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.

The Determination of Free Sulfur in Soft Vulcanized Rubber by a Volumetric Method

1932 ◽  
Vol 5 (3) ◽  
pp. 360-362 ◽  
Author(s):  
W. D. Guppy
Keyword(s):  
Hydrogen Sulfide ◽  
Sulfuric Acid ◽  
Organic Compounds ◽  
Subsequent Oxidation ◽  
Vulcanized Rubber ◽  
Elementary State ◽  
Previously Treated ◽  
Mineral Sulfides ◽  
Free Sulfur

Abstract The methods so far proposed for the determination of the free sulfur in vulcanized rubber depend upon the removal of the sulfur by extraction of the rubber with hot acetone, and subsequent oxidation to sulfuric acid of the sulfur in the extract. The extract is liable however to contain, in addition to sulfur in the elementary state, organic compounds containing sulfur derived from the rubber resins, accelerator, or antioxidant. In the subsequent oxidation this sulfur will be oxidized to sulfuric acid to an extent which depends on the method of oxidation used. In the present work, a method of analysis has been developed which is more rapid than the existing methods, and in which it is considered that the determination of the sulfur present in the elementary state is less likely to be affected by organic compounds containing sulfur. It has been found that when vulcanized rubber placed in contact with a metal, such as tin or aluminum, is boiled in hydrochloric acid, hydrogen sulfide is generated by the action of the nascent hydrogen produced. This reaction occurred with rubber which had been previously treated with acid alone to decompose metallic sulfides, but no hydrogen sulfide was obtained from rubber which had been previously extracted with acetone and was free from metallic sulfides. As these results showed that the reactions were not due to the presence of mineral sulfides, or of sulfur combined with the rubber, it was concluded that the hydrogen sulfide was formed by the reduction of the free sulfur.

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.

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 by Titration

1936 ◽  
Vol 9 (2) ◽  
pp. 318-321
Author(s):  
B. Faĭnberg
Keyword(s):  
Rapid Method ◽  
Recent Article ◽  
Method Of Determination ◽  
Preliminary Extraction ◽  
Free Sulfur

Abstract In a recent article on the “Iodometric Method of Determination of Free Sulfur” by Bolotnikov and Gurova (J. Rubber Ind. U. S. S. R., 10, 61 (1933); Rubber Chem. and Technology, 8, 87 (1935)), the authors described a rapid method for determining free sulfur in rubber without a preliminary extraction.

Development of a method for multielemental determination in water by EDXRF with radioisotopic source of 238Pu.

2019 ◽  
Vol 7 (2A) ◽  
Author(s):  
Camilo Fuentes Serrano ◽  
Juan Reinaldo Estevez Alvares ◽  
Alfredo Montero Alvarez ◽  
Ivan Pupo Gonzales ◽  
Zahily Herrero Fernandez ◽  
...  
Keyword(s):  
Thin Layer ◽  
Expanded Uncertainty ◽  
Considerable Decrease ◽  
X Ray ◽  
Precipitation Efficiency ◽  
Method Of Determination ◽  
Sensitivity Curves ◽  
Order Of Magnitude ◽  
Metrological Parameters

A method for determination of Cr, Fe, Co, Ni, Cu, Zn, Hg and Pb in waters by Energy Dispersive X Ray Fluorescence (EDXRF) was implemented, using a radioisotopic source of 238Pu. For previous concentration was employed a procedure including a coprecipitation step with ammonium pyrrolidinedithiocarbamate (APDC) as quelant agent, the separation of the phases by filtration, the measurement of filter by EDXRF and quantification by a thin layer absolute method. Sensitivity curves for K and L lines were obtained respectively. The sensitivity for most elements was greater by an order of magnitude in the case of measurement with a source of 238Pu instead of 109Cd, which means a considerable decrease in measurement times. The influence of the concentration in the precipitation efficiency was evaluated for each element. In all cases the recoveries are close to 100%, for this reason it can be affirmed that the method of determination of the studied elements is quantitative. Metrological parameters of the method such as trueness, precision, detection limit and uncertainty were calculated. A procedure to calculate the uncertainty of the method was elaborated; the most significant source of uncertainty for the thin layer EDXRF method is associated with the determination of instrumental sensitivities. The error associated with the determination, expressed as expanded uncertainty (in %), varied from 15.4% for low element concentrations (2.5-5 μg/L) to 5.4% for the higher concentration range (20-25 μg/L).

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