July, 1924
INDUSTRIAL AND ENGINEERING CHEXISTRY
a noticeable odor of ammonia is given off, and upon removal from the bath the specimen may show a light coating of boric acid crystals, provided it is withdrawn from the bath almost a t once. Moreover, subsequent examination of the specimen under the microscope will show that scarcely any nitride is left, whereas the same specimen cooled in the furnace would show a high concentration of nitride needles a t the surface. I
I Ambunti of boroh Absorbed in lmm. Case af Different Temperatures
723
medium causes an increase in surface concentration of boric alloy. The hardness increases with the surface concentration, but never reaches any value comparable with the hardness of a steel surface containing an equal amount of carbon and treated in the same way. In fact, these results seem to bear out Guillet’s statement on boron steels-viz., that after heat treatment they show elasticity and resistance to shock, but no great degree of hardness. It will be noticed that the curves of absorption and temperature show a decided maximum, occurring between 1100” and 113.5” C. Boron steels show many similarities in the mechanism of their absorption and diffusion phenomena to carbon steels. This might, of course, be predicted from the relative positions of the two elements in the periodic table. The very close resemblance to the two systems is brought out by the similarity of the equilibrium diagrams shown above, and this similarity is confirmed by microscopic examination. ACKNOWLEDGMENT The authors wish to express their gratitude for generous aid received from the C . M. Warren Fund of the American Academy of Arts and Sciences.
The Use of Cool Solutions in the Jones Reductor”z By G. E. F. Lundell and H. B. Knowles
Temperafure “C.
BUREAU O F STANDARDS, WASHINGTON, D. C.
FIG. BOR BORON ABSORBEDIN ~ - M MCASE . AT DIFFERENT TEMPERATURES
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A microscopic examination of the specimen that had been heated for 10 hours in ammonia showed a structure that bears out the conclusion already drawn as to the action of nitrogen on a boron steel. At the very edge the nitrogen had been abrorbed to the extent of about 10.5 per cent, as shown by the large amount of iron-nitrogen eutectoid occurring in this region. Below this was a region of decreasing nitrogen concentration, while still farther in was a comparatively small band of boric pearlite. Fig. 4 shows a composite appearance of a cross section of this specimen. The large, black areas a t the top are the iron-nitrogen eutectoid; the lower portion shows clearly the decreasing needle concentration and the boron-iron eutectoid region. Up to this point the investigation had been concerned with the manner of penetration and chemical properties of the alloys formed more than with the physical properties of the specimens. A series of runs was then made, the object of which was to produce a maximum surface concentration of boron-iron alloy, and to find the relation between this concentration and hardness. Table I1 (see also curves in Fig. 5 ) shows the results of these runr. Boron in Ferroboron Per cent 14
32
TABLE I1 Time of heating, 4 hours Boron in Fmp. 1-Mm. Case Shore C. Per cent Hardness 8 50 0.27 12 0.53 15 9 00 17 1.08 1000 2.96 25 1100 22 1160 1.32 19 900 0.88 1.7s 24 1000 3.02 1100 32 2.92 28 1150
Brinell No. 82.5 91.0 110 162
150 110 155 20 1 183
All the foregoing specimens were quenched from above 900” C. These figures bring out very clearly the fact that increase in temperature or increase in boron content of the hardening
NE of the chief drawbacks to the wider adoption of the Jones reductor3 has been the belief, fostered by most texts, that reductions must be performed in hot or boiling solutions. The specification of such solutions has undoubtedly discouraged many who would otherwise have employed the reductor, while the faithful observance of these directions has caused much expense and inconvenience. This will be apparent when one considers that three different solutions must be kept hot or boiling, that large quantities of two of these must be constantly available when much work is done, and that the handling of boiling hot water or acid (oftentimes in a hurry) is not pleasant. The use of cool solutions for certain reductions is occasionally mentioned in the literature-for example, by Holladay4 and Johnson.6 A few texts specify hot solutions6 for one reduction and cool solutions for another.’ The experience of the authors goes to show that quantitative reductions result a t room temperatures (15” to 27” C.) and the usual speeds (2 to 4 minutes) in all present applications of the Jones reductor. As the use of cool solutions is so desirable, particu-
0
Received March 19, 1924. Published hy permission of the Director, U. S. Bureau of Standards. 9 For details concerning t h e construction of this desirable aid in volumetric reduction-oxidation analyses, consult Scott, “Standard Methods of Chemical Analysis,” Vol. I, 3d ed., p. 320, D. Van Nostrand Co.; Blair, “The Chemical Analysis of Iron,” 8th ed., p. 88, J. B. Lippincott & Co.; Treadwell-Hall, “Analytical Chemistry,” Vol. 11, 5th ed., p. 637, John Wiley & Sons, Inc. 4 “Notes on Reductor Technique” (as applied t o molybdenum), Scott, “Standard Methods of Chemical Analysis,” Vol. I, 3d ed., p. 320, D. Van Nostrand Co. 5 “Determination of Uranium in Steel,” Johnson, “Chemical Analysis of Special Steels, et?.,” 3d ed., p. 365, J. Wiley & Sons, Inc. 6 Mellor, “A Treatise on Quantitative Inorganic Analysis,” p. 415, Chas. Griffin & Co.; Schoeller and Powell, “The Analysis of Minerals and Ores of the Rarer Elements,” pp, 120, 165, and 187, Chas. Griffin & Co.; Scott, loc. cit., p. 370. 7 Mellor, loc. cit., p. 190; Schoeller and Powell, loc. cit., p. 3; Scott, Zoc. a t . , pp. 320 and 356. 1 2
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
724 ELEMENT AND ITS
Weight Taken Gram
Iron (11)
0.1114
VALENCY AFTER REDUCTION
Titanium (111)
Molybdenum (111)
i
TABLE I-COMPARISONSOF HOTAND COOLREDUCTIONS IN -WEIGHT FOUND BYHot Reduction Gram
{
0.1113
.... ....
0.1108 0.0999 0.1012 0.0542
0.1110
....
0.0854
....
i .... :::: ....
0.1103
0.1104
I \
Cold Reduction Gram
0.0983
Chromium (11)
0.1238
{
Uranium (< IV)
0,1024
i ::::
0.1242
.... ....
0.1294
....
0.1112 0.1112
....
0.1000
.... 0.0503 .... 0.1104
0.1101 0.1105 0.1055
....
....
0.1243 0.0656
....
0.1335 0.1099
larly in routine work where the acid and water solutions can be siphoned from storage carboys directly into the reductor, the following data, which show the results of comparative reductions of iron, titanium, molybdenum, vanadium, chromium, and uranium in hot and in cool solutions, are presented.
EXPERIMENTAL The reductions cited in Table I were made in a reductor having a bore of 19 mm. and a column of amalgamated 20 to 30-mesh zinc 43 cm. long. The usual reduction procedure was followed and there were added in order: 25 to 50 cc. of dilute sulfuric acid ( 5 per cent by volume), 150 cc. of the same acid containing the substance to be reduced, 100 cc. more of acid, and, finally, 100 cc. of water. The reductions were performed a t an average speed of approximately 100 cc. per minute, or 4 minutes for the passage of all solutions through the reductor. The reduced iron solutions were caught in empty receivers; the other solutions were caught under a fivefold excess of ferric sulfate, except in test runs which were made to ascertain the stability of the reduced compounds in air. All solutions were titrated with a 0.1 N solution of potassium permanganate.
RESULTS The data in Table I demonstrate that reductions of iron, titanium, molybdenum, vanadium, and chromium in the Jones reductor proceed quickly and quantitatively in cool solutions to the valences indicated. It is also apparent that the reduced solutions of all the elements except iron are extremely unstable, and that quantitative determinations in these cases are impossible unless corrective measures, such as catching the reduced solution under an excess of ferric sulfate, are employed. The experiments dealing with uranium show that its reduction proceeds below the quadrivalent stage in cool as well as in hot solutions. For its quantitative determination it is necessary to follow the usual expedient of oxidizing the reduced solution to the quadrivalent condition by exposure to the air before titration.8 Further experiments with all the foregoing elements save chromium (which was omitted because of the difficult end point) gave equally good results: (1) when the reduction period was shortened to two minutes; (2) when the 5 per cent by volume solution of sulfuric acid was replaced by a 1 per cent solution, or by a 3 or 15 per cent by volume hydrochloric acid solution; and (3) when the zinc column was shortened to 23 cm. and reductions were made a t the usual speed. More rapid speeds gave satisfactory results with iron, molybdenum, 8
Pulman, A m . J . Sci., 141 16, 229 (1903); Ibbotson and Clark, Chem.
A'evs, 103, 146 (1911).
THE JONES REDUCTOR
TemDerature
0,0982 0.0981 0.0894
Vanadium (11)
Vol. 16, No. 7
c.
80 to 85 27 16 90 to 100 22 t o 26 90 t o 100 22 to 261 80 to 86 27 27 15
15 80 to 85 27 27 27 80 to 85 27 27
27
REMARKS
No ferric sulfate in receiving flask Reduction in 1.5 minutes
No ferric sulfate in receiving flask
No ferric sulfate in receiving flask Difficult t o judge end point in all runs
No ferric sulfate in receiving flask Calculated on basis of reduction t o UOa N o ferric sulfate in receiving flask and calculated as above
and uranium, but not always with titanium and vanadium. The longer zinc column should therefore be used for rapid cool reductions of these two. It was also found that there is no need for extreme dilutions of the compound to be reduced, and that 0.2 or 0.1 N solutions are reduced with ease. Satisfactory reductions were also had when no acid was passed through the reductor before and after the introduction of the compound to be reduced. This procedure is desirable in routine analyses, and in such cases a slightly more acid solution (6 to 10 per cent sulfuric or 10 to 20 per cent hydrochloric acid) should be used, followed by enough water (150 to 200 cc.) to wash out the reduced solution. I n this connection it might be well again to call attention to the fact that a reductor that has been standing idle for some time always gives a high blank unless i t is washed with acid. At the conclusion of the work just described, the amalgamated zinc was analyzed and found to contain 5 per cent of mercury instead of its original content of 1per cent. Further reductions were therefore made with a fresh 1 per cent amalgamated zinc, and good results were obtained with a 43-cm. column; incomplete reductions were noted in certain cases when a 23-cm. column was used. A zinc freshly amalgamated with 5 per cent of mercury was found to be as satisfactory as the old zinc, as was also a zinc freshly amalgamated with 1 per cent of mercury and then activated by passing through it a sulfuric acid solution containing about 6 mg. of platinum derived from two pyrosulfate fusions in platinum. It is interesting to record that no evidence of the formation of ozone or of hydrogen peroxide was found in experiments in which air was purposely introduced into the reductor. Some reductions, however, were incomplete when air was purposely admitted. These were apparently caused in a few cases by incomplete contact of the solution with the zinc, and in the majority of cases by reoxidation of the sensitive reduced solution by the entrapped air during the passage of the solution from the zinc to the ferric sulfate solution in the receiver. The exclusion of air during a reduction is therefore a wise precaution, though the customary explanation does not appear to be correct. Finally, it is plain that hot solutions or prolonged reductions are as unnecessary as they are inconvenient in Jones reductor work, and it is to be hoped that future texts will not perpetuate these useless and trouble-making precautions. New Dye Plant Completed-The new dye plant of the Graniteville Manufacturing Co., Graniteville, s. C., has been completed, giving this company one of the largest exclusive khaki sulfur dyeing plants in the world. It has a production capacity of 500,000 yards of khaki per week. This company is reported to have perfected a process that will greatly minimize the possibilities of variation of shades in dyeing.
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