A Vulcanization of Rubber Latex by Potassium Ferricyanide

1937 ◽  
Vol 10 (4) ◽  
pp. 762-767
Author(s):  
D. Spence ◽  
J. D. Ferry
Keyword(s):  
Potassium Ferricyanide ◽  
Rubber Latex ◽  
Oxidizing Agents ◽  
Serum Components

Abstract (1) Vulcanization of rubber is produced by heating latex, from which the diffusible serum components have been removed, with potassium ferricyanide in the absence of air. (2) In the course of the treatment, the ferricyanide is reduced to ferrocyanide. (3) A similar effect may be produced by certain other metallic oxidizing agents in the absence of air.

Sterically Crowded Heterocycles. III. A General Approach to Imidazo[1,2-a]pyridines by Ferricyanide Oxidation of Quaternary Pyridinium Salts

1996 ◽  
Vol 61 (1) ◽  
pp. 126-138 ◽  
Author(s):  
Richard Kubík ◽  
Stanislav Böhm ◽  
Iveta Ruppertová ◽  
Josef Kuthan
Keyword(s):  
Potassium Hydroxide ◽  
Potassium Ferricyanide ◽  
Pyridinium Salts ◽  
Oxidizing Agents ◽  
Quaternary Pyridinium Salts ◽  
Substituted 1

Substituted 1-(pyridin-2-yl)-2,4,6-triphenylpyridinium perchlorates 1b-1e were converted with potassium ferricyanide and potassium hydroxide to sterically crowded 2-phenyl-3-[(Z)-1,3-diphenyl-3-oxopropenyl]imidazo[1,2-a]pyridines 2b-2e accompanied by minor isomeric 2-benzoyl-3,5-diphenyl-1-(pyridin-2-yl)pyrroles 3c-3e. 4-Phenyl-2,6-di(4-substituted phenyl)-1-(pyridin-2-yl)pyridinium salts 4a, 4b gave exclusively corresponding imidazo[1,2-a]pyridines 5a, 5b while the ferricyanide oxidation of 1-(5-iodo- and 5-cyanopyridin-2-yl)-2,4,6-triphenylpyridinium perchlorates 6a, 6b led to mixtures of major imidazo[1,2-a]pyridines 7a-7c and minor pyrroles 8a-8c. Some mechanistic aspects of the oxidation procedure are discussed in connection with a resistance of 2,6-diphenyl-1,3,5-trimethylpyridinium perchlorate (9c) towards the oxidizing agents.

Some Properties of Rubber Latex

1938 ◽  
Vol 11 (3) ◽  
pp. 479-481
Author(s):  
Ernst Schmidt ◽  
Paul Stamberger
Keyword(s):  
Aqueous Phase ◽  
Electrophoretic Deposition ◽  
Distilled Water ◽  
Cent Solution ◽  
Rubber Latex ◽  
Rubber Particles ◽  
Serum Components

Abstract Rubber latex of the commercial type preserved by ammonia was freed almost completely of its serum components by a method involving two steps: 1. Electrophoretic deposition of the rubber particles on a membrane, followed by 2. Dispersion of the resultant paste in a 0.6-per cent solution of ammonia in distilled water. This process was repeated until the aqueous phase obtained from this separation was free of non-rubber components in the latex.

Spontaneous Coagulation of Rubber Latex

1939 ◽  
Vol 12 (3) ◽  
pp. 469-469
Author(s):  
Paul Stamberger
Keyword(s):  
Contact Resistance ◽  
Hevea Brasiliensis ◽  
Gel Formation ◽  
Conductivity Measurements ◽  
Rubber Latex ◽  
Decomposition Processes ◽  
Bacterial Decomposition ◽  
Conductivity Cell ◽  
Serum Components

Abstract As early as 1913, Whitby advanced the view that spontaneous coagulation in rubber latex takes place before decomposition processes begin. Arguments against this view have since been advanced by several investigators, and the opinion generally held at present is that the coagulation of fresh latex is caused by formation of acid from the bacterial decomposition of the serum components. Recent investigations made on latex of Hevea brasiliensis have provided confirmation of the view held by Whitby. Experiments were conducted throughout on latex obtained immediately after collection from the trees, which had been tapped three or four hours previously. The formation of ions from decomposition of latex was followed by conductivity measurements. The conductivity of latex did not change until coagulation was complete. This occurred 6–11 hours after collection of the latex, varying from sample to sample. The resistance of the conductivity cell increased after gel formation, due to contact resistance on the electrodes.

The Creaming of Hevea Latex by Colloids

1938 ◽  
Vol 11 (4) ◽  
pp. 608-623
Author(s):  
C. F. Vester
Keyword(s):  
Negative Charge ◽  
Dispersed Phase ◽  
Rubber Content ◽  
Rubber Latex ◽  
Ionogenic Groups ◽  
Rubber Particles ◽  
Dispersing Medium ◽  
Almost All ◽  
Short Time ◽  
Serum Components

Abstract Hevea latex is generally considered to be a suspension of rubber particles of various dimensions up to about 3 µ. The rubber hydrocarbon contains no “ionogenic groups,” and it is believed that part of the serum components imparts a negative charge to the rubber particles. Almost all latex imported into Europe is preserved by means of 0.5 to 0.7 per cent of ammonia. This ammonia plays a three-fold part: (1) it prevents premature souring of the latex; (2) it increases somewhat the charge on the particles; and (3) it attacks all types of serum components so that within a short time the “preserved” latex is hardly comparable with natural latex. As with all suspensions in which the dispersed phase is lighter than the dispersing medium, rubber latex exhibits the phenomena of creaming. The density of the rubber particles is approximately 0.914, that of the medium, 1.020. By means of creaming, it is possible to obtain a latex (1) which has a higher rubber content, whereby transportation space and cost are saved, and (2) which contains no components having a tendency to deposit a sediment. The natural creaming of latex, which is of no importance technically, was observed by Faraday as early as 1825.

TEM comparison of osmium vs osmium with potassium ferricyanide secondary fixatives and the impact of secondary fixative temperature on tissue preservation/contrast quality

1996 ◽  
Vol 54 ◽  
pp. 910-911
Author(s):  
J. W. Horn ◽  
B. J. Dovey-Hartman ◽  
V. P. Meador
Keyword(s):  
Osmium Tetroxide ◽  
Potassium Ferricyanide ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Microscopic Evaluation ◽  
Cacodylate Buffer ◽  
Transmission Electron Microscopic ◽  
Glutaraldehyde Solution ◽  
Temperature Impact ◽  
The Impact

Osmium tetroxide (OsO4) is a universally used secondary fixative for routine transmission electron microscopic evaluation of biological specimens. Use of OsO4 results in good ultrastructural preservation and electron density but several factors, such as concentration, length of exposure, and temperature, impact overall results. Potassium ferricyanide, an additive used primarily in combination with OsO4, has mainly been used to enhance the contrast of lipids, glycogen, cell membranes, and membranous organelles. The purpose of this project was to compare the secondary fixative solutions, OsO4 vs. OsO4 with potassium ferricyanide, and secondary fixative temperature for determining which combination gives optimal ultrastructural fixation and enhanced organelle staining/contrast.Fresh rat liver samples were diced to ∼1 mm3 blocks, placed into porous processing capsules/baskets, preserved in buffered 2% formaldehyde/2.5% glutaraldehyde solution, and rinsed with 0.12 M cacodylate buffer (pH 7.2). Tissue processing capsules were separated (3 capsules/secondary fixative.solution) and secondarily fixed (table) for 90 minutes. Tissues were buffer rinsed, dehydrated with ascending concentrations of ethanol solutions, infiltrated, and embedded in epoxy resin.

Autoantibodies to Thrombomodulin: Development of an Enzyme Immunoassay and a Survey of their Frequency in Patients with the Lupus Anticoagulant

1992 ◽  
Vol 67 (05) ◽  
pp. 507-509 ◽  
Author(s):  
John Gibson ◽  
Margaret Nelson ◽  
Ross Brown ◽  
Hatem Salem ◽  
Harry Kronenberg
Keyword(s):  
Enzyme Immunoassay ◽  
Lupus Anticoagulant ◽  
Specific Binding ◽  
Technical Problem ◽  
Serum Samples ◽  
Citrate Buffer ◽  
The Mean ◽  
Sample Dilution ◽  
Negative Population ◽  
Serum Components

SummaryIn order to investigate the possibility that autoantibodies to thrombomodulin (TM) may exist in patients with the lupus anticoagulant (LA) and perhaps be implicated in the pathogenesis of recurrent thrombosis seen in such patients, we developed an enzyme-immunoassay to screen serum samples for anti-human TM activity. The major technical problem encountered in developing this assay was to reduce the non-specific binding of serum components from both the LA positive and the negative population. Considerable reduction of non-specific binding was achieved by use of a phosphate/citrate buffer at pH 8.0 and the use of an optimal sample dilution of 1/40. In addition, samples were always tested in parallel in blank wells and results are expressed as an OD ratio. Samples from 113 patients with the LA were assayed and compared to 78 patients referred for LA testing but found to be negative. The mean OD values for the LA positive patients (± SD) was 1.36 (0.44) with a range of 0.78-2.57. This was virtually identical to the values for the LA negative population (1.38 ± 0.40, range 0.76-2.77). The results of this study indicate that there is no evidence for the presence of a significant autoantibody activity to TM in patients with the LA when compared to LA negative patients. If such autoantibodies do exist their frequency must be quite low.

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