V O L U M E 27, N O . 6, J U N E 1 9 5 5 purple color. I n general, one should not exceed the end point by more than 0.4 ml. This solution is diluted to volume, and its absorbance determined in the same manner as for the solutions used in preparing the calibration curve. The total thorium corresponding t o this observed absorbance is read from the calibration curve. From the total thorium present and the amount of thorium added as standard thorium solution, the amount of extracted thorium ip determined: Grams of T h = Thtotat - 0.23218J4 nhere V is milliliters used and M is the molarity of the standard thorium solution. Typical results obtained by Method I1 on synthetic samples are reported in Table 11. Interferences. It 4 as felt that the mesityl oxide extraction of thorium with lithium nitrate as thP salting-out agent might be useful in procedures other than the one described above, and for this reason an interference study was made. .I group of cations and two anions m-ere investigated as t o their interference in the determination of thorium by the recommended extraction-spectrophotometric titration procedure. The results of this study are shown in Table I11 and indicate strong interference from zirconium, iron, tin, and phosphate. Other anions which form stable complexes with thorium or which form insoluble compounds v, ith thorium would also be expected to interfere. Qualitative tests indicated t h a t uranium(T'1) s-as probably eytracted quantitatively, that zirconium was about 25% eytracted and t h a t iron(II1) vas about 10% extracted.
949 APPLICATIONS
Method I serves very satisfactorily for the analysis of an occasional thorium-aluminum alloy. Method I1 seems t o be ideally suited for the anal!-sis of many thorium-aluminum allol-s on a routine basis. The method is rapid, as it requires only one standard solution, only one initial pH adjustment, and the measurement of a single absorbance for each thorium determination. The method is accurate, as the final measurement is made spectrophotometrically rather than visually. This modification of the usual spectrophotometric titration should be very useful in adapting many other spectrophotometric titrations to a routine basis, as it eliminates the construction of all but the initial calibration curve. LITERATURE CITED
Fritz, J. S.,and Ford, J. J., AXAL.CHEM.,25, 1640 (1953). Grundmann, H., Alz~minium,24, 105 (1942). Kolthoff, I. AI., and Sandell, E. B.. "Textbook of Quantitative Inorganic .halysis," pp. 326-7, l\lacmillan. S e w Pork, 1948. Levine, H., and Grimaldi, F. S., U. S. Atomic Energy Comm. Rept. AECD-3186 (1950). Willard, H. H., and Gordon, L., h n ~ CHEM., . 20, 165 (1945). RECEIVED for rerieiv August 2 7 , 1954. Accepted February 10, 1955. Based in part on a dissertation submitted b y R . E. Edwards in partial fulfillment of the requirements for the degree of master of science, Iowa State College, h i e s , Iowa, August 1953. Contribution S o . 372 from t h e Institute for Atomic Research and Department of Chemistry. Iowa State College, Arnes, Ioxra. Work was performed in the d m e s Laboratory of the Atomic Energy Commission.
Determination of Total Sulfur Content of Sedimentary Rocks by a Combustion Method MAYNARD E. COLLER and RICHARD K. LElNlNGER Geological Survey,
lndiana D e p a r t m e n t of Conservation, Bloomington, Ind.
Total sulfur has been determined in common sedimentary rocks b y a combustion method. Sulfur contents range from 0.001 to 5.0%. Experiments show that the combustion method can be used in analyzing sedimentary rocks in which sulfur is present as sulfide, sulfate, or both. Pulverized samples from 0.100 to 0.500 pram in weight are used in this method. Each sample is placed in a No. 6 Leco combustion boat and covered with t w o fluxes: 0.50 gram of standard ingot iron and approximately 1.0 gram of 30-mesh granular tin. The boat with sample then is placed in the combustion tube of a Burrell L-nit Package AIodel T29A tube furnace which is controlled at a temperature of 1310" to 1320" C. After the sample has been heated for 1 minute, oxygen is admitted at a rate of about 1 liter per minute. The sulfur dioxide formed is absorbed in a starch solution and is titrated with standard potassium iodate in a Leco sulfur determinator. Thirteen values obtained for National Bureau of Standards standard sample la, argillaceous limestone, range from 0.273 to 0.2i6y0 sulfur (certificate value 0.27 % by calculation),
S
I X C E 1947 the Indiana Geological Survey has made a study of the limestone and dolomite resources of Indiana and has collected many samples for analysis. Because the sulfur content of limestone is specified for many commercial uses, the development of a rapid method for its determination became de&able. The survey has also sampled many clays and shales;
the sulfur content of these materials is important because of the adverse effects of sulfur during firing or glazing of ceramic wares. The classical wet methods for sulfur, as mentioned by Hillebrand and Lundell (3) and as found in the book of -4STLI standards ( 1 ) . were too long and time-consuming since they depended upon the weighing of sulfur as barium sulfate. Combustion methods found in the literature ( 2 ) were primarily for use on steel or other metals. The Laboratory Equipment Corp. ( 4 ) had distributed instructions for the use of its sulfur apparatus, but no methods were found for nonmetallic compounds. The rapidity of the combustion method was so advantageous that the adaptation of this type of procedure to sedimentary rocks was attempted. PRELIMIXARY INVESTIGATION
An investigation of t h e temperature of combustion showed that 1310" to 1320" C. gave the most uniform factor, and was the easiest temperature with which to rvork-Le., there was less strain on the eyes when placing the boat in the tube and when extracting it, and there seemed to be less danger of the molten sample cutting through the boat and causing damage to the tube and its liner. Other temperatures tried were 1260") 1385", and 1425 C. rln attempt was made to obtain fusion of the sample using no fluxing material. The fusions mere sporadic and mostly incomplete, giving a wide variation in the factors obtained. Granulated tin ( 5 ) and copper strip ( d , 4 ) were tried as fluxes, but the time consumed in the determination )!as so variable as t o cause indecision as t o the completeness of the determination,
ANALYTICAL CHEMISTRY
950 Fusions were also incomplete when iron millings alone 14 ere tried as a flux. Best results were obtained by using both iron millings and tin as fluxing materials. Table I shows that quantitative results were obtainable regardless of the form in which the sulfur was present. The samples of Table I were prepared by adding the minerals gypsum and marcasite to calcite to give the desired sulfur content. The crystals used x-ere the best available at the time but were not necessarily pure. These minerals Jvere used because the sulfur content of limestone is normall!- present as one of these two minerals or as pyrite, which is of the same chemical composition as marcasite.
Table I. Percentage of Sulfur, Prepared Samples Sample NO. 26 27 28 29 30
S Added. (Approximate) Residiial 0.12 0.12 0.12 0 .I?
S Determined 0.002 0 13 0.11
0.12 0.12
Source of Sulfur Residual Gypsum ( G i Marcasite (hl) I / 3 G ; % / a 11 2/3 G ; 1 1 , 11
-4combustion tube liner is placed in the tube in the center of the hot zone of the furnace to protect the tube from slag and spillage. Care must be exercised that this liner is not drawn suddenly into the cold zone of the tube, as the heat shock could possibly crack the combustion tube. The standard Leco No. B combustion boat, long size, is use! in the determination. The boats are ignited overnight a t 1000 to 1100” C. in a muffle fuinace to remove any small traces of sulfur they may contain before being used. One hundred to 200 boats may be ignited a t once and stored in a large container, so that they do not adsorb any sulfur from gases in the air.. The cheap unit cost of each boat justifies its usage for only one determination. The titration apparatus, a Leco sulfur determinator, Model 400s (Figure l), is connected to the exit end of the combustion tube with a convenient length of glass tubing, approximately 10 t o 11 inches. The joints are butted as closelr as possible and Tygon tubing is used at each joint. The solutions used are supplied to the buret, automatic pipet, and titration vessel from storage bottles by use of air or oxygen pressure through a controlling manifold stopcock. A glass float valve in the bubbler prcventc hxkflow of solution into the hot comliustion tube.
‘Table 11. Percentage of Sulfur, Prepared Samples S
Sample
Added 0.27 0.27 0.27
xo.
S Deterruined 0.26
0.23 0 23
Source of Sulfur Galena ( G I Barite (B)
‘/?c;; “2B 4U8EERAy STOPPEP
STOPPER IRON M I L L I N G S d POWDERED SAMPLE
3XYGEN
TITRATIOF.,
ASSEMBLY 2 - T U B E C O M B U S T I O N FURNACE W I T H C O N T R O L 1 FR
i
Figure 2.
Combustion tube assembly
Oxygen is supplied from a standard commercial oxygen tank through a pressure-reducing valve and a Leco KO.1150 combustion purifying train. This train is used for flow measurement and the purification of the oxygen before its entrance into the comhustion tube. A 2- to 4-liter bottle is placed between the purifying train and the inlet of the combustion tube. The bottle rreates a reserve oxygen supply for the sample to draw upon during the fusion period. This bottle is fitted with a three-way *topcock so that the oxygen may be turned off during the preheat period without disconnecting the apparatus or disturbing the lireosnre adjustments. REAGENTS
Figure 1. Combustion sulfur apparatus Table I1 shows results on samples prepared from other ininerals which are sometimes associated with limestone and clay deposits. 4PP4RATUS
The combustion furnace is a Burrell Vnit Package tube furnacc, Model T29A (Figure l), heated by silicon carbide Globar elrments and controlled by a Brown Pyrovane electronic controller -41-inch internal diameter hIcDanel high temperature combustion tube (Figure 2), is preferred but a ’/*-inch or a ll/p-inch tube may be used. A tube 30 inches in length allows placing the tube in the furnace to give sufficient protection to the rubber stopper a t the fore end of the tube, but a series of refractor\baffles should be used to help protect the stopper a t the exit end. One of these baffles should be cut off and placed with the flat surface butting solidly against the rubber stopper. A thin wad of glass wool is placed in the exit end of the tube t o filter out any combustion dusts. This glass wool filter should be replaced each morning if the apparatus is in daily use. The filter must he conditioned by running five unweighed samples through the furnace ahead of any regular standards. Approximately once each week the combustion tube should be scraped and the elit end drawn dowlv into the hot zone with ovygen flowing t o remove xnv accumulated residue
Combustion Accelerators. TIN. 30-mesh granular tin combustion accelerator may be obtained from the Laboratory Equipment Corp. or any other good supply house. ISGOTIRON.This accelerator should be fine, m l l mixed millings which have been previously analyzed for sulfur content. Solutions. STARCH SOLUTION.Prepare a solution of 0.3 gram of Arrowoot starch, 0.3 gram of potassium hydroxide, and 4 to 5 grams of potassium iodide per liter. Mace a paste of the starch m d add slowly, with rapid stirring, t o 500 to 600 ml. of boiling water containing the potassium hydroxide. Bring to a boil, cool, dilute somewhat, and add the potassium iodide. Then dilute to the desired volume. Po~.~.ss~rnr IODATE SOLUTIOX.Dissolve 0.4150 gram of potascium iodate in 500 ml. of distilled water. Add 2 grams of potasGlum iodide and approximately 0.4 gram of potassium hydroxide 12 pellets are sufficient) and dilute with distilled water to 2 liters. This solution is approximately equivalent to 0.0001 gram of sulfur, but a factor should be established each day under the conditions of that day’s operation. HYDROCHLORIC ACID. Dilute a volume of reagent grade hydrochloric acid with an equal volume of distilled water. PROCEDURE
Spread a 0.500-gram sample of pulverized material evenly in a combustion boat and cover with 0.50 gram of standard ingot iron and approximately 1.0 gram of 30-mesh granular tin. If the sulfur content is higher than O.ZO%, add a preliminary buret of iodate or reduce the sample size proportionately.
V O L U M E 27, NO. 6, J U N E 1 9 5 5
951
Rinse out the titration vessel with distilled water and then add
The value for Bureau of Standards S o . 98 is shown as a range, since only tT7-o values were available on the certificate (0.06yo sulfur trioxide and 0.08% sulfur trioside) and they did not seem to warrant use of a definite value of 0.028% sulfur.
50 ml. of starch solution, 2 ml. of hydrochloric acid, and enough standard potassium iodate solution t o give a faint blue color to the mixture. Insert the boat with sample into the Combustion tube and center it in the combustion tube liner in the hot zone (1310’ to 1320” C.) of the furnace. Replace the stopper and, with the three-way stopcock in the oxygen line turned to the off position, set an interval timer for the 1-minute preheat period. After the sample has heated for 1 minute, turn the stopcock to admit oxygen at the rate of approximately 1 liter per minute. This flow rate should not be changed - after the factor has been established. As the sulfur dioxide flows into the starch-iodide solution it is titrated continuously with the standard potassium iodate solution, keeping the solution a faint blue color a t all times. Each operator should determine from experience the depth of blue color he prt=fcrs for the end point and use that end point for a11 determinations. This titration should not take more than 3 minutes. Rinse the titration vessel n-ith distilled water and prepare for the next determination. Turn off the oxygen a t the three-way stopcock, remove the inlet stopper, withdraw the boat, and visually inspect it to see whether a good fusion has taken place. Discard the hoat n i t h fusrd mateiinl, as the boats are not reused in this method. The sulfur content of the sample is calculated thus: (Buret reading - correction for steel flux) X factor =
Table 111. Percentage of Sulfur. Bureau of Standards Samples Sample KO.
la 88 97 98
Combustion Method.
hv.
0.27 0.027 0.017 0 027
Combustion Method, Range of 1 3 Runs 0.273-0.216 0.025-0.028 0.016-0.018 0.026-0.028
ACKXOFLEDG3IENT
Acknorvledgnient for preliminary work on temperature of combustion and use of t i n ns n flus is made t o E. R. Vance, Timken Roller Bearing Co. The rew1tP of his work hnve nut been publiPhed. LITERATURE CITED
yo S
(1) Am. Soc. Testing lIaterials, Philadelphia. Pa.. “Book of ASTXI Standards,” Designation C 25-47, Vol. 3 , p. 22S, 1952. ( 2 ) .Zm. Soc. Testing Materials, Philadelphia, Pa., “ AIethods for Chemical .Inalysis of lletals,” 1950. ( 3 ) Hillehrand, TV. F., and Lundell, G. E. F.. “.Ipplied Inorganic .Inalysis,” Wiley, X e w T o r k , 1929. (4) Laboratory Equipment Corp., St. Joseph, Ilich.. “Instructions
The factor is obtained from Sational Bureau of Standards samples of the same approximate compoqition and sulfur content as the unknown samples. R E X LTS
The method gave highly reproducible and accurate results n-hen the combustion values Lvere compared against National Bureau of Standards samples of limestone ( S o . la), dolomite (No. 88), and clays (h’os. 97 and 98). The certificate values shown in Table I11 are the values for sulfide sulfur and sulfur trioxide taken from the certificates and recalculated to total sulfur.
Certificate Value. (Recalculated) 0.27 0.027 0.017 0.024-0.03‘7
for Leco Sulfur Deterininator for Iodometric AIethod with Special .Iccelerator. ” 1950. ( 5 ) Vance. E . R., Tiniken Roller Bearing Co., Canton, Ohio, personal communication. RECEIVED for r e r i e x October 7 . 19.54. Accepted February 7 , 1955. Presented a t t h e Pittsburgh Conference on .\nalytical Chemistry and Applied SpectroscoL>y, March 2, 1933. Published with the permission of t h e State Geologist, Indiana Department of Conservation, Geological S u r r e y .
Test for the Vicinal Dithiol Group DAVID H. ROSENBLATT and GEORGE N. JEAN Chemical Corps Medical Laboratories, Army Chemical Center,
Manganous acetate in a system containing pyridine and water may be used as a specific reagent for vicinal dithiols. Eleven representative monothiols and one nonvicinal dithiol fail to give the test. Under suitable conditions vicinal dithiols may be estimated in the presence of monothiols and nonvicinal dithiols.
T
HE use of compounds containing thiol groups on adjacent
carbon atoms, especially of 2,3-dimercapto-l-propanol (variously knon-n as DTH, British antilewisite, B.4L, or dimercaprol), in the treatment of arsenical and heavy metal poisoning has been a subject of continuing interest. I n a comprehensive Stocken review of the literature on 2,3-dimercapto-l-propanol, and Thompson (11 ) indicated that few studies had been made of the chemical reactions of this substance. The only analytical method for aliphatic vicinal dithiols noted by those authors is that of Aldridge (I), which the present ttuthors have found to be long and involved. to require hazardous reagents and expert technique, and to be applicable, in its present form, only to very dilute solutions. Other authors (a,9, 10) have noted the color with heavy metals, and the reactions of 2,3-dimercapto-l-propanol limitations of these reactions for analytical methods. It was the object in the present study to evolve a relatively simple test as a part of the positive identification of 2,3-dimercapto-l-propanol.
Md.
I n particular the authors wanted to distinguish it from 1,3-di mercapto-2-propanol, which presents similar physicochemica properties. The difference b e h e e n the reaction of 2,3-dimercapto-l-propanol with manganous acetate in pyridine and that of 1,3-dimercapto-2-propanol was first observed by the authors during a study of the conductometric titration of these dithiols with heavy metal acetates in pyridine ( 7 ) . I t was noted that there was a substantial difference in the conductances of the dithiol solutions after addition of manganous acetate, and, more rdevant to the present work, that rrhen the nitrogen sweep was terminated and the solutions were exposed to air there were decreases in both conductance and color (dark green). These decreases were comparatively rapid in the case of the 1,3-dimercapto-2-propanol. whereas the color produced by 2,3-dimercapto-l-propanolappeared sufficiently stable for colorimetry. Under similar conditions, 2-mereaptoethanol produced a much less intense coloi (lavender) and a far lower conductance. I t has been reported (2) that manganous ion fails to give a cola! reaction with 2,3-diniercapto-l-propanolor to catalyze its oxidation in neutral aqueous solution. I t is also noteworthy that toluene-3.1-dithiol. under the acidic conditions of the test for tin ( 1 3 ) , forms neither a colored complex nor a precipitate with as much as 1% manganous sulfate. On the other hand, there is
