1.0216 - - 1,0220 1.0244 - - 1-0205 1.0153 1.0121 1.0208 1.0239 1.0225 1.0256 1.0276 I - - 1.0499 1.0206 1.0221 1.0293 - - Water Per Cent. 96.35 96-82 92.06 96.01 95-84 92-25 95-16 95.58 96.66 97.55 95.34 95.14 95.94 95-54 94.04 95.1 G 96-12 96.68 92.22 92.32 96.21 98.11 95-58 94.39 Total Solids per Cent. 3.65 3.18 7-94 3.99 4.16 7.75 4.84 4-42 3.34 2-45 4.66 4.86 4.06 4-46 5.96 4.84 3.88 3.32 7-88 7.70 3-79 1.89 4.42 5.61 Mineral Matter per Cent. (Ash) 0-94 0.77 1.40 1.07 1.39 2.52 1.10 1.22 0.82 0.64 0.54 1-01 0.86 0.62 0.99 1 -66 0.97 2.28 1-88 1 *42 0.76 0.42 0.72 1.12 Iron per Cent.0.25 0.28 0.59 0.29 0.48 1.09 trace 0.49 trace 0.28 0.28 0.35 0.29 0.18 0.21 0.56 0.33 trace 0.84 0.49 0.32 trace 0.22 0.36 These results show that, notwithstanding the probably closely similar methods of preparation, there are yet wide variations in the composition of the different inks. Thus, the total amount of solid matter (dried at 100’ C.) ranges from 1-89 to 7.94 per cent., the ash from 0.42 to 2.52 per cent., and the iron in the iron-gall inks from 0.18 to 1.09 per cent. From time to time during the past five years I have examined samples of several of the different kinds of inks mentioned in the table, and the results indicate that the composition of an individual preparation by the same manufacturer remains fairly constant.I have been unable to devise any satisfactory method of estimating gallotannic acid and allied substancespresent in ink. A method of absorption by means of hide powder might yield satisfactory results if gallic acid were not also a usual con- stituent. On the other hand, the #‘ provisional ” colouring matter in inks interferes with the estimation of the gallotannic and gallic acids together by the colorimetric method which I devised for the valuation of tannin materials for ink-making (‘‘ Inks and their Manufacture,” p. 85).82 THE ANALYST. The tannin in freshly-prepared ink appears to be in the form of a soluble iron tannate, which slowly oxidises on contact with air, forming an insoluble tannate. I have frequently examined the deposit which forms when a solution of gallotannic acid and ferrous sulphate is allowed to stand in contact with the air, and have found that when washed with cold water and dried at 100" C.it yields from 7.8 to 8.8 per cent. of ferric oxide, corresponding to 5 4 to 6-54 per cent. of iron. Of the known insoluble iron tannates, the one that corresponds best with this proportion of iron is that described by Wittstein (Jnlzi*csber. der Cheiiz., 1848, 28, 221) and by Schiff' ( A m . Chem. Phawn., 1875, 175, 176), which contains 5-53 per cent. of iron, and has the formula- Fe ( w w 3 > 3 I If, as seems probable, this is the tannate formed in the gradual darkeningof ink upon paper, any excess of iron or gallotanic acid beyond the quantities required to forill this compound should be unnecessary, or even injurious, to the permanence of the writing.The dye-stuffs in the blue-black inks referred to in Table I. varied in colour froiii pale greenish-blue to indigo and deep violet, md no two gave identical reactions-at all events, when mixed with the iron tannate to form the pigment in writing. It is mainly owing to these differences that it becomes possible to distinguish between the handwriting done with different kinds of ink, and in some cases it is not even necessary to apply chemical tests for the purpose. Thus, in the case of words written with inks having respectively an azure blue and an indigo colour while wet, it is easy to distinguish the colours under the microscope months after the writing has attained its maximum intensity.I n examining writing to determine whether it has been done with a particular ink, it is advisable to prepare a colour scale with that ink, consisting of four washes ranging from the faintest to the darkest possible tone, the paper being left for at least twenty-four hours. The scale is then compared under the microscope with different parts of the writing in question, and is subsequently used in comparative chemical tests when such are permissible. The broad surfaces of colour are comparable with the surfaces of the written characters a6 seen under the microscope, and there is thus obtained what practically amounts to a magnified record of the microscopical appearance. Lovibond's tintometer will also be found useful in coinparing different speciineiis of handwriting and matching the colours obtained in chemical reactions with those given by the colour scales prepared from known or suspected inks.With regard to the use of photography as a means of differentiating inks in writing, I have made numerous experiments with colour-sensitive plates and screens, but find that the differences of intensity shown in the negatives are no greater than may be seen with the naked eye. I am, therefore, unable to confirm Minovici's (B~ill. della SOC. Fotogra$a Itnl., 1900, 12, 349) experience in this respect.THE ANALYST. 83 For the differentiation of inks in handwriting by chemical methods a wide choice of reagents is available, but those I have used will, as a rule, be found sufficient, viz. : 1. Hydrochloric acid (5 per cent.solution). 2. Oxalic acid (5 per cent. solution). 3. Stannous chloride (10 per cent. solution). 4. Nascent hydrogen (50 per cent. HC1 with zinc). 5. Bromine (saturated aqueous solution). 6. Bleaching powder (saturated solution). 7. Titanous chloride (the impure commercial solution). 8. Potassium ferrocyanide ( 5 per cent. solution containing 1 per cent. of HCl). Of these reagents, the two first act mainly upon the iron tannate, and leave the provisional colouring matter. The third and fourth bleach the iron tannate, and reduce the provisional pigment, changing its colour. The fifth and sixth reagents may act on both pigments, causing more or less superficial bleaching. The titanous chloride solution is a powerful reducing agent towards both pigments, whilst the acidified ferrocyanide solution acts mainly upon the iron liberated from the iron tannate.I n the table on p. 84, showing the reactions given by my samples of commercial inks, the reagents were applied by means of a brush, and the writing examined under the microscope both by reflected and by transmitted light, first after five minutes’, and again after twelve hours’, exposure to the air. The colorations which appeared upon the wrong side of the paper were sometimes also very characteristic, especially in cases where there had been superficial bleaching. In the tests with titanous chloride, blotting-paper was applied after the lapse of five minutes. I had recently to decide whether two specimens of handwriting were in the same ink and were done at one and the same time.The first question was easily solved, but from the results of my experiments I found that it was not possible to dis- tinguish between inks after they had attained their maximum degree of intensity, or until after the provisional colour had begun the fade. I t is, as a rule, possible to distinguish colorirnetrically between freshly written and old writings up to about the sixth day, after which the iron tannate has become almost completely oxidised, and differentiation is no longer possible until after the lapse of a year or more, according to the degree of permanency of the provisional pigment. As a rule, the pigments employed offer greater resistance to the action of chemical reagents, but are infinitely less stable than iron tannate when exposed to the action of light and air, and eloquent testimony to this difference is given by a comparison of certain manuscripts of the seventh and eighth centuries with type-written documents which have been put aside for a year or two.II.-REACTIONS GIVEN BY ENGLISH INKS IN HANDWRITING.Hydrochloric Acid, 5 per Cent.. Oxalic Acid, 5 per Cent. Stannous Chloride, 10 per Cent, Xascent Hydrogen. Bromine (Aqueous Solution). Bleaching Powder. Titanous Chloride. Potassium Ferro- cyanide, 5 per Cent., +HC1,1 per Cent. Inks. Dry. Dry. Dry. Moist. Dry. Moist. Moist. JIoist. Moist. Dry. Moist. Dry. Moist. Dry. Moist. DW. Arnold‘s Blue-black Blackwood’s Blue-blacl >, ‘’ Record ’ Carr’s Blue-black :, Black Blue-black j Day and Martin’s Draper’s ‘‘ Dichroic ” Faber’s Blue-black Sreenish- blue bright blue gray dark blue Larkened deep blue deep violet light blue purple deep blue bright blue deep blue bright blue bright blue larkened bright blue light blue deep blue bright blue blue deep blue reddened bright blue blue- black green- blue blue dark blue violet- gray deep blue deep violet blue deep violet deep blue bright blue bright blue blue blue blue- gray bright blue blue violet- black green- blue dull blue green- blue pink- brown bright blue blue- black green- blue bright blue light gray blue gray gray- blue red- violet bright blue purple deep blue blue bright blue bright blue bright blue gray bright blue bright blue deep blue bright blue green- blue deep blue pink- violet blue gray- violet green- blue blue pink- gray blue gray- violet green- blue red- violet bright blue pink deep biue green- blue bright blue bright blue bright blue gray bright blue bright blue green- gray pale blue Gay - blue green- blue red- pink light blue gray- violet blue- violet bright blue gray iurple- blue blue- gray deep blue violet bright blue purple violet- blue violet- blue blue bright blue bright blue light gray violet- blue bright blue rose, then Ileach’r light green- blue light green- blue violet blne- violet bright blue violet- black lilac violet Fellow- gray deep violet violet- gray deep violet mauve light bltie violet deep violet violet- blue bright blue bright blue bright blue light gray deep violet bright violet cream pale mauve blue- gray lilac pink bright violet gray- violet violet bright blue nsarly >leached violet blue- gray mauve violet bright blue red- purple violet violet blue bright blue blue light gray violet light blue deep violet- blue bright blue light green- blue violet- blue pink- violet blue gray- violet violet violet pale pink violet blue- gray mauve pink- violet green- blue red- violet violet violet violet- blue bright blue blue light blue- gray deep violet light violet violet- gray blue g.ray- violet mauve red- pink violet grag- violet deep violet deep blue little action dark blue black deep blue violet - black bright blue deep purple deep blue larkened dark blue dark purple Larkened larkened deep blue deep blue blue, some deac hing deep blue dark blue slight ileachin€ surface de.*ching blue blue black violet-black blue smudged dark blue violet -black deep blue violet-black blue with ilack patches deep violet greenish deep blue slight bleaching slight bleaching gray- black nearly black yellow on violet deep blue, some bleaching deep purple, some bleaching surfacc bleachin% surface bleaching slight b!eachin g slight bleaching bleaching d it r k e n e d surface bleaching deep blue little change blue-gray slight bleaching gray ana black yellow on violet blue with light patches yellow over violet yellow on blue yellow on blue green-gray black spot; nearly black gray and black blue-gray deep blue deep blue fawn stain nearly black dark blue, gray smudge zone yellow on blue yellow and black deep blue black lirty green peen-blue light orange blue-gray dark brown lark gray- blue deep maroon Ireen-blue purple- bro w n navy blue blue-gray deep blue lsrk green- gray leep graen light brown icep green- blue peen-gray bleached )live-green yellow- gray nearly black maroon gray-blue green-gray green- brown green- brown orange )live-green brown yellow- brown -ose-brown orange .ose-brown yellow- brown gray dark olive- green green- brown brown red-brown lark olive- yellow green - brown dirty yellow yellow - brown olive- brown brown violet- black gray gmy- brown IJUl’ple - bright green-blue r i g h t blue green- black deep blue deep blue nearly black deep violet )right blue deep purple blue green-blue deep blue dark blue deep blue green-gray indigo- blue bright blue deep blue- black deep blue green-blue deep green-blue deep violet black dark blue green- black :reen-blue blue peen and black deep blue deep blue deep blue green- violet peen-blue ;, Black ose-brown Field’s ( ( Non-corrosive Halsey’s Blue-black Lyon’s Blue-black Mordan’s ‘ ‘ Azuryte ’’ ,, Blue-black ,, “Jet-black’ deep blue dark blue dark blue dark piwple mrple-black blue-gray ;reen-blue light green-blue deep blue dark blue deep blue green-gray Morrell’s Blue-black Paul’s Blue-black ,, Black deep blue deep blue gray slight bleaching deep blue bleached blue blue black Pridge’s Blue-black nearly black deep blue green-blue ,, Black very dark blue-gray smudge deep blue yellow and black gray.blue blue-black dark blue blue-green Stephens’ Blue-black Vicker’s ‘( Penwing ” Walkden’s Blue-black ,, Black surface bleaching surface bleaching surface bleaching nearly black green-blue ?iink-brown blue blue and blackTHE ANALYST.85 DISCUSSION. Mr. E. R. BOLTON asked if the author had made any use of starch-grain plates in his photographic experiments. Mr. CHAPMAN said that in determining tannin in hops, he had found it satis- factory to precipitate the tannin as cinchonine tannate. Possibly in the case of inks also that method might be useful for the separation of the tannic acid from the gallic acid, as cinchonine tannate was very insoluble, whereas the gallate was soluble. I t was perhaps not very widely known that titanous chloride was now a compara- tively cheap reagent. The ordinary solution to which Mr. Mitchell had referred contained a littie lead, but otherwise was tolerably pure, while the perfectly pure salt was not prohibitively expensive. It was a very useful reagent in the estimation of iron, etc., being a much more powerful reducing agent than stannous chloride. The PRESIDENT asked if the author knew of any black or blue-black ink that was absolutely indelible to ordinary bleaching agents. He himself had never met with one capable of resisting the action of potassium permanganate followed by sulphurous acid. Mr. MITCHELL, in reply, said he did not know of a blue-black ink that would withstand any powerful bleaching agent. Certain type-writing inks which were impregnated with fine carbon might be taken as practically permanent in this respect, and all the so-called “ safety ” inks contained such an admixture of carbon. A thoroughly well-made iron-gall ink, however, would be permanent for eight or ten centuries, and in Germany the use of such inks for official documents was insisted upon. With regard to photography, he had used only ordinary and Cadett spectrum plates, with the ‘‘ absolutus ” screen, and here, as he had said, no greater difference in intensity was obtained than was apparent to the naked eye. The method suggested by Mr. Chapman for the estimation of gallo-tannic and gallic acids did not overcome the difficulty caused by the provisional colour.