September 15, 1942
ANALYTICAL EDITION
For larger amounts of metaphosphate the. iron concentration is adjusted to 2 p. p. m. and 5 ml. of 6 N nitric acid are added to standards and unknown. Extraction is not necessary.
Literature Cited
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ill Fshev. J. J.. IND.ENU.CHEM.. ANAL.Eo... 11.. 362 (1939). . . (2) Fost& M. D., Ibid.. d.. 5, 234 (1933). ~
Acknowledgments
725
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(3) Partridge. E. P., private rivate communication. (4) Vanossi, R., Amles moo. qulm. argentina. 29, 48 (1941). Certain preliminary experiments were performed by Man~ .AN*=. ANAL. ,. , 10 J. ,T., .n*.\and Mellon, M. G . , IND.ENQ C n Hm ~M ED., , Woods. calgon, I ~~ ~~. ., (5) riel R~~~~workinc workinff on an N, y, A, project, calgOn, 13, 551 (1941). supplied the glassy sodium metaphosphate.
Evaluation of Metal-Cleaning Compounds I
A Quantitative Method 0. M. MORGAN AND J. G. LANKLER National Aniline Division. Allied Chemical and Dye Corporation, New Ycmk, N. Y.
A new q u a n t i t a t i v e method has been developed for the e v a l u a t i o n of metal-cleaning compounds. Since mineral oil fluoresces b r i g h t l y under u l t r a v i o l e t light and this f l u o r e s c e n c e is capable of being photographed, 3 c o n v e n i e n t means is provided for detecting and recording oil residues on metal s u r f a c e s both before and after c l e a n i n g .
T
HE property of removing oil from metals is relatively easy to recognize and evaluate qualitatively, but somewhat more difficult to evaluate quantitatively. Practically any alkali cleans most of the oil from the metal and unless a quantitative evaluation of the residual oil can be made, the true value of the metal cleaner is left as a matter for,conjecture. A survey of the literature for methods of evaluating the performance of metal-cleaning compounds did not disclose an accurate method for the detection of traces of oil. A real need existed for a quantitative test which would be both rapid and capable of permanent record for the comparison of cleaning products. The measurement of one or several physical or chemical characteristics of an a h l i n e cleaning solution is not sufficient to establish quantitatively its merit aa a cleaning agent. Hence, a performance test involving the cleaning of uniformly soiled metal samples and the observation of the residual traces of oil appeared to be the best method of studying metal cleaners.
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To establish the minimum v.ioihln . ~ . ~omnnnt . y~y u . nf vnairl Luu.Jualoil, gravimetric oil determinations were made on metal test panels representative of the lower limits of observation. It was found that 0.000004 gram of oil per sq. em. is visually detectable. A test of this kind is probably most accurately defined as “visually quantitative”.
Method of Oiling the Metal The metal test strips, 5 X 10 em. (2 X 4 inches) in size are scrubbed by hand with a 0.50 per cent solution of Nacconof NR at 110” F., thoroughly rinsed in warm water, rinsed in alcohol, and dowed to dry. Strips of wool flannel 4.7 X 9.7 em. (1.875 X 3.875 inches) are saturated with a mineral oil composition such as is used in the rolling of brass. These oil-saturated wool strips are alternated with the metal strips t o fonn a stack with protecting metal plates and oil-saturated wool strips above and below the stack of experimental strips. The stack of plates is placed between the jaws of a hydraulic press, the edges of the stack of plates being carefully squared up. A pressure of 35 kg. per sq. om. (500 pounds per sq. inch) is a p plied, and the pressure maintained until no more oil oozes out from the edge of the stack, the edges being constantly wiped with a clean cotton cloth, At the end of this process the presaure is released, and the strips are removed and retained in a perfectly horizontal position until taken out of the stack, one at a, time, for the cleaning experiment.
Principle of Testing Method Mineral oil fluoresces brightly under ultraviolet light. Animal and vegetable oils which do not fluoresce in their own right can be made to fluoresce by the addition of an oilsoluble fluorescent dyestuff such as Fluorescent Oil Green H. W., obtainable from Wilmot & Cassidy, 108 Provost St., Brooklyn, N. Y. Since this white fluorescence of the various oils is proportional to the amount of oil adhering to the metal surface and since clean metal appears black under ultraviolet light, a natural scale of measurement is established for evaluating the e5ciency of a metal-cleaning compound. Extremities of this scale are shown in Figure 1. The amount of oil adhering to the panel on the right, as determined from an average of ten such panels, is 0.000113 gram per sq. om. The average oil deviation from the mean in this set of ten panels was 7.3 per cent by weight. The fluorescence is capable of being photowaphed, thereby providing a permanent rkcord of the cleaning ability. By the use of this method fine distinctions can be made between cleaning compounds
FIGURE1. LUMINOGRAM OF STEELWITH MINERAL OIL Left c1ean steel. “0 011 Rlght. Oiled steel, 113 x 14- gram per aq cm
INDUSTRIAL AND ENGINEERING CHEMISTRY
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idly controlled in the-development of U ~ L L L L I L I L ~ C and prints, hut atherwist? no special precautions are taken The pictui"es taken under ultraviolet light are referred to as Luminogranis. A series of these luminograms is soon t o be published ( I ).
Illustration of Method . . ... . .
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A series of metal strips illustrating the gradation of scale covered by this test method is shown in Figure 3. This particular series deals with the cleaning ability of a single alkali, sodium metasilicate, and is reproduced here because it is typical of the pictorially quantitative record available. The strip on the left is a reference piece of clean steel. The series represents five tests at 140" F., the concentration of sodium metasilicate ranging from 2 to 10 per cent. The soaking time is 5 minutes. As the concentration increases there is a progressive reduction in the amount of oil residual on the metal surfaces. Gravimetric oil determinations TT-ere run on this selected set of test panels prior to photographing, not as part of the method. but to demonstrate the sensitivity of the test. Oripirial panels carried 0.000113 gram per sq. cm. of mineral oil. ~~~~
F~oaKx 2. PwO'rotiaar~Ic AHKhNOmlENT TAXING LUXIN~GRAVS A . Ultrsviolet lamp
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Panel No.
4 x 5 view camera with Xi-2 filter and Tri-X film Slot for.oamera hdjvstment D. Distance from ohmera lens t o OBSOI, approrimatels S I ; inches E. Easel F. Mctsi atrigs. 2 X 4 illelles E.
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Method of Cleaning
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0.000038 o.no0021
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OIL, CLEANED WITH SODIUM FIcul%s3. LuMIioGHAM OF STEEL WITH MINE:RAL Eight hundred cubic centimeters of the METASILICATE cleaning solution are placed in a 1000-cc. h i t rerereme piece of olea" steei beaker. The beaker is immersed in a con1 2 3 4 5 St& No. stanetemperature bath at the desired 2 421 o 14 s 4 1 Sodium metasilioate oonoentrstion. % 38 40 Residual oil, gram P P 89. ~ am. X IC-$ t,emnerature md the metal test plate is h c G ~ i nthe beaker from a hook-ior the required period of time. The metalI is withdrawn and rinsed in running water The present test not only indicates the amount of oil resist 100" F. for one minute and then hung in the air to dry. The metal strim are finally placed in rack of such a nature dent on the metal surface but also illustrates the distributhat the strips-do not touch-each other until it is possible t o tion of the oil. If a metal surface carries only a small amount photograph R complete serie,s from any given set of experiof oil by weight, but the oil is concentrated in a relatively ments. small area, a good deal of damage can be done to any superMethod of Recording Results ficial coating that may be applied. It is very difficult to define the distribution of the oil by methods other than the After cleaning, the metal strips are either examined visually or one described in this paper. photographed under ultraviolet light. A diagram of the arrangement of the apparatus for taking these pictures is presented in Fieure 2. The ultraviolet light source used in the Summary mesent work-is a Hanovia analytic matiel quests lamp, which provides H powerful source of e ultraviolet light. Any strong The new testing technique, developed for the evaluation source of ultraviolet li bt that is properly filtered to remove esof the performance of metal-cleaning compounds, not only sentidly dl of the visihTe spectrum is satisfactory. aids in selecting the proper types of cleaning compounds The camera is equipped with a Wratten K-2 filter, and Tri-Xfilm, and the pictures are taken at f. 4.5 with s 10-minute exfor specific cleaning jobs, but also establishes new criteria posure. The camera is placed approximately 90 om. (30 inches) for a clean metal surface, thereby raising the standard for the from the uihiert.~ fn,eins it, direetlv. The ultraviolet radiation ...-_ _ _ .~., ~ . . . ~ ~ ~ technology of metal cleaning. from %heHanovia lamp is inoidinc to the surface of the subject at an angle of 45", the lamp also being about 90 cm. (30 inches) from the midpoint of the subject. The film developer used in this Literature Cited work is DK-GOA, which is designed t o give maximum oontrast. (1) Morgan, 0. M.. and Lankler. J. G.,IND. ENG. CHEM..34 The paper is Eastman's Azo'F. 3, on which an elon-hydroquinone (October. 1942). develnDer is used. Temperature and developing time are care~~~
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