ANALYTICAL
EDITION
Industrial VOLUME 4 NUMBER 3
JULY 15, 1932
AND ENGINEERING
Chemistry PUBLISHED B Y T H E AMERICAN CHEMICAL SOCIETY HARRISON E. HOWE,EDITOR
Estimation of Small Amounts of Iron in Copper BARTPARK,Michigan College of Mining and Technology, Houghton, Mich.
S
OME time ago the author was requested to determine the percentage of iron in some copper in the form of turnings which appeared clean, bright, and free from dust and oil. Ten-gram samples were dissolved in nitric acid, the solution@neutralized with ammonium hydroxide, and a slight excess added. The solutions were boiled, allowed to stand on a hot plate for several hours, the precipitated ferric hydroxide was filtered out, washed, and dissolved in dilute hydrochloric acid (1 to 15), and, after the addition of 5 cc. of bromine water, reprecipitated with ammonium hydroxide and washed free from copper. The precipitates were again dissolved in dilute hydrochloric acid, and the iron was estimated by the salicylic acid colorimetric method described by Yoe ( I ) , which consists essentially of adding salicylic acid t o a neutral solution of ferric iron and comparing the color with that of a standard sample treated in the same way. The results were very discordant. I n six runs the percentages were 0.0045, 0.0065, 0.0031, 0.0049, 0.0035, and 0.0039. No trouble was experienced in checking the colorimeter readings against standard solutions containing approximately the same amount of iron. The estimation of minute amounts of such a widespread element as iron requires special precautions to avoid contamination from outside sources. The beakers, funnels, etc., used were thoroughly cleaned and then boiled out with concentrated hydrochloric acid and washed with distilled water. Blanks were run and corrections were made, where necessary, for the iron present in the reagents. An investigation of other possible causes of such erratic results showed that most of the iron was on the copper and not in it. Two hundred grams of turnings were treated with 500 cc. of water and 50 cc. of hydrochloric acid in the cold for about 2 hours. The turnings were filtered off and washed free from acid. A very little copper dissolved during the treatment, approximately 0.5 gram. Iron was determined in the filtrate. One 200-gram sample gave 0.0046 and another gave 0.0066 per cent iron. (All results are based on the weight of copper.) Duplicate 10-gram samples of the acid-washed copper were treated as before, and the iron found in the acid-washed turnings was 0.00086 and 0.00084 per cent, a satisfactory check. The manner of contamination of the surface was next investigated. The cutting tool offered a possible source of
contamination and, in order t appreciable amount of iron rubs off and contaminates the sample, the following experiment was performed. A piece of copper wire bar was cleaned and placed on a- clean lathe. The outside layer, about one-eighth inch (0.32 em.) was turned off with a stellite cutting tool and discarded. A sample was turned off with the stellite tool and caught on a clean piece of paper. Then a sa\mple was cut with a regular high-speed steel tool. Stellite was employed again, the two tools were alternated until about 3 pounds (1.36 kg.) of turnings had been collected. Each time the stellite was used a small amount of surface was turned off and discarded before starting to collect turnings. I n this manner two samples were obtained from the same wire bar, one cut with and the other with high-speed steel. Two hundred grams of each sample were treated with dilute hydrochloric acid, .as previously described. The first washing from the high-speed steel turnings yielded0.00016 per cent iron, and those from the stellite turnings only 0.00006 per cent. The samples were treated with another wash of 500 cc, of water and 50 GC. of hydrochloric acid, qnd after standing for 2 hours this was removed and a third wash put on them. Iron was estimated in each of the wash solutions. I n both the second and third washings the amount of iron found was too small to allow comparison in a colorimeter, but wqs estimated to be about 0.00001 per cent. This corresponded to the amount found by running a blank on the hydrochloric acid, The first washing, therefore, must have iron on the surface of the copper. Fifty-gram samples of the washed and unwashed turnings were dissolved in nitric acid, and the iron determined as before, with the following results: Stellite unwashed Stellite washed
0 00069T 0 :00063’%
High-speed steel unwashed High-speed steel washed
0.00080% 0.00063%
The source of the iron in the washings from the stellite turnings is not apparent. The stellite itself contained very little iron, less than 5 per cent. With copper in the form of turnings, a fairly large surface is exposed, and a small amount of the iron in the copper undoubtedly dmolves in the hydrochloric acid wash. This could Fardly be 10 per cent of the iron present in the copper, however. Even though pains were taken to prevent incidental contamination, the author is
247
ANALYTICAL EDITION
248
inclined to think this the most probable source of the greater part of the iron found in the washings. Whether or not the cutting tool plays an important part in adding iron to the sample depends upon the extent of contamination from other sources. The following results, obtained from analysis of a piece of blister copper, serve as an illustration: -IRON-
NATVRE OB SAMPLE Surface turnings, stellite Inside turnings, stellite Inside turnings, high-speed steel Washings from inside high-speed steel turninga Washinns from inside stellite turnings 5 Weighed as FezOa.
Unwashed
Washed
%
%
0.036” 0.00074 0.0018 0.00083 0.0019 0.00083 0.00104 0.00077
Vol. 4, No. 3
Here again the’washings from the steel-cut sample yielded more iron than those from the one cut with stellite. The amount, however, is so small in comparison with the difference between the percentages found in the washed and unwashed turnings as to be negligible. The above results indicate that it is advisable to wash samples of copper with dilute hydrochloric acid when an accurate determination of iron is desired.
_____
T,TTPWRATTTRM CTTli’n __-_-____
(1) Yoe, “Photometric Chemical Analysis,” Vol. I, p. 243, Wiley, 1928. RECEIVED November 10, 1930.
Specification of Color on Dyed Fabrics by Spectroanalysis E. M. SHELTON~ AND ROBERTL. EXERSON, Cheney Brothers, South Manchester, Conn.
T
B y a modification of i f s sample holder, the illumination was too narrow to facturer c o n t a i n many ~~~~~~l Electric recording analyter has give a representative view of a fabric sample, for barked shifts thousands of samples of been made applicable to analysis of color on in t h e r e c o r d e d ocdyed fabrics, either retained as curred w i t h c h a n g e s in t h e standards for color lines or in fabrics. A Program Of work for applying spectroanalysis to color on fabrics is described, position of the sample. This connection with dyeingformulas covering recording of color produced by individual was p a r t i c u l a r l y serious in a w h i c h they i l l u s t r a t e . As standards for commercial prodyestugs, standard color lines, commercial fabric with a distinct rib effect such as a bengaline, but it was duction, such samples are frematches, loss of color during fastness tests, f o u n d ,,hat e v e n in cornparaq u e n t l y open to suspicion of having become soiled or faded, and c d c d a t i o n of dYeformulas* tively smooth weaves the surface irregularities were sufficient and a p e r m a n e n t r e c o r d of the original condition of a sample would prevent occasional to cause noticeable shifts in the position of the curve cordisputes from this cause, Since commercial matches usually responding to changes in brightness with slight rotary shifts deviate in some degree from the standard, some numerical in the position of the sample in the sample holder. The measure of the discrepancies would be of great value in es- manufacturer changed the optical system so as to increase tablishing tolerances. Moreover, a numerical record defining the width of the area illuminated to approximately 3 mm., effecting some improvement. There still remained difficulty a color should be of value in systematic filing of the samples, A spectrophotometric analysis of the light reflected from in obtaining reproducible readings because of vertical shifts the colored sample is to the physicist the most satisfactory in the curve resulting from slight rotation of the sample when record and definition of the appearance of the sample. replaced in the holder. Figure 1 illustrates the curves obWhether the interpretation and use of such data by a textile tained from a sample of fabric when viewed in two positions manufacturer would be practicable has been open to question, 90 degrees apart. In the case of a satin this difference has but the time-consuming and expensive methods of color been observed to be as much as 55 per cent. analysis which until recently were the only ones available ROTARYSAMPLEHOLDER prohibited any extensive practical trials. The invention of automatic recording color analyzers, notably one by ProFollowing a preliminary demonstration of an experimental fessor Arthur C. Hardy a t Massachusetts Institute of Tech- rotary sample holder by the General Electric Company, an nology, subsequently developed and marketed by the General inexpensive sample holder of this type was constructed Electric Company, has radically simplified the task of prepar- and has proved highly satisfactory. Its construction is shown in Figure 2. A circular sample of fabric about 25 ing the spectrophotometric curves. The purpose of this paper is to describe the experience a t the mm. in diameter is cut out with a die and placed behind a laboratory of Cheney Brothers in recording the colors of glass window in t,he holder which is mounted on the end of the fabric samples in terms of spectrophotometric curves using shaft of a small motor. To correct for possible error due to the General Electric recording color analyzer with modifica- viewing the sample through glass, the magnesium carbonate standard is cut in the shape of a thin disk which may be tiom noted below. The recording color analyzer has been described elsewhere slipped into the sample holder behind the same glass window. by Hardy (a), and a general description will not be repeated. The motor is so mounted in the cabinet of the color analyzer The machine, as delivered to Cheney Brothers’ laboratory that the light strikes the sample at 90 degrees and is taken in January, 1930, was arranged to view an area of the sample off at 45 degrees exactly as in the original fixed sample holder, about 1 mm. wide and 18 mm. long. The sample was held the only difference being that the sample is rotated conin a fixed position. It was found at once that this band of tinuously. Experiments showed that the speed of rotation February 1.5, 1932, research chemist for the Tannin Corporation, may vary Over a wide range, and it is only necessary to avoid certain critical speeds a t which synchronism with the flicker LOO E. 42nd St., N. Y. C. HE files of a textilemanu-
