720
INDUSTRIAL AND ENGINEERING CHEMISTRY
ficationwith acetic acid, place the solution in the mercury cathode cell and proceed with the determination of aluminum as given in procedure I. If preferred, &hydroxyquinoline may be used instead of ammonium hydroxide as a reagent far the precipitation of aluminum.
Discussion Aluminum in a Bureau of Standards Standard Sample No. 62a (manganese bronze) was determined by the above procedure. A few comparative results are given: Procedure of This Paper
% 0.928 0.925 0.922
47.
0.925
The use of an acetic acid medium eliminates the two-tep procedure of Gerke and Lyubomirskaya (5)for the sepdration of iron and also increases the accuracy of the determination. The maximum accuracy that Shubiu (If), using a sulfuric acid medium, could obtain was 0.07 per cent, whereas with the acetic acid medium the minimum accuracy is 0.008per cent. The procedure is far superior to the old sodium hydroxide separation, whose main disadvantage was that the sodium hydroxide dissolved to a slight extent the iron and manganese hydroxides (B).
Vol. 14, No. 9
Acknowledgments The authors wish to express their appreciation to A. Devor, Erie Center, University of Pittsburgh, for the sample of octyl alcohol and to E. I. du Pont de Nemours & Co., Inc., for the sample of Antifoam L F X.
Literature Cited (1) Am. SOC.Testing Materials, "A. S. T..M.. Methods .. . -. .of .Chemical . . . Analysis of Me tala'', 'Tentative Method3 Of Chemical Analysis of Mmganese :Bronue, B 27:36T, pp. 113, 129 (1939). (2) Churchill. H. V., and Bridges, R. W.. "Chemioal Analysis of Aluminum", p. 10. New Kensineton. Penna.. Aluminum Research Laborat Craighesd, C. M., IND.NNG.C~AEM..ANAL. ti^., z,IUY (IYBU). Easly, H. F., Ibid., 9,82 (1937). Gerke, F. K., and Lyubomirskaya. N. V., Zavodskaya Lab., 6, 746 (1937). Hillebrand and Lundell, "Applied Inorganic Analysis", p. 390 New York. John Wiley & Sons. 1929. Holler, A. C., Chemist-Analyst (publication pending). Lundell, G. E. F.. Hoffman, J. I., and Bright. H. A.. "Chemical Analvsis of Iron and Steel", I). 48. New York, John Wiley & Sons; 1931. (9) Melaven. A. D.. IND.ENQ.Cam., Cam%.,ANAL.ED.,2,180 (1930). (10) Mellan. I., "Organic Reagents in Inorganic Analysis", p. 176, Philadelphia, P. Blakiston's Son & Co.. Philadelnhia. Co., 1941. ZavodskayaLab., (1936). (11) Shubin. M. I., Zavodskaya Lab., 5, 407 (1936) ~
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Testing Writing Inks With Rubber Fountain Pen Sacs ROBERT S. CASEY AND ROGER MACDONALD, W. A. Sheaffer Pen Co., Fort Madison, Iowa
Many commercial writing inks hasten deterioration of soft-rubber fountain pen parts. Soft rubber affects stability of some writing inks, particularly permanent inks. Methods of testing are proposed.
T.
H E present . necessity . '. for conserving rubber and extendmg the hie of existing rubber articles prompts the authors to report their observations of the action of writing inks on soft-rubber fountain pen parts, and to propose a comparative test.
F I G ~I E , SACS FROM SCRAP Box
There is a dearth of published data on this subject, though Waters (6) stated, "The general use of the self-filling pen, which has almost supplanted the older kind with the medicine dropper, seems to be good evidence that the rubber bags are not damaged by ink. The failure of a bag in an old pen is no proof that the ink is to blame. Rubber does not last indefinitely." These latter two statements are true., It is well known that oxygen acts upon soft rubber, causing loss of tensile strength and eventual hardening. However, many substances have a profound effect on the rate of such aging (3). Casual observations over limited periods of time may reveal no serious action of inks on rnhber sacs, but examination of the sacs customarily dismantled from pens returned for repair always shows some hardened and broken from causes other than mere time in service. Figure 1 shows a representative handful of sacs taken from a scrap box, with some of the worst specimens moved into the foreground. The condition of these sacs is duplicated by sacs subjected to the authors' aging test. Incidentally, the effectof stress on aging is also illustrated by the sacs that became twisted in the pen barrel and hardened p r e maturely The authors subjected sacs, after immersion in inks, to oxygen or air a t elevated temperatures, the recognized methods of accelerated testing (4), and found that many writing inks greatly hastened and some retarded the aging of the sacs.
September IS, 1942
ANALYTICAL EDITION
721
After sacs were removed, the 25-ml. portions of ink were shaken, 10 ml. of each were centrifuged, the precipitate WBS washed free of salubles and whirled again, and sediment volume was recorded. 1
3
2
4
5
6
7
8
9
OF WRITIUG INKS ON SACS FIGURE3. EFFECT
This is the method previously suggested (2!) for determining the volume of precipitate formed by writing fluids in stability or other tests, instead of the qualitative comparative estimate called for in government specifications (1). A refinement is the use of ‘Constable protein” tubes shown in Figure 4. These tubes enable a much more precise evaluation of ink sediment; they bold 10 ml. and the lower portion is graduated in 0.005-ml. divisions to 0.1 ml.
FIGURE2. EFFECTOF WFUTINQINKS ON SACS, AFTER PARALLEL SOAKING AND ACCELEEATED AGIN~
New sac6 were cut in two lengthwise, keeping one half of each
as a control. The test halves were immersed in the writing inks
to be tested and the controls immersed in distilled water. To eliminate the effect of possible variation in sacs, two or three halves were put in each sample of ink.. To study simultaneously the effect of rubber on inks, particularly permanent inks, immersion was in 25 ml. of liquid for 2 weeks in 25 X 150 mm. test tubes loosely stoppered with nonabsorbent cotton, in accordance (except for addition of the sacs) with the stability test in the Federal Specification for Writing Inks ( 1 ) . After immersion dl half-sacs were removed, blotted dry, clipped on racks, and placed in a Bierer-Davis oxygen bomb (4) under 21.1 kg. per sq. em. (300 pounds er square inch) pressure at 70“ C. The Geer oven test (47 bas also been used, ciroulating air at 70“ C. Moderate flexing with the fingers revealed the progress of deterioration at periodic inspections. All sacs became soft and tore readily, finally becoming hard and brittle. There was a deciaed difference in the time required to reach each stage exhibited by sacs immersed in different inks. The hombaging was continued until the controls hardened, noting the condition of test sacs. Alternatively, the time required for each sac to reach the softened or hardened state may be taken as a measure of the relative service life of sacs when used with the different inks. As a variant of this test the authors are studying the action on sacs and inks of alternate immersion and bomb-aging; and are also studying sacs in combination with similar tests on pyroxylin plastic of which fountain pen holders and other parts are made. Figures 2 and 3 show typical results on sacs aged together for the same length of time after soaking in different brands of writing inks. I n Figure 2 (lower) the sac is tearing under very slight tension, while the upper sac shows no failure under vigorous flexing. Figure 3 shows the condition of sacs after testing with a group of commercial permanent blue-black writing inks. It was found that contact with the rubber sacs affected the stability of some permanent writing inks, causing precipitation.
F I ~ U R4. E CONSTABLE PROTEIN TUBES
These test methods have been used in this laboratory over the past 6 years in connection with writing ink formulation and comparison.
Acknowledgments The authors wish to express their thanks to the W. A. Sheafler Pen Company for permission to publish these results and to John E. Hauck and David Jamerson for assistance in the experimental work.
Literature Cited Federal Standard Stack Catalog (Section IV, Part 5 ) . Federal Specification for Writing Inks. TT-1-563 (Par. F4j), Washineton. D. C.. Government Printing Office,1931.
(1) Anon..
(2) Casey, R.S., IND. ENG.C ~ E M32, . , 1584-7 (1940). (3) Davis, C . C., and Blake, J. T., “Chemistry and Technolow of Rubber”, A. C. S. Monograph 74, 1st ed., Chap. XIII, New Vnrk. .. Rpinhold Publishine -Coro.. . 1937. (4)Ibid., p. 819. ( 5 ) Waters, C. E.. Natl. Bur. Standards, Giro. C426, p. 14 (1940).
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