ROY NEAL, C. F. BAILEY, and ROBERT S. CASEY W. A. Sheaffer Pen Company, Fort Madison, Iowa
MIXING writing ink is a simple process.
Ink is a con- stains be removable from washable fabrics if accisumer itern and everyone is familiar with its use, ~t dentally spilled. The latter type of inks constitute the is inexpensive, the major part of the costOf commercial secalled "washable" inks. The removal of ink stains ink being- in -packaging and distribution (1). ~~~t of from fabrics has been discussed by Casey, Bechtel, and the desirable propeki& a writing ink should have are Grove ($1. easy to understand and may be evaluated with rela- , The first inks were undoubtedly a dispersion or paste tivelv a ~ ~ a r a t u sIn . manv writhe with a 1" which carbon in the form of lampblack was the ~" s i m ~ l e -~ " eases ~~~~-~ coloring matter. It is known that such inks were used variety of pens on several kinds of paper suffices. Egypt and China long before the Christian ~ ~ ~ in - andh testing ~ writing ~ inks~there ~ in ancient ~ , era. are no more hazards &olved tl?aLin other well-disciBecause of the water insolubility of carbon, it must plined and supervised chemical laboratory work. The above facts make this topic a particularly suit- be in a very finely divided form and must be held in susable one for experimental study by elementary chem- pension by a "protective colloid" in order to make a disistry classes. Any student, even with only a minimum persion suitable for ink. Many substances have been of experience in laboratory techniques, can make the suggested for effectingsuch stabilization, including some simple mixtures which are described below. The dis- alkaline solutions (the hydroxide ion is thought to be cussion which accompanies the formulas gives sugges- the effective medium), soap, gelatin, glue, gum arabic, tions for independent investigation and student re- and dextrin. Carbon black may be purchased from chemical search. Such investigation~may be varied widely in scope and are limited only by the student's ability, ex- supply houses, but it is preferable tbat the student prepare his own. Carbon black is formed when almost perience, and time available for the project. Facts concerning the nature of writing ink, its manu- any organic compound is burned with a supply of air facture, and many of its properties have been given in insufficient for complete combustion. The smoky papers from this Laboratory (I,$), reppints of which are flame may be allowed to impinge on a cold surface and available. Waters (15) has presented valuable in- the collected black scraped off, or the smoke may be formation in a government bulletin (15) which may be conducted through a series of chambers in such manner had for 15 cents from the Superintendent of Documents, tbat the carbon particles settle. Washington, D. C. Mitchell (X), Schmitt (I$), and CARBON INK Reynolds (10) also have contributed importantly to this Carbon is prepared by impinging a yellow gas flame subject. Most of the properties desired in a writing fluid for onto a "cold finger" glass condenser through which a general use are quite simple. Writing ink should flow stream of water is passing; the flame should be shielded. readily and evenly from the pen and make a smooth, As the carbon collects it may be scraped off and the coleven mark on the paper. The color should be pleasing lection continued until a su5cient quantity is obtained. and should have sufficient contrast to be readily legible. It is rinsed in alcohol and air dried. An intimate mixture is prepared in a mortar, using The ink should be inert to steel pens as well as to all parts of fountain pens with which it comes in contact; 2 g. of the carbon and 2 g. of soap flakes. A small it should not cause deterioration of the various metal, amount of water is added and mixed to form a paste, plastic, and rubber parts used in fountain pens. The which is then gradually mixed with water in a beaker. ink must be stable-that is, it must not deteriorate with More water is used to rinse the last of the paste from the accompanying precipitation of sediment nor should it mortar into the beaker, and the mixture is stirred for about two hours. The total amount of water to be used support the growth of mold or other microorganisms. If the writing ink is to be used for business purposes, in these operations is 100 cc. This type of ink is not suitable for long continued use for making entries and signatures on permanent records, the ink marks on paper must remain legible after expo- in fountain pens. sure to ordinary deteriorating influences, such as strong light and, more particularly, soaking in water, which IRON GALL INK would occur in case of fire or flood. If the ink is to be The well-known color reaction between iron salts and used for school or home use, the permanent feature is tannins is the basis of iron gall ink which has been used not necessary, and in fact, it is desirable that the ink for centuries. Tannins occur in the bark, leaves, and ~
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JOURNAL OF CHEMICAL EDUCATION
other parts of many plants and trees, frequently in pathological growths (thus "gall nuts" on certain kinds of oaks constitute one of the principal sourcei of tannic acid). A water extract of certain tannins or a solution of the purified tannic or gallic acids mixed with an iron salt gives a blue-black color. Writing on paper with such a solution leaves only a faint mark, which turns darker with aging. After this darkening has taken place, the deposit on paper is insoluble in water, making the record "permanent." Soluble dyes are added to make the writing initially legible. The following is the present Federal Specificat,ion formula for writing ink (6): Gallic acid FeSO,. 7H,O Tartaric acid Soluble Blue, Colour Index No. 707 (11) Water to make 1 liter
10.0 g. 15.0 1.0 3.5
the water fastness and brightening the colors. A patent issued to Schladehach and Hahle in 1927 (18) is among the most important literature contributions to this class of inks. Typical fluids of this kind may be made thus: NaOH Colaur Index No. 477 (11) Watw to make 1 liter
This formula will give a blue ink; brown can be produced by subst,it,utingthe same amount of Colour Index No. 561 (11). PRUSSIAN BLUE INK
The pigment may he obtained commercially as "soluble Prossian blue" [potassium ferric ferrocyanide, KFe(FeCBNe),H20, Colour Index No. 1288 ( I f ) ] or the student may prepare his own. For such preparation the procedure of Itzkovich and Shmul'yan (7) is satisThe formula just given supersedes this earlier one ( 5 ) : factory. 50 cc. of a 10 per cent solution of ferrous Tannie acid chloride is added to an equal volume, of a 10 per cent G d i o acid solution of sodium ferrocyanide. 50 cc. of a three per FeSO1.7HaO cent solution of potassium chlorate and 8 cc. of dilute HCI. dilute U. 8. P. hydrochloric acid (1:3 by vohme) are added. The phenol 1.0 precipitate is recovered by filtering, washing, and drying Soluble Blue, Colour Index No. 707 (11) 3.5 Water to make 1 liter in'an oven at about 105OC. The filtration is attended with some difficulty. In view of the wide distribution of tannins in nature, Ink may be prepared from Prussian blue according it is feasible and desirable for the student to gather his to the following formula (14): own supply. The common shrub sumac, since it occurs so widely, furnishes an excellent source. The leaves Oxalic acid 0.5 g. in 50 co. water Sugar (sucrose) 0.25 should be gathered in late summer or early fall before Prussian blue 1.0 they have changed color, and they are then air dried. Tannin may he extracted by heating the leaves with The mixture is shaken well and is decanted after 24 water on a steam bath for about eight hours; boiling hours. water should not be used. Solutions of tannin are highly susceptible to spoilage from the growth of micro- WASHABLE INK organisms. If such solutions are not used in ink at The following typical formula has been given (1): once, a small amount of preservative should be added, Glycerine 10.0 g such as phenol or thymol. The tannin content of the Thymal 0.5 dry leaves is about 20 to 30 per cent; from this informaSoluble Blue, Colour Index No. 707 (11) 5.0 tion, the weight of leaves required to furnish tannin to Water to make 1 liter be substituted for tannic and gallic acids in the above formula may be calculated. A product of better sta- A variety of colors may be had by the use of suitable bility vill be obtained if the amounts of tannin and dyes instead of the blue dye listed. ferrous sulfate called for in the formula are reduced MIXING PROCEDURE appreciably, by 50 per cent or even more. Few city water supplies are suitable for ink making. Many other materials may be utilized as sources of Water purified by distillation or by the ion exchange tannin ( 9 ) . Most iron gall inks are prone to precipitate sediment process is suggested; rain water is also suitable. Mixing is done to best advantage with a mechanically on long standing unless stabilized by modern manufacturers' secret processes. The reaction, although im- driven stirrer, although if none is available, hand stirperfectly understood, probably is similar to the one ring su5ces. which causes the colored material to become water inTESTING INKS soluble after drying on paper. Simple writing with.a variety of pens on different ALKALINE INK k i d s of paper will give the student an opportunity to Here is a type which depends on direct dyes (those observe the behavior of different lrinds of inks under having an affinityfor cellu!ose without recourse to mor- practical conditions of use and to evaluate the effects of danting) for permanence against water soaking. Alkali various additives. Other methods of testing have is often u;ed uith such dyes as a means of improving been described (4, 6, 15). '
SEPTEMBER, 1941
I n this connection it would be instructive to study the effects of small amounts of surface active materials to cause "quick drying" by promoting rapid penetration into the paper. Also, small amounts of many watersoluble organic liquids as well as alkaline solutions (10) have this effect. The kinds of paper used for testing should range from a good grade of well-sized bond paper through ordinary grades to the cheapest grades. For the benefit of the student who would like t o delve further into the subject and for the instmctor who wishes to amplify the project, a study of the references cited above will suggest fruitful approaches. LITERATURE CITED ( I ) (:ASEY, R. Y., Cbrm. Inrlwlrre~,58, 216 (1916). (2) (.'.\SEY. R. 15, I d . E n g . ('Item., 32, l3Ul (11J10). (.I) ('.\BEY, It. S., B. BECHTEI.. .$so(:. S. GROVE, .In., J. Home E c n . , 38,619 (1946). Idnd.Eng. Chem., Anal. (4) CASEY,R. S., AND R. MACDONALD, Ed,, 14,720 (1942).
(5) Federal Standard Stock Catalog (Section IV, Part 5), Fed. Spec. far Ink, Writing. TT-1-563, U. S. Government Printing Office, Washington, D. C., 1931. (6) Federal Standard Stock Catalog (Section IV, Part 5 ) , Fed. Spec. for Ink, Writing. TT-I-563a, U. 5. Government Printing Office, Washington, D. C., 1941. P., AND J. SHMUL'YAN, Lakokrasochnuyu Znd. (7) ITZKOVICH, Za, No. 3, 43 (1933); Chem. Abstracts, 28, 3997 (1934). (8) MITCAELL, C. A., "Inks, Composition and Manufacture," 4th ed., J. B. Lippincott Company, Philadelphia and New York. (8) NTRRENSTEIN. Natural Oreanic Tannins." J. & A. ~., ~ - M.. ~ "The ~ Churchill, icd,'~ondon,1934. (10) REYNOLDS, W. B.,Chem. Eng. News,24, 916 (1946). (11) ROWE,F. M., ''Colour Index," 1st ed., Society of Dyers and Colourists, Brandford, Yorkshire, 1924. (12) . . SCBLADEBACH. . H... AND H. HKHLE.U. S. Patent,. 1.645.117 . . (1927). (13) S m m q C. A., J. CFIEM. EDUC.,21,413 (1944). A,, Papeta'e, 45, 737 (1923); Chem. (14) VANDERSTICHEL, ALtmets, 17,3419 (1923). 15) WATERS,C. E., "Inks," U. S. Dept. of Commerce Circular C426, U. S. Government Printing Office, Washington, D. C., 1940.
"CllY\llA, STI.Il1E.S in the HISTORY uf CIIEhllSTHY," i i n new prricvlis.ul whirl8 will shortly appear urder tlrc s p m w n l ~ i pof ~ l r eEdgar Frths Smith 1lrrnwi.tl (\Jlwtiw oi the l'niver*lty of tknnsylvarri~. It will tw arl international journal iur thr pulh.atior~u i contrib~rion.; to chemical history. We welcome it to the field.
