Extraction of Slag and Oxide Inclusions in Iron or Steel Electrolytic Method FRANK W. SCOTT,Inland Steel Co., East Chicago, Ind.
.
ANY methods of exA f i ELECTROLYTIC method, rapid, simple T h e o u t e r cell i s a l a r g e Of about t r a c t i o n other than in operation, and inexpensive, f o r the determouth reagent 3 liter capacity, with a cork to electrolytic have been mination of oxides found in plain carbon steel fit. The inner cell is a devised for the determination and iron as inclusions, has been successfully r e a g e n t bottle with the b o t of non-metallics in iron and steel, developed. Magnesium iodide is used as the tom cut off. The cork of the but none have been satisfactory for all t y p e s of o x i d e s . The electrolyte and is found to be superior to a n y outer cell has a hole cut in it to fit the neck of the inner cell, and outstanding method a t the presused heretofore. these are fastened together so e n t t i m e is t h e D i c k e n s o n The sulfides are not determined, but only the as to support the inner cell. method (2)which will extract silioxides of manganese, silicon, and iron. I n the The cork f i t t i n g t h e s m a l l e r con dioxide and aluminum oxide “killed” steels where the principal inclusion is bottle has a hole punched in from “killed” steels with varying degrees of accuracy. However, manganous silicate, the recovery is practically it for the platinum wire to pass this m e t h o d will n o t give a 100per cent; in the “rimmed” steels, slighfly less. through* The cathode is made of the quantitative extraction of incluT h e accuracy of the method has been deterordinary copper Screen used in sions which contain ferrous and mined through the use of slaggy material containw i n d o w screens. A piece is manganous oxide from ‘‘riming various percentages of ferrous, manganous, cut as long as the circumference ming” steels (4). In fact, after a detailed study of .extraction and as wide as the straight sides silicon, and aluminum oxides. This material methods proposed to date and of the large bottle. Two strips was actually formed in the rimmed ingot of steel, of screen are f a s t e n e d as conoutlined by C. H. Herty, Jr., and was collected for the study. It is believed tacts to the screen It is and others (4),and by Westcott, that such material is a definite improvement over then rolled up and inserted into Eckert, and Einert ( 7 ) ,it is seen the use of synthetically prepared compounds, as the bottle, where it unrolls and that none are satisfactory for use upon steel. A l a r g e s a m p l e it is the same physically and chemically as the forms a cylinder. The contact must be used, as it is absolutely inclusions dispersed throughout the steel itself. s t r i p s a r e b e n t d o w n on the outside of the bottle neck and necessary, in a study of inclufastened together with a third sions, to have enough non-metallics extracted for the determination of their physicaland chemi- band of wire screen. Figures 1 and 2 show the cell in detail. cal properties. Also the extraction must b e fairly rapid and PREPARATION OF ELECTROLYTE must not require from 2 to 6 weeks as does the Dickenson The electrolyte used is magnesium iodide solution conmethod. As regards previous work on electrolytic methods, nothing taining a small amount of free iodine, Magnesium was was found regarding the extraction of oxide impurities from chosen because it should, and actually does, prevent the steel. It has been shown that manganous oxide could not be formation of ferrous hydroxide owing to magnesium hydroxide extracted in an acid or ferrous sulfate solution ( 5 ) . being less soluble. As the solution becomes slightly more I n the steel industry a constant effort is being put forth to alkaline due to evolution of hydrogen during electrolysis, make a better product, and a cleaner steel is one of the desired magnesium hydroxide is precipitated. However, very little achievements. However, before the cleanliness of steels precipitation does occur, and the iron is plated out without produced by various means can be compared, a method must being hydrolyzed. Magnesium iodide is a good conductor, be found to determine the amount, the character, and the and iron can be plated out at the rate of 1 gram per hour a t 1 source of the oxide impurities. This paper gives a method for ampere and 4 volts. the extraction of these oxides from a solid block of steel, and it To make 3 liters of solution, 120 grams of resublimed iodine has bcen found to be better than any method published or are weighed into three 600-cc. beakers, and 400 cc. of distilled suggested to date. water added to each. Metallic magnesium is added gradually with stirring, until the iodine color disappears. The solution DESIGNOF CELL is filtered and 5 grams of iodine dissolved in it, and enough The design of the cell has required much consideration and distilled water added to make the solution to 3 liters. It is experiment, but the one finally chosenis simple of construction, then ready for use. costs only a few cents to make, and is easy to manipulate. It The same solution may bc used repeatedly by filtering after consists of two parts, an inner cell separated from the outer by each determination, and dissolving 5 grams of iodine in it. means of a piece of filter paper. The steel or iron specimen is PREPARATION OF STEEL SPECIMEN suspended in the inner cell by means of a platinum wire; the iron and metallic constituents go into solution, are ionized, and The size of the specimen is controlled by the time desired to pass from the inner cell to the outer through the filter paper, spend on the determination and the cleanliness of the steel. and are plated out on the copper-screen cathode. The carbon, Ordinarily a 50-gram specimen is large enough. The portion sulfur, and oxides remain in the inner cell and are collected in to be decomposed is submerged in the solution, and the rea filter paper cone which is removed for study of the residue. mainder is unaffected. 121
122
ANALYTICAL EDITION
Any shape or size may be used. It must be filed clean of all oxides and cleansed of grease and oil. A platinum wire is wrapped around one end of the specimen and the contact protected by a piece of rubber sheeting or tubing held in place by rubber bands. It is also a good plan to coat the rubber and any part of the specimen not submerged with collodion to prevent corrosion and rust. The weight of the sample a c t u a l l y used is found by weighing the piece before and after electrolysis, as there is always a little piece left, held by the contact above the solution.
Vol. 4, No. 1
about 200 cc. being sufficient. If the steel has had silicon added to it, 150 cc. of boiling hot 10 per cent potassium hydroxide are used as a wash, allowing it to filter by gravity, This will remove all silicic acid, and does not dissolve any manganous oxide. Rimmed steel does not receive this alkali wash. The residue is then washed free of alkali with boiling hot water. The residue and paper are dried, and the carbon burned out at a low red heat. Although many methods may be used for the analysis of the oxides, the following is suggested: The ignited residue is placed in a platinum dish and dissolvedin 10per cent hydrochloric acid containing 15 cc. of 25 per cent sulfuric acid. As soon as the iron oxide goes into solution, the glassy particles of silicates and the white aluminum and other oxides may be seen. The solution is boiled down and the sulfuric acid fumed strongly to dehydrate any dissolved silica. This is cooled, the sulfates ASSEMBLYOF CELL AND dissolved in a little hot water and a few drops of nitric acid, ELECTROLYSIS and the silica is filtered off. This is ignited and determined as silicon dioxide by volatilization with hydrofluoric acid. When the cell is made, the The residue from the silica volatilization is fused with electrolyte prepared, and the potassium bisulfate until it is decomposed. It is then leached steel specimen fastened to the out in the filtrate from the silica. This solution is made FIGURE 1. CELLASSEMBLED wire, the determination may strongly ammoniacal, and the hydroxides are filtered off. be started. An ashless 11- The precipitate is dissolved in nitric acid, reprecipitated with 1. Outer oell 2. Inner oell cm. filter paper is folded as for ammonia, filtered, and washed with hot water. It is then 3. Copper-soreen cathode use in a funnel and slipped dried, ignited, and weighed as iron oxide. I n low-carbon 4. Contact strips 6. Cork support for inner cell into the inner cell so as t o act steels, below 0.10 per cent, this is the iron from the ferrous 6. Cork support for steel speoimen 7. Platinum-wire contact to specias a receiver for the oxides. oxide of the steel and is considered as such. In higher carbon men An 11-em. h a r d e n e d filter steels, it is often contaminated with an appreciable amount of 8. Steel Bpecimen 9. Filter-paper cone to colleot paper is f a s t e n e d over the oxides metallic particles and is calculated as metallic iron. The total 10. Filter paper Separating cella b o t t o m of t h e i n n e r cell silicon dioxide and manganous oxide found in the residue are by means of rubber bands. corrected for the silicon and manganese coming from the The steel specimen is placed so ai to touch the center of the metallic residue, as shown by the steel analysis. This is filter-paper cone, and is supported by the wire passing through especially important in killed steels with 0.80 to 1.00 per cent the hole in the cork of the bottle. carbon and high manganese and silicon contents. The electrolyte is poured into the large cell, the wire screen connected to the negative terminal of a 12-volt storage battery, and the inner cell placed in position. It gradually fills with the solution coming in through the filter paper. The current is regulated by means of a variable resistance in the circuit, and held a t 1 ampere. A greater amperage may be used, but the temperature will become too high and the ferrous iodide will be decomposed. The best temperature for the operation should be below 25’ C. As the sample becomes FIGURE 2. CELLPARTSUNASSEMBLED smaller, more voltage must be impressed to maintain 1ampere. The cell will operate until the steel is decomposed to the The iron oxide contains a small amount of manganese surface of the solution. tetroxide (MnaOr) and aluminum oxide, and therefore it is fused with potassium bisulfate until it is all in solution, cooled, TREATMENT OF RESIDUE AND ANALYSIS OF OXIDES leached out, and added to the filtrate from the iron determinaWhen the electrolysis is complete, the inner cell is removed, tion. This is then boiled down to 75 cc. and transferred to a and the solution allowed to drain. The rubber bands are cut 300-cc. Erlenmeyer flask. To the solution in the flask, 30 cc. of acid mixture (1313 cc. and the paper used to separate the two solutions removed. The filter-paper cone containing the oxides and carbon of water, 625 cc. of concentrated nitric acid, 325 cc. of phos“skeleton” is placed in a weighing bottle. Two grams of phoric acid, 250 cc. of sulfuric acid); 15 cc. of silver nitrate iodine are added, the paper torn up with stirring, and the solution (16 grams in 2000 cc. of water); and 20 cc. of ambottle filled with alcohol. The solution is allowed to stand, monium persulfate solution (600 grams in 2040 cc. of water) stoppered, with frequent stirrings, for at least 24 hours. This are added. This is brought t o the boiling point and allowed to treatment will decompose small metallic particles which boil briskly for 1 minute, and is then cooled to 20” C. Cold have fallen from the specimen. However, in high-carbon water (75 cc.) is added and the manganese titrated with a steels, it is practically impossible to remove all the steel standard arsenite solution (1 cc. = 0.0005 gram of manbecause of the carbon coating of the particles. Several ganese). This gives the total manganese, and after correctalcoholic treatments with iodine will remove all but a small ing for the trace due to metallic contamination, is calculated as manganous oxide. This method is as accurate as the amount, from 1 to 10 mg. of iron. The residue is then filtered by suction on an ashless KO.589 bismuthate method and probably less open to error. If the aluminum oxide is desired, the silver nitrate is “Blue Ribbon” paper, using a platinum cone. It is washed several times with small amounts of alcohol, and then with removed as silver chloride, and the aluminum determined as cold potassium iodide solution, until the washings are no aluminum phosphate after separating the iron from the longer the color of iodine. It is then washed with cold water, aluminum with an excess of sodium hydroxide. The first
IXDUSTRIAL AND ENGIXEERING
January 15, 1932
precipitation always contains a trace of iron and must be purified by a t least one other separation. It is perhaps better t o determine the aluminum oxide on a separate sample using the direct hydrochloric acid method for separation
CHEMISTRY
oxides were then analyzed to determine the effect of the treatment. The analyses are given in Table 11. These oxides were not the usual synthetic oxides prepared in the laboratory but were material taken from various rimmed ingots. They were the same as the inclusions dispersed throughout the steel, but which, during the rimming action, rose and were trapped in the upper portions of the ingot, These oxides are actually, chemically, and physically similar to the slags found in the steel as inclusions, and as such are much superior to the synthetic product for these experiments. Of course, the composition cannot be controlled, but i t was found that in the six samples collected none were alike. The analyses of these slags are shown in Table I. TABLEI.
COMPOSITION OF SLAGS
CON0TITUENT
MNO IN MANGANOUS slLlC4TE,'/o FIGURE3. EFFECTOF ELECTROLYTIC EXTRACrION ON MnO
and determination as aluminum phosphate in ammonium acetate solution. However, it may be determined satisfactorily on the solution containing the manganese as given above.
ACCURACY OF DETERMINATION The accuracy of the electrolytic extraction and recommended treatment of the oxides has been studied and found to give better results than any method used heretofore. It is known that all the manganese and ferrous sulfides are decomposed by the iodine to form free sulfur and the corresponding iodide. A wet oxidation and gravimetric determination of the sulfur in the electrolytic residue, calculated in terms of grams of steel electrolyzed, will give the ordinary sulfur determination on the steel drillings. There is no evidence of sulfidic sulfur. Also, the phosphides and the carbides are completely decomposed.
123
1 % Si01 2.51 2.96 Ala04 MnO 49.78 Total Fe as FeO 43.21 40.32 Aotual FeO 1.85 FeoOs Fe 0.95 0.61 CaO 0.70 0.021 Total S 0.140 4 Insu5oient sample.
28:
2
3
4
5
6
%
%
%
%
%
5.56 26.41 7.81 10.42 5.56 1.67 29.66 5.36 41.40 57.20 29.93 44.98 39.88 35.38 8.36 38.47 34.35 30.10 3.74 33.69 5.61 3.19 5;13 4.29 0.37 1.87 0.78 0.74 0.15 2.70 0.80 0.88 0.07 2;90 1.45 0.014 0.092 0.114 0.142 0.210 O 0.260
11.86 4.57 32.51 37.18 31.89 5.00 0.68 10.10 2.66 0.690 0.170
The effect of the electrolytic extraction and the subsequent treatment of the oxides has been compared with the effect of heating the oxides in a stream of pure, dry chlorine gas a t a temperature of 450" to 500" F. (232" to 260" C.). The method of volatilization of iron in a current of pure chlorine is quite old, having been suggested by Fresenius in 1865 (3). This method of determining oxides in steel has been recently tested, revised, and recommended in spite of the fact that in the presence of phosphorus; sulfur, and carbon, there is an appreciable loss of oxides (1, 6). I n this case, in the absence of the carbon and in the presence of the low percentage of the phosphorus and sulfur, the recovery is better than could be expected on a sample of steel. After the samples had been in the gas stream for a period of 4 hours, they were cooled and washed with cold water until the washings were free of chlorides. Then they were analyzed, and the analyses are shown in Table 11. OF VARIOUS EXTRACTION METHODS ON SLAGS TABLE11. EFFECT
SLAG EXTRACTION SAMPLE METHOD
1 2 50
So
60
MNO I N
70
80
~NGANOOS
90
/a0
SILICATE,^^
FIGURE4. EFFECTOF ELECTROLYTIC EXTRACTION ON Si02
3 4 5
In order to determine the accuracy of the extraction, oxides of varying composition of iron, manganese, silicon, and alum h u m were placed in contact with the steel specimen for a period of 24 to 36 hours, during which the iron was electrolyzed a t the rate of 1gram per hour. These oxides had been ground to pass through a 100-mesh screen, and therefore offered a large surface to the action of the various solutions. After the extraction they were removed from the cell and treated with alcoholic iodine, then were filtered and washed with alcohol, potassium iodide solution, and cold water, then with hot water and 10 per cent solution of potassium hydroxide, and finally with hot water until all the alkali was removed. The
6
Fresenius Diokenson Eleotrolytio Fresenius . Diokenson Eleotrolytio Fresenius Diokenson Elootrolytio Fresenius Dickenson Eleatrolvtio Fresenius Dickenson Electrolytio Fresenius Diokenson Electrolytio
Si02
AlxOx
MnO
TOTAL Fe AS FeO
%
%
%
%
2.19 0.05 1.71 10.09 0.06 9.51 4.92 0.08 4.94 25.73 None 25.43 8.13 None 6.10 11.91 None 10.22
2.59 1.67 2.79 5.33 2.67 4.21 1.67 1.10 1.55 30.12 18.40 29.20 5.03 3.61 4.97 4.74 0.76 4.64
28.82 0.97 40.48 29.93 4.58 36.69 44.66 0.45 48.44 24.71 6.61 29.05 38.34 1.45 40.82 29.29 0.39 29.30
40.00 1.36 44.83 39.49 1.88 41.52 33.35 0.23 34.54 8.04 2.89
8 0 - . 0_.
37.60 2.50 38.84 36.02 1.10 39.85
Also, the oxides were treated by the Dickenson method in the presence of a piece of steel. Although the method was originally introduced by J. E. Stead, it was developed in greater detail by Dickenson ( 2 ) . This method of dissolving the iron in dilute nitric acid has been tried critically by Herty, Fitterer, and Eckel (4),and the procedure they recommend was used in this case. The results of this treatment of the oxides are also found in Table 11.
.ANALYTICAL EDITION
124
From Table I1 it can be seen that the recovery of the manganous oxide is related t o the percentage of the manganous oxide in the manganous silicate, (MnO),(SiOz),. This fact is very important as the oxides found in killed steels which have been deoxidized with ferromanganese and ferrosilicon
Vol. 4, No. 1
the electrolytic method is plotted against the per cent in the manganous silicate. From the curve it is quite apparent that the recovery of the manganous oxide in the manganous silicates found in killed steels is very high, close to 100 per cent, and over 80 per cent is recovered in the extraction of rimmed steels. The alkali treatment dissolves a small amount of silica, as can be seen in Table 11. The recovery of the silica is also related to the percentage of manganous oxide in the manganous silicate. In Table IV is shown the recovery of the silica after the electrolytic treatment. The silica recovery increases as the manganous oxide percentage decreases, and therefore it can be concluded that in killed or s i l i c o n - t r e a t e d steels, where the oxides are high in silica, the recovery is high, actually close t o 100 per cent. The treatment of the electrolytic residue with 10 per cent potassium hydroxide is not used on rimmed-steel extractions, and so the effect there is eliminated. In Figure 4, the per cent of silica recovered in the electrolytic extraction and treatment of the oxides is plotted against the percentage of manganous oxide in the manganous silicate. TO TABLE Iv. COMPARISON OF sios RECOVERED MnO/ (MnO), (SiOJ RATIO
are almost entirely manganous silicates with very little or no ferrous oxide. This relationship of recovery of manganous oxide to the percentage in the manganous silicate is shown in Table 111.
+
OXIDE RECOVERED Dickenson Eleotrolytic method method
MANQANOUS
MnO SAMPL~CMnO Si02
1 2 3 4 5
6
+
Fresenius loo method
95.20 79.89 91.14 53.12 85.21 73.27
%
57.89 72.29 78.08 82.56 85.24 90.10
%
%
1.95 11.06 0.79 22.09 3.22 1.20
81.32 88.62 84.69 97.05 90.75 90.10
From Table I11 it can be seen that the electrolytic extraction of the oxides is less harmful than either of the others. Although the chlorine gas method appears to be nearly as good it must be recalled that oxides of iron and manganese' are appreciably affected and lost if carbon, phosphorus, and sulfur are present, as is the case in an actual extraction. I n Figure 3, the per cent of manganous oxide recovered by
ELECTROLYTIC
EXTRACTION
95.20 79.89 91.14 53.12 85.21 73.27
TABLE111. COMPARISON OF MnO RECOVERED TO MnO/(MnO),(SiOz), RATIO SLAQ
Si02 RECOVERED BY
MnO (MnO) (SiOz)
SLAQ
SAMPLE
The effect of the electrolytic extraction on the ferrous oxide cannot be determined, as the residue was contaminated with iron. The alumina is recovered totally, or nearly so. In the analysis of the residue from rimmed steels, where the alumina is present the alkali treatment is omitted and the alumina completely recovered.
COMPARISON OF OXIDE DETERMINATIONS ON CARBON STEELS BY DIFFERENT METHODS Several samples of high-carbon basic open-hearth steel, deoxidized with spiegeleisen and ferromanganese in the
OF OXIDEANALYSIS ON DIFFERENT STEELS OBTAINED BY VARIOUS METHODS TABLEV. COMPARISON
,-SAYPLE
1 2
c
STEELANALPSIS Total manganous S si silicate
P si02 % % % % % Near top and outside of ingot 0.84 0.76 0.028 0.024 0.128 0.02971 0.02356 0,00189 0.00162 0,01990 0.01437 DESCRIPTION
%
&In
%
Near top and center of ingot
0.72 0.62 0.025 0.024 0.198 00 : 0802 00286 0.0326 3a Near top and outside of ingot 0.75 0.62 0.025 0.025 0.198 0,0092 0.00163 0.0180 3b Near top and center of ingot
MnO
%
OXIDE ANALYSIS Si02 MnO
%
%
W E I G H T EXTRACTION OF METHOD
TOT~L
OXYGEN SAMPLE
%
USED
Grams
0.00615 0.0140 58.574 Dickenson 37.079 Electrolytic 14.29 0,0009 85.71 20.70 0.00027 79.30 0.00553 72.21 27.79 0.0089 9.044 Fresenius
0.0509 nickenson 0,0014 27.506 27.049 Electrolytic 90.56 36.53 9.44 0.0337 6,00027 63.47 0.00259 0.0293 0,0274 0.0052 84.05 15.95 0,0158 6.924 Fresenlus 0.0075 0.0017 18.48 0,0008 0.0044 49.744 32.097 Electrolytio Dickenson 86.50 13.50 0.00022 81.52 0.00141 0,0129 0.0051 71.67 28.33 0.0080 12.414 Fresenius
0.80 0.62 0.029 0.027 0.200 0,0200 80.50 19.50 29.708 Electrolytic Dickenson 0,0009 28.671 9.19 0.0095 0.00017 90.81 0.00168 0.0039 0.00185 0.0161 0.0296 0,0218 0.0078 73.31 26.69 0.0134 10,112 Fresenius
4a Near top end outside of ingot 0.55 1.42 0.027 0.028 0.182 00:00212 0760 0.00087 0.0300 0.00125 0.0460 39 47 60 53 0:0007 0 0264 46.078 24.667 Electrolytio Dickenson 58:96 41:04 0.0502 0,0382 0,0120 76.10 23.90 0.0231 10.731 E'resenius 4b Near top and center of ingot
0.0134 0.0026 83.75 23.81 16.25 0.0010 0.0077 37.071 29.814 Dickonson Electrolytic 0.00048' 76.19 0.00162 0.0154 0.0063 70.97 29.03 0.0096 9.740 Fresenius
6
0.00485 81.51 0.0028 55.560 Electrolytic 38.889 Dickenson 13.49 0.0004 51 18.49 0,00012 86 0.00077 0.0011 0.0177 0.0029 85:92 14.08 0.0100 10.370 Fresenius
6
0.62 1.42 0.033 0.029 0.186 0.0160 0.00210 0.0217 Near top and center of ingot 0.73 0.87 0.031 0.026 0.2Zp 0O:OOOS9 00595 0.0206 Near top and outside of ingot 0 . 7 6 0.87 0.032 0.029 0.200 0.0160 0-.00170 0.0219
0.0134 0.0077 31.185 82.918 Diokenson Electrolytio 5.88 0,0009 94.12 16.25 0.00010 83.75 0.00160 0.0026 0.0141 0.0078 64.38 35.02 0,0093 9.944 Fresenius
I N D U S T R I A I, A N D E N G I N E E R I N G C H E M I S T R Y
January 15, 1932
OF RESULTS OBTAINED BY ELECTROLYTIC METHOD ON TABLE VI. TYPES
SAMPLE 1
2 3 4 5 6
C
STEELASALYSIS Mn P
7
S
Si02
%
%
%
%
%
0.04
0.35 0.39 0.02
0.039
0.019
0.00510 0.00324 0.00272 0.00265 0.00315 0.00675
0.08
0.03 0.03 0.04 0.06 Determined by the
0.04 0.27
0.072 0.004
0.019 0.010 0,012
0.034 0.024
0.041 0.040 0.041
0.27 direct hydrochloric acid method.
furnace, and with ferromanganese and ferrosilicon in the ladle, have been analyzed for manganous silicates by the electrolytic, Dickenson, and chlorine gas extractions. These samples were cut from adjacent positions and so should be nearly identical in regards to oxide content. The extractions were carried out in the same manner as has been outlined, and the results are shown in Table V. The total oxygen in the steel is calculated from the oxygen of the silicon dioxide and the manganous oxide on the assumption that the steel is completely deoxidized, and all the oxygen is combined in these oxides. Table V shows the Dickenson method to be very destructive to the manganous silicates found in the killed steel. However, it is true that an analysis of the residue recovered by this method may give an indication of the relative amounts of manganous oxide and silicon dioxide in the silicates. The time required for the determination is prohibitive t o routine analysis. The chlorine gas extraction a t the low temperature used gives apparently good results, but the fact that only 10 grams may be used in the extraction causes the oxide residue to be so small that very accurate results are difficult to obtain. Also, the small sample makes the analysis representative of a local condition. Another difficulty is that a t this low temperature of volatilization the manganese is not volatilized but remains in the residue and must be washed out with the cold water.
125
RIMMED STEELS
ELECTROLYTIC EXTRACTION MnO A1103 A12OP % % % 0.00309 0.00150 0.00289 0.00084 0.00024 0.02310 0.00072 0.00620 0.0067 0,00156 0.00650 0.00087 0.00677
FeO
9%
0.272 0.227
0.407 0.295 0.173 0.405
TOTAL01 I N STEEL % 0.065 0.054 0.103
0.070 0.044 0.088
Carbon has a power of absorption that makes this step difficult, and error may occur here as the actual manganous oxide is present in such small quantities. The electrolytic extraction gives the best results, most nearly representative of the steel. A large sample is used and the oxides extracted are enough for an accurate analysis. All the methods use clean and polished solid pieces of steel, eliminating any surface oxidation which may occur in any method using drillings or millings. I n Table VI are shown types of results obtained through electrolytic extraction on rimmed carbon steels. LITERATURE CITED Bardenhauer, P., and Oberhoffer, P., Mitt. Kaiser- Wilhelna Inst. Eisenforsch. DUsseldorf, 9, 195-200 (1927). Diekenson, J. H. S., J . Iron Steel Inst. (London),113, 177 (1926). Fresenius, R., 2.anal. Chem., 4, 72 (1865). Herty, C. H., Jr., Fitterer, G. R., and Eokel, J. F., Bur. Mines, Carnegie Inst. Tech., and Mining Met. Advisory Boards, Mining Met. Inves., Co6p. Bull. 37 (1928). Herty, %. H., Jr., Fitterer, G. R., and Marshall, W. E., Jr.. Ibid., 44 (1929). Wasmuht, R., and Oberhoffer, P., Arch. EisenhQttenw., 2, 829-42 (1929). Westoott, B. B., Eckert, E”. E., and Einert, H. E., IND. ENQ. CHEM.,19, 1285 (1927). RECEIVED April 1, 1931.
Improved Soxhlet Extraction Apparatus I). S. BINNINGTON, Department of Agricultural Chemistry, University of .Wanito3z, Winnipeg, Canada
A
LTHOUGH a large number of different devices are available for the continuous extraction of solids with volatile solvents, the familiar Soxhlet apparatus is still widely used because of its general adaptability. The various types of Soxhlet apparatus now in use have, however, certain manifest disadvantages. The use of cork stoppers is undesirable because of leakage and the presence of extractable matter (3). Ground-glass connections, although obviating the latter difficulty, do not entirely eliminate leakage and are distinctly fragile. In extraction apparatus such as the Wiley-Soxhlet of 1912 ( 2 ) ,the Underwriters Laboratory model of 1912 ( I ) , the Bailey-Walker of 1914 (5),or the Pickel of 1919 ( d ) ,these disadvantages have been overcome, but in these types the solvent functions a t or near its boiling point which is undesirable, as pointed out by Ford in 1912 ( 2 ) , when working with nonhomogeneous solvents. A further objection is the limited amount of sample that the extraction tube will contain. Probably the most successful type of Soxhlet extractor now available is that employing a ground-glass joint between the condenser and extractor, and a mercury seal between the extractor and flask. I n the apparatus described here the mercury seal is retained, but all other joints exposed to the
vapor of the boiling solvent are eliminated-a characteristic of the improved types of apparatus referred to above. The modified apparatus is illustrated in Figure 1, which is practically self-explanatory. The body of the extractor is extended considerably above the vapor inlet, and condensation is effected by means of a separate condenser inserted into this upper portion, and is held in place by a wide flange on the top. The entire apparatus is constructed of Pyrex glass, which, together with the absence of fragile ground joints, makes a very rugged and serviceable outfit, well adapted to routine work. It will be noted that the water inlet and outlet tubes of the condenser are practically vertical, instead of the usual bent-at-right-angles type. This arrangement was adopted for convenience in setting up a battery of extractors, such as illustrated in Figure 2, which shows a battery of six modified extractors heated by a water bath operated by a 330-watt immersion heater. A set-up of this kind is perfectly safe for use with the most volatile or inflammable solvents, and has been operated in these laboratories for some time with excellent results. Ether and carbon bisulfide extractions extending over a period of 3 to 4 days have been made without any
