The Rapid Semimicrovolumetric Determination of Sulfur in Natural and Synthetic Rubber Vulcanizates

1957 ◽  
Vol 30 (1) ◽  
pp. 354-361 ◽  
Author(s):  
Bella B. Bauminger
Keyword(s):  
Zinc Oxide ◽  
Sulfuric Acid ◽  
Hydrochloric Acid ◽  
Schematic Diagram ◽  
Total Sulfur ◽  
Synthetic Rubber ◽  
Combustion Apparatus ◽  
Mineral Fillers ◽  
A Current

Abstract In the first part, a modified form of combustion apparatus for sulfur analyses is described, and the principle of the method and the apparatus itself are illustrated by a schematic diagram. In the determination of sulfur in natural-rubber, Butyl-rubber, and Krylene mixtures which contain no mineral fillers such as barytes and whiting, 50 mg. of finely divided vulcanizate is covered with aluminum oxide, decomposed in a current of oxygen at 1000° C, and the sulfuric acid formed is determined gravimetrically. An analysis requires about 30 minutes. Differences between the analytical values obtained and the calculated values never amount to more than ±1 per cent. In the second part of the work, a newly developed procedure for the determination of total sulfur in rubber mixtures which contain barytes, lithopone, whiting, etc., is described. The sample is covered with a mixture of vanadium pentoxide and zinc oxide and is then decomposed in a current of oxygen at 1000° C Here too the sulfuric acid which is formed is titrated acidimetrically. An analysis requires about one hour. The final part of the work deals with a new method for the determination of sulfur in synthetic-rubber vulcanizates, such as Neoprene, Perbunan, Hypalon, etc. The sulfuric acid formed by their combustion is precipitated by a hydrochloric acid solution of 4-amino-4′-chlorobiphenyl, and titrated with sodium hydroxide. Zinc, chlorides, and nitrates have no disturbing effects on the reaction. The method was tested with vulcanizates of known compositions and was found to give satisfactory results.

Contributions to the Analysis of Rubber. IV. Determination of Manganese in Crude Rubber; in Rubber Mixtures and in Fillers

1940 ◽  
Vol 13 (2) ◽  
pp. 430-436
Author(s):  
P. Dekker
Keyword(s):  
Sulfuric Acid ◽  
Nitric Acid ◽  
Hydrochloric Acid ◽  
Reliable Method ◽  
Orthophosphoric Acid ◽  
Manganese Ions ◽  
Potassium Periodate ◽  
Mineral Fillers ◽  
Manganese Compounds

Abstract A scheme for the determination of manganese in mineral fillers, compounding ingredients, crude rubber, rubber mixtures and rubberized materials is described. It is shown that with this method the use of potassium persulfate and two drops of orthophosphoric acid, as proposed by Kehren for the oxidation of colorless manganese ions to red permanganate ions, is advisable. When potassium periodate is used, small quantities of manganese escape detection. It is further shown that there is no appreciable difference between concentration with nitric acid and evaporation with hydrochloric acid and a little sulfuric acid. If, however, the ash is decomposed by soda-potash mixture, the manganese contents are considerably higher. Doubtless these higher values can be accounted for by manganese compounds which are occluded in silicates, and which can be regarded as harmless. A reliable method for the decomposition of the manganese compounds is therefore desirable. The results of analyses of the manganese contents of a large number of various materials are tabulated, and the maximum manganese contents of various materials allowed by the Netherlands Government Rubber Institute are given.

A Rapid Method for Determining Sulfur and Ash in Rubber by Ignition of the Rubber in Oxygen

1936 ◽  
Vol 9 (3) ◽  
pp. 492-495
Author(s):  
B. Kreps
Keyword(s):  
Rapid Method ◽  
Volumetric Method ◽  
Total Sulfur ◽  
Method Of Determination ◽  
A Current

Abstract 1. The rapid method of determination of total sulfur and ash by ignition of rubber in a current of oxygen is not less accurate than the method of Henriques. 2. The proposed method can be used with all kinds of rubber mixtures except those containing litharge. 3. In the analysis of mixtures containing barytes, all sulfur except that contained in barytes is determined. 4. The method is particularly useful in the determination of sulfur and ash in Resinites (Thiokol), and the sulfate can be determined by the volumetric method.

Kinetic centrifugal analyzer and manual determination of serum urea nitrogen, with use of o-phthaldialdehyde reagent.

1978 ◽  
Vol 24 (12) ◽  
pp. 2199-2202 ◽  
Author(s):  
S S Levinson
Keyword(s):  
Sulfuric Acid ◽  
Acid Solution ◽  
Serum Urea ◽  
Urea Nitrogen ◽  
Standard Curve ◽  
Dilute Sulfuric Acid ◽  
Point Analysis ◽  
Ethylenediamine Dihydrochloride ◽  
A Current

Abstract o-Phthaldialdehdye reagent was used in assaying urea with a miniature centrifugal analyzer. Seventeen samples can be assayed kinetically in 2 min at a current cost of less than a penny per test. The reaction is initiated in the instrument upon simultaneous mixing of the o-phthaldialdehyde reagent containing 10 microliter of sample with dilute sulfuric acid/N-(1-naphthyl)ethylenediamine dihydrochloride reagent. The reaction is monitored kinetically at 546 nm during the initial 2 min, when the rate is nearly constant. The reaction of o-phthaldialdehyde with urea reaches equilibrium by about 7 or 8 min, but the method cannot be used for end-point analysis because of interference by the blank reaction. A 1.2 g/liter solution of o-phthaldialdehyde used in conjunction with 2 mol/liter sulfuric acid solution was found to be most suitable for centrifugal analyzers. I also describe a manual version of the procedure that gives a linear standard curve up to 1.0 g of urea nitrogen per liter.

scholarly journals Spectrophotometric Determination of Saponin in Yucca Extract Used as Food Additive

2000 ◽  
Vol 83 (6) ◽  
pp. 1451-1454 ◽  
Author(s):  
Yoko Uematsu ◽  
Keiko Hirata ◽  
Kazuo Saito ◽  
Ichiro Kudo
Keyword(s):  
Sulfuric Acid ◽  
Detection Limit ◽  
Hydrochloric Acid ◽  
Minor Component ◽  
Food Additive ◽  
Porous Polymer ◽  
Saponin Fraction ◽  
A Minor ◽  
Color Reactions

Abstract A spectrophotometric method was developed for the determination of saponin in Yucca extract or its preparation for food additive use. A saponin fraction of Yucca extract was prepared by column chromatography with porous polymer, and hydrolyzed with a 2 mol/L mixture of hydrochloric acid–ethanol (1 + 1) to generate sapogenin. Sapogenin amounts were determined by measuring absorbance at 430 nm, based on the color reactions with anisaldehyde, sulfuric acid, and ethyl acetate. Recoveries from Yucca extracts were 91.5–95.1%, and the detection limit was 10 mg/kg. Commercial Yucca extracts for food additive use were composed of 5.6–6.4% (w/w) saponin, making it a minor component.

Investigation of the Thermal Conductivity of Rubber

1938 ◽  
Vol 11 (2) ◽  
pp. 359-371 ◽  
Author(s):  
L. Frumkin ◽  
Yu Dubinker
Keyword(s):  
Thermal Conductivity ◽  
Zinc Oxide ◽  
Carbon Black ◽  
Natural Rubber ◽  
Considerable Increase ◽  
Large Percentage ◽  
K Value ◽  
Synthetic Rubber ◽  
Coefficient Of Thermal Conductivity

Abstract 1. The apparatus for the determination of the coefficients of thermal conductivity which is described is satisfactory for the investigation of rubber mixtures. 2. A review of the results of the determinations of K values of various mixtures leads to the following conclusions: (a) The thermal conductivity of rubber mixtures containing synthetic rubber is greater than that of mixtures containing natural rubber. (b) The addition of zinc oxide even in considerable quantities to rubber mixtures containing a large percentage (55 per cent) of carbon black does not substantially increase thermal conductivity. (c) In the case of carcass mixtures a considerable increase in the coefficient of thermal conductivity is observed when the content of zinc oxide is increased from 7.5 to 15 per cent by weight; on further increase in the zinc oxide K increases but little. (d) The K value of carcass mixtures before vulcanization is smaller than that of the same mixtures after vulcanization by an average of 23 per cent. (e) The thermal conductivity of uncured tread mixtures is the same as that of vulcanized mixtures. (f) The coefficient of vulcanization has no effect on the K value of unloaded mixtures and mixtures containing fillers. (g) The K value of rubber mixtures increases sharply with addition up to 60 per cent by volume of fillers with good thermal conductivity (zinc oxide and graphite), but only slowly with the addition of fillers of medium thermal conductivity (carbon black). In other words, the curve of the relation between the coefficient of thermal conductivity and the percentage by volume of graphite and of zinc oxide is convex to the filler axis and is concave in the case of carbon black.

Gas Diffusion-Flow Injection Determination of Free and Total Sulfur Dioxide in Wines by Conductometry

1998 ◽  
Vol 63 (6) ◽  
pp. 770-782 ◽  
Author(s):  
Petr Kubáň ◽  
Pavel Janoš ◽  
Vlastimil Kubáň
Keyword(s):  
Sulfuric Acid ◽  
Detection Limit ◽  
Sulfur Dioxide ◽  
Flow Injection ◽  
Gas Diffusion ◽  
Total Sulfur ◽  
Diffusion Flow ◽  
Pvdf Membrane ◽  
Relative Standard

Sensitive flow injection analysis methods for the determination of free and total sulfur dioxide in wines are presented. The bound S(IV) was liberated by alkaline hydrolysis with 4 mol/l NaOH. All forms of S(IV) were liberated from the sample zone by sulfuric acid and subsequently transported through a microporous PVDF membrane. The penetrated gases were collected in water for preselected period and determined by conductometry with detection limit 1 mg/l and relative standard deviations 0.8 and 0.6% at 10 and 150 mg/l (n = 10) for free and total S(IV), respectively. The results are comparable with those obtained by standard titrimetric procedures with visual (Czech State Standard) and/or potentiometric indication.

Importance of Acidic Components in Compounding Ammonia-Preserved Latex with Zinc Oxide

1943 ◽  
Vol 16 (2) ◽  
pp. 342-364
Author(s):  
W. G. Wren
Keyword(s):  
Zinc Oxide ◽  
Hydrochloric Acid ◽  
Experimental Work ◽  
Controlling Factor ◽  
Ammonium Salts ◽  
Caustic Alkali ◽  
Naturally Occurring ◽  
Acidic Components

Abstract In view of the experimental work described above, it appears that changes in viscosity of zinc oxide-compounded latex are due largely to the presence of ammonium salts of naturally occurring acids. These salts enable zinc to pass into solution, and to be absorbed by the latex globules, thus giving rise to the thickening commonly experienced. The amount of zinc passing into solution is directly proportional to the amount of acid present, and it is therefore suggested that determination of the acids by either of the methods described (viz., titration to pH 11 with caustic alkali, or from pH 7 to the end-point with hydrochloric acid), would form a sound basis for the classification of latices in regard to their behavior on compounding with zinc oxide. The investigations thus indicate that the variability of latex is due, in part at least, to the presence of acidic substances and may, therefore, be controlled by preventing the formation of the acids, or by their removal. Summary.—It is demonstrated that naturally occurring acidic substances control the solubility of zinc oxide in ammonia-preserved latex, and it is concluded that they are probably the controlling factor in determining the increase in viscosity which occurs in latex compounded with zinc oxide. In support of this view, it has been shown that the addition of various types of acid to ammonia-preserved latex markedly increases thickening after mixing with zinc oxide, and that the removal of naturally occurring acids reduces the thickening. It is suggested that titration of the acids in latex by the methods described forms a sound basis for the classification of latices in regard to their behavior on compounding with zinc oxide.

Sign in / Sign up

Export Citation Format

Share Document