Showing papers on "Phosphotungstic acid published in 1981"

Dispersed and compact chromatin demonstrated with a new EM method: phosphotungstic acid hematoxylin block-staining.

Abstract: Glutaraldehyde/KMnO4 double fixation and phosphotungstic acid hematoxylin (PTAH) block-staining, before dehydration were found to reveal, with great detail and sharpness, the nuclear distribution of compact heterochromatin masses as electron-lucent patches. By contrast the areas of decondensed and dispersed chromatin acquired a high electron density due to the binding of the large PTAH molecule to basic groups in the loosened chromatin network. The method was tested on human blood leukocytes, on the thymus gland from immature rats, containing mitotic figures, and on mature avian erythrocytes. The results indicated that each cell type acquires a specific pattern of electron densities in the nucleus which depends upon the relative amounts of compact and dispersed chromatin present in that nucleus. Since the tissues are stained in-block immediately after fixation, artifacts of stain localization, due to alcohol dehydration, are avoided. Thus, PTAH block-staining “translates” the state of aggregation of the chromatin into characteristic and specific density patterns of the nuclei. This method may prove useful in differentiating active from inactive portions of the genome, at the ultrastructural level.

Sialic acid determination method

Abstract: A method for determining sialic acid in blood plasma consisting essentially of the steps of precisely diluting the sample and cooling it, extracting with a mixture of chloroform and methanol, adding water to the mixture and separating the phases, adding phosphotungstic acid to the upper layer, centrifuging the resulting mixture and removing the supernatant, suspending the resulting precipitate, adding resorcinol reagent and heating, cooling the reaction mixture and adding butyl acetate-n-butanol to obtain a blue color which can be compared with standard curves to make the determination.

Determination of Insect Infestation in Food: A Semiautomated Calorimetric Analysis for Uric Acid with Immobilized Uricase

Abstract: A semiautomated differential calorimetric procedure for the determination of uric acid is reported. Samples are treated with hydrochloric acid, incubated at 55–60°C in a water bath, and neutralized with sodium hydroxide. Uric acid is extracted with sodium acetate and is determined with phosphotungstic acid as the color reagent. Uric acid is destroyed with uricase, and the calorimetric analysis is repeated for a blank measurement. The reaction specificity of uricase and its immobilization in a nylon coil contribute to the reliability of the method, which permits analysis of 30 samples/hr. Recovery studies and analyses of actual samples show that uric acid can serve as a chemical index of insect infestation in a variety of foods. The sensitivity of the method is approximately 5 μg uric acid/g of sample and is adequate to ascertain objectionable levels of stored product insect excreta contamination in food products.

Preparation of dihydrodicyclopentenyl methacrylate

Abstract: PURPOSE:To obtain the titled compound through simple procedures in a short proc- ess, by reacting dicyclopentadiene with acrylic acid in the presence of a heteropoly- acid of tungsten or an acidic salt catalyst thereof. CONSTITUTION:Dicyclopentadiene is reacted with acrylic acid in the presence of a heteropoly-acid of tungsten or an acidic salt thereof, preferably a catalyst of silicotungstic acid or phosphotungstic acid, in an amount of preferably 0.5-2wt% based on the dicyclopentadiene and acrylic acid, at 40-100 deg.C, preferably 50-70 deg.C, to give the titled compound. EFFECT:Although neutralization, washing with water and filtration steps are required after the reaction in the case of the conventional boron trifluoride as a catalyst, the catalyst of the present invertion does not require the steps due to the good thermal stability thereof. No problems of corrosion in the reactor.

Synthesis of trioxane

Abstract: PURPOSE:To prepare trioxane useful as a raw material of polyoxymethylene, in high selectivity and conversion, in an industrial scale, by the thermal reaction of formaldehyde in the presence of a heteropolyacid. CONSTITUTION:Trioxane is prepared in high selectivity and conversion, by the thermal reaction of formaldehyde (pref. hydrous formaldehyde containing 30- 80wt% of formaldehyde) in the presence of a heteropolyacid (pref. a heteropolyacid having W, Mo and/or V as ligand element, especially, silicotungstic acid, silicomolybdic acid, phosphotungstic acid and/or phosphomolybdic acid), pref. at 60- 200 deg.C. Since the solubility of formaldehyde increases with increasing concentration of the heteropolyacid, the produced trioxane has high concentration, and the deposition of paraformaldehyde or the corrosion of the reactor can be prevented.

Electrochromic display material

Abstract: PURPOSE:To make it possible to stabilize the driving voltage of electrochromic display material (ECD), perform constant voltage driving by means of an usual battery and prolong the life by using opposed electrodes consisting of phosphotungstic acid or phosphomolybdic acid. CONSTITUTION:In respect to ECD consisting of a solid EC material and electrolyte 9, phosphotungstic acid powder or phosphomolybdic acid powder is applied to opposed electrode base plate 5 at the pressure of 1 to 10t/cm , voltage applying lead terminal 14 (stainless steel mesh which was previously prepared) is inserted into phosphotungstic acid powder 15 so as to be placed on the center position and is fixed at the time of pressing the powder in order to use it as an opposed electrode instead of normal conductive film 6 and EC film 7. It is more effective to mix graphite powder together with phosphotungstic acid and phosphomolybdic acid at the rate of 1:1-1:7 and mold them by pressing in order to reduce resistance. Thus, the necessity of a constant voltage driving equipment is removed and it makes possible to keep reversibility of the EC phenomenon sufficiently and prolong the life.