Determination of Total Sulfur in Vulcanized Rubber Mixtures

1952 ◽  
Vol 25 (2) ◽  
pp. 371-374 ◽  
Author(s):  
Horst Frey
Keyword(s):  
Iron Oxide ◽  
Ion Exchange ◽  
Barium Sulfate ◽  
Aqueous Sodium Hydroxide ◽  
Total Sulfur ◽  
Aqueous Sodium ◽  
Vulcanized Rubber ◽  
Exchange Agent ◽  
Volumetric Methods

Abstract A method is described, which, by means of a resin ion-exchange agent, makes possible the elimination of the disturbing effects of foreign cations, particularly iron and chromium, in the determination of the total sulfur in vulcanized rubber mixtures. By this procedure, rapid volumetric methods for determining sulfate, even in the analysis of mixtures containing iron oxide or chromium oxide pigments, can be utilized. The procedure involves precipitation of the sulfate by benzidine and determination by titration with aqueous sodium hydroxide. The method is more rapid and more reliable than ordinary gravimetric methods involving precipitation of barium sulfate.

Determination of Total Sulfur in Rubber

1944 ◽  
Vol 17 (1) ◽  
pp. 227-233 ◽  
Author(s):  
C. L. Luke
Keyword(s):  
Hydrogen Sulfide ◽  
Barium Sulfate ◽  
Hydriodic Acid ◽  
Small Samples ◽  
Distinct Advantage ◽  
Total Sulfur ◽  
Unequal Distribution ◽  
Usual Manner ◽  
Volumetric Methods

Abstract With the recent increase in research on natural and synthetic rubber, there has arisen a need for a rapid method for the determination of total sulfur in rubber samples where only a semimicrosample can be spared for analysis. The usual methods in which the rubber is oxidized by digestion with acid, followed in some cases by fusion to complete oxidation, and the sulfur is precipitated and weighed as barium sulfate, yield good results on semimicro-samples, but are time-consuming, because quantitative precipitation of the sulfate cannot be attained unless the solution is allowed to stand overnight before filtration. Several volumetric methods, most of which depend on the precipitation of sulfur as barium sulfate, have been described, but none is very satisfactory in the determination of small amounts of sulfur. St. Lorant has proposed a volumetric method for the determination of microsamples of sulfate, in which the sulfate is reduced to sulfide with hydriodic acid, and the hydrogen sulfide is distilled off and determined colorimetrically. The author has recently developed a modification of this method which has proved to be very satisfactory for the analysis of sulfur in small samples of rubber. The procedure consists essentially of oxidation of the rubber in the usual manner, reduction of the sulfate to sulfide, separation of the hydrogen sulfide by distillation, and titration of the latter iodometrically. The new method is very rapid (20 to 25 minutes for the distillation and titration), and is not subject to the errors of adsorption, occlusion, and solubility encountered in the gravimetric barium sulfate method, or to difficulties in detection of the end-point encountered in some volumetric methods. It possesses the distinct advantage over some of the gravimetric methods that it is applicable to the analysis of rubber containing barium, lead, and calcium. The only serious objections to the method from the standpoint of general use are that hydriodic acid is expensive and that the applicability of the method is somewhat limited because of the fact that no more than about 5 mg. of sulfur can be handled conveniently. This means that the sample size must be small when analyzing rubber high in sulfur; and when small samples are used there is always the danger of error due to unequal distribution of sulfur in the sample.

Fluorometric Determination of Chlortetracycline in Low Level Mixed Feeds

1964 ◽  
Vol 47 (6) ◽  
pp. 1157-1161
Author(s):  
Stanley E Katz ◽  
Joseph Spock
Keyword(s):  
Ion Exchange ◽  
Sodium Carbonate ◽  
Fluorometric Determination ◽  
Aqueous Sodium ◽  
Exchange Column ◽  
Aqueous Sodium Carbonate ◽  
Ion Exchange Column ◽  
Low Levels ◽  
Mixed Feeds

Abstract The fluorometric determination of low levels of chlortetracycline in mixed feeds is based upon the separation of the chlortetracycline on a Decalso ion exchange column after extraction from the feed. The chlortetracycline is eluted from the resin after conversion to isochlortetracycline by hot aqueous sodium carbonate. The isochlortetracycline is measured fluorometrically. Results agree with microbial assays.

The retroaldol reaction of 3-methyl-2-butenal

1983 ◽  
Vol 61 (1) ◽  
pp. 171-178 ◽  
Author(s):  
J. Peter Guthrie ◽  
Brian A. Dawson
Keyword(s):  
Sodium Hydroxide ◽  
Equilibrium Constant ◽  
Rate Constants ◽  
Equilibrium Constants ◽  
Aqueous Sodium Hydroxide ◽  
Initial Increase ◽  
Aqueous Sodium ◽  
Rate Determining Step ◽  
Kinetics Of

In aqueous sodium hydroxide solutions at 25 °C, 3-methyl-2-butenal, 1c, undergoes retroaldol cleavage to acetone and acetaldehyde. The kinetics of the retroaldol reaction were followed spectrophotometrically at 242 nm and showed simple first order behavior. When 3-methyl-3-hydroxybutanal, 2c, was added to aqueous sodium hydroxide solutions at 25 °C, there was an initial increase in absorbance at 242 nm, attributed to formation of 1c, followed by a 20-fold slower decrease; the rate of the slow decrease matches the rate of disappearance of 1c under the same conditions. Analysis of the kinetics allows determination of the three rate constants needed to describe the system: khyd = 0.00342; kdehyd = 0.00832; kretro = 0.0564; all M−1 s−1. The equilibrium constant for enone hydration is 0.41. Rate constants for the analogous reactions for acrolein and crotonaldehyde could be obtained from the literature. There is a reasonable rate–equilibrium correlation for the retroaldol step. For the enone hydration step, rate and equilibrium constants respond differently to replacement of hydrogen by methyl. It is proposed that this results from release of strain after the rate-determining step by rotation about a single bond; this decrease in strain is reflected in the equilibrium constant but not in the rate constant.

THE DETERMINATION OF OESTROGENS IN BODY FLUIDS

1954 ◽  
Vol 11 (2) ◽  
pp. 189-196 ◽  
Author(s):  
HANNELORE BRAUNSBERG ◽  
MARGARET I. STERN ◽  
G. I. M. SWYER
Keyword(s):  
Stationary Phase ◽  
Sodium Hydroxide ◽  
Chromatographic Separation ◽  
Aqueous Sodium Hydroxide ◽  
Body Fluids ◽  
Aqueous Sodium ◽  
Elution Pattern ◽  
Phenolic Extract

SUMMARY A micro-method is described for the chromatographic separation of oestrone, oestradiol and oestriol from a phenolic extract of body fluids. The stationary phase is 3·1n aqueous sodium hydroxide held by Celite 535 as the supporting medium. Oestrone and oestradiol are eluted with benzene:petroleum ether, b.p. 60–80° C, 4:1 (v/v), and oestriol with a 17:3-chloroform:butanol mixture. A diagram of the apparatus used is shown. The elution pattern, and data showing how it changes with temperature, are included.

Turbidimetry of inorganic sulfate, ester sulfate, and total sulfur in urine.

1980 ◽  
Vol 26 (8) ◽  
pp. 1178-1181 ◽  
Author(s):  
P Lundquist ◽  
J Mårtensson ◽  
B Sörbo ◽  
S Ohman
Keyword(s):  
Polyethylene Glycol ◽  
Nitric Acid ◽  
Perchloric Acid ◽  
Barium Sulfate ◽  
Wet Oxidation ◽  
Total Sulfur ◽  
Sulfate Ester ◽  
Healthy Persons ◽  
Inorganic Sulfate

Abstract We describe simple and precise methods for the determination of inorganic sulfate, ester sulfate, and total sulfur in urine. The methods are based on turbidimetry of sulfate as barium sulfate in the presence of a small amount of preformed barium sulfate and with polyethylene glycol as a stabilizing agent. Inorganic sulfate is directly determined, whereas ester sulfate is measured after removal of inorganic sulfate, followed by acid hydrolysis. Total sulfur is determined after wet oxidation of the sample with nitric acid and perchloric acid in the presence of vanadate as a catalyst. We also report excretion values for healthy persons on a self-selected diet. Men excrete significantly higher amounts of inorganic sulfate and total sulfur than women, but this sex-related difference becomes insignificant if excretion values are expressed relative to creatinine.

Determination of Total Sulfur in Fertilizers

1964 ◽  
Vol 47 (3) ◽  
pp. 436-438
Author(s):  
J E Barker
Keyword(s):  
Coefficient Of Variation ◽  
Barium Sulfate ◽  
Collaborative Study ◽  
Total Sulfur

Abstract The gravimetric barium sulfate method for sulfur was adapted to the determination of total sulfur in fertilizers. Accuracy and ruggedness studi e s were made and the method was subjected to collaborative study. The coefficient of variation found in the collaborative study is 2 % .

Spectrophotometric Assay of Karathane Technical and Karathane Formulations

1974 ◽  
Vol 57 (3) ◽  
pp. 653-657
Author(s):  
Ronald F Black ◽  
C P Kurtz ◽  
Harry Baum
Keyword(s):  
Statistical Analysis ◽  
Petroleum Ether ◽  
Concentration Level ◽  
Sodium Hydroxide Solution ◽  
Collaborative Study ◽  
Aqueous Sodium Hydroxide ◽  
Spectrophotometric Assay ◽  
Aqueous Sodium Hydroxide Solution ◽  
Aqueous Sodium

Abstract A spectrophotometry procedure for the determination of total dinitrooctylphenols and dinitrooctylphenyl crotonates in Karathane Technical (dinocap) and Karathane formulations has been collaboratively studied. The sample is dissolved in petroleum ether; the total mono- and dinitrooctylphenols are then selectively extracted with aqueous sodium hydroxide solution and examined photometrically at 410 nm. The dinitrooctylphenyl crotonates are hydrolyzed in aqueous pyridine solution and measured photometrically at 442 nm. Five collaborators analyzed Karathane Technical, Karathane LC, and Karathane WD in duplicate on each of 2 days. Statistical analysis indicates that between- laboratory precision, s, of the dinitrooctylphenyl crotonate determination, excluding outliers, was 2.05, 0.71, and 0.79% absolute at the 76, 38, and 18% assay levels, respectively. The precision of the dinitrooctylphenol determination on the same sample series was s = 0.071% at the 2.3% concentration level, 0.18% at the 1.88% level, and 0.457% at the 2.20% level, respectively. It is recommended that another collaborative study be conducted with an increased number of collaborators, incorporating changes in the procedure suggested by the collaborators.

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