Extraction of Slag and Oxide Inclusions in Iron or Steel Electrolytic Method

FRANK W. SCOTT, Inland Steel Co., East Chicago, Ind .

ANY methods of ex- t r a c t i o n other than electrolytic have been

devised for the determination of non-metallics in iron and steel, but none have been satisfactory for all t y p e s of ox ides . The outstanding method a t the pres- e n t t i m e is t h e Dickenson method (2) which will extract sili- con dioxide and aluminum oxide from “killed” steels with varying degrees of accuracy. However, this m e t h o d will n o t give a quantitative extraction of inclu- sions which contain ferrous and manganous oxide from ‘‘rim- ming” steels (4). In fact, after a detailed study of .extraction methods proposed to date and outlined by C. H. Herty, Jr., and others (4), and by Westcott, Eckert, and Einert ( 7 ) , it is seen that none are satisfactory for use upon steel. A l a rge s a m p l e must be used, as it is absolutely necessary, in a study of inclu- sions, to have enough non-metal- lics extracted for the determination

A f i ELECTROLYTIC method, rapid, simple T h e o u t e r cell i s a l a rge - in operation, and inexpensive, f o r the deter- mouth reagent Of about

3 liter capacity, with a cork to mination of oxides found in p la in carbon steel fit. The inner cell is a and iron as inclusions, has been successfully r e a g e n t bottle with the b o t - developed. Magnesium iodide is used as the tom cut off. The cork of the electrolyte and is found to be superior to a n y outer cell has a hole cut in it to used heretofore. fit the neck of the inner cell, and

these are fastened together so The sulfides are not determined, but only the as to support the inner cell. oxides 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 “killed” steels where the principal inclusion is bottle has a hole punched in manganous silicate, the recovery is practically it for the platinum wire to pass 100per cent; in the “rimmed” steels, slighfly less. through*

The cathode is made of the The accuracy of the method has been deter- ordinary copper Screen used in mined through the use of slaggy material contain- window screens. A piece is ing various percentages of ferrous, manganous, cut as long as the circumference silicon, and aluminum oxides. This material and as wide as the straight sides was actually formed in the rimmed ingot of steel, of the large bottle. Two strips

of screen are f a s t e n e d as con- and was collected for the study. It is believed tacts to the screen It is that such material is a definite improvement over then rolled up and inserted into the use of synthetically prepared compounds, as the bottle, where it unrolls and it is the same physically and chemically as the forms a cylinder. The contact 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 fastened together with a third

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 must not require from 2 to 6 weeks as does the Dickenson method.

As regards previous work on electrolytic methods, nothing was found regarding the extraction of oxide impurities from steel. It has been shown that manganous oxide could not be extracted in an acid or ferrous sulfate solution (5) .

I n the steel industry a constant effort is being put forth to make a better product, and a cleaner steel is one of the desired achievements. However, before the cleanliness of steels produced by various means can be compared, a method must be found to determine the amount, the character, and the source of the oxide impurities. This paper gives a method for the extraction of these oxides from a solid block of steel, and it has bcen found to be better than any method published or

DESIGN OF CELL The design of the cell has required much consideration and

experiment, but the one finally chosenis simple of construction, costs only a few cents to make, and is easy to manipulate. It consists of two parts, an inner cell separated from the outer by means of a piece of filter paper. The steel or iron specimen is suspended in the inner cell by means of a platinum wire; the iron and metallic constituents go into solution, are ionized, and pass from the inner cell to the outer through the filter paper, and are plated out on the copper-screen cathode. The carbon, sulfur, and oxides remain in the inner cell and are collected in a filter paper cone which is removed for study of the residue.

. suggested to date.

121

PREPARATION OF ELECTROLYTE The electrolyte used is magnesium iodide solution con-

taining a small amount of free iodine, Magnesium was chosen because it should, and actually does, prevent the formation of ferrous hydroxide owing to magnesium hydroxide being less soluble. As the solution becomes slightly more alkaline due to evolution of hydrogen during electrolysis, magnesium hydroxide is precipitated. However, very little precipitation does occur, and the iron is plated out without being hydrolyzed. Magnesium iodide is a good conductor, and iron can be plated out a t the rate of 1 gram per hour a t 1 ampere and 4 volts.

To make 3 liters of solution, 120 grams of resublimed iodine are weighed into three 600-cc. beakers, and 400 cc. of distilled water added to each. Metallic magnesium is added gradually with stirring, until the iodine color disappears. The solution is filtered and 5 grams of iodine dissolved in it, and enough distilled water added to make the solution to 3 liters. It is then ready for use.

The same solution may bc used repeatedly by filtering after each determination, and dissolving 5 grams of iodine in it.

PREPARATION OF STEEL SPECIMEN The size of the specimen is controlled by the time desired to

spend on the determination and the cleanliness of the steel. Ordinarily a 50-gram specimen is large enough. The portion to be decomposed is submerged in the solution, and the re- mainder is unaffected.

122 A N A L Y T I C A L E D I T I O N Vol. 4, No. 1

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 solu- tion.

FIGURE 1. CELL ASSEMBLED 1. Outer oell 2. Inner oell 3. Copper-soreen cathode 4. Contact strips 6. Cork support for inner cell 6. Cork support for steel speoimen 7. Platinum-wire contact to speci-

men 8. Steel Bpecimen 9. Filter-paper cone to colleot

oxides 10. Filter paper Separating cella

ASSEMBLY OF CELL AND ELECTROLYSIS

When the cell is made, the electrolyte prepared, and the steel specimen fastened to the wire, the determination may be started. An ashless 11- cm. filter paper is folded as for use in a funnel and slipped into the inner cell so as t o act as a receiver for the oxides. An 11-em. hardened filter paper is fas tened over the bot tom of t h e i n n e r cel l by means of rubber bands.

The steel specimen is placed so ai to touch the center of the filter-paper cone, and is supported by the wire passing through the hole in the cork of the bottle.

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 smaller, more voltage must be impressed to maintain 1 ampere. The cell will operate until the steel is decomposed to the surface of the solution.

TREATMENT OF RESIDUE AND ANALYSIS OF OXIDES

When the electrolysis is complete, the inner cell is removed, and the solution allowed to drain. The rubber bands are cut and the paper used to separate the two solutions removed. The filter-paper cone containing the oxides and carbon “skeleton” is placed in a weighing bottle. Two grams of iodine are added, the paper torn up with stirring, and the bottle filled with alcohol. The solution is allowed to stand, stoppered, with frequent stirrings, for a t least 24 hours. This treatment will decompose small metallic particles which have fallen from the specimen. However, in high-carbon steels, it is practically impossible to remove all the steel because of the carbon coating of the particles. Several alcoholic treatments with iodine will remove all but a small amount, from 1 to 10 mg. of iron.

The residue is then filtered by suction on an ashless KO. 589 “Blue Ribbon” paper, using a platinum cone. It is washed several times with small amounts of alcohol, and then with cold potassium iodide solution, until the washings are no longer the color of iodine. It is then washed with cold water,

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 a t 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 dissolved in 10 per 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 dissolved in a little hot water and a few drops of nitric acid, and the silica is filtered off. This is ignited and determined as silicon dioxide by volatilization with hydrofluoric acid.

The residue from the silica volatilization is fused with potassium bisulfate until it is decomposed. It is then leached out in the filtrate from the silica. This solution is made strongly ammoniacal, and the hydroxides are filtered off. The precipitate is dissolved in nitric acid, reprecipitated with ammonia, filtered, and washed with hot water. It is then dried, ignited, and weighed as iron oxide. In low-carbon steels, below 0.10 per cent, this is the iron from the ferrous oxide of the steel and is considered as such. In higher carbon steels, it is often contaminated with an appreciable amount of metallic particles and is calculated as metallic iron. The total silicon dioxide and manganous oxide found in the residue are corrected for the silicon and manganese coming from the metallic residue, as shown by the steel analysis. This is especially important in killed steels with 0.80 to 1.00 per cent carbon and high manganese and silicon contents.

FIGURE 2. CELL PARTS UNASSEMBLED

The iron oxide contains a small amount of manganese tetroxide (MnaOr) and aluminum oxide, and therefore it is fused with potassium bisulfate until it is all in solution, cooled, leached out, and added to the filtrate from the iron determina- tion. This is then boiled down to 75 cc. and transferred to a 300-cc. Erlenmeyer flask.

To the solution in the flask, 30 cc. of acid mixture (1313 cc. of water, 625 cc. of concentrated nitric acid, 325 cc. of phos- phoric acid, 250 cc. of sulfuric acid); 15 cc. of silver nitrate solution (16 grams in 2000 cc. of water); and 20 cc. of am- monium persulfate solution (600 grams in 2040 cc. of water) are added. This is brought to the boiling point and allowed to boil briskly for 1 minute, and is then cooled to 20” C. Cold water (75 cc.) is added and the manganese titrated with a standard arsenite solution (1 cc. = 0.0005 gram of man- ganese). This gives the total manganese, and after correct- ing for the trace due to metallic contamination, is calculated as manganous oxide. This method is as accurate as the bismuthate method and probably less open to error.

If the aluminum oxide is desired, the silver nitrate is removed as silver chloride, and the aluminum determined as aluminum phosphate after separating the iron from the aluminum with an excess of sodium hydroxide. The first

January 15, 1932 I X D U S T R I A L A N D E N G I X E E R I N G C H E M I S T R Y 123

precipitation always contains a trace of iron and must be purified by a t least one other separation. It is perhaps better to determine the aluminum oxide on a separate sample using the direct hydrochloric acid method for separation

MNO IN MANGANOUS slLlC4TE,'/o

FIGURE 3. EFFECT OF ELECTROLYTIC EXTRACrION ON MnO

and determination as aluminum phosphate in ammonium acetate solution. However, it may be determined satis- factorily on the solution containing the manganese as given above.

ACCURACY OF DETERMINATION The accuracy of the electrolytic extraction and recom-

mended 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 corre- sponding iodide. A wet oxidation and gravimetric determina- tion 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.

50 S o 60 70 80 9 0 /a0

MNO I N ~ N G A N O O S SILICATE,^^ FIGURE 4. EFFECT OF ELECTROLYTIC

EXTRACTION ON Si02

In order to determine the accuracy of the extraction, oxides of varying composition of iron, manganese, silicon, and alu- mhum 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 1 gram 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

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 experi- ments. 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.

CON0TITUENT TABLE I. COMPOSITION OF SLAGS

1 2 3 4 5 6 % % % % % %

Si01 Ala04 MnO Total Fe as FeO Aotual FeO FeoOs Fe CaO

Total S 28:

2.51 10.42 5.56 26.41 7.81 11.86 2.96 5.56 1.67 29.66 5.36 4.57 49.78 41.40 57.20 29.93 44.98 32.51 43.21 39.88 35.38 8.36 38.47 37.18 40.32 34.35 30.10 3.74 33.69 31.89 1.85 5.61 3.19 5;13 4.29 5.00

0.78 0.68 0.95 0.37 1.87 0.61 0.74 0.15 2.70 0.80 10.10 0.70 0.88 0.07 2;90 1.45 2.66 0.021 0.014 0.092 0.114 0.690 0.140 0.142 0.210 O 0.260 0.170

4 Insu5oient sample.

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" t o 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). In 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.

TABLE 11. EFFECT OF VARIOUS EXTRACTION METHODS ON SLAGS TOTAL Fe SLAG EXTRACTION

SAMPLE METHOD Si02 AlxOx MnO AS FeO % % % %

1 Fresenius 2.19 2.59 28.82 40.00 Diokenson 0.05 1.67 0.97 1.36 Eleotrolytio 1.71 2.79 40.48 44.83

2 Fresenius . 10.09 5.33 29.93 39.49 Diokenson 0.06 2.67 4.58 1.88 Eleotrolytio 9.51 4.21 36.69 41.52

3 Fresenius 4.92 1.67 44.66 33.35 Diokenson 0.08 1.10 0.45 0.23 Elootrolytio 4.94 1.55 48.44 34.54

4 Fresenius 25.73 30.12 24.71 8.04 Dickenson None 18.40 6.61 2.89 Eleatrolvtio 25.43 29.20 29.05 8.00

5 - _.

Fresenius 8.13 5.03 38.34 37.60 Dickenson None 3.61 1.45 2.50 Electrolytio 6.10 4.97 40.82 38.84

4.74 29.29 36.02 Diokenson None 0.76 0.39 1.10 Electrolytio 10.22 4.64 29.30 39.85

6 Fresenius 11.91

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.

124 . A N A L Y T I C A L E D I T I O N 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 re- covery of the silica is also related to the percent- age of manganous oxide in the manganous sili- cate. In Table IV is shown the recovery of the silica after the electrolytic treatment. The silica recovery increases as the manganous oxide per- centage decreases, and therefore it can be con- cluded that in killed or s i l i con- t rea ted steels, where the oxides are high in silica, the recovery is high, actually close to 100 per cent. The treat- ment 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 man- ganous oxide in the manganous silicate.

From Table I1 it can be seen that the recovery of the manganous oxide is related t o the percentage of the manga- nous 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

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.

TABLE 111. COMPARISON OF MnO RECOVERED TO MnO/(MnO),(SiOz), RATIO

MANQANOUS OXIDE RECOVERED S L A Q MnO Fresenius Dickenson Eleotrolytic

SAMPL~C MnO + Si02 loo method method method % % %

95.20 57.89 1.95 81.32 88.62 1

2 79.89 72.29 11.06 91.14 78.08 0.79 84.69

97.05 3 82.56 22.09

90.75 4 53.12 85.21 85.24 3.22 5

6 73.27 90.10 1.20 90.10

From Table I11 it can be seen that the electrolytic extrac- tion 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.

In Figure 3, the per cent of manganous oxide recovered by

TABLE Iv. COMPARISON OF sios RECOVERED TO MnO/ (MnO), (SiOJ RATIO

Si02 RECOVERED BY SLAQ MnO ELECTROLYTIC

SAMPLE (MnO) + (SiOz) EXTRACTION

95.20 79.89 91.14 53.12 85.21 73.27

The effect of the electrolytic extraction on the ferrous oxide cannot be determined, as the residue was contaminated with iron.

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

The alumina is recovered totally, or nearly so.

TABLE V. COMPARISON OF OXIDE ANALYSIS ON DIFFERENT STEELS OBTAINED BY VARIOUS METHODS STEEL ANALPSIS

W E I G H T EXTRACTION OXIDE ,-- Total

SAY- manganous ANALYSIS T O T ~ L OF METHOD PLE DESCRIPTION c &In P S si silicate si02 MnO Si02 MnO OXYGEN SAMPLE U S E D

% % % % % % % % % % % Grams

1 Near top and outside of ingot 0.84 0.76 0.028 0.024 0.128 0.02971 0.02356 0.00615 79.30 20.70 0.0140 58.574 Electrolytic

2 Near top and center of ingot 0.72 0.62 0.025 0.024 0.198 0 0802 0.0509 0.0293 63.47 36.53 0.0337 27.506 Electrolytic

3a Near top and outside of ingot 0.75 0.62 0.025 0.025 0.198 0,0092 0.0075 0.0017 81.52 18.48 0.0044 32.097 Electrolytio

3b Near top and center of ingot 0.80 0.62 0.029 0.027 0.200 0,0200 0.0161 0.0039 80.50 19.50 0.0095 28.671 Electrolytic

4a Near top end outside of ingot 0.55 1.42 0.027 0.028 0.182 0 0760 0.0300 0.0460 39 47 60 53 0 0264 24.667 Electrolytio

4b Near top and center of ingot 0.62 1.42 0.033 0.029 0.186 0.0160 0.0134 0.0026 ' 83.75 16.25 0.0077 29.814 Electrolytic

6 Near top and center of ingot 0.73 0.87 0.031 0.026 0.2Zp 0 00595 0.00485 0.0011 81.51 18.49 0.0028 55.560 Electrolytic

6 Near top and outside of ingot 0 . 7 6 0.87 0.032 0.029 0.200 0.0160 0.0134 0.0026 83.75 16.25 0.0077 82.918 Electrolytio

0,00189 0.00162 0.00027 85.71 14.29 0,0009 37.079 Dickenson 0,01990 0.01437 0.00553 72.21 27.79 0.0089 9.044 Fresenius

0 : 00286 0.00259 6,00027 90.56 9.44 0,0014 27.049 nickenson 0.0326 0,0274 0.0052 84.05 15.95 0,0158 6.924 Fresenlus

0.00163 0.00141 0.00022 86.50 13.50 0,0008 49.744 Dickenson 0.0180 0,0129 0.0051 71.67 28.33 0.0080 12.414 Fresenius

0.00185 0.00168 0.00017 90.81 9.19 0,0009 29.708 Dickenson 0.0296 0,0218 0.0078 73.31 26.69 0.0134 10,112 Fresenius

0:00212 0.00087 0.00125 41:04 58:96 0:0007 46.078 Dickenson 0.0502 0,0382 0,0120 76.10 23.90 0.0231 10.731 E'resenius

0.00210 0.00162 0.00048 76.19 23.81 0.0010 37.071 Dickonson 0.0217 0.0154 0.0063 70.97 29.03 0.0096 9.740 Fresenius

O:OOOS9 0.00077 0,00012 86 51 13.49 0.0004 38.889 Dickenson 0.0206 0.0177 0.0029 85:92 14.08 0.0100 10.370 Fresenius

0-.00170 0.00160 0.00010 94.12 5.88 0,0009 31.185 Diokenson 0.0219 0.0141 0.0078 64.38 35.02 0,0093 9.944 Fresenius

January 15, 1932 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 125

TABLE VI. TYPES OF RESULTS OBTAINED BY ELECTROLYTIC METHOD ON RIMMED STEELS

STEEL ASALYSIS 7 ELECTROLYTIC EXTRACTION TOTAL 01 SAMPLE C Mn P S Si02 MnO A1103 A12OP FeO I N STEEL

% % % % % 1 0.04 0.35 0.039 0.019 0.00510 2 0.08 0.39 0.072 0.034 0.00324 3 0.03 0.02 0.004 0.024 0.00272 4 0.03 0.04 0.019 0.041 0.00265 5 0.04 0.27 0.010 0.040 0.00315 6 0.06 0.27 0,012 0.041 0.00675

Determined by the 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 com- pletely deoxidized, and all the oxygen is combined in these oxides.

Table V shows the Dickenson method to be very destruc- tive 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.

% % % 9% % 0.00150 0.00309 0.272 0.065 0.00084 0.00289 0.227 0.054 0.00024 0.02310 0.407 0.103

0.00620 0.0067 0.295 0.070 0.00072 0.173 0.044 0.00650 0,00156

0.00087 0.00677 0.405 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.

In 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.

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.

Eisenforsch. DUsseldorf, 9, 195-200 (1927).

CHEM., 19, 1285 (1927).

RECEIVED April 1, 1931.

Improved Soxhlet Extraction Apparatus I). S. BINNINGTON, Department of Agricultural Chemistry, University of .Wanito3z, Winnipeg, Canada

LTHOUGH a large number of different devices are available for the continuous extraction of solids with A 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 undesir- able 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 dis- advantages 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 non- homogeneous 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. In 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