The Polarographic Determination of Organic Accelerators of Vulcanization

1941 ◽  
Vol 14 (4) ◽  
pp. 914-919 ◽  
Author(s):  
Gerard Proske
Keyword(s):  
Double Bond ◽  
Organic Compounds ◽  
Analytical Determination ◽  
Polarographic Method ◽  
Rubber Industry ◽  
Vulcanized Rubber ◽  
Color Reactions ◽  
Analytical Utility ◽  
Kjeldahl Nitrogen

Abstract In spite of the great importance which vulcanization accelerators have attained in the rubber industry, there is still an almost complete lack of analytical methods, both for determining the accelerator contents of rubber mixtures and for identifying accelerators in vulcanized rubber. Apart from the wholly unsatisfactory and uncertain method of deciding the existence of organic accelerators in vulcanized rubber by a Kjeldahl nitrogen determination, there is little of value in the literature. Twiss and Martin have described a few qualitative reactions of accelerators. Recently Shimada described some color reactions of accelerators with cobalt oleate, but the analytical utility of these reactions is very doubtful. Of far more promise than these is the polarographic method, the value of which in the analytical determination of a series of important accelerators was proved in an investigation which will be described in the present paper. It had already been proved in earlier polarographic investigations that organic compounds containing nitrogen with a double bond can be reduced electrolytically, provided groups with a tendency to rupture are close to the double bond. Shikata and Tachi have shown this to be true of azobenzene, and Winkel and Proske of dimethylquinoxaline.

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.

Sulfur Bond in Vulcanizates Implications of Halogen Reactions

1947 ◽  
Vol 20 (3) ◽  
pp. 627-648
Author(s):  
S. R. Olsen ◽  
C. M. Hull ◽  
Wesley G. France
Keyword(s):  
Double Bond ◽  
Carbon Tetrachloride ◽  
Sulfur Atom ◽  
Side Reactions ◽  
Double Bonds ◽  
Vulcanized Rubber ◽  
Iodine Chloride ◽  
Allyl Sulfide ◽  
Sulfur Bond

Abstract 1. When iodine chloride is used for the determination of double bonds in sulfur-vulcanized rubber or GR-S, it undergoes side reactions induced by combined sulfur. 2. Bromine in carbon tetrachloride is believed to give a satisfactory measure of the double bonds in a rubber-sulfur vulcanizate dissolved in dichlorobenzene-chloroform mixture. 3. The relation of one double bond consumed per sulfur atom combined in the rubber-sulfur type vulcanizate was confirmed. 4. Organic accelerators (in the absence of metal activators) catalyze the combination of sulfur without altering the ratio of one double bond loss per sulfur atom combined. 5. The introduction of a metal oxide or soap, such as zinc, causes a different type of vulcanization, which results in less than one double bond consumed per sulfur atom combined. 6. The reactions of propyl sulfide, dodecyl sulfide, propyl disulfide, allyl sulfide, methallyl sulfide, and butylmethallyl sulfide with iodine chloride and with bromine, respectively, are described. 7. The behavior of rubber-sulfur vulcanizates resembles that of butylmethallyl sulfide in reactions with iodine chloride and bromine, respectively; this suggests an alkyl-allyl type sulfur bond. 8. The theory of vulcanization proposed by Armstrong, Little, and Doak, based on the α-methylenic concept of Farmer, is supported by the findings of this investigation.

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 Vulcanized Rubber

1942 ◽  
Vol 15 (2) ◽  
pp. 376-377
Author(s):  
J. G. Mackay ◽  
C. H. J. Avons
Keyword(s):  
Nitric Acid ◽  
Hydrochloric Acid ◽  
Barium Sulfate ◽  
Barium Chloride ◽  
Acetone Extract ◽  
Volumetric Method ◽  
Watch Glass ◽  
Rubber Industry ◽  
Vulcanized Rubber

Abstract The following comments pertain to a paper of the above title by Mackay and Avons, published in Transactions of the Institution of the Rubber Industry, Vol. 16, pages 117–122, October 1940, and reprinted in Rubber Chemistry and Technology, Vol. 14, pages 520–524, April 1941. H. P. Stevens draws attention to the penultimate paragraph on p. 522 in which it is pointed out that the bromine method of oxidation is tedious and the reagent unhealthful, whereas perchloric acid may be dangerous. As a result of many years experience he is of the opinion that neither reagent is necessary. After adding nitric acid to the acetone extract in the flask, which should be covered with a watch glass, and when the reaction has subsided, about 0.5 gram of potassium chlorate is added and the mixture kept warm at 50 to 60° C. The top of a water oven is convenient; but the heating must be limited, as the yellow oxides of chlorine are rapidly driven off near 100°, and the liquid changes back from yellow to orange. The flask can be left to itself for an hour or two, but further addition of chlorate may be necessary to complete the oxidation. The contents are evaporated to dryness and taken up twice with concentrated hydrochloric acid preparatory to precipitation with barium chloride. A volumetric method may be preferable when a large number of routine tests have to be made, otherwise the final estimation can be made as barium sulfate.

THE THYMOLYTIC ACTIVITY OF 6- AND 9-HALOCORTICOIDS AND RELATED STEROIDS

1965 ◽  
Vol 49 (2) ◽  
pp. 262-270 ◽  
Author(s):  
Ralph I. Dorfman ◽  
P. G. Holton ◽  
Fred A. Kind
Keyword(s):  
Double Bond ◽  
Subcutaneous Injection ◽  
Fluocinolone Acetonide ◽  
Relative Potency ◽  
Subcutaneous Route ◽  
Adrenalectomized Rats

ABSTRACT Adrenalectomized rats were used for the determination of the relative potency of various 6- and 9-halo substituted corticoids administered subcutaneously or by gavage using thymus weightas the endpoint. By subcutaneous injection, fluocinolone acetonide was the most active corticoid at 700 times that of cortisol. This compound was also the most active corticoid by the gavage route and was judged to be 570 times as active as the standard cortisol. The introduction of the 16,17-acetonide and 16,17-acetone 21-acetate groups into 17α,21-dihydroxy-9α,11β-dichloropregna-1,4-diene-3,20-dione increased the activity by a factor of 42 and 100, respectively. The introduction of the δ1 double bond into 6α-fluoroprogesterone 16,17-acetonide caused an increase of 10-fold in thymolytic activity assessed by the subcutaneous route

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