Determination of Free Sulfur in Hard Rubber

1955 ◽  
Vol 28 (4) ◽  
pp. 1221-1225 ◽  
Author(s):  
C. Wynne-Evans
Keyword(s):  
Sodium Sulfite ◽  
Volumetric Method ◽  
Aqueous Sodium ◽  
Free Sulfur

Abstract The volumetric method for the determination of sulfur by means of aqueous sodium sulfite has been adapted for the determination of free sulfur present in hard-rubber vulcanizates. This work was carried out because there was not a speedy free sulfur method applicable to hard rubbers, and the investigation has shown that, by the use of aqueous sodium sulfite, it is possible to obtain reliable and extremely accurate free sulfur results in a little over three hours, against the usual three to four days by other methods which are discussed.

The Determination of Free Sulfur by a Volumetric Method Part II

1933 ◽  
Vol 6 (4) ◽  
pp. 512-517
Author(s):  
W. D. Guppy
Keyword(s):  
Hydrogen Sulfide ◽  
Organic Compounds ◽  
Sulfur Compounds ◽  
Acetone Extract ◽  
Volumetric Method ◽  
Organic Sulfur Compounds ◽  
Vulcanized Rubber ◽  
Volumetric Determination ◽  
Free Sulfur

Abstract 1. The method previously described for the volumetric determination of free sulfur in vulcanized rubber has been compared with the older gravimetric methods in cases where other organic compounds containing sulfur are present in the vulcanizate. 2. The volumetric method gave lower results than the methods involving oxidation of the acetone extract in the case of vulcanized rubber containing aldehydeamine condensation products of thiouram disulfide compounds. This indicated that the sulfur combined with some organic compounds was not reduced by the reagents used. 3. The results with the accelerator tetraethylthiouram disulfide showed that in some cases part of the sulfur in organic compounds was reduced under the conditions of the reaction. 4. The acetone-soluble and the acetone-insoluble portions of brown substitute contain organic sulfur compounds. Part of the sulfur in these compounds was reduced to hydrogen sulfide by the action of nascent hydrogen. 5. The sulfur compounds present in white substitute were stable toward the reducing agents used in the estimation of free sulfur. 6. The sulfur compounds formed by the vulcanization of ebonite were in part reduced to hydrogen sulfide with tin and acid. Variations in the composition of the mixing and in the vulcanizing conditions altered the amount of these reducible compounds. 7. The volumetric method previously described cannot be used for the determination of the free sulfur in ebonite, brown substitute or in vulcanized rubber containing brown substitute. In the case of vulcanized rubber containing brown substitute or of ebonite the method can be used to determine the amount of sulfur in the acetone extract. 8. The volumetric method can be employed for the determination of the free sulfur in soft vulcanized rubber containing white substitute and in reclaimed rubber.

Determination of Free Sulfur in Stocks Cured with Sulfur Containing Accelerators

1962 ◽  
Vol 35 (2) ◽  
pp. 498-500
Author(s):  
E. P. Khehaskova ◽  
N. A. Okhapkina ◽  
V. N. Provorov
Keyword(s):  
Sodium Sulfite ◽  
Sodium Stearate ◽  
Cadmium Acetate ◽  
Strontium Nitrate ◽  
Vulcanized Rubber ◽  
Normal Method ◽  
Sulfur Containing ◽  
Sulfite Solution ◽  
Free Sulfur

Abstract For the determination of free sulfur in vulcanized rubber the normal method is the sulfite method, consisting of the heating of a sample of rubber with a solution of sodium sulfite. The free sulfur reacts with the sulfite, forming thiosulfate, which is determined by iodometric titration. The unreacted excess of sulfite is removed with formalin. The method gives good results in the analysis of stocks which do not contain sulfur-containing accelerators. In the presence of these accelerators the results are high: in some cases the method is quite inapplicable, as it is impossible to establish the endpoint of titration accurately. This may be explained by the circumstance that the accelerators and the products of their decomposition during vulcanization can pass into the solution of sodium sulfite and react further with the iodine. The method of determination of free sulfur proposed by Hardmann, consisting of the acetone extraction of the rubber in the presence of copper gauze, is protracted and complicated. A certain improvement in the sulfite method of Bolotnikov and Gurova was introduced in the ASTM method (1952). Sodium stearate is added to the sodium sulfite solution for better wetting of the rubber, and a certain amount of paraffin to prevent the formation of foam. After termination of heating the solution the stearic acid is precipitated with strontium nitrate and certain accelerators with cadmium acetate. For the majority of stocks this method gives correct results, but in a number of cases it is difficult to establish the end of titration at all.

Determination of Free Sulfur in Rubber. I. Iodometric Method of Determination of Free Sulfur

1935 ◽  
Vol 8 (1) ◽  
pp. 87-90 ◽  
Author(s):  
V. Bolotnikov ◽  
V. Gurova
Keyword(s):  
Sulfuric Acid ◽  
Sodium Sulfite ◽  
Erlenmeyer Flask ◽  
Method Of Determination ◽  
Free Sulfur

Abstract Up to the present time the determination of free sulfur has been carried out by extracting the rubber by acetone, followed by oxidation of the sulfur with bromine to sulfuric acid. This method has very substantial drawbacks, such as the fact that each determination of sulfur requires many hours, and the results of the analysis are received in the best cases on the second day. The method developed by the present authors is based on the iodometric method for the determination of sulfides, sulfites, and hyposulfites in the presence of one another. The rubber is treated with a solution of sodium sulfite Na2SO3, which transforms the free sulfur into hyposulfite, thus: Na2SO3 + S → Na2S2O3. The resulting solution. contains Na2SO3and Na2S2O3. The sample, about 2 g. of finely cut rubber, is put into an Erlenmeyer flask of 250–300 cc. capacity, and 100 cc. of 5% solution of sodium sulfite are added. Tests have shown that the best extraction of sulfur takes place in the presence of an excess of Na2SO3 over that required by the reaction. Five grams of dry sodium sulfite enough to extract from 0.05 to 2% S.

Determination of Free Sulfur in Rubber

1936 ◽  
Vol 9 (3) ◽  
pp. 514-519
Author(s):  
E. W. Oldham ◽  
L. M. Baker ◽  
M. W. Craytor
Keyword(s):  
Organic Compounds ◽  
Acetone Extract ◽  
Volumetric Method ◽  
The Cost ◽  
Free Sulfur

Abstract Values obtained by the volumetric method herein described compare favorably with those obtained by gravimetric methods when corrections are applied to the latter for the sulfur in the organic compounds in the acetone extract. The precision of the method is excellent, as duplicates in each set usually check within 0.01 per cent of free sulfur on the compound. This method is much faster than previous methods. The cost of the reagents is low when compared with most other methods.

Determination of Total and Free Selenium in Vulcanizates

1936 ◽  
Vol 9 (1) ◽  
pp. 167-171
Author(s):  
E. Cheraskova ◽  
L. Veisbrute
Keyword(s):  
Nitric Acid ◽  
Sodium Sulfite ◽  
Iodometric Titration ◽  
Hydrazine Sulfate ◽  
Sulfurous Acid ◽  
Aqueous Sodium ◽  
Rubber Compounds ◽  
Sulfite Solution ◽  
Total Selenium

Abstract The total selenium in rubber compounds may be determined by disintegrating with nitric acid and then separating the selenium by reducing the nitric acid solution with hydrazine sulfate, or by reducing with sulfurous acid after evaporation of the nitric acid. Free selenium is determined by extracting the rubber with aqueous sodium sulfite, from which selenium is precipitated by formalin. Free sulfur is determined volumetrically by iodometric titration after precipitating selenium from sulfite solution.

Formation of sodium disulfite in a solid-gas system

1991 ◽  
Vol 56 (8) ◽  
pp. 1575-1579 ◽  
Author(s):  
Jiří Vobiš ◽  
Karel Mocek ◽  
Emerich Erdös
Keyword(s):  
Sodium Sulfite ◽  
Heterogeneous Reaction ◽  
Optimum Conditions ◽  
Kinetic Measurements ◽  
Dissociation Pressure ◽  
Partial Pressures ◽  
Gas System ◽  
Gaseous Sulfur ◽  
Equilibrium Dissociation

The formation of sodium disulfite by the heterogeneous reaction of solid active sodium sulfite with gaseous sulfur dioxide in the presence of water vapour was investigated over the temperature range of 293 to 393 K at SO2. H2O and O2 partial pressures of 1.2-7.4, 1.2-6.4 and 0-11.3 kPa, respectively. The effect of the reaction time was also examined. Kinetic measurements were supplemented with the determination of the equilibrium dissociation pressure of SO2 in contact with sodium sulfite at 373.15 K. The major aim of the work was to establish the optimum conditions for attaining the maximum degree of conversion of the solid reactant to sodium disulfite. The conditions for the formation of virtually pure sodium disulfite were found.

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