INDUSTRIAL AND ESGINEERING CHEMISTRY
360
isobutylene determination. I n the absence of isobutylene, the rate would have been constant from the very first. Whenever this synthetic butene-2 was used, its known content of isobutylene was taken into account or, if necessary, as for the determination of the data in Table I X , the isobutylene was first removed with 68 to 70 per cent acid. The other olefin samples contained no extraneous olefin; the impurities were the corresponding paraffins or air. The time required for an analysis depends somewhat on the details of the apparatus and on the skill of the operator. It is about half an hour for each olefin. For the foregoing two analyses, all absorbents were in bottles, as each had been adjusted to the maximum recommended strength; hence, the total time, because of additional manipulations, was slightly greater than if the reservoir4 of Figure 2 had been used.
Jlodifications It is perhaps obvious that some modifications in the method may be made without introducing errors for samples of more or less known composition. For example, in the analysis of samples having small concentrations of olefins, only one concentration of acid need be used for each olefin. Also, the number of passes per portion of acid, especially in determinations of propylene and ethylene, may be increased. Isobutylene in samples containing much butene-2 or much
VOL. 10. NO. 7
butadiene can be determined with a somewhat advantageously increased specificity with acids weaker than 68 to 70 per cent. The data presented should prove helpful in selecting conditions for such modifications. For the analysis of any sample in general, however, it is believed that the recommendations given represent an optimum over-all compromise among the several conflicting factors involved and that observance of them will yield rapid and reliable analytical results.
Literature Cited (1) Christoff, 2. p h y s i k . Chem., 55, 622 (1906); International Critical Tables, hfcGraw-Hill, Vol. 111, p. 280 (1926). (2) Davis, J . Am. Chem. SOC.,50, 2780-2 (1928). (3) Davis and Crandall, Ibid., 52, 3769-85 (1930). (4) Davis and Daugherty, IND.ENQ.CHEM.,Anal. Ed., 4, 193-7 (1932). (5) Davis and Schuler, J. Am. Chern. Soc., 52, 721-38 (1930). (6) Dobryanski, Neftyanoe Khoz., 9, 565-73 (1925). (7) Frey and Huppke, IND. ENQ.CHEM.,25, 55 (1933). (8) Hurd and Spence, J . A m . Chem. SOC.,51, 3356-7 (1929). (9) Manning, King, and Sinnatt, Dept. Scientific and Industrial Research, Tech. Paper 19 (1928); Ellis, “Chemistry of Petroleum Derivatives,” p. 1120, New York, Chemical Catalog Co., 1934. (10) Markovich and Dementera, Khimteoret, 2, 131-43 (19353. (11) Markovich and Moor, .Veffyanoe Khoz., 19, 604-13 (1930) RECEIVEDl p r i l 18, 1938. Presented before t h e Division of Petroleum Chemistry a t the 95th Meeting of the hmerican Chemical Society, Dallas, Teras, l p r i l 18 t o 2 2 , 1938.
Volatilizing Chromium as Chromyl Chloride A Rapid Method Applicable to Determination of Manganese in Stainless Steel FRED WILSON SMITH Carnegie-Illinois Steel Corporation, South Works Chemical Laboratory, Chicago, Ill.
A new and rapid method is described for the accurate determination of manganese in stainless and other high-chromium steels, in which the chromium is rapidly volatilized from a perchloric acid solution of the sample. The method is also applicable to other determinations in which large quantities of chromium are objectionable.
C
HROMIUM, when present to the extent of more than 2 or 3 per cent, interferes with the determination of manganese by the persulfate-arsenite method. Consequently, high-chromium steels require a separation of chromium prior to the determination of manganese. Heretofore, the author has used the zinc oxide separation, which is effected by adding zinc oxide paste to R dilute sulfuric acid solution of the steel which has been oxidized by nitric acid. The mixture containing ferric and chromium hydroxides and the excess zinc oxide is diluted to 200 ml., and filtered, and the manganese is determined on an aliquot of the filtrate. This method is time-consuming for two reasons: Two-gram samples of stainless steels may require from 0.5 t o 2 hours t o dissolve in 9 iV sulfuric acid, and the subsequent filtration of the bulky precipitate formed by the Bine oxide is also slow. The author h s t attempted to overcome this drawback by using perchloric acid to dissolve the steel, which makes solu-
tion possible in 5 to 10 minutes. He also confirmed the experience of other chemists in this laboratory that if oxidation of the iron following solution in sulfuric acid is postponed until after the separation of chromium, the filtration is much faster. An attempt to combine these two improvements by reducing the iron with sulfurous acid after solution in perchloric acid indicated that it is very difficult, from a practicable analytical viewpoint, to keep the iron in the reduced state in perchloric acid solution. The object of the first part of this investigation was to find a means of speeding up the preliminary operations of dissolving the steel and separating the chromium. A possible solution of this problem was suggested by a consideration of the possibility of removing chromiun by conversion t o a gaseous rather than a solid compound. The formation of the red gas chromyl chloride, Cr02C12,was studied for this purpose. The fact that chromyl chloride can be evolved from a mixture of a solid chloride and potassium dichromate in h o t concentrated sulfuric acid is known from the old qualitative test used to distinguish chlorides from bromides. I n this test the gases evolved, bromine from bromides and chromyl chloride from chlorides, are absorbed in a dilute ammonium hydroxide solution, The ammonium bromide and hypobromite formed are colorless, while the chromyl chloride forms yellow chromate ions. I t follows that the addition of a solid chloride to a hot sulfuric acid solution of hexavalent chromium will volatilize some of the chromium and it is possible that the reaction may be driven nearly to completion by excess of salt, provided that the chromium which is reduced to the trivalent
JULY 15, 1938
-4NALYTICAL EDITION
361
stage is reoxidized. As shown beT l B L E I. COMP.4RIso.i OF O L D A N D h ' E W ~ ~ E T H O D S low, this is done by fuming with --Manganese Found-perchloric acid between salt addiC:imposition of Sample . method ZnO XaC1 tions. Sample C P S Si Ni Cr Ti method Perchloric acid with a little hy% % % % % % % % % drochloric acid will dissolve stain-1 0.07 9.45 17.4 0.496 0.42 0.420.42,0.42,0.42 B 0.07 0:OiO 01008 O:i4 $1 00 18.98 ... 0.38 0.37: 0.37 less steel in 5 to 10 minutes and the C 0.95 0.014 0 . 0 0 8 0.26 0 24 0.15 ... 0.31 0.30, 0.31 D-l 0 19 0.013 O.OOG 0 . 5 8 0 73 2T.27 . .. 0.42 0.42, 0.42 chromium is oxidized to the hexaD-2 , . . 0.43, 0.43 valent state by a few minutes of E-1 0 : O S 0 : 0 2 2 0:006 0 : Z j 1 1 36 18'45 ... O'kG 0.54, 0.54 E-2 ... 0.83,0.53 fuming. The addition of sulfuric F 0:Oj o:oi2 o 00s 0'35 9 4: 17'63 0'59 0.59, 0 . 5 0 G 10.60% 110,0.09% A I ) 0.16 5.03 0.49 0.39 0.40,0.40 acid followed by 0.5 gram of soH-1 ,. ,.. ,.. .. 9 03 19 14 ... 0.40 0.41 dium chloride gare a copious evoluH-2 .. ... ,.. ,. . 0.39 0.40 I .. ... ,.. 1: 8.63 li'45 , . . 0.38 0.37,0.38 tion of a red gas. An early experiJ .. ... ... .. 9 00 18 65 .. . 0.45 0.45, 0.47 Ii .. ... ... .. 9.95 17.63 ., , 0.59 0.61, 0.61 ment showed that the sulfuric acid L .. ... ... .. 9 48 17.28 ,.. 0.38 0.38,0.39 was not necessary for the volatiliza11 ... 8 49 17 933.. , , . 0.36 0.33,0.36 Bureau of S k n d a r d s No. 101; certificate ralue for M n 0 m a . . 0 . 5 5 , 0.56 tion of chromyl chloride if the steel Bureau of Standards S o . 73, certificate value for S i n 0 276 .. 0.26,0.26 is dissolved in perchloric acid. Experimentation was then directed to determine if chromium could be sufficiently volatilized as chromyl acid mixture to avoid burns by the steam generated from the chloride with sodium chloride from a perchloric arid solution, water in the acicl mixt,ure. so that manganese could be determined accurately. Minor variations from the above procedure do not affect I n further experiments the chromium not volatilized was results appreciably. The essential precautions are to be sure determined in the perchloric acid solution of stainless steel that the steel is completely dissolved and that the chromium remaining after the sodium chloridP treatment, and a techis sufficiently eliminated. Excessive acid concentration innic was finally developed for volatilization of 99 per cent of terferes with t'he oxidation of manganese by silver nitrate and the chromium present in the original sample. Where a high ammonium persulfate and, therefore, should be avoided. I n concentration of sodium salts is undesirable, a somewhat the case of stee!s that are dissolved with difficulty, any furlonger but nearly as effective method of volatilizing the ther addition of perchloric acid necessary to keep the salts chromium was developed, using hydrochloric arid instead of in solution should be held at, a minimum, preferably no more sodium chloride. than 5 ml. The addition of 10 ml. excess of perchloric acid I n the third phase of this investigation, the effect of the just before dilution led to low results. Slightly low results, perchloric acid-sodium chloride treatment decided upon as presumably due t o peroxide formation, are avoided by the suitable for application in the determination of manganese first addition of ammonium persulfate immediately after was studied for 20 other elements to reveal possible interferdilut'ion. For steels containing 0.5 to 2 per cent of silicon, ence of this treatment in the determination of these elements. a few drops of hydrofluoric acid aid in their solution. It is advisable to use 0.5-gram samples for determining Determination of Manganese manganese when 0.80 to 1.50 per cent of manganese is present Preliminary experiments indicated that the volatilization in the steel. For these smaller samples the same quantities of acids may be used. of chromium could be effected and controlled by adding 2 to 4 grams of solid sodium chloride in 0.5-gram portions after Judging the completeness of the volatilization of chromium the chromium had been oxidized by the perchloric acid. by the color of the solution is deceptive for two reasons: The addition of salt deepens the color of the iron to a reddish brown Following this treatment, the determination of manganese which fades as the hydrochloric acid formed is boiled out, could be completed by the well-known persulfate-arsenite method. and different types of steel give different final colors. The best criterion is the lack of red fumes within a few seconds PROCEDURE. To a 1-gram sample in a 500-ml. Erlenmever after an addition of salt. If too much chromium is left in flask add 5 ml. of 6 AVhydrochloric acid and 20 ml. of perchloric the solution, on the addition of the ammonium persulfate acid (70 to 72 per cent). Place the flask upon a hot plate to heat the formation of a yellow solution is first noticed, with a rapidly until the steel is dissolved and the chromium is oxidized. Allow the solution to fume 1 minute after oxidation of the chrorather slow development of the permanganate color. This miumtotheredhexavalent form. Add 2 to 4 grams of solid sodium fault is also indicated by the indefinite end point and usually chloride in small portions on a spatula or a glass spoon. hlake by the lack of agreement of the rePults on duplicate samples. two additions of the salt after the last evolution of the red chromyl With practice, the volatilization of t'he chromium to the chloride. Boil 1 minute after the condensing vapors have Tvashed degree desired is easily effected. most' of the salt around the neck of the flask down into the solution. DETERhIISATIOKS TO TESTTHE AfETHOD. TO test the Add cautiously 20 ml. of a mixture of 250 ml. of nitric acid, speed and accuracy of this procedure] determinations were 125 ml. of 85 per cent phosphoric acid, 186 ml. of 50 per cent made, comparing the results obt'ained by the new method with sulfuric acid, and 440 ml. of water. Boil 1 minute. Test the soluthose obtained by the zinc oxide method and with values astion to make sure it is free of chlorides at this stage by adding a few drops of 1 per cent silver nitrate solution. If necessary, consigned to authoritative standards. The time required for a tinue the boiling until the solution is chloride-free. Add 10 ml. single determination will vary from 20 to 30 minutes, deof 1 per cent silver nitrate solution, 100 ml. of hot water, and 5 pending upon the kind of steel. However, the method is well ml. of 20 per cent ammonium persulfate solution. When the adapted to group determinations. The author alone has solution boils, add 10 ml. more of 20 per cent ammonium persulfate solution and boil 30 seconds. Cool rapidly in a water made as many as eighteen manganese determinations on bath and titrat'e with standard sodium arsenite solution. stainless st'eel samples in one hour, with a reproducibility and accuracy as recorded in Table I. IXTERPRETATIOX O F RESULTS. The flask need not be removed from the hot plate until the This procedure affords a rapid and accurate method for the determination of mangasolution is ready for the cooling bath, but the fingers should nese in high-chromium steels. That it provides a fast and be kept well away from the neck of the flask when adding the
INDUSTRIAL AND ENGINEERING CHEMISTRY
362
efficient means of eliminating fairly large amounts of chromium is indicated by its effectiveness in reducing the chromium content of a 1-gram sample of the 27 per cent chromium steel to a point where the residual chromium gave no color interference in the titration of manganese.
Extent of Elimination of Chromium CHLORIDETREATRIENT. Inasmuch as the volatilization of chromium was found effective for manganese determination, i t was considered desirable to ascertain just how completely i t can be eliminated, in order that this method might be used in other determinations in which chromium interferes. SODIUM
TABLE11. CHROMIUM ELIMIXATIOX BY SODIUM CHLORIDE Type of Sample
Method of Treatment with Solid NaCl
Cr in Residue
% 18% Cr
25% Cr
in portions, rinse, pius 3 grams, rinse, plus 2 grame
VOL. 10, NO. 7
color was restored before adding the next portion of hydrochloric acid. This prolonged heating necessitated adding two or three 10-inl. portions of perchloric acid (70 to 72 per cent) to prevent the solution from being evaporated to dryness. Hydrofluoric acid also causes loss of chromium as a red gas of unknown composition. Where sodium salts are undesirable, hydrochloric acid in small portions can be used for the elimination of chromium with results comparable to those attained by the use of sodium chloride. The green color noted above is attributed to the formation of trivalent chromium, which is made possible by the cooling effect of the vaporization of the water in the concentrated hydrochloric acid. The time required for reoxidation and the extra perchloric acid necessary make the hydrochloric acid treatment somewhat less desirable than the sodium chloride treatment, except in cases where sodium salts may be objectionable or time is not a factor. If sufficient time can be devoted to an analysis, it is posqible to eliminate 99 per cent of the chromium, when concentrated hydrochloric acid is added after repeated oxidations, by heating the perchloric acid solution.
j grams
0 . 2 8 (av.)
The amount of chromium remaining after various methods of salting was determined on 1-gram samples of 18 and 25 per cent chromium steels. The results and methods used are indicated in Table 11. After each addition of salt, most of the fumes of chromyl chloride are tlriven out of the flask and the solid particles are allowed to dissolve before the next addition of salt. The flask or beaker is removed from the hot plate and allowed to cool somewhat before rinsing. The solution is heated to fumes of perchloric acid before subsequent salt additions. If the sides of the flask or beaker are rinsed after most of the chromium is volatilized, a resalting with 1 gram more of sodium chloride will reduce the amount of chromium from 18 per cent t o less than 0.06 per cent. Adding the salt all a t once is not effective. Without rinsing, the chromium content is reduced to less than 0.50 per cent, sufficient for manganese determinations. With 25 per cent chromium steels, two rinsings and resaltings are required to lower the chromium to 0.28 per cent. At least 99 per cent of the chromium in the sample can be easily eliminated by using the proper technic, depending upon the amount of chromium present.
Effect of Sodium Chloride-Perchloric Acid Treatment on Determination of Other Elements
Since 99 per cent of the chromium can be volatilized, as has been shown above, it remained to determine the effect of this treatment on the analysis of other elements. This investigation was made, therefore, to indicate the analyses in which the volatilization of chromium would be feasible. With this objective, numerous determinations were made on 20 elements. I n general, the procedure followed involved determining the amount of the element in question in known samples with and without the sodium chloride treatment. Standard steels, c. P. metals, c. P. compounds, standard solutions, and Bureau of Standards steels were used as samples. Solution was usually effected by 5 ml. of 6 N hydrochloric acid and 15 to 25 ml. of perchloric acid (70 to 72 per cent) for each gram of sample. I n many cases, additional control analyses were made, using acids other than perchloric. After the chromium was volatilized, the element being studied was determined in the residue and the controls by the usual methods, modified where necessary by the presence of perchloric acid. RIost of the methods were derived from the United States Steel Corporation (19-21) and Hillebrand and Lundell (2-17). INTERPRETATION OF RESULTS.The results of experiments TABLE 111. ELIMINATION OF CHROMIUM BY HYDROCHLORIC ACID 6 and 7 indicate that the greater part of the tin is volatilized, T y p e of and experiment 65 shows that this loss is due primarily to the Sample Concentrated H C l Method Cr in Residue fuming with salt. % Experiments 11, 12, and 58, shorn a large apparent loss of 18% Cr 10 ml. 3.37, 3.68 Two 5-ml.. portions , A : . ! 2 .81, 0.84 portions arsenic. However, experiments 58b and 59 indicate that these Five 2-ml. portions 0.39 rL:--" tests are not a true measure of the loss, since it is much less if > 0 . 1 2 , 0 . 1 4 , 0.50, 0 . 3 2 Six 3-ml. portions Iortions, rinse, tthree h r e 3-ml. 22% Cr Six 3-ml. portions, the solution is diluted before reduction or if gravimetric portions 0.26, 0.28 iortions, rinse, thre 27% Cr Six 3-ml. portions, three 3-ml. methods are used. ilpparently, it is difficult to get all of the portions 0.28, 0.54 "."arsenic reduced in the presence of perchloric acid. Another possible explanation is that the peroxides which might be HYDROCHLORIC ACID TREATMENT AND EFFECT OF HYDRO- formed reoxidize some of the arsenic. I n experiments 60 and 62, the loss of arsenic as determined by distillation is 1.5 to FLUORIC ACID. The possibility of avoiding the accumulation of large amounts of sodium salts in the solution by the use 4 per cent. Experiments 23, 61, and 64 indicate t h a t the sodium of concentrated hydrochloric acid in place of sodium chloride chloride-perchloric acid treatment apparently interferes with was also studied. The method using hydrochloric acid had the reduction of selenium, but no loss is detected by distillaalso been tried by H. H. Willard (18) and by Benedettition in experiment 63. Pichler and Spikes (1). The residual chromium and the Experiment 24 indicates that perchloric acid interferes with methods of addition of hydrochloric acid are tabulated in the complete precipitation of titanium by cupferron. ExperiTable 111. Although considerable chromyl chloride was ment 25 shows that if other steel constituents are not reevolved upon the addition of 3 ml. of hydrochloric acid the moved, they interfere so seriously that color comparison is solution frequently turned green shortly thereafter. The impossible. Experiment 34, in which potassium dichromate solution was then heated for several minutes until the red y".
JULY 15, 1938
ANALYTICAL EDITION
363 -
was added and chromium remoi-et1 TABLEIV. EFFECTOF SODIVM CHLORIDE-PERCHLORIC ACIDTREATMENT ON by sodium chloride, indicates that DETERNISATION O F OTHER ELEMEKTS chromium may be volatilized suffi--Amount Found Usingociently to avoid interference with the Preliminary Treatment HClO development of the color. ExperiAmount andment 36 shows that perchloric acid Ewt. Sample and Method Present None HCIO Loss SaCl interferes with the sodium thiosulfate % % % % % 11 and 12 .Irsenicb separation also. L-ndoubtedly, if Volumetric (4)(diluted t o 70 1111 0.2 021 0.03 0.0.5 75 the perchloric acid were completely 58, Gravimetric (,!) 0.13 0.16 0 2 0.22 .. \ olumetric (diluted t o 70 nil. I 58b 0 2 0.18 0.008 0.011 94 reduced, sodium thiosulfate and Volumetric (diluted t o 3.50 nil.) 59 0.2 0.18 0.14 21 0.14 60 Distillation 0.2 0.18 0,006 0.001 4 cupferron separations could be used. 82 Distillation 53 . . 0.06 1.5 0.70 Experiments 44, 45. 57, and 5G 6 and i Tln Volumetric (.j) 9.5 9.6 9.8 indicate that perchloric acid inter0.c9 99 63 H?S precipitate in distillate 100 . ... Trace Large IOSJ feres with the phosphate-thiosulfate 23 Selenium Volumetric KI-thiosulfare 0.22 0.224 ..., 0 179 17 separation of aluminum, but not 61 Volumetric KI-thiosulfate . .. 0.21 0 13 40 0.23 with the ammonium hydroxide sepa63 Distillation .... Nil 0.23 Si1 0 64 Gravimetric 502 reductiou 0 23 .... 0.17 0 18 20 ration. When phosphorus is pres41 and 45 .Iluminum ent, the aluminum can be separated Phosphate (1) 93 .... 90 60 30 44 and 45 Phosphate (1.31 0.37 .... 0.10 '1.03 90 from the perchloric acid by precipi57 Phosphate (1.3) .... 0.04 0.24 72 0.06 56 NHIOH (.1 2.) 92.4 92.4 95 tating with ammonium hydroxide, 95.4 0 1 Phosphorus filtering, and washing. Then the Volumetric ( 1 9 ) , distillation 0.091 .... .... 0.001 0 21 Volumetric 0.091 aluminum in the mixed precipitate .... .... 0.096 0 7 Vanadium of d1P04 and Al(OH)3 can be disColorimetric distillation 0.165 .... Xi1 0 4 and 5 Volumetric solved in hydrochloric acid and re0.043 0.043 0.05 .. Volumetric ( 9 ) 6 and S 0.05 0'043 0 0.046 precipitated as phosphate only, by 13 Colorimetric (101 0.165 .... 0:165 0 165 0 16 lIolybdenum, colorimetric the phosphate-thiosulfate method. 0.39 .. .. 0.39 0.39 0 41 Columbium, gravimetric 0.51 0 0.48 0.49 0.48 Low results typified by experi24 Titanium m e n t 38 w e r e o b t a i n e d f o r Colorimetric ( 2 1 ) . cupferron 0.496 .. . 0.23 0.27 .. 36 Colorimetric, thiosulfate .... 027 0.496 0.27 .. tungsten, and WOa continued to 25 Colorimetric, F e present 0 496 Impossible t o match colors 31 Colorimetric, pure solution precipitate in the filtrates. This 0.25 0.25 0.25 0.25 0 34 Colorimetric, pure solution, Cr phenomenon was attributed to the added and removed 0.25 0.25 0.25 0.25 0 29 Nickel, volumetric ( 6 ) formation of phosphotungstates, 9.22 .... 9.22 9.22 0 37 Copper, volumetric ( 2 ) .., . 0.30 0.30 0.30 0 since phosphorus is not removed by Cobalt, grai-imetric ( 7 ) 39 .... . ... 0.194 0.197 0 perchloric acid, but is removed by Zirconium, gravimetric ( f 5 j 0.12 .... 0.12 49 0 0.12 hydrochloric acid which is used in Tungsten, gravimetric (16) 18.25 . . .. 13.2 38 15.7 .. Tungsten, gravimetric (la) 2.58 the usual solution of the sample. 43 .... 2.38 2.36 0 Uranium, gravimetric ( 1 1 j 49 15 50 47.5 49.00 48.96 0 However, by making several recov95 46 a n d 48 Zinc, gravimetric (51 .... 92.9 93 2 0 eries, results were obtained in ex52 Boron, gravimetric (17 ) 21.66 22.1 21.7 22.0 0 periment 43 which indicate that there Beryllium, gravimetric ( 1 4 ) 53 11.5 0 11.25 10.8 11.5 is no appreciable loss due to salt. 54 Sulfur, gravimetric ( 2 0 ) 0.191 0.192 0.194 0 A preliminary experiment indidpparenr. losses less t h a n t h e experimental error are considered nil. I n t h e methods marked cated that little, if any, iron is lost "distillation" the gases evolved were absorbed in water and the solution was analyzed for t h e element being tested. by sodium chloride-perchloric acid b Control analyses on 4 s contained HClOi but were not heated. treatment. The remaining experiments indicate t h a t the perchloric acidsodium chloride treatment causes no appreciable The excess chloride is boiled out as hydrochloric acid, and the loss of selenium, aluminum, phosphorus, vanadium, molybanalysis is finished by the usual persulfste-arsenite method. denum, titanium, cobalt, nickel, copper, columbium, zirA technic has been developed for volatilizing 99 per cent conium, tungsten, uranium, zinc, beryllium, boron, or sulfur. of the chromium from steels containing up to 25 per cent of The results and interpretation of these exDISCUSSIOX. chromium. This consists of alternate additions of salt in periments to reveal the effect of the sodium chloride treatment portions to a perchloric acid solution of the steel and of rinsing on the determination of the twenty elements listed are of a the sides of the container with distilled water. X similar and preliminary nature and should be considered as indicating equally effective but somewhat longer method of volatilizing the course of future investigations with regard to the apchromium has been developed. using small volumes of concenplicability of this method for separating chromium. trated hydrochloric acid. The method described for the determination of manganese Of the twenty elements tested, the perchloric acid-sodium in stainless steel has been in use for several months in this chloride treatment for volatilizing chromium causes loss of laboratory and has proved generally satisfactory. S o atarsenic and tin; interferes with the methods used for the tempt was made to attain greater precision than that usually determination of selenium, titanium, aluminum, and tungsten: expected from the persulfate-arsenite method. but does not interfere with the determination of phosphorus, Summary vanadium, molybdenum, cobalt, dolumbium, nickel, copper, zirconium, uranium, boron, beryllium, or sulfur by the methods -4rapid, accurate method for volatilizing chromium prior used in this investigation. to the determination of manganese in high-chromium steels is described. Solution of a 1-gram sample is effected by n -4cknowledgment 4 to 1 mixture of perchloric acid (70 to 7 2 per cent) and G Ar The author wishes to express his appreciation for the cohydrochloric acid. The chromium is volatilized by the addioperation and assistance received from L. P. Chase, chief tion, in small portions, of 2 to 4 grams of sodium chloride. ~~
5
INDUSTRIAL AXD EYGINEERING CHEhlISTRY
364
chemist of the South Works of the Carnegie-Illinois Steel Corporation. He is also grateful to the chemists of this laboratory who have made many suggestions regarding some of the analyses and possible applications.
Benedetti-Pichler. A. A . . and Soikes. W. F.. Mikrochemie. ’ Festschrifte von Hans Molisch, i936,.3&-41. ’ Hillebrand and Lundell, “Applied Inorganic Analysis,” p. 200, S e w York, John Wiley RE Sons. 1929. ILtJ
-p.
(8) Hillebrand and Lundell, “Applied Inorganic Analysis,” p. 334 (9) Ibid., Sewp ,York, 380, John Wiley RE Sons, 1929. I b i d , , p, 362, (11) Ibid., p. 388. (12) Ibid., p. 397. (13) I b i d . , p. 399. (14) Ibid., p. 404. (15) Ibid.. D. 446.
Literature Cited
IULU.,
VOL. 10, NO. 7
0 1 4
ALY.
Ibid., p. 217. Ibid.,p. 238. Ibid.. D. 320. Ibid.; p. 326.
$!!! !b”d’; ” ?5!’ j l i ) 102d., p. 011. (18) Smith, G. F., Chemical Co., “Mixed Perchloric, Sulfuric, and Phosphoric Acids and Their Applications,” p. 9, 1935. (19) U. S. Steel Corp., “Methods of the Chemists of U. S. Steel Corp. for Sampling and Analysis of Alloy Steels,” p. 27, 1921. (20) Ibid., p. 27. (21) Ibid., p. 77.
RECEIVED .Ipril
18. 1938.
Determination of Acetaldehyde in Wines d’
hI. .A. JOSLYN AND C. L. COMAR University of California, Berkeley, Calif.
IK
COKSECTIOS with studies on the course of oxidation in wines the authors were interested in the accurate determination of small amounts of aldehyde, of the order of magnitude of 50 mg. per liter, in the presence of sulfur dioxide and the other commonly occurring volatile iodine-reducing substances. Of the available methods ( 1 , 7 ) .the bisulfite and hydroxylamine procedures appeared to offer more possibilities. Therefore the reliability of three modifications of such procedures was investigated, both as to recovery of aldehydes from wines and from pure solutions and also as to the influence of the addition of sulfite.
Indirect Bisulfite Procedure I n this procedure a n excess of bisulfite is added to the solution of aldehyde, the mixture is allowed to stand for the period of time necessary to complete the sulfonic acid formation, and the excess of bisulfite is determined by titration with standard iodine solution. This procedure, apparently first suggested by Ripper ( I @ , has been widely used in the determination of aldehyde by Parkinson and Kagner ( I S ) , Valaer (19), Joslyn (8),and others. It has been subject’ed to a considerable study by Langedijk (IO), Kolthoff and Furman (9),Donnally (4), and Parkinson and Wagner ( I S ) , and a number of modifications have been suggested. The authors have used a modification based on the suggestions of Kolthoff and Furman (9) to stabilize the bisulfite solution by the addition of 5 to 10 per cent of alcohol and to determine the excess bisulfit’e by rapidly adding the aldehyde solution to an excess of iodine and back-titrating with st’andard thiosulfate solution. Mix 100 cc. of the aldehyde solution, 10 cc. of 0.1 N sodium bisulfite solution containing 10 per cent of ethyl alcohol hy volume, and 10 cc. of alcohol (if the sample contains none) in a 300-cc. Erlenmeyer flask which is stoppered and allowed to stand at room temperature for 30 minutes. (Aldehyde solutions obtained by distillation were-cold when bisulfite was added, so that the solutions xere not at room temperature during the whole of the storage period.) Then add 10 cc. of 0.1 N iodine solution from a freely flowing pipet, and back-titrate the excess of iodine with 0.1 N thiosulfate solution. As a blank, to the same volume of water and alcohol add 10 cc. of the bisulfite solution, stand for 30 minutes, add iodine, and back-titrate as above (1 cc. of 0.1 N thiosulfate is equivalent to 0.0022 gram of acetaldehyde).
Kolthoff and Furman (9) report that when about 30 to 50 per rent more bisulfite than is theoretically necessary is added and the mixture is allowed to react for 30 minutes the proceduie is very exact even for 0.01 i Y bolutions of acetaldehyde and formaldehyde. Ripper (16) had previously reported that 15 minutes are sufficient for 25 cc. of a 0.5 per cent solution of acetaldehyde to which are added 50 cc. of a potassium bisulfite solution containing 12 grams of potasbium bisulfite per liter. Parkinson and Wagner ( I S ) used higher concentrations of bisulfite but dealt with stronger aldehyde solutions than did the authors. It is obvious that the presence of sulfur dioxide or other volatile iodine-reducing substances in the wine would interfere with this method.
Direct Bisulfite Procedures The quantity of bisulfite bound by the aldehyde is determined by oxidizing the excess of bisulfite with iodine under conditions such that the aldehyde-bisulfite complex is not dissociated, then hydrolyzing the latter, and titrating the sulfite liberated with standard iodine solutions. Although, according to Jaulmes and Espezel ( 7 ) , such a procedure was suggested as early as 1896 by Reiter, the rational development of the most suitable conditions for the reactions involved depended upon such studies of the cheniistry of these reactions as were made early by Kerp (9) and later by Stewart and Donnally (16) and Jaulmes and Espezel ( 7 ) . Although a number of procedures of this kind are now available (Clausen, 3, Friedemann and Kendall, 6, Friedeinann and Graeser, 6, Tomoda, 17, Donnally, &, and Jaulmes and Espezel, 7 ) the latter procedure has been selected because it was developed for conditions that are found in wine distillates. Place 100 cc. of aldehyde solution (containing between 0.01 and 0.03 gram of acetaldehyde) in a 500-cc. Erlenmeyer flask, and add 50 cc. of neutral buffer solution (3.35grams of KHzP04and 15 grams Na2HPO4.12H20 per liter, or 24 grams of NazHPOa~12Hz0 and 25 cc. of N sulfuric acid per liter) and 10 cc. of bisulfite solution (18.9 grams of anhydrous sodium sulfite and 150 cc. of N sulfuric acid per liter). Stopper, shake, and let stand 20 minutes. Add 1 cc. of freshly prepared 0.2 per cent starch solut,ion, 100 cc. of water, and 10 cc. of acid solution (250 cc. of concentrated hydrochloric acid, 22” BB., per liter). Then titrate the excess bisulfite with 0.1 N iodine solution. Add 100 cc. of alka-
