Jan., 1918
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
THE DETERMINATlON OF MANGANESE IN STEEL IN THE PRESENCE OF CHROMIUM AND VANADIUM BY ELECTROMETRIC TITRATION By G . L. RELLBY, M. G . SPBNCBR, C. B ILLINGWORTH AND T. GRAY
Received July 14, 1917
The determination of manganese in steel in t h e presence of chromium and vanadium has long offered difficulties t o the analyst in steel works laboratories. Numerous methods have been developed with the object of alleviating or overcoming these difficulties. Cain' and \Tatters2 recommend devices for the separation of the manganese. Cornelius3 and Dedericks,* although not particularly concerned with the analysis of+'steel, have recommended procedures available for the quantitative separation of manganese from chromium and vanadium. Talminger6 has proposed a method of t h e latter type, using von Knorre's procedure, viz., the precipitation of manganese by ammonium persulfate. KoesterO has investigated Engel's method for the electrodeposition of manganese in the presence of chromium, and finds chromium occluded. Cain' finds t h a t the Ford-Williams method gives high results due t o the occlusion of chromium. Even in the Volhard-WoX8 method chromium and vanadium interfere. The two methods most in use for the determination of manganese in steel are known as the persulfate and bismuthate methods. I n the first of these the manganese in a nitric acid solution of the steel is oxidized with ammonium persulfate and silver nitrate, after which it is titrated with sodium arsenite. Wdowiszewskig reports good results with this method, even in the presence of I per cent chromium. I n this laboratory, however, i t has been noted t h a t the method rapidly becomes less useful as the percentage of chromium rises, owing t o the obscurity of the end-point. I n the bismuthate method the manganese in a solution of the sample is oxidized with sodium bismuthate, the excess filtered out and an added excess of ferrous sulfate titrated with permanganate. Here even a trace of chromium may cause trouble and this difficulty rapidly increases with the larger percentage of chromium often met in commercial steels. By cooling t h e solution thoroughly with ice before oxidizing the manganese the tendency of the chromium t o oxidize is depressed, and if this procedure is followed by rapid filtration fairly satisfactory determinations of manganese may be made even in the presence of 5 per cent of chromium in the sample. The consistently successful analysis of such material by this method, however, requires a high degree of skill. Demorestlo suggests titrating the solution with sodium arsenite until the color of the permanganate disappears. He h a s tested this method by titrating solutions of steel t o which chromium corresponding t o 3 per cent of 1
THISJOURNAL, 3 (1911), 630.
Met. b Chem. Eng., 9 (1911), 244. Phnrm. Ztg., 68, 427. 4 I b i d . , p. 446. 6 Chem -Ztg., 34 (19101,1877. a 2. Elektvochem., 17 (1911),57. 7 L O G . cit 8 Stahl u . Eisen, 88 (1913). 633. 9 I b i d . , 28 (1908),1067. bo THISJOURNAL, 4 (1912), 19. 2
8
I9
the weight of the sample has been added as chromate immediately before titrating. Under the usual conditions of analysis most of the chromium is present as chromic salt and such amounts of chromium in this state make the end-point obscure. I n the presence of 5 per cent or more of chromium all of these methods, except those which involve the separation of manganese, are extremely uncertain. I n this paper we describe a method which has sufficient :accuracy for all technical purposes and which, without the separation of chromium and vanadium, is not interfered with b y these elements under t h e conditions of analysis. The oxidation of the manganese in this method may be accomplished either by the bismuthate or persulfate procedures, and titration is made electrometrically, using mercurous nitrate as the reducing agent. I n the course of the examination of a long list of reducing agents this was the only reagent found which would reduce permanganate quantitatively and rapidly a t ordinary temperatures without reducing chromates or vanadates. THE
STANDARDIZATION
OF
THE
MERCUROUS NITRATE
SOLUTION I O . 5 g. of mercurous nitrate are dissolved in I j o cc. of water t o which 2 cc. of nitric acid have been added. Any undissolved salt is removed by decantation and the solution made up t o a volume of one liter. This is compared electrometrically on the apparatus made for this laboratory by the Leeds & Northrup Company,1 with a solution of potassium permanganate which has been standardized against sodium oxalate. The permanganate solution contains 0 . 5 g. of Mn per liter, each cc. being equivalent t o o . o j per cent of Mn in a I-g. sample of steel. The medium in which the titration is made is a solution containing 50 cc. of sulfuric acid (sp. gr. 1.58) and zoo cc. of water. The:temperature should not be above 40'. For purposes of this titration, permanganate is added t o the solution in any convenient amount and titrated with mercurous nitrate. The details of the titration will be given a t a later point in this article.
THE REACTION
When titration is complete, the solutions have a brown color suggesting dissolved manganese dioxide. The solutions, however, appeared t o be quite stable. When- solutions containing I O cc. of permanganate had,been titrated and were allowed t o stand in a stoppered Erlenmeyer flask a t room temperature, no precipitates appeared after some weeks. Filtration removed only a small amount of the solids. With solutions containing as much as 40 cc. permanganate solution, a faint turbidity appeared after 24 hrs. On warming, even t o 40°, manganese dioxide was precipitated. After titrating 40 cc. of the KMn04 solution with mercurous nitrate, t h e titration was continued with ferrous sulfate of equivalent concentration on t h e same apparatus. This was found t o require 1 2 CC. 1
THIS JOURNAL,^ (19171,780.
20
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
of ferrous sulfate. It is believed t h a t the latter reaction was the reduction of quadrivalent manganese t o the bivalent state. Our efforts t o prove this point were not entirely successful. When the solutions after titration were warmed, both in the original volume of 2 j o cc., and diluted t o larger volumes up t o one liter, t h e amount of MnOz precipitated varied in a n uncertain manner. Changing the temperature from 40' t o boiling did not serve t o indicate a procedure which would give consistent results. The MnOz so precipitated was collected on asbestos and, after washing, mixed with dilute sulfuric acid. An excess of ferrous sulfate was then added and t h e solution titrated with permanganate electrometrically. From 8 t o I O cc. of ferrous sulfate were required for titration, an amount always less t h a n t h a t required for a similar titration before precipitation. One possible explanation of this is t h a t t h e manganese dioxide as formed is in a hydrated condition and while in this condition it may be t h a t i t very readily undergoes decomposition in part into manganous sulfate and oxygen. T h a t there is a diminution in oxidizing power by precipitation is shown by the fact t h a t t h e oxidizing power of the precipitate and filtrate combined is insufficient t o oxidize 1 2 cc. of ferrous sulfate as is done when t h e titration with ferrous sulfate is made without precipitation. I n t h e foregoing discussion 40 cc. of t h e solution were taken as a unit in t h e study of the quantitative precipitation of manganese dioxide. I n t h e discussion which follows we shall adhere t o this volume. T o determine t h e amount of mercurous salt present in the mercurous nitrate solution 40 cc. were diluted to 2 0 0 cc., and 2 0 0 cc. of a solution containing j g. of sodium chloride gradually added with stirring. This was followed by t h e addition of I O g. of sodium acetate in t h e form of a filtered solution. The precipitate was washed with water containing a little sodium chloride and finally with water alone. It was dried a t I jo'. Two determinations gave 0 . 3 0 0 5 g. and 0.2999 g., respectively. The Hg2(N03)? present in 40 cc. of this solution was found from t h e average of these determinations t o be 0.3340 g. From t h e data supplied by t h e known concentrations of the permanganate and mercurous nitrate solutions, and from t h e oxidizing power of the solution towards ferrous sulfate after titration with permanganate, we can construct t h e following equation: 4 MnVI1
+ 14 Hg'
=
3 MnIV
+
I
Mn"
+ 14 Hg"
Basing our calculation on the known strength of the permanganate solution, theory requires t h a t t h e mercurous nitrate in 40 cc. should be 0.3346 g., which corresponds closely with 0.3340 g. found. Correspondence is also found in t h a t 1 2 cc. of an equivalent solution of ferrous sulfate would be required for t h e reduction of three atoms of quadrivalent manganese. While the reaction given above quite certainly indicates with accuracy t h e oxidizing power of t h e s o h tion as left after titration, i t has seemed t o us necessary t o make an effort t o secure additional information
1701.
IO,
No.
I
in its support. We give below a brief outline of some of our observations with their implications as understood by us, omitting, however, experimental details because of t h e inconclusive character of t h e work. When manganous sulfate' is added t o t h e solution of permanganic acid before titration with mercurous nitrate, i t has the effect of diminishing the amount of mercurous nitrate necessary. The effect, however, is not a regular one, for t h e addition of small amounts of manganous salt produces -a proportionately larger effect upon t h e titration t h a n large additions. Such additions noticeably alter t h e color of the solution, changing i t from brownish yellow t o brownish red, suggesting t h e formation of manganic salts. Barnebey1 reviews t h e explanations which have been offered t o account for the effect of manganous salts upon the titration of ferrous iron with permanganate in t h e presence of hydrochloric acid. H e quotes Volhard as suggesting t h a t t h e action of manganous salts on t h e permanganate results in the formation of quadrivalent manganese, while Birch suggests t h e formation of trivalent manganese. When t h e solution after titration with mercurous nitrate is treated with manganous salt, t h e same reddish color appears as when the manganous salt is added before titration. If we are correct in our belief t h a t the product of t h e reaction is manganic sulfate in both instances, this would constitute additional evidence of the presence of quadrivalent manganese in the titrated solution. From the fact t h a t we are unable t o remove MnOz from t h e solution by filtration after titration, this substance, if present, must be evident either as a sulfate or in the colloidal condition. Witzemann,2 discussing the conditions under which colloidal solutions of manganese dioxide are stable, points out t h a t small amounts of either salts or acids cause immediate precipitation. Evidence for the existence of sulfates of quadrivalent manganese is meagre. Fremy3 states t h a t MnO(S04) is formed b y acting on hydrated MnOz with concentrated sulfuric acid in air. The fact t h a t a moderately high concentration of sulfuric acid is necessary t o prevent t h e precipitation of manganese dioxide in this titration may be construed as indicating t h e formation of a sulfate of quadrivalent manganese. From the reaction as given above it appears t h a t after titration one-fourth of the manganese is present as manganous salt. We precipitated the quadrivalent manganese by boiling a diluted solution and determined t h e manganese in the filtrate. The filtrate from the titration of 40 cc. of permanganate should have contained t h e equivalent of I O cc. of this solution. We always found i t t o be larger t h a n this (about I j cc.), as might have been expected from t h e fats t h a t the manganese dioxide precipitated was always too small in amount t o correspond t o t h e theory. Blum4 states t h a t precipitated manganese dioxide is not 1 9
a 4
J . A m . Chem. Soc., 36 (1914), 1441. Ibid., 37 (1915), 1079. compl, 83 (1876), 475. J . A m . Chem Soc., 84 (1912), 1394.
Jan., 1918
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 CHEMISTRY
oxidized by sodium bismuthate in nitric acid. We added 3 0 cc. of nitric acid (sp. gr. I . 13) t o a solution in which 40 cc. of permanganate solution had been titrated and which therefore probably contained quadrivalent manganese. The solution was then oxidized with sodium bismuthate, filtered through asbestos arid titrated. The average of four determinations indicated a manganese content corresponding t o 3 I . 5 cc. of t h e permanganate solution. T o test t h e completeness of oxidation of manganous salts under these conditions, we oxidized a solution of manganous sulfate in a similar mixture of acids and found t h e oxjdation t o be complete. Our failure t o secure a n amount or permanganic acid corresponding t o 40 cc. of t h e original solution of permanganate may have been caused by t h e failure of t h e quadrivalent manganese t o oxidize completely, owing t o t h e nature of t h e solution. A colloidal solution of manganese dioxide, if i t were possible for i t t o exist, might be expected t o react as in this case. From the foregoing and other considerations, our quandary as t o t h e course of t h e reaction may be set forth as follows: ( I ) The relation of permanganate and mercurous salt seems t o be definitely established. ( 2 ) The presence of manganese corresponding in oxidizing capacity t o 3 MnOz for 4 K M n 0 4 reduced, appears equally certain. (3) The presence of so large a n arnount of bInOz apparently in solution or suspension seems improbable. (4) The solution upon filtration through paper or asbestos after titrating leaves too much on t h e filter t o correspond t o complete solution. (j) If we accept t h e statement t h a t undissolved manganese dioxide is not oxidized by sodium bismuthate in nitric acid solution, less t h a n onefourth of t h e manganese can be present in t h a t form instead of three-fourths as shown in t h e reaction. (6) The ease with which warming t h e solution precipitates MnOz from these solutions after titration might correspond t o the precipitation of suspended manganese dioxide or t o the decomposition of trivalent or quadrivalent manganese sulfates. It is not impossible t h a t t h e reaction might lead t o z n/In(S04)2 Mn2(S04)3, b u t t h e color of t h e solution after titration does not indicate t h e presence of manganic salt. ( 7 ) The red color produced by t h e addition of manganous salts t o t h e titrated solution is probably due t o t h e formation of manganic salts and therefore furnishes evidence of t h e probable presence of compounds cf quadrivalent manganese. The fact t h a t a red color is not produced by interaction between t h e MnIV and MnI' shown in t h e reaction we explain as due t o :he low concentration of Mn", for t h e effect described appears only when relatively large additions of manganous salt are made. (8) Since t h e final equilibrium corresponds t o t h e disappearance of septivalent manganese and t h e formation of compounds of quadrivalent and bivalent manganese, we are a t a loss t o understand why t h e reaction should not have been either 2 hlnVII 6Hg' = z MnIV 6 Hg" or z MnVII 8 Hg' = MnIV + Mn" 8 Hg" instead of t h e more complex one first shown, which is t h e sum of these.
T H E T I T R A T I O N O F P E R M A N G A N I C ACID I N T H E P R E S E N C E O F CHROMATES A N D VANADATES
This titration is best carried out in t h e presence of a moderately high concentration of sulfuric acid. W e have used 5 0 cc. of acid of sp. gr. I . j8, and 2 0 0 cc. of water. With a lower concentration of acid, manganese dioxide separates from solution and irregular results are obtained i n titration. Sitric acid does not interfere, b u t i t must be free from nitrous acid, which is best accomplished by treating it with a small amount of sodium bismuthate and filtering t o remove the excess. T o titrate permanganic acid, the resistance of the electrometric titration apparatus is adjusted t o bring t h e beam of light on t h e scale. During t h e addition of the mercurous salt the beam remains stationary or shows a slight anomalous rise of potential until the end of the titration is approached. At this time the addition of more mercurous nitrate causes t h e beam t o move in t h e opposite direction from which it returns more or less slowly after each addition until the endpoint is reached, when it usually remains off the scale. The addition of a few drops of KMnOe serves t o cause it t o return. The titration having been carried out rapidly t o this point, may be completed by adding the mercurous nitrate solution drop b y drop. T h e end-point is sharp, and it is not affected by t h e presence of chromates or vanadates, b u t it is subject t o the influence of temperature. TABLEI-THE
TITRATION OF P O T A S S I U M PERMANGANATE WITH MERNITRATE IN THE PRESENCE O F CHROMATES AND VANADATES Titrations made in 50 cc. His04 (sp. gr 1.58) and 200 cc. Hz0 KMn04 Hgz(N0s)z G. Cr as G. V as cc. cc. Chromate Vanadate None None 5.0 5.0
CUROUS
5.0 10.0 10.0 20.0 20.0 40.0 40.0
5.0 9.95 9.95 19.85 19.90 39.85 39.80
+
+
+
0,020
0 020
None
None
0.020
0 020
0.020
0.020
None
None
0.020
0.020
None
None
TABLE 11-THE INFLUENCE OF TEMPERATURE Volume and Concentrations as in Table I Temperature
KMn04 cc.
+
+
21
SO 0
20.00
HgZ(r\T03)2
cc. 19.90 19 90 19 95 19 90 19.90 19.95 21.1 21.4
The titrations shown in Tables I and I1 were made with a solution of permanganate containing 0 . 0 0 0 5 g. of h/In per cc. This corresponds t o 0 . 0 5 per cent M n in a I-g. sample of steel. T H E D E T E R M I N A T I O S O F MANGANESE I N S T E E L A F T E R OXIDATION W I T H SODIUM B I S M U T H A T E
This method of oxidation is carried out exactly a s described by B1air.l After filtering, a small piece of ice is added, followed by 5 0 cc. of sulfuric acid (sp. gr. I . 5 8 ) . The volume should be 2 5 0 cc. and t h e temperature not above 40° at t h e time of titration. The procedure in titration is then as described above (Table I). I n Table I11 analyses of samples of steel issued b y t h e Bureau of Standards are given. T o certain of 1
"The Chemical Analysis of Iron," 7th Ed., p. 122.
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
22
these, 0 . 0 2 g. Cr as chromate was added immediately before titration. TABLE 111-ANALYSES OF STEELS WITH
AND WITHOUT CHROMIUM ADDEDA S CHROMATE AFTER OXIDATION WITH SODIUM BISMUTHATE -Mn FOUNDNo Cr 0.020 g. SAMPLE Added Cr Added M n PRESENT$ 9a 0.895 0.910 0.915 0.910 sa 0.850 0.550 19a 0.860 19a 0.560 30* 0.563 0.565 30 0.155 0.156 3 1* 0.160 31 0.215 32* 0.216 0.220 32 0.305 0.300 35 35 0.310 Sample 30 contains 1.35 percent Cr and 0 . 2 1 per cent V; Sample 31 contains 3.51 Der cent Cr and 19.55 aer cent W: . Samule - 32 contains 0.89 per cent Cr. t Except on Samples 30 and 31 the official values given throughout this paper are those obtained by bismuthate oxidation.
*
I n oxidizing manganese with sodium bismuthate in steel containing chromium, i t is customary t o add large amounts of ice and t o filter quickly, for in cold solutions in which the bismuthate is allowed only a short time t o act t h e oxidation of chromium is reduced t o a minimum. Success in this method, however, depends largely upon compensating errors, for some chromium is always oxidized and t h e oxidation of manganese tends t o be slow or incomplete a t these very low temperatures. I n this new method we had much better success by oxidizing between 2 0 and 35'. The only danger here is t h a t after the removal of t h e bismuthate the permanganate may oxidize some of the chromic salt, being itself reduce& When the titration is made with ferrous sulfate and permanganate That it in the ordinary way this causes no error. does not cause error in this method can be due only t o the fact that a t temperatures below 40' the oxidation of chromium by permanganate proceeds slowly. It is a t once evident, however, t h a t with high percentages of either chromium or manganese the danger of error from this source will be diminished ( I ) b y oxidizing in the neighborhood of 20°,'(2) b y adding ice after oxidation is complete and befoie filtering, and (3) by titrating immediately after filtration. TABLEIV-DETERMINATIONOF MANGANESE IN STEELS CONTAINING SAMPLES
17 PER CENT OF CHROMIUM Mn Found after Separation 0.385 0.260
............... .................
A 1201.. A 1204
Mn by Electrometric Titration 0.395 0.258
I n Table IV manganese is shown as determined in steels containing 17 per cent of chromium. Since these steels are not readily soluble in nitric acid, t h e samples were dissolved in hydrochloric acid and repeatedly evaporated t o a small volume with nitric acid. The solutions were then oxidized with sodium bismuthate as usual. Manganese was also determined in these samples after precipitation with ammonium persulfate. I n Table V the influence of time is shown where the percentages of chromium and manganese are both high. Bureau of Standards' Sample g a was treated with I g. of potassium dichromate before solution a n d I g. afterwards. This gave rise t o a very large amount of chromic salt as well a s much chromate. These solutions were then titrated after different intervals.
Vol.
IO,
No.
I
Where such large amounts of chromium are present (over 30 per cent) i t would be safer t o oxidize both the chromium and the manganese. EFFECTOF TIMEUPON THE MANGANESE FOUND WHEN THE PERCENTAGES OF BOTHMANGANESE AND CHROMIUM ARE HIGH Time of Standing after Filtration2 Percentage Percentage Minutes Found Present 0.895 0.915
TABLE V-THE
0.910 ~._..
10 10 20 20
0.875 0.815 0.830 0.885
.... .... .... .... ....
To test the suitability of t h e method for determining the higher percentages of manganese, we dissolved the Bureau of Standards sample of manganese ore, No. 25, in hydrochloric acid and evaporated with sulfuric acid until fumes appeared. It was then diluted t o a liter. To portions of this representing 0.04 g. of the sample, nitric acid and sodium bismuthate were added. Fourteen titrations gave results ranging from 56.17 t o 56.44. The average was 56.27. Bluml says t h a t t h e most probable value for the manganese in this sample lies between 5 6 . 2 0 and 56.30. While these results are good t h e method is not recommended for determinations where such a high percentage of accuracy is needed as is the case in ores and ferro-manganese. I n steels a n error of one- or two-hundredths of a per cent is almost unavoidable under all methods and is rarely import a n t , It is in this field t h a t t h e usefulness of t h e method lies. T H E DETERMINATION
OF MANGANESE I N S T E E L A F T E R
OXIDATION W I T H AMMONIUM P E R S U L F A T E
One of the advantages of the ammonium persulfate method for determining manganese is t h a t the filtration of the solution is not necessary. Where many routine determinations are made this is a valuable quality in a method because of the time saved. We accordingly attempted t o develop this method for use on the electrometric apparatus. I n titrating permanganate in sulfuric acid with mercurous nitrate in the presence of ammonium persulfate the relation of one solution t o the other is slightly different from t h a t which obtains when the persulfate is absent, but the relation is definite. This titration has t h e disadvantage of being more sensitive t o temperature differences than is the, titration in sulfuric acid alone. However, i t gives results generally accurate enough for most technical purposes. TABLE VI-THE
TITRATION OF
POTASSIUM PERMANGANATE I N TAB PRESAMMONIUM PERSULFATE Solutions contained 50 cc. Has04 (sp. gr 1.58) 2 g. amyonium persulfate and 200 cc. of water. Tempeiature, 20 Cc. KMnOa Cc. Hga(N0a)a Factor' 10.0 9.9 1.010 10.0 9.8 1.020 20.0 19.5 1.026 20.0 19.5 1.026 30.0 29.0 1.034 1.031 30.0 29.1 40.0 38.8 1.031 40.0 38.8 1.031 1 T h e subtraction of a blank of 0.1 cc. from the mercurous nitrate makes the factor more nearly constant.
ENCE OP
I n Table VI titrations of potassium permanganate a t 20' are shown. The effect of temperature is demonstrated in Table VII. 1
LOG.cit., p. 1396.
Jan., 1918
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
TABLE VII-THE
INFLUENCE OF TEMPERATURE UPON THE TITRATION OF POTASSIUM PERMANGANATS IN THE PRESENCE OF AMMONIUM PERSULFATE The solution was identical with that used in Table VI Temp. OC. Cc. KMnO4 Cc. Hgz(N0s)z Factor 10 20 19.6 1.020 10 20 19.7 1.015 15 20 19.5 1.026 20 19.5 20 1.026 20 20 1.026 19.5 25 20 1.020 19.6 30 20 1.010 19.8 35 20 1.010 19.8 20 35 20.5 0.97 20 35 20.0 1 .oo 40 19.8 20 1.01 40 21.0 20 0.95 60 20 21.6 0.93 60 20 21.8 0.92 80 20 21.6 0.93 20 80 22.0 0.91
I t will be evident from the results shown in Table VI1 t h a t the temperature of t h e solution should be kept close t o z o o C. The increase in the amount of mercurous nitrate used in titrating a t the higher temperature is undoubtedly due t o the partial reoxidation of the manganese. A t low temperatures this proceeds so slowly as t o cause no trouble. Additional difficulties arise in trying t o work a t temperatures above 40' C. in t h a t the behavior of the galvanometer is irregular. When the steel is dissolved in nitric acid i t is not generally possible t o use more than 0 .z g. of the sample. We have found a preferable procedure t o be the use of a 0.5 g. sample in sulfuric acid. However, where the manganese is below 0 . 5 per cent I g. samples may be used. Our method is t o dissolve 0 . 5 g. of the steel in 65 cc. of sulfuric acid of sp. gr. I . 2 0 and when solution is complete t o oxidize with nitric acid added dropwise. After boiling a minute or two the E,olution is diluted with hot water t o a volume of zoo cc., heated t o boiling and I O cc. of silver nitrate solution ( 2 . 5 g. in a liter) and 2 0 cc. of ammonium persulfate solution (100 g. in a liter) added. Boiling is allowed t o continue about one minute when the solution is allowed t o cool slowly, or rapidly with the aid of ice, according t o convenience. When the solution is nearly cool enough, a little more sulfuric acid is added and the solution adjusted t o about zoo. Titra.tion is then made. At the time titration is made in this method all of the chromium and vanadium present in the steel is in the oxidized condition, while in the method previously described these elements are oxidized only in part by the sodium bismuthate. I n Table VI11 analyses of Bureau of Standards sample steels are shown, some of which already contain chromium and vanadium, but an additional amount of chromium as chromate has been added in alternate determinations t o illustrate the independence of the presence of' chromic acid shown by this method. Samples weighing 0.5 g. were used and titration was made with permanganate and' mercurous nitrate of such strength t h a t I cc. was equivalent t o 0 . 0 5 per cent in a half-gram sample. I n this method it is not important t o make the titrations a t once, as in the case after the filtration following oxidation with sodium bismuthate. Eight portions of Sample 35 were oxidized a t the same time
23
TABLEVIII-THE
DETERMINATION OR MANGANESE IN STtELS AFTER OXIDATION WITH AMMONIUM PERSULFATE Temperature, 10 to 25' C. Volume, 250 cc. Sample, 0.5 g. -Mn FOUND--? 0.02 g. Cr Added as N o Cr Chromate Added 0.896 0.896 0.900 0.902 0.844 0.844 0.830 0.850 0.545 0.556 0.556 0.558 0.158 0.154 0.165 0.144 0.205 0.220 0.299 0.301 0.298 0.309
SAMPLE 9a 9a 19a
1 -Q_A-
30 30 ..
31 31
32 35 35
M n PRESENT 0.915 0.850 0.563 0.156 0.216 0.300
and titrated a t intervals during the succeeding 524 hrs. The lowest result was 0.298 and the highest 0.314 less t h a n 0 . 0 2 per cent difference. The two methods have been in use in this laboratory during some months. Young men without previous chemical training and with only a few weeks' experience in laboratory work after a few minutes' instruction have been able t o make analyses of steels containing chromium, vanadium, molybdenum and tungsten, which could have been made by other methods only by men of large experience and a high degree of skill. Approximately a thousand determinations have been made by these methods and compared with other standard methods. SUMMARY
I-A method has been shown for the determination of manganese in the presence of chromium or vanadium. 11-A method in two modifications has been shown for the electrometric determination of manganese. 111-A study of the reaction between permanganic acid and mercurous nitrate has been made. IV-The method does not require special skill for its application. RESEARCH DEPARTMENT MIDVALE STEELCOMPANY PHILADELPHIA
REAGENTS FOR USE IN GAS ANALYSIS VI-THE ABSORPTION OF HYDROGEN BY SODIUM OLEATE By R. P. ANDERSON AND M. H. KATZ Received August 16, 1917
Bosshard and Fischlil have suggested the use of a solution of sodium oleate containing nickel in suspension, for the gas-analytical absorption of hydrogen. Inasmuch as they did not determine definitely the optimum conditions for the use of the reagent or its specific absorption,2 experiments were undertaken t o obtain data on these points. At the very outset the authors met with the difficulty of not being able t o duplicate the results of Bosshard and Fischli in getting complete absorption of hydrogen. After various attempts, the method was abandoned, and this note has beell prepared for publication in order t h a t this experience with t h e reagent may be placed on record. The procedure t h a t is recommended by Bosshard 12.ongew.
Chem.. 28, I (1915). 365. THISJOURNAL, 1 (1915).587.
a Anderson,
