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T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
Vol. 13, No. 6
The Determination of Cobalt and Nickel in Cobalt Steels’s2 By G.E.F. Lundell and J. I. Hoffman BUREAUOF STANDARDS, DEPARTMENT OF COMMERCE, WASHINGTON, D. C.
Unfortunately there is available for t h e determina- filtered. This quantitatively separates chromium, tion of cobalt in steels no such simple, rapid, and ac- vanadium, and any residual tungsten and molybdenum curate method as t h e dimethylglyoxime method for from cobalt, nickel, manganese, copper, and iron. nickel. There are some methods, such a s t h e a- The precipitate is dissolved in sulfuric acid b y the aid nitroso-&naphthol method1’ * -and t h e sodium cobalti- of sodium himlfite a n d treated with hydrogen sulfide nitrite method,2 which a i m at the separation of cobalt t o xemove copper quantitatively. After expulsion of as such. These methods all call for more or less in- hydrogen sulfide a n d reoxidation, a double precipitavolved preliminary treatments, a n d t h e final cobalt tion with ammonium hydroxide serves t o remove iron. precipitates cannot be directly dried, ignited, and The combined filtrates are then electrolyzed for nickel weighed, b u t must be converted into other forms. and cobalt, which are weighed, dissolved, and treated Most methods for the determination of cobalt aim a t with dimethylglyoxime t o obtain nickel. Manganese, t h e simultaneous determination of nickel a n d cobalt which does not interfere in the electrolysis, may appear with subsequent deduction of nickel a s determined as a deposit on the anode, as a sludge, or remain in separately. Such are t h e p h ~ s p h a t e ,t~h e ~ y a n i d e , ~solution. PROCEDURE and the electrolytic6 methods. The method t o be described is of the last-named type Dissolve 2 t o 4 g. of the sample in 50 cc. of dilute a n d is based, for the most part, on well-known facts. hydrochloric acid (1 : 1) a n d oxidize with 5 cc. of The effects of some interfering elements, notably concentrated nitric acid (sp. gr. 1.42). Digest until vanadium in the electrodeposition of cobalt, have been the tungstic acid is bright yellow, add 150 cc. of hot discovered and overcome. The method is not a short water, and boil for 1 min. Filter and wash free from one and is therefore not suitable for routine works iron with dilute hydrochloric acid (1 : 9). Treat analysis. It is, however, a well-tested, accurate method the impure tungstic acid with a small amount of a which is suited t o the primary standardization of cobalt 1 0 per cent solution of sodium hydroxide, and if a n y steels for cobalt and nickel. I n addition, it possesses dark-colored residue remains, dissolve i t in hydrothe merit, from the standpoint of the analyst engaged chloric acid and add t h e solution t o the main filtrate. only occasionally in the analysis of this type of material, Evaporate this filtrate twice with 30 cc. of hydroof providing for the simultaneous accurate determina- chloric acid (sp. gr. 1.2), b u t not t o complete dryness tion of chromium, vanadium, copper, and manganese on account of the slight volatility of divanadyl chloride. in t h e same sample. Take up in hydrochloric acid (sp. gr. 1.11), filter, if The method was developed during the analysis tungstic or silicic acid is present, and separate by means a t the Bureau of Standards of the Ridsdale British of ether6 the major portion of the iron, together with Standard Chrome-Tungsten-Vanadium-Cobalt Steel molybdenum, from nickel, cobalt, copper, chromium, “W.” This steel also contains nickel, molybdenum, vanadium, and manganese. a n d copper, in addition t o the ordinary steel constituBoil the acid extract t o expel the ether, add 4 cc. ents. The method was also carefully tested in the of sulfuric acid (sp. gr. 1.84), a n d evaporate t o the apanalysis of the Bureau of Standards Chrome-Vanadium pearance of fumes. Dilute t h e solution t o 300 cc., Standard Steel No. 30a, t o which had been added add 40 cc. of a saturated solution of potassium perknown amounts of nickel and cobalt. sulfate, and boil until the manganese is completely precipitated a s oxide. This requires about 10 min. PRELIMINARY REMARKS O N PROCEDURE Pour the hot solution into 200 cc. of a warm 5 per T h e following digest of the method will make cent solution of sodium hydroxide. If the precipitate clear the purpose of the various steps. The steel is is not black add a small amount of potassium persulfate dissolved in hydrochloric and nitric acids, and any solution. When the precipitate has settled, filter tungstic and silicic acids are filtered off and treated through asbestos and wash7 with a 2 per cent solution with sodium hydroxide. Any insoluble matter is of sodium hydroxide.8 Place the crucible with the filtered off, dissolved in hydrochloric acid, and added precipitate in t h e original beaker, add 100 cc. of water, t o the main solution. The major part of the tungsten 5 cc. of sulfuric acid, and a crystal of sodium bisulfite, and silicon is thus eliminated, and any contaminating and warm until the precipitate has dissolved. Filter, cobalt, nickel, or chromium recovered. The solution wash with hot water, and repeat the persulfate oxidais then subjected t o a n ether treatment, which removes tion, t h e sodium hydroxide precipitation, and t h e the major part of the iron, together with the most of filtration and washing, in order t o remove all chromium a n y molybdenum present. The acid extract is then and vanadium. Combine the sodium hydroxide fitheated with sulfuric acid till fumes escape, after which trates.g chromium, vanadium, a n d manganese are oxidized Dissolve the precipitate containing nickel, cobalt, by potassium persulfate. The hot oxidized solution copper, manganese, and iron as before, filter off the is poured into hot sodium hydroxide solution, and asbestos, neutralize with ammonia, acidify with sul1 Received February 11, 1921. furic acid (1 cc. of acid for 100 cc. of solution), and 2 Published by permission of the Director of the Bureau of Standards. pass in hydrogen sulfide. Filter off any copper sulfide * Numbers refer to references at end of article, p. 643.
June, 1921
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
a n d wash with a 1 per cent solution of sulfuric acid saturated with hydrogen sulfide.1° Boil t h e solution t o remove hydrogen sulfide, adding persulfate toward t h e end t o destroy sulfur. Dissolve any manganese dioxide which has separated out b y the addition of the least possible amount of sodium bisulfite. Make ammoniacal and filter. AS the ferric hydroxide invariably contains a little cobalt, i t should be dissolved in 20 cc. of sulfuric acid (1 : 4), reprecipitated with ammonia, and filtered.ll Evaporate the combined filtrates t o a volume of 100 cc. I n case a precipitate has formed, acidify t h e solution with sulfuric acid, add a crystal of sodium bisulfite, and warm. The solution should now contain ammonium sulfate equivalent t o 10 cc. of concentrated sulfuric acid. Neutralize with ammonium hydroxide (sp. gr. 0.90), and add 35 cc. in excess and 2 g. of sodium bisulfite. Electrolyze in a volume of 150 cc. for 6 t o 8 hrs., using gauze electrodes and a current density of 0.2 t o 0.3 ampere per dm2. Wash the cathode with cold water, dry a t 100’ C., and weigh.12 The electrolyte, which usually contains from 0.1 t o 1.0 mg. of nickel and cobalt (mainly cobalt), should be tested as follows: Boil with a n excess of ammonium persulfate, keeping the solution strongly ammoniacal t o precipitate manganese, filter, wash,13 and treat with hydrogen sulfide. If a precipitate forms, filter on a small filter, wash with water containing a little ammonium chloride and ammonium sulfide, ignite, and weigh as combined oxides of nickel and cobalt. Multiply b y t h e empirical factor 0.75, and add t o the cathode weight.14 Dissolve the nickel and cobalt on the cathode a n d the oxides recovered from the electrolyte in 20 cc. of nitric acid (sp. gr. 1.42), neutralize with ammonium hydroxide, and then make just acid with hydrochloric acid. Add sufficient 1 per cent alcoholic solution of dimethylglyoxime t o react with both nickel and cobalt, make faintly ammoniacal, and allow t o digest for 2 hrs.16 Filter through asbestos, dissolve back into the original beaker by means of 20 cc. of warm nitric acid (1 : I ) , and precipitate and digest as before. Filter through a tared Gooch crucible, wash with a little hot water, dry a t 120’ C., and weigh. Calculate nickel and subtract from the total nickel and cobalt. DETERMINATION O F C H R O M I U M AND VANADIUM
If determinations of chromium and vanadium are desired, the two filtrates from t h e sodium hydroxide separation7 should be combined and analyzed according t o the electrometric titration method of Kelley, Wiley, Bohn and Wright,lS Johnson’s method,17 or the Bureau of Standards procedure,’s which is as follows: Evaporate t h e solution, make up t o exactly 500 cc. and divide into two 250-cc. portions, A and B. D E T E R M I N A T I O N O F CHROMIUM-Acidify Portion A with sulfuric acid, add 5 cc. of silver nitrate solution (2.5 g. per liter), and boil with 5 cc. of a 10 per cent solution of ammonium persulfate until the persulfate is
541
entirely destroyed (about 10 min.). Cool, a d d ferrous sulfate, and titrate with permanganate. I n this operation quinquivalent vanadium is reduced t o the quadrivalent condition b y the excess for ferrous sulfate added and then oxidized back t o the quinquivalent condition by the permanganate, thereby causing no net change. Sexivalent chromium is permanently reduced t o the trivalent condition. The chromium may therefore be calculated from the difference between the volume of ferrous sulfate added and the ferrous sulfate equivalent of t h e permanganate consumed. D E T E R M I N A T I O N O F VANADIUM-Acidify Portion B with sulfuric acid, boil, and reduce in a Jones reductor containing ferric alum and phosphoric acid in t h e receiver.lg Titrate the hot solution with permanganate. I n order t o obtain accurate results a blank (which usually requires about 0.8 cc. of 0.03 N permanganate) must be carried through the various steps of the determination with the proportionate amounts of sodium hydroxide, potassium persulfate, sodium bisulfite, and asbestos. I n this operation vanadium is reduced t o the bivalent condition and afterwards oxidized t o the quinquivalent state, while chromium is reduced t o t h e bivalent condition and afterwards oxidized t o the trivalent state. The volume of permanganate consumed by vanadium is therefore represented by the difference between the volume of permanganate used in B and one-third of the permanganate equivalent of the ferrous sulfate required by the chromate in A. D E T E R M I N A T I O N O F MANGANESE-ManganeSe may be conveniently determined in the nitric acid solution (References 11, 12, and 13), by the bismuthate method. DETERMINATION O F CopPER-Copper may be determined as described in Reference 10. TESTS O F T H E P R O C E D U R E
The experiments listed in Table I were performed in order t o establish the accuracy of t h e electrolytic method for cobalt and nickel under such varying conditions as might obtain in steel analysis. Unless otherwise specified, the electrolyses were carried out in 150-cc. solution, containing 25 g. ammonium sulfate and 35 cc. ammonium hydroxide (sp. gr. 0.90), a t 0.20 t o 0.30 ampere per dm2. for 16 hrs. The data show that: 1-The deposition of cobalt is seldom complete and recoveries must be carried out as specified in the method. 2-The addition of ammonium acetate or sodium bisulfite (particularly the latter) has a beneficial effect. 3-Potassium, manganese, and chromium sulfates, moderate amounts of platinum, and chlorides are without harmful effect. &Vanadium does not interfere seriously in the deposition of either nickel or cobalt alone, but does interfere most seriously when both are electrolyzed simultaneously. ,!+Tungsten interferes in depositions involving cobalt or cobalt and nickel, but not nickel alone. 6-Ferrous salts, chromates, tartrates, and molybdenum interfere markedly.
Table I1 summarizes the results obtained in the analysis, by the method as described, of the British Standard “W” and the Bureau of Standards Standard
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
542
TABLE I-EFFECT
EXPT. 11
21 31 4‘ 54 6 7 8 9 10 11 12 13 14 15 168 176 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
OF
Substances Added
VARIOUSSUESTANCES ON THE ELECTRODEPOSITION OF COBALT AND NICKEL Weight of Weight of Nickel-Cobalt Deposit on Nature Taken Cathode of Gram Gram DeDosits 0.0977 Co 0.0965 Dark gray Platinum-like 0,0979 N i 0.0970 Gray 0.1939 0.0979 NI 0.0977 Co Good gray 0.1951 0.0979 N! 0.0977 Co Good gray 0.1954 0.0979 NI 0.0977 Co Dark gray 0.0972 0.0977 Co Platinum-like 0.0980 0.1952 Gray 0.1952 Good .gray Purplish and discolored 0.0308 Good gray 0.1947 Good gray 0.1948 Good gray 0.1953 Good gray 0.1953 Good gray 0.1955 Good gray 0.1955 Good gray 0.1957
................................................. ........................ ......................... ................................................. 2 g. NaHS03 ...................................... 2 E. NaHSOs.. . . . . . .. . .. . . ....... . . . . . . . . . . .. . .. . . ................................................. ~~
~
0.0225 0.1185 0.0983 0.0971 0.1212 0.0976 0.0984 0.0100 0.0000 0,0922 0.0284 0.1956 0.2011 0.0983 0,1034 0.0032 0.1954 0.1967 0.1951
.si
..........
Good gray Good gray Dark but good
..........
P1atinum:like Dark but good
..........
.......... ..........
THE PROPOSED METHOD (Results Expressed in Per cent) Cobalt Nickel Chromium Vanadium Manganese Present Found Present Found Present Found Present Found Present Found
.... .......... .......... 4.73 4.73 ............. .......... ........... . .... ....... 4.73 4.73 Bureau of Standards Cr-V Standard No. 30a.. . 2.44 Bureau of Standards Cr-VStandard N o . 30a... 2.44 Bureau of Standards Cr-V Standard No. 30a. . . 2.44
5
6
7
1
Wet peroxidation used as describedin Reference 8.
4.78 4.69 4.69 4.68
0.44 0.44 0.44 0.44
0 41 0.42 0.43 0.43
..
..
3:03 3.03
2:64 2.94 2 932
0.798
2.45 2.45 2.46
2.57 2.57 2.67
2.58 2.54 2.56
1.02 1.02 1.02
1.04 1.04
0.21 0.21 0.21
i :65
Cobalt, 4.63 to 6.06 Nickel, 0.41 to 0.48 Chromium, 2.91 t o 3.12 Vanadium, 0.71 to 0.8b Manganese, 0.08 to 0.14 Copper, 0.047 to 0.07
Cobalt and nickel were added t o Standard No. 30a t o give the percentages indicated in the table.
Expts. 5, 6, and 7 demonstrate conclusively the accuracy of t h e method a s applied t o the determination of cobalt and nickel. T h e data also show t h a t t h e method satisfactorily provides for t h e determination of manganese, chromium, vanadium, and copper, in t h e presence of tungsten a n d molybdenum.
+a. 0001:
-0.0004 -0.0004 -0.1648 -0.0009 4.0006 -0.0003 -0.0003 +0,0002 +0.0002 +a. 0001 -0.1731 -0.0771 +O. 0004 -0.0006 -0.0744 -0.0003 +0.0007 -0.1556 -0.1956 -0.1034 -0.1672 0.0000 +O. 0055 -0.0004 +0.0047 -0.1924 -0.0002 +0.0011 -0.0005
c Copper Present Found
0.097 0.103 0.090 0.089
.. .
...
0.795
0.102 0.102 0.102 0.102
O:Ob5 0.055
0:&5 0.068
0.19 0.20 0.20
0.805 0.805 0.805
0.819 0.820 0.818
0.063 0.063 0.063
0.062 0.065 0.060
...
...
0:?98 0:?88
n
7972
* By electrometric titration, Kelley, Wiley, Bohn and Wright’s method.
No. 30a t o which cobalt and nickel had been added. Standard “W” contains 16.20 per cent tungsten, 0.05 per cent molybdenum, in addition t o t h e percentages of other elements listed in Table 11. The values given in Table I1 are the averages of t h e ranges of the values reported by British, Scotch, French, Italian, and American chemists, which are as follows:
Error Gram -0.0012n -0.00092 4.00172 -0.00052 -0.0002* -0.000.52
Purplish and discolored Good gray Good gray Good gray Dark but good Slightly copper colored Good gray Slightly discolored Good erav 0 DO01 0.OOOi 6.0006 and 0.0000 g respectively. Sblutidn contahed 38’g. (NHhSOd.”
TABLE 11-ANALYSES MADS BY Material Used 1 BritishStandard “ W ” l . . . . . . . . . . . . 2 BritishStandard “ W ” l . . . . . . . . 3 BritishStandard“W” 4 B:itishStandard”W”
Vol. 13, No. 6
3-The determination of manganese is free from the troublesome interference of chromium or cobalt. 4-Elements like cerium, zirconium, and titanium (see Note 5 below) would be quantitatively present in the ammonium hydroxide precipitate along with iron. %Titanium, if present, would be oxidized by persulfate and might escape complete precipitation b y sodium hydroxide. This would affect only t h e determination of chromium and vanadium, and the error could be avoided by boiling t h e alkaline solution for 2 or 3 min. 6-Uranium in the absence of vanadium would go with cobalt and iron and be caught subsequently with iron in t h e ammonium hydroxide precipitate. I n the presence of vanadium, uranium would divide between t h e sodium hydroxide filtrate and t h e precipitate. I n this case i t would not interfere with the cobalt and nickel determination, or with the chromium and vanadium determinations if the electrometric or Johnson methods were employed.
COMMENTS O N THE METHODS
SUMMARY
The following comments are worthy of note: 1-The method demonstrates t h a t i t is possible t o separate chromium and vanadium completely from iron, manganese, nickel, and cobalt b y a persulfate oxidation i n . acid solution, followed b y two sodium hydroxide precipitations performed b y pouring t h e hot acid solution into a n excess of hot alkaline solution. 2-Phosphorus and aluminium undoubtedly also quantitatively accompany chromium and vanadium.
I-This paper presents a method for the accurate determination of cobalt and of nickel in cobalt steels. The method is based on the electrodeposition of cobalt and nickel in a solution freed from iron, chromium, and such interfering elements a s tungsten, molybdenum, vanadium, and copper. 11-Methods for accurate determinations of chromium, vanadium, copper, and manganese in the same portion of steel are also provided.
June, 1921
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y REFERENCES
1-W. W. Scott, “Standard Methods of Chemical Analysis,” 2nd Ed., D. Van Nostrand Co., 148. 2-A. A. Blair, “The Chemical Analysis of Iron,” 8th Ed., Lippincott Co., 175. 3-C. M. Johnson, “Chemical Analysis of Special Steels,” 2nd Ed., John Wiley & Sons, Inc., 304. 4-Johnson, LOC.cit., 307; Blair, LOC.cit., 180. 5-Johnson, LOC.cit., 316; Blair, LOC.c i t . , 177. 6-J. W. Rothe, Milt.kgl. Tech. Versuchsanstalt zu Berlin, 1892, Part 111; Blair, LOC.cit., 177, 202. 7-It is important that the filter be not allowed to run dry, lest the hydroxide coagulate and retain traces of vanadium which would subsequently prevent a satisfactory deposition of cobalt and nickel. 8-Sodium peroxide was employed in two preliminary experiments for the oxidation and separation of chromium and vanadium from iron, cobalt, etc. A. A. Noyes, W. C. Bray and E. B. Spear [Tech. Quarterly, 21 (1908). 141, and also C. M. Johnson [Chem. Met. Eng., 20 (1919), 5881. The separation was complete (Expts. 1 and 2. Table 11), but the procedure was abandoned because it was necessary to repeat the separation twice and the precipitates were difficult to handle. 9--For the determination of chromium and vanadium see page 541.
543
IO-This precipitate represents a quantitative recovery of copper, and the percentage may, therefore, be determined by ignition to oxide or, preferably, by electrolysis in a small volume of solution. 11-If manganese is to be determined, the precipitate should be dissolved in 40 cc. of nitric acid (1 : 31, and reserved. 12-If a determination of manganese is desired dissolve any anode deposit in the solution described in preceding reference. 13-If a determination of manganese is desired add the precipitate to the solution reserved for manganese (two preceding references ) 14-The factors for NiO, COO and Cos04 a5e 0.786, 0.787, and 0.734, respectively. The use of the factor 0.75 on a precipitate weighing 2 mg. could, therefore, not occasion an error greater than 0.004 per cent on a 2%. sample. With large precipitates, ignition to metal in hydrogen must be carried out. Cf. Treadwell-Hall, “Analytical Chemistry,” Vol. 11, 4th Ed., page 139, John Wiley & Sons, Inc. 15-There is no difficulty a t all in precipitating traces of nickel in the presence of any amount of cobalt if this method is followed. The precipitate will contain cobalt, however, and must be purified as directed. 16-T~rs JOURNAL, 11 (ISIS), 632. 17-Johnson, LOC.cit., 8. 18-Unpublished method originating with Dr. I,. F. Witmer a t the Bureau of Standards. 19-D. L. Randall, A m . J. Sci., 141 2 4 , 313.
Improved Deniges Test for the Detection and Determination of Methanol in the Presence of Ethyl Alcoho1112 By Robert M. Chapin BrocxEMrc DIVISION,BUREAUO F ANIMALINDUSTRY,
u. s.
The examination of alcoholic products for methanol has been a problem of interest t o many chemists. If a certain few published papers are consulted the matter would appear t o be rather simple, a t least from the qualitative side. But a thorough survey of the voluminous literature, comprising a large number of methods with contradictory comments and conclusions, does not lead one t o undertake exacting work along this line with entire confidence. One of the most recent investigators, Gettler,3having reviewed fifty-eight existing tests, recommends subjecting the sample t o nine qualitative tests, sebuentially applied. I n passing i t may be noted t h a t his eighth test, a refractometric one, is essentially quantitative in nature, being based upon a numerical difference between physical constants, and is only secondarily of qualitative significance. Also his first seven tests are merely tests for formaldehyde, applied after treating the sample with a single oxidizing agent. If this oxidizing agent is capable of producing formaldehyde from any substance other t h a n methanol, all the seven tests must be subject t o a common source of error. PureIy qualitative findings, however, seldom afford solid ground for action in matters of commercial or legal importance. The question “How much?” is almost certain t o arise. It is a pertinent question here, inasmuch as several investigators4 have stated t h a t methanol is naturally produced in certain fermentations. If methanol, like fusel oil, is a normal constituent of alcoholic products, then the legitimacy of its presence in a n y case may be satisfactorily settled only b y quantitative examination. The analytical chemist needs, first, a simple but dependable qualitative test which shall possess semiquantitative value in t h a t Received February 16, 1921. a Published by permission of the Secretary of Agriculture. 8 J . Biol. Chem., 4!2 (1920), 311. 4 von Fellenberg, Milt. Lebensm. Hyg., 5 (1914), 172; Biochem. Z.,86 (1918). 45; Takahashi, J . Coll. Agr. I m g . Uniu. Tokyo, 5 (191.3, 301; J. A m . Chem. SOC.,89 (1917), 2721. 1
DGPARTJIENT O F AGRICULTURE, WASHINGTON, D.
c.
it is able t o serve as a “limit test,” and, second, a quantitative method which shall enable him t o assert with positiveness very nearly the exact percentage present. The quantitative method must be subjected t o intensive study in order: (1) To develop its highest inherent precision. (2) To devise methods for the elimination of interfering substances. (3) In case elimination is impossible, to determine the size of the “blank” involved by the presence of each such substance.
The DenigBsl test seems most promising for both qualitative and quantitative application. It consists in treating the alcoholic solution with potassium permanganate and acid, whereby methanol is oxidized t o formaldehyde. The latter is detected by Schiff’s reagent in the presence of sufficient sulfuric acid t o prevent development of color from acetaldehyde. There appears no evidence t h a t other proposed oxidizing agents, such as bichromate and acid or persulfates,2 are inherently superior t o permanganate and acid. The latter agent is preeminently simple and convenient, requiring no heat for its action and finally affording a colorless solution. No reagent effects a quantitative yield of formaldehyde. All require strict adherence t o a standard set of conditions under which i t is assumed t h a t a certain concentration of methanol originally present results in a certain concentration of formaldehyde a t the end. Likewise, for the demonstration of formaldehyde there appears t o be no reagent any more convenient or reliable t h a n Schiff’s reagent, prepared according t o 1
Compt. rend., 150 (1910). 832.
Preliminary experiments have indicated t h a t persulfates, especially in strongly acid solution, may produce a notable quantity of formaldehyde from pure ethyl alcohol. T h e possibility of such a reaction has been noted by previous observers in the application of several oxidizing agents. Bichromate and acid, in comparison with permanganate and acid, appears to afford a high yield of acetaldehyde from ethyl alcohol, but a low yield of formaldehyde from methanol. 2
