Determination of Titanium in Plain-Carbon, High-Chromium, and 18 Chromium-8 Nickel Steels THOS.R. CUNNINGHAM, Union Carbide and Carbon Research Laboratoriej, Inc., Long Island City, N. Y.
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H E addition of titanium to high-chromium steel and also to 18 chromium-8 nickel steel has necessitated the development of a rapid, accurate method for determining this element. The method here described can be worked in 1 to 1.25 hours and comprises the solution of the sample in dilute sulfuric acid, precipitation of the titanium with cupferron in the presence of the ferrous iron, filtration, ignition, and completion of the determination colorimetrically. The colorimetric method for titanium is based on the light-straw to amber color developed when hydrogen peroxide is added to a sulfuric acid solution containing titanium; it is limited to solutions containing not more than 0.1 mg. of tit,anium per cc.
PROCEDURE One-half to 1 gram of the sample of drillings is treated in a 150-cc. covered beaker with 100 cc. of 10 per cent sulfuric acid and the liquid heated gently until all action appears to have ceased. The solution is cooled to approximately 20" C., some ashless paper pulp is introduced, and a cold, freshly prepared, 6 per cent solution of cupferron (ammonium nitrosophenylhydroxylamine, CeHsN. NO. ONHS is added dropwise, with constant stirring, until the precipitate just assumes a reddish brown color. Additional cupferron only causes more iron to be precipitated. The precipitate, which contains all of the titanium, together with a small amount of iron, is filtered on an 11-cm. paper containing a considerable amount of ashless paper pulp, washed 12 to 15 times with cold 5 per cent sulfuric acid, and then 5 times or more, if the steel is known to contain small percentages of molybdenum or tungsten, with 5 per cent ammonium hydroxide. The paper and residue are transferred to a 50-cc. platinum crucible and ignited a t a temperature just sufficient t o destroy the carbon of the filter paper. The contents of the crucible are fused with approximately 1 gram (a sufficient amount) of potassium pyrosulfate and the melt is dissolved in 25 cc. of 10 per cent sulfuric acid. The solution is transferred to a Camp comparison tube, cooled to room temperature, and the titanium determined colorimetrically in the following manner: COLORIMETRIC DETERMINATION Three cc. of 3 per cent hydrogen peroxide are added and the solution is mixed, which will result in the development of a light-straw t o amber color, proportional in intensity to the amount of titanium present, To the other comparison tube there is added 25 cc. of cold 10 per cent sulfuric acid, the same amount of potassium pyrosulfate as used t o make the fusion, 3 cc. of hydrogen peroxide, and from a IO-cc. buret a measured amount of standard titanium sulfate solution (1 cc. = 0.0005 gram titanium) which contains slightly less titanium than the sample. The volume of the standard is then made equal to that of the sample by the addition of the necessary amount of 10 per cent sulfuric acid. The color of the standard should now be slightly less intense than that of the sample. Equal additional volumes of the standard titanium solution and of 10 per cent sulfuric acid are then
added to the standard and sample, respectively, each of the solutions being mixed and compared after each addition until the colors of the two solutions match exactly. The number of cubic centimeters of the standard titanium sulfate used, multiplied by 0.0005 and by 100, and divided by the weight of sample taken, gives the percentage of titanium in the steel. I n case the steel contains an appreciable amount of copper, the hot sulfuric acid solution of the sample is filtered on a 9-cm. paper containing a small amount of ashless paper pulp, and the filter paper and residue washed well with 10 per cent sulfuric acid. The filtrate is cooled to about 20" C. and the cupferron precipitation made as described in the second paragraph. The paper holding the sulfuric-acid insoluble and metallic copper is transferred to a 250-cc. beaker, treated with 25 cc. of nitric acid (sp. gr. 1.135), and the solution warmed to dissolve the copper. Approximately 50 cc. of hot water and a slight excess of ammonium hydroxide are introduced, the solution heated to boiling, filtered, and the paper and precipitate washed well with hot water. The precipitate is ignited a t a low temperature to burn off the carbon of the filter paper, added to the ignited cupferron precipitate, and the combined precipitates fused with potassium pyrosulfate. The melt is dissolved in 10 per cent sulfuric acid, and the titanium determined colorimetrically as previously described. Should the steel be known to contain vanadium, the ignited cupferron precipitate is transferred to a 100-cc. platinum dish, treated with 5 cc. of hydrofluoric acid (48 per cent) and 10 cc. of perchloric acid (60 per cent) and the solution evaporated on a sand bath until the volume has been reduced to 5 cc. or less. Any chromium carbide that fails to dissolve during the solution of the sample in sulfuric acid will be rendered soluble by the strong fuming with perchloric acid. The solution is diluted with warm water to 50 cc., treated with an excess of 5 cc. of 10 per cent sodium hydroxide, boiled for several minutes, and filtered on a 9-cm. paper. The paper and precipitate are washed thoroughly with hot water, ignited, fused with a small amount of potassium pyrosulfate, and the determination completed for titanium as described. The vanadium and chromium pass into the filtrate as soluble sodium vanadate and sodium chromate. I n the event the titanium content of the'steel is sufficiently high to render the color method impractical, the determination is carried out as follows: ALTERNATE METHOD One gram of the sample is dissolved and the cupferron precipitation made as described in the second paragraph. The paper and precipitate are transferred to a platinum dish and ignited a t a temperature just sufficient to destroy the carbon of the paper. The contents of the dish are treated with 5 cc. of hydrofluoric acid (48 per cent) and 10 cc. of perchloric acid (60 per cent) and the liquid evaporated on a sand bath to the complete expulsion of all perchloric acid. The perchloric acid residue is fused with several grams (as sufficient amount) of sodium pyrosulfate and the melt dis-
305
ANALYTICAL EDITION
306
Vol. 5, No. 5
solved in 50 cc. of 10 per cent sulfuric acid. An excess of 5 cc. of 10 per cent sodium hydroxide is added, the solution boiled for several minutes, and filtered on a 9-em. paper. The paper and precipitate are washed thoroughly with hot water. Any vanadium present is converted to sodium vanadate and will pass into the filtrate. The precipitate is dissolved off the paper with 25 cc. of hot sulfuric acid (1 t o 4) and the filter washed well with hot water.
containing the titanium is then passed through the reductor into 25 cc. of ferric sulfate solution and the reductor washed with three 30-cc. portions of hot 6 per cent sulfuric acid, followed by one 30-cc. portion of water to remove the last traces of titanium. When the titanium solution is passed through the reductor, the tip end of the reductor tube should dip beneath the surface of the ferric sulfate solution. A blank is run on the reductor in exactly the same way the determination was made, except that the same volume of 6 per cent TITANIUM RECOVERED FROM TITANIUM-FREE STEELSSALTED sulfuric acid is substituted for the titanium solution. WITH KNOWN AMOUNTS OF TITANIUM SULFATE To prove the accuracy of the method several samples of S T E ~ L TITANIUM TITANIUM titanium-free steels were salted with a known amount of FOUND ERROR EXPT. KINDOF STEEL TAKEN ADDED titanium sulfate and put through the method as described. Grams Gram Gram Gram The results obtained are given in the table. $0.00005 0.5 0.0033a 0.00335 1 18-8 2 3
Ingot iron 6%Cr
4)
6% Cr
ib 7
,"pg'-8%
V,
sd. N ~82. Ni-Cr
0.5 0.5 0.5
0.0030
0.5
0 00265
0.6
..... .....
.....
0.00297 0.0045 0 0045
0.0036 0.0035 0.00260
-0.00003
.....
RECEIVED June 1, 1933
.. ..... f
.
.
..
.
.
-0.00005
cast ironc 2 0.0010 A result of 0.0033 eram titanium was obtained bv the second Drocedure described. b A result of 0.72 per cent titanium was obtained on 1 gram of this sample by the second procedure described. C The Bureau of Standards obtained 0.048 per cent titanium on this sample against our result of 0.05 per cent by color.
The solution obtained as described in the preceding paragraph (which will contain all of the titanium) is treated with 1 gram of tartaric acid, made ammoniacal and then acid with an excess of 2 cc. of sulfuric acid (sp. gr. 1.84) per 100 cc. of solution. The liquid is saturated with hydrogen sulfide and if any precipitate forms i t is filtered on a 9-em. paper containing some ashless paper pulp, washed thoroughly with hydrogen sulfide water containing 1 per cent sulfuric acid and 1 per cent tartaric acid, and discarded. An excess of 2 cc. of ammonium hydroxide (PP,gr. 0.90) is then added to the filtrate and hydrogen sulfide is passed through the liquid for 5 minutes longer. Some ashless paper pulp is added, the solution filtered on a 9-em. paper, and the precipitate of ferrous sulfide washed well with ammonium sulfide water containing 1 per cent ammonium sulfate and 1 per cent ammonium tartrate, and discarded. The filtrate (having a volume of approximately 150 cc.) is boiled to expel hydrogen sulfide, acidified with an excess of 30 cc. of sulfuric acid (1 to l), and cooled to 20" C. Some ashless paper pulp is introduced and the titanium is precipitated by the addition, dropwise and with constant stirring, of a cold, freshly prepared, 6 per cent solution of cupferron. An excess of the reagent is indicated by the formation of a snowwhite precipitate which rapidly disappears. The titanium precipitate is filtered on an 11-cm. paper containing some ashless paper pulp, washed twelve to fifteen times with cold 5 per cent sulfuric acid, and then five times with 5 per cent ammonium hydroxide. The paper and precipitate are transferred to a platinum crucible and ignited, first a t a low temperature and finally at 1050" to 1100" C., cooled, and weighed. The weight of titanium oxide found, multiplied by 59.95, and divided by the weight of sample taken, gives the percentage of titanium in the steel. If desired, the titanium oxide may be fused with a small amount of potassium pyrosulfate, the melt dissolved in 100 cc. of 6 per cent sulfuric acid, and the warm solution (about 75" C.) passed through a zinc reductor into ferric sulfate solution [prepared by dissolving 100 grams of ferric sulfate in 150 cc. phosphoric acid (sp. gr. 1.72), and 850 cc. of water containing 20 cc. of (1 to 1) sulfuric acid], the resulting ferrous sulfate then being titrated with standard 0.05 N potassium permanganate (1 cc. = 0.002395 gram titanium). Approximately 100 cc. of 2.5 per cent sulfuric acid are first passed through the reductor [12 in. (30.5em.) in length by 0.75 in. (19.1 mm.) in diameter] and discarded. The hot 6 per cent sulfuric acid solution
A Modified Soxhlet THOMAS R. LISTONAND WILLIAMM. DEHN Chemistry Laboratory, University of Washington, Seattle, Wash.
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H E depicted form of Soxhlet can be assembled from stock laboratory apparatus excepting that the rubber band C sealing the two Buchner funnels is made from an inner tube of an automobile tire. Since all sizes of used inner tubes are cheaply available, all sizes of Biichner funnels can be used; hence all practical sizes of these modified Soxhlets can be assembled. The two T tubes D,held by rubber tubing A , are connected by the rubber tubing B. The lower Buchner, supplied with closely fitting filter paper weighed down by a lead or iron ring, is charged with the material to be extracted, and the parts are adjusted with screw clamp E' closed and screw clamp E open. Heating the flask containing the solvent carries the vapor through B to the condenser which delivers the solvent into the Buchners, and gravity completes
FIGURE 1
the circuit of the solvent. When necessary or desirable, heating can be discontinued and with screw clamp E closed, and screw clamp E' open the liquid on the solid in the Buchners can be drawn down by making connection with the vacuum pump. Ordinarily this filtering is not necessary, or may be made a t the end of process of extraction. This form of apparatus is useful for all extraction made in Soxhlets, and more especially for recrystallization of large masses by the use of limited volumes of solvents. RECEIVED August 1, 1933
