I
H. P. MEISSNER, E. R.
CONWAYl, and H. S. MICKLEY
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge
39, Mass.
Synthesis of Hydrogen Persulfides This report gives data on the first quantitative examination of the variables involved in preparing hydrogen persul-
fides from an inorganic polysulfide and an inorganic acid
Hydrogen persulfides are easily made, are very reactive, and may have considerable industrial interest if yields as good as those reported here can be obtained under operating conditions. Little quantitative information has been published on raw oil production or its conversion to pure persulfides. Results of the study of this synthesis from organic acids and sodium polysulfide are reported.
T H E persulfides of hydrogen, first prepared by Scheele (77) in 1777, may be synthesized in a number of different ways, including the oxidation-reduction of either sodium thiosulfate or sodium hyposulfite in the presence of hydrochloric acid (5, 6), the reduction of sulfur dioxide by hypophosphorous acid (4, the electrolytic reduction of sulfur dioxide dissolved in a mineral acid (72), and the reaction of a n alkali polysulfide with hydrochloric acid (7-3, 70, 78). Thermodynamic calculations have been reported to show that the gas phase synthesis from hydrogen sulfide and sulfur may also be possible (72), but a review of these calculations suggests that their precision is too low to warrant definite conclusions, and that there seems little basis for optimism. The primary product of all syntheses for the hydrogen persulfides is “raw oil,” a solution of sulfur and hydrogen sulfide in a mixture of hydrogen persulfides. These persulfides form a homologous series having the general formula HzS,. Individual members of this series having n values from 2 to 6 have been Present address, Calco Chemical DiviCo., Bound
sion, American Cyanamid Brook, N. J.
separated from raw oil by fractional distillation, and homologs of even higher molecular weight are thought to exist (7, 2, 7-70). Under ordinary conditions, these persulfides are yellow liquids much like olive oil in appearance (74, 75), with specific gravities ranging from 1.3 to 1.7. They are immiscible in water, but are soluble in such solvents as carbon disulfide, chloroform, and benzene. Hydrogen persulfides are unstable, decomposing ultimately to hydrogen sulfide and sulfur; their stability increases with decreasing temperature. The rate of decomposition is greatly accelerated by the presence of various substances, including bases and oxidizing agents. Neutral water accelerates the decomposition, but stability increases with increasing acidity. Neither the individual hydrogen persulfides nor raw oil is today produced commercially. O n the other hand, these materials are easily made, are very reactive, and as such might have considerable industrial interest if good yields could be attained under reasonable operating conditions. To date, little quantitative information has been published either on raw oil production or on its subsequent conversion to pure persulfides. I n earlier investigations, yields have apparently been low, especially in the initial production of raw oil, regardless of the method of synthesis used. No study of the variables involved in raw oil production by any of these processes has been published. The object here is to report the results of a quantitative investigation of the raw oil synthesis from inorganic acids and sodium polysulfide. Care was taken to re-examine the claim of Walton and Parsons (78) that only hydrochloric acid could be used in this reaction.
Experimental Procedure
The general procedure involved mixing a n aqueous solution of sodium polysulfide rapidly into a n excess of miner%i acid. The sodium polysulfide solutions used were prepared on a steam bath by reaction of an aqueous solution of sodium sulfide crystals (NaZS. 9 & 0 ) with elemental sulfur in a n oxygen-free atmosphere. All experiments were made with freshly prepared polysulfide, Raw oil was produced by allowing such a polysulfide solution to flow into a cooled, stirred acid solution contained in a glass vessel, usually of 1-liter capacity. The polysulfide addition rate and the cooling rate were regulated to maintain a constant reaction temperature. During the course of the reaction, hydrogen sulfide^ was evolved, sulfur was precipitated, and droplets of raw hydrogen persulfide oil were formed. As raw oil has a greater density than the aqueous phase, these droplets settled to the bottom of the reaction flask, if stirring was not too violent. After the addition of the sodium polysulfide solution was completed, stirring was stopped and the product oil was settled, separated, dried, weighed, and analyzed. I n one experiment the acid was added to the polysulfide; no product other than hydrogen sulfide (H,S) and sulfur was obtained. The variables studied were temperature, sodium polysulfide composition, sodium polysulfide concentration, acid type, acid concentration, and stirring: the ranges covered are shown in Table I. The following measurement procedures were used. Hydrogen Persulfide (Raw Oil) Composition. The raw oil was analyzed by the quartz powder method of Feher. VOL. 48, NO. 8
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B
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BO
60
w 40
20
formula Tu'azS,, where x denotes the atoms of sulfur associated with 2 atoms of sodium. The atoms or sulfur in a solution were determined directly by analysis, while the atoms of sodium present were calculated from the weight of sodium sulfide monohydrate used in its preparation. No attempt was made to determine the true composition of the sodium polysulfide solution-i.e., the distribution of S---, S2--, etc.: ions. Sodium Polysulfide Concentration, This is reported as M , the molarity, expressed as moles of Na2S, present per liter of solution. This concentration was calculated directly from the measured volume of the solution and the moles of sodium sulfide nonahydrate used in its preparation. Free Acid Concentration in Reacting Bath. This is defined as the total equivalents of acid present, minus the total equivalents of sodium added as polysulfide. In early runs? strong acid was added to the reaction vessel simultaneously Ivith polysulfide solution. and at such a rate that the free acid concentration remained constant. I t was thus established that within certain limits )-ields \\'ere independent of free acid concentration. In subsequent runs, surficient acid was initially placed in thc reaction vessel to keep the free acid concentration within these limits during thr: run. In these cases: no further acid \vas added during addition of polysulfide. Stirring Conditions. Four mixing conditions were studied. Three or these were explored in a 3-necked, 1-liter, round-bottomed flask fitted with a glass propeller stirrer, and the fourth in a 400-ml. beaker equipped with four Lucite baffles and a stirrer.
0
0
/
2
4
3
S O D / U N POLYSUL f/DE COMPOS/T/ON ( V A L U E O F x /N N a g S X l Figure 1. Effect of Sodium Polysulfide Composition. Na2S,-HCI reaction with rapid mixing. T = 0" C.
Talpay, and Heuer (13), and the composition reported as HZS,,, where 71 represents the atoms of sulfur associated with 2 atoms of hydrogen. Hydrogen Persulfide Yields, The quantity of product made was determined by direct weighing and the yield
Acid HC1
Acid Concn., Wt. % 10-37
Experimental results of
reported as (moles of HrS,, produced),' (100 moles of Na& added). Temperature. Temperature was measured by a thermometer inserted directly into the reaction vessel. Sodium Polysulfide Composition. This material was assigned the average
Table 1. Range of Variables Studied Sodium Sodium Polysulfide ' Polysuljide Reaction Compn. x Molarity, Ten$. , in ATa,Sz M C. 1 6-4 6 0 3-4 0
Stirring Conditions Slow, rapid. very rapid and
H2S04
H3P04
1 348
5-75 37-60
1 8-4 9 3 4
0 3-2 2
INDUSTRIAL A N D ENGINEERING CHEMISTRY
-10-t50 0
trolled Rapid Rapid
con-
I . Slow mixing, I-liter flask. Stirrer speed maintained a t 5 to 10 r.p.m.. liquid slowly swirling. At this speed, the oil separated readily, and formed a heavier layer below the aqueous phase. 2. Rapid mixing, 1-liter flask. Stirrer speed maintained a t 50 to 150 r.p.m. In the early work it was noted that yield appeared insensitive to stirrrr speed in this range, which was l o ~ v enough so that the freshly formed oil could settle to the bottom of the flask. 3. Very rapid mixing, 1-liter flask. At stirrer speeds above 150 r.p.m., oil droplets bvere kept suspended in the aqueous layer, where they came in contact with freshly added sodium polysulfide. This resulted in a reduction in yield. T o avoid this difficulty whilc attaining better mixing, an air jet \vas used to disperse the entering polysulfide feed. The air entered through a small nozzle: arranged to cause the air jet to impinge upon the entering sodium polysulfide: and to carry it rapidlj, beneath under the acid surfacc. Thesr conditions served to mix the sodium polysulfide rapidly into the aqueous phase, but did not prevent settling of the oil droplets out of the aqueous layer. 4. Stirred baffled reactor. The 1-
d
liter flask did not permit a n adequate variation in mixing conditions unless the air jet was used. Consequently, a reaction vessel was constructed in which the mixing rate was a pronounced function of stirrer speed. I t consisted of a 400ml. beaker with four Lucite baffles spaced 90’ apart bonded to the inside of rhe beaker. A straight impeller was centrally located and positioned one impeller diameter above the bottom of the beaker. The speed of the motordriven impeller was controlled by a rheostat. With this arrangement, the mixing rate was a pronounced function of the impeller speed, giving a “controlled” mixing rate. No air jet was used. The sodium polysulfide solution \vas added to the acid by means of a glass nozzle I / Q ~inch in inside diameter, tvhich formed a jet that penetrated the liquid surface.
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Precision and Reproducibility
Error is introduced into the calculation of both yield and composition of raw oil, if hydrogen sulfide remains dissolved in the raw oil. This dissolved gas was removed prior to analysis by subjecting the samples to reduced pressure, but uncertainty was introduced in determining when to stop such degassing, as raw oil will decompose slowly under reduced pressure to evolve hydrogen sulfide. Because of this uncertainty, it was estimated that a n error of u p to 5% in the yield value might have been introduced. Dissolved sulfur is a further possible source of error in the determination of raw oil composition. All attempts to separate the raw oil from the sulfur by solvent extraction and vacuum distillation proved to be so unreliable that they were abandoned. In consequence, when dissolved sulfur was present, the value of n calculated as indicated above is too high. The general reproducibility of experimental results was relatively poor. Product yields apparently could be determined with greater precision than the product composition ( n ) values. Difficulties associated with the quantitative removal of the product phase from the aqueous acid phase, and of the dissolved hydrogen sulfide from the raw oil, are believed to be among the factors responsible for variations in product yield. The poor reproducibility of the product composition is also attributable, at least in part, to variations in the amount of dissolved sulfur. Factors like variations in localized alkalinity and temperature and in trace impurities also have an adverse effect upon reproducibility. For several runs, a detailed accounting of all materials in and out of the reactor was undertaken. I t was found that material balances (including measurement both of the hydrogen sulfide evolved during the reaction and of the sulfur precipitated) could be made with
SOO/UM P O L Y S U L F / D E C O M P O S / T / O N ( V A L U E OF x /N N a e S x ) Effect of acid type. Experimental results of Na&, _ _ reactina with hydrochloric, sulfuric, and ’phosphoric acids with rapid mixing. T = 0” Molarity 2
c.
reasonable success. The material balances show that the net synthesis reaction satisfies the relation
+ 2H+ = y HzS, + (1 - y ) HzS + [ x - y n - ( 1 - r)l s +
Na&
2 Na+
(1)
Experimental Results
Both the yield and composition of the raw oil produced were influenced, a t least to some degree, by the type of acid used, the composition of the sodium polysulfide-Le., the value of x in NaQS, -the mixing conditions, the molarity of the sodium polysulfide, the acid concentration, and the temperature. Acid Type. I t was found that sodium polysulfide could be successfully acidified with hydrochloric, sulfuric, or
phosphoric acid to form raw oil. I n general, product yields were in the order hydrochloric > sulfuric > phosphoric. This is in direct contradiction to the claims of Walton and Parsons (78),who state that only hydrochloric acid yields the desired product. Walton and Parsons do not present details of the experimental procedures used with these other acids, and so the reasons for their negative results are not apparent. Sodium Polysulfide Composition. The yield of raw oil increases strongly with an increase in x, in both hydrochloric and sulfuric acid media, as is evident from inspection of Figures 1 and 2, A . The value of n in the empirical raw oil formula HzS, also increases with x, as is clear from Figures 1 and 2, B. Trends cannot be deduced for phosVOL. 48, NO. 8
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polysulfide solution. Consequently, in this equipment the additional decomposition resulting from the increase in vertical velocity associated with more rapid stirring counteracts the improved yield that might otherwise be expected. Sodium Polysulfide Molarity. The yield of raw oil drops significantly as the molarity of sodium polysulfide is increased from 1 to 2, as shown in Figure 1, A . However, examination of Table I1 indicates that no additional gain in yield occurs from the use of molarities less than unity, and no further reduction in yield occurs at molarities above 2. Molarity of the sodium polysulfide exerts an entirely analogous influence upon product composition, as shown in Figure 1, B, in that the molarity resulting in the higher yield also gives a product with a lower value of n.
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80 Table II. Experimental Results of Na&-Hydrochloric Acid Reaction with Rapid Mixing
60
(T =
Hjidrogtvz PersuQde (Raw Oil)
40
PolySodium sulfide Polysu&de .MolarC o m p n . , ~ ity, in iVu2SZ M
20
0
0
I
2
3
4
5
SODIUM POL Y S U L f lDE COMPOS/T/ON ( V A L U E O F Y /N N a g S x ) Figure 3. Effect of mixing conditions. chloric acid reaction
phoric acid, as only one experimental point is available. Inspection of Figure 2 suggests, however, that for a given value of x , yields are highest in hydrochloric acid and lowest in phosphoric acid, while the value of n is lowest in hydrochloric acid and highest in phosphoric acid. Mixing Conditions. The effect of mixing conditions on the yield and product composition obtained during experiments carried out in the 1-liter flask is shown in Figure 3. For values of x in the range of 2.5 to 3: an increase in the rate of mixing from slow to very rapid caused a 21/2-fold increase in product yield. As the product yield improved with better mixing, the value of n decreased.
1 350
o o C.)
Experimental results of Na&-hydro-
Presented in Figure 4 are the results of mixing tests carried out in the baffled reaction vessel. The product yield goes through a pronounced maximum, while the value of n exhibits a definite minimum when plotted as a function of stirrer speed. Visual observation of the equipment performance provides the explanation of the form of the curves. As stirrer speed is increased, the mixing conditions constantly improve. However. shortly before the maximum in the yield curve is reached, the vertical velocity component of the fluid becomes great enough to circulate droplets of the product phase from the bottom of the vessel to the surface of the fluid. At the surface, these droplets of product are decomposed by the freshly added sodium
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Initid-
Yield,
Final Acid
moles/
Concn., Wt. %
4.17 4.56
0.3 0.6
37-14 37-10
2.30
0.9
37-10
2.64
1.2
23-14
3.22
0.9
20-10
3.57
1.0
28-10
4.55
1.0
28-10
1.60
2.0
21-10
1.78
1.9
21-14
2.11
1.8
16-10
2.58
2.0
13-10
3.02 3.18
1.7 1.8
21-14 15-1@
3.60 4.09
2 1
2 0
26-18 20--14
4 54
2.1
20-14
3.18
4.1
17-10
700 Compn., moles n in
Na& 59 72 74 38 36 40 39 52 52 57 59 70 69 16 15 16
16 26 24 31
30 35 40 39 47 47 54 58 60 38 38
3.90
3.8
16-I@
54 51
Has,
5.5 5.8 5.5 4.3 4.2 4.6 4.7 4.9 5.0 5.1 5.1 5.8 5.9 4.5 4.5 4.3 4.3 5.0 5.2 5.6 5.8 6.2 5.9 9.3 5.8 7.0 6.0 6.6 6.4
6.5 6.3 6.1 6.2
E
Acid Concentration, I n the range of 10 to 37 weight yo,the concentration of the hydrochloric acid used had little effect upon this reaction, as is evident from the data of Table 11. Sulfuric acid concentration, on the other hand, had a more significant effect. Figure 5 shows that yield was a maximum and the value of n a minimum at about 35 weight yo acid. Further study of these figures shows that the curves are relatively flat in the region between 25 and 50 weight % acid (6 to 14N) but exhibit steep slopes a t both lower and higher concentrations. The acid concentration reported here is the initial concentration of the pool of acid into which the polysulfide solution is introduced. This free acid concentration was maintained relatively constant in experiments designed to test the effect of acid concentration. Temperature. Although the data scatter badly, somewhat lower yields and higher n values appear to result from zin increase in reaction temperature. This is evident from Figure 6, in which product yield and composition obtained with sulfuric acid are plotted as functions of reaction temperature.
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80
60
Reaction Mechanism
The foregoing results appear consistent with the following postulated mechanism. A. The net reaction for the digestion of sulfur in sodium sulfide may be written : NazS
+
(x
-
1 ) S = NazS,
(2)
40
20
This reaction is really the sum of a group of reactions:
+ S = NazS2 NazSZ + S = NazS3 NazS3 + S = NazSa NaZS
(3) (4)
(5)
Similar reactions may be written for Na2S6, Na&, and Na&. While there is some doubt about the existence of Na2S3 (77), the existence of the other individual polysulfides has been demonstrated (77, 73, 76). B. Reactions 3, 4, 5, and the like all proceed simultaneously. I n consequence, each of the polysulfides from Na& to Na2S7is probably present, at least to some degree, in a freshly prepared reaction product. With time, a series of slow disproportionation reactions of the type Nag& NazS4 = ZNazSs (6)
+
NazSa
+ NaZSS
=
2NazS4, etc.
(7)
probably occurs, resulting in a redistribution of sulfur among the various polysulfides. The fact that reactions of types 6 and 7 exist is supported by the “aging” of these solutions even under nitrogen. The slow rate of the disproportionation reactions is shown by the
0 7 00
800
9 00
IO00
$T/RREr? S P E E D , R. P. Ad. Figure 4. Effect of mixing rate. Experimental results of Na&,-hydrochloric acid reaction with controlled mixing in baffled mixing vessel, acid concentration always 24 to 10 weight %. T = 0” C. Sodium polysulfide composition. Molarity 2
fact that the individual pure polysulfides have been isolated. C. At p H values less than about 13, sodium polysulfide solutions react with hydrogen ions. The initial result of the acidification reaction is to form a mixture of hydrogen persulfides. The Na& is converted to H2S2, the Na& to H2S3, etc. D. At p H values greater than about 1, all of the hydrogen persulfides (including raw oil) decompose to release sulfur and H2S. The decomposition of the hydrogen persulfides is also brought about by a wide variety of metallic salts and oxidizing agents (78). H2Sz and H & appear to be especially sensitive to p H and contaminants. The over-all result of the acidification of a
sodium polysulfide solution then is strongly influenced by the environment surrounding the newly formed H2S, molecule. If the p H of this environment is significantly greater than unity, substantial decomposition of the H& and particularly of HzS2 and HzS3 is probable. The presence of contaminants may also bring about the decomposition of the HzS,. The over-all result of the acidification of sodium polysulfide may then be represented by Reaction 1. Interpretation of Results
The experimental results can now be interpreted in terms of the foregoing hypothesis. VOL. 48, NO. 8
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135 1
10
8
B 6
4 1.0
0.8
0.6
0.4
0.2
0 SUL FURIC A C / D CONCENTRATION WElGHT PERCENT Effect of sulfuric acid concentration.
Acid Type. Raw oil is produced by acidifying sodium polysulfide with each of the three inorganic acids studied as according to Reaction 1, the effective agent in acidification is the hydrogen ion. Sodium Polysulfide Composition. As x is increased by adding more sulfur to a sodium polysulfide solution, the yield of hydrogen polysulfides resulting from acidification is increased for two reasons. Reactions 3, 4, and 5 are driven further to the right, increasing the available moles of polysulfide ions. Furthermore, as x is increased, the fraction of the total polysulfides represented by S2-- and S3-- is reduced. The experimental data show that the value of n in the empirical raw oil formula H&, never falls below 4 regardless of x, a n indication that no H&
1 352
T
=
0" C.
Molarity 2.
Rapid
and HzS3 survive acidification. Consequently, a reduction in the fraction of the total polysulfides represented by S2-- and Sa-- decreases the decomposition during acidification and improves the raw oil yield. Mixing Conditions. The effect of the mixing rate is explained by Hypothesis D. Just before the sodium polysulfide solution is added to an acid, the polysulfide ions present are in a highly basic atmosphere and so are relatively stable. As the solution is mixed with acid, the p H of the atmosphere around the polysulfide ions is lowered. During the acidification, some hydrogen persulfides are formed while the surrounding atmosphere is still at a p H a t or above unity. I n such an atmosphere, the hydrogen persulfides are unstable and
INDUSTRIAL A N D ENGINEERING CHEMISTRY
tend to decompose. The extent of decomposition of the polysulfides depends upon the length of time they remain in a nonacidic environment, which, in turn, depends upon the mixing rate. The higher the mixing rate, the closer is the approach to complete conversion of all the polysulfide ions to hydrogen persulfide molecules. The decrease observed in n as higher mixing rates were used may be explained in terms of the above, and of Hypothesis E. When higher yields were obtained, the ratio of precipitated sulfur to moles of product oil decreased, so that less sulfur was available for solution per mole of raw oil. This resulted in a decreased value of n. Polysulfide Molarity. The effect of the sodium polysulfide molarity on composition and yield of the raw oil appears to be the result of the interplay between two competing mechanisms A change in molarity changes the polysulfide composition, tending to give lower yields at lower molarities, as implied by Equation 5. On the other hand, lower molarities tend to reduce decomposition of polysulfide during the synthesis reaction, because of faster acidification of the more dilute solution. In the molarity range of 1 to 2. the increase in speed a t which acidification was accomplished in the equipment used seemed to be more important. as the low molarity gave greater yields Outside this range, however, the competing effects seemingly cancelled. These results suggest, however, that, if the mixing rate can be increased beyond the values attained here, high polysulfide molarities should give better vields. Acid Concentration a n d Type. The effect of the acid used is explained also by Hypothesis D. The degree of decomposition during the acidification of the sodium polysulfide solution is dependent upon the concentration and type of acid used. The rapid acidification of the medium surrounding the polysulfide ions minimizes decomposition. High hydrogen ion concentrations promote rapid acidification. Increased mixing rates are obtained when the acid medium has a low kinematic viscosity and a high diffusivity. The acid radical has an effect upon the decomposition rate, Oxidizing agents such as concentrated sulfuric acid cause decomposition of the raw oil. Sodium chloride (formed in the reaction with hydrochloric acid) causes slow decomposition of the raw oil. The raw oil yields obtained by acidification with hydrochloric acid solutions show no significant change over the range 10 to 37 weight yo hydrochloric acid (2.9 to lZAV in hydrogen ion). Over this concentration range. the kinematic viscosity at 0' C. of the acid solution increases only l2yO. Within
1
this range of hydrochloric acid concentration, an increase in hydrogen ion concentration does not significantly increase the yield. This indicates that either the physical mixing rate is controlling or the expected improvement due to higher hydrogen ion concentration is compensated by increased decomposition due to higher chloride ion concentration and/or higher local temperatures at the reaction site. In contrast, the sulfuric acid concentration has a marked effect on the results. The yield increases steadily with acid concentration up to a value of 35 weight % (9N in hydrogen ion). At higher acid concentrations, the yield decreases. The kinematic viscosity of sulfuric acid a t 0’ C. increases by a factor of 4 as the concentration increases from 35 to 70y0 acid. This increase in viscosity may decrease the yield by slowing the physical mixing of acid and polysulfide and/or through the lowered diffusivity of the acid. With other factors constant, a plot of the yield against the logarithm of the relative viscosity gives a straight line with a slope of -0.20 in the range of 35 to 65y0 acid, indicating that in this concentration range the yield varies inversely as the 0.20 power of the kinematic viscosity. At concentrations above 6570, the yield decreases more than would be expected from variation in the acid viscosity alone. I t is thought that this decrease is due to the increasing oxidizing properties of concentrated sulfuric acid. The yields with sulfuric acid are lower than those with hydrochloric acid, probably chiefly because of the higher kinematic viscosity of the former acid. If the curve of Figure 2,A, for sulfuric acid is multiplied by the 0.20 power of the ratio of the kinematic viscosities of 5070 sulfuric and 20% hydrochloric acids, the curves for sulfuric and hydrochloric acids nearly coincide. When phosphoric acid was used as the acidifying agent, the acid concentration varied between 60 and 37 weight yo (26 to 14N in hydrogen ion). At the same weight per cent, the kinematic viscosity of phosphoric acid solutions is somewhat greater than the kinematic viscosity of sulfuric acid solutions. Consequently, the observed lower yield when phosphoric acid was used might result from a lower mixing rate. However, the single data point available does not permit significant comparisons. Temperature. The reaction temperature affects both the stability of the product and the rate at which the reagents are mixed. High temperatures increase the product decomposition rate, and because of a decrease in viscosity and increase in diffusivity, increase the mixing rate. These effects are antagonistic, but the data indicate that
50
40
30
A 20
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0
0
Figure 6. Effect of reaction temperature. Experimental results of Na&sulfuric acid reaction with rapid mixing. Sodium polysulfide composition always Na& Molarity 2. Acid concentration always 50 weight %
the effect of temperature on stability is the more important.
literature Cited (1) Becker, C. L., “Investigation of Possibility of Producing Sodium Disulfide Commercially,” S.M. thesis, Chemical Engineering Department, Massachusetts Institute of Technology, 1949. (2) Bloch, I., Hon, F., Ber. 41, 1961-85 (1908). (3) Butler, K. H., Maas, O., J . Am. Chem. SOC.52.2184-98 (1930). Deines, 0. von, Ann. 440, 213-14 (1924). Deines, 0. von, Z. anorg. u. allgem. Chem. 117, 13-16 (1928). Zbid., 177,124-8 (1929). Feher, F., Baudler, M., Z. anorg. Chem. 253, 170-2 (1947). Ibid., 254,251-4 (1947).
(9) Ihid.. D D . . 289-92.
(iOj
Ibid.: %8,132-49 (1949). (11) Feher, F., Berthold, H. J., Ibid., 273, 144-60 (1953). (12) Feher, F., Heuer, E., Angew. Chem. A59, 237-8 (1947). (13) Feher, F., Talpay, B., Heuer, E., Z. anorg. Chem. 255, 316-22 (1947). (14) Hodgman, C. D., “Handbook of Chemistry and Physics,” Cleveland, Ohio, 29th ed., Chemical Rubber Piihlishing. Go..1945. - ...~ ....(15) “lnternatiogal Critical Tables,” McGraw-Hill, New York, 1933. (16) Pearson, T. G., Robinson, P. L., J . Chem. Soc. t430, pp. 1473-97. (17) Scheele, C. W., Chemische Abhand~, lung von der’Luft und dem Feuer,” pp. 162, 163, 1777. (18) Walton, J. H., Parsons, L. B., J . Am. Chem. Soc., 43,2539-48 (1921 ). ~
RECEIVEDfor review July 28, 1955 ACCEPTED February 21,1956 VOL. 48, NO. 8
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