Ml Of Acid Research Articles

Dissolution of Samples by Heating with a Microwave Oven in a Teflon Vessel for Instrumental Analyses

The Bureau of Mines developed a method for rapidly dissolving ores, slags, furnace products, and ashes for atomic absorption and other instrumental analyses. The method makes use of a microwave oven for heating the sample in a uniquely designed, commercially available Teflon (fluorocarbon polymer) vessel which is able to withstand the heat and pressure of the reactions. The inert quality of Teflon allows the use of various acid combinations and strong acid concentrations as dissolving solutions. Samples prepared using this method can be analyzed for elements at major, minor, and trace levels of concentration from a single solution. These elements include Si, Al, Ca, Mg, Fe, Cu, Mn, Ni, Co, Na, K, etc., with accuracy equal to or better than other conventional dissolution methods.The method is relatively inexpensive because of the durability of the vessel (more than 75 dissolutions) and the number of possible assays per sample: it requires about 20 ml of acid per sample; heating time is about 10 s per sample.

南極オキアミ中フッ素の簡易迅速定量法

A simple and rapid analytical procedure was investigated for determination of iflouride in Antarctic Krill Euphursia superba. An ionselective electrode method was adopted to simplify and make rapid the procedure. The fluoride content in krill was obtained by measuring the concentration of fluoride of the extrabled solution with an ion meter. For extraction of fluoride, 0.05 N HCLO4 solution was the most suitable. The most satisfactory results were obtained by using 100 ml of acid and shaking for 45-60 minutes on 1-2g of sample. The presence of cations, anions, and protein of ordinary cotents did not interfere. Recoveries of fluoride on eighteen samples were 90-100% and coefficient of variation was 3.34%. Fluoride contents in krill were 470-510 ppm and C. V. was 2.12% by this proposed method.

A color reaction of steroid aglycones of the spirostan series with sulfuric acid solutions

Thus, the most intense maximum with ~ = 12'10 s is observed in the reactlon of diosgenin with 96% acid at 60=C for 30 min, while c486 reaches its maximum value, of 23'10 ~, under the conditions of the reaction of diosgenin with a 72% aqueous solution of the acid in the presence of catalytic amounts (0.0001%) of Fe(III). The coloration develops at 50=C in 60 min and remains unchanged for noL less than 5 h. A callbratlon graph is linear in the range of 0.01-0.1 mmole of diosgenin in 4 ml of acid.

Reactions of powders of zirconium and niobium carbides in their homogeneity ranges with some acids

In the work described below a study was made of the reactions of zirconium and niobium carbides in their homogeneity ranges with some mineral acids. It was considered of great interest also to investigate the gaseous products of acid decomposition of the carbides. Experiments were carried out, using hydrochloric, sulfuric, and nitric acids as reactants, on powders of the zirconium carbides ZrC0.7~, ZrCo.80, ZrC0.88, and ZrC0.92 and of the niobium carbides NbC0.63 , NbC0.69 , NbC0.84 , and NbC0.94. The zirconium and niobium carbides were prepared by synthesis from the elements. Data on the chemical compositions of the carbides aregiven in Table 1. A study was made of the chemical stability and reaction kinetics of the above-mentioned zirconium and niobium carbides in 6 N, 12 N, and 18 N sulfuric, hydrochloric, and nitric acids. Chemical stability was investigated at a 100-fold excess of acid relative to the weight of the carbide sample, during 2-h heating at a constant acid concentration. As a measure of chemical stability the percentage of the insoluble residue was employed (Table 2). The insoluble residue was subjected to chemical analysis. From Table 2it will be seen that the chemical stability of the carbides grows with rise in their carbon content and that the reactions of the carbides with nonoxidizing acids produce no change in their chemical composition. In order to develop methods for the materials chemical analysis of the carbides, a study was made of the kinetics of their reactions with the acids. Comparable results for the reactions of powders of various specific surfaces were obtained by expressing experimental data in grams per square meter (amount of reacted carbide from unit surface of carbide powder). The reaction Mnetics of the carbides in the acids was determined as follows. A 1.0000-g carbide powder sample was placed in a conical flask with a ground reflux condenser, after which 100 ml of an acid of the required concentration was poured into the flask and then boiled for 2 and 5 h at the temperatures indicated in Tables 2and3. After 5, 10, 15, 30, 45, 60, 90, and 120 rain or 1, 2, 3, and 5h, 0.2, 1, or 2ml of the solution was withdrawn with a pipet, each withdrawal being followed by the addition to the flask of 0.2, 1, or 2 ml of the same acid in order to maintain the solvent concentration constant. The amount of zirconium or niobium which had passed into the solution was determined photometrically with xylenol orange [5, 6], trilonometricall y [7], or by the Cupferron gravimetric method [8]. The results obtained are depicted in Figs. 1-4. The greatest reactivity in the homogeneity ranges was found to be exhibited by the carbides of lowest carbon content, ZrC0.75 and NbC0.63. The greatest chemical stability was shown by carbides of compositions close to stoiehiometric. This was a general finding, applicable to the reactions with all the nonoxidizing acids, both boiling and cold. In cold 12 N sulfuric acid 0.017 g/m 2 of ZrC0.92 and 0.126 g/m 2 of ZrC0.75 decomposed during 24-h te~t.% This fact can be explained as follows. During the formation of steichiometric

Isolation and assay of noradrenaline, dopamine, 5-hydroxy-tryptamine, and several metabolites from brain tissue using disposable bio-rad columns packed with sephadex G-10

Using disposable Bio-Rad columns packed with Sephadex G-10, the methods for isolation and determination of NA, DA, 5HT, 5HIAA, and GABA from the same brain tissue are described. Preparation and maintenance of the columns requires a minimum amount of time, and once prepared, the columns can be easily regenerated by washing the resin with 3 ml of 0.01 N NH 3 and 6 ml of 0.01 N HCl. Brain tissues are prepared by homogenizing in 1 ml of 0.4 N HCLO 4. After centrifugation, the supernatant is poured onto the resin. The columns can be placed directly on top of test tubes (15 × 150 mm) to allow collection of the eluate. GABA (96–98%) is removed in the first 2.2 ml of acid washed through the columns. NA and DA (100%) are contained in 2.8 ml of acid eluate. 5HT (94–98%) is washed from the column with 4 ml of an acid-ethanol solution. Finally, 5HIAA (100%) is removed with 2.0 ml of Na 2CO 3 solution. All determinations were made fluorimetrically. Also, a manual method, using Bio-Rad columns packed with G-10 resin, for isolating NA, DA, HVA, DOPAC and GABA from the same brain tissue is given as a modification of the semiautomated methods of Westernik and Korf (1976). The procedures for column preparation, maintenance, and regeneration are identical for both methods described in this paper. However, after homogenizing the brain tissue in HCLO 4, a KOH/HCOOH buffer is added to precipitate excess perchlorate ions. This procedure appears to destroy about 8–10% of the catecholamines and metabolites present in the homogenate. These methods provide recovery values, reproducibility, and sensitivity compatible with cation exchange and some solvent extraction methods.

モモ果実の品質保持に対する低温流通の効果

In our country white flesh peach fruits are mostly harvested at shipping maturity, i. e. initial stage of ripening, to protect from over-softening and bruising during distribution which is usually carried out at ambient room temperatures (25°C-30°C). 2-4 days are needed from producers to consummers. Recently there has been increased public interest in peaches harvested at the full ripe stage. The fruit is shipped at a low temperature in order to offer higher quality peaches to consummers.The present experiment was designed to simulate the conditions of transportation facilities for distribution. Peach fruit was held for 4 days after harvest at the room temperature of about 27°C or at 3°C. Their tastes were compared by 100 panel members and further quality changes were estimated by measuring total sugar, titratable acidity, ground color of peel and softening. Three cultivars belonging to fruits having white flesh, ‘Sunago’‘Hakuho’and‘Aichi Hakuto’were used in the experiment.1. When harvested at conventional shipping maturity and held at 3°C, there was no advantageous effect of low temperature on the taste of fruits.2. When harvested at full ripe stage and held at 3°C, sweetness was superior to the fruits harvested at shipping maturity and held at room temperature thereafter. At that time, the fruits at 3°C contained 8.8% total sugar and had 40ml of acid determined by titration with 0. 1N sodium hydroxide in 100ml juice, while the fruits held at room temperature displayed 8.3% and 55ml, respectively.3. The decreasing rates of sugar content during 4-day-holding in fruits held at room temperature and 3°C were 3.4% and 1.1%, respectively, and the decreasing rates of titratable acidity were 12.3% and 7.0%, respectively. The ground color of peel in the fruits at room temperature turned from light green to light yellow and fruit flesh softened to some extent during holding, while these changes in the fruits at 3°C were hardly detectable. It seemed therefore that the changes of ground color of peel and softening were strongly influenced by storage and shipping temperatures, but total sugar content and titratable acidity were hardly influenced at all.4. Total sugar content in peach fruits increased with the stage of ripening at harvest time, and then decreased at overripe or senescent stage. Titratable acidity decreased with the stage of ripening. The fruits softened characteristically, and the ground color of peel changed markedly from light yellow during ripening.In conclusion, the optimum time of harvest is the most important factor for distribution of peach fruit having good quality. This time is the full ripe stage of fruits for the case of short-haul transportation facilities as in our country when fruits are held at a low temperature.

Neutralization of acid decalcification of dental tissue

One of the changes resulting in carious infection of the dental tissues is considered to be decalcification by acids which bacteria produce. The decalcification would proceed under the neutralization process of a small quantity of acids by dissolution of the dental tissues surrounding the infected site.The reaction was investigated using equipment capable of recording pH changes in suspension of dental tissue powder after addition of a certain amount of acid. Dentin or enamel powder was suspended in 100 ml of CO2-free distilled water, 1 ml of acid was added, the mixture was stirred at 37°C and the pH movement of the suspension was measured. The pH value dropped immediately after addition of the acid, and thereafter increased slowly to return to the constant value. According to the curve of pH change, the pH value at 2 hrs. afer acidification was defined as this final constant pH. Effect of powder size, the concentration of suspension, kind and amount of acids on the pH change was investigated, and dissolved Ca and P in the suspension were estimated.The results were as follows:Smaller particles of tooth powder and higher concentration of the suspension caused a slighter drop and a faster recovery of pH. Lactic acid had the strongest decalcification capacity as compared with other acids: acetic, formic, propionic, succinic, and butyric acid. The solubility of enamel is less than that of dentin because the final pH of enamel is lower and recovery time is longer than that of dentin.Assuming that acids were produced at the dentino-enamel junction, acids would be immediately neutralized by the dissolution of dentin which dissolves ealier than enamel and enamel would hardly be affected. These results also explain the formation of the half-moon shaped decalcification which is observed only at the dentin site of rat molars in the early stage of experimental caries described in a previous report. (Onisi et al. 1968).

Use of a Titrimetric Method to Assess the Bacterial Spoilage of Fresh Beef

A new method of determining bacterial spoilage in fresh beef is presented. The technique is based upon the fact that as beef undergoes refrigerator spoilage, there is a gradual increase in the production of alkaline substances by the spoilage flora. The level of these substances was measured by titrating meat homogenates to a p H 5.00 end point, employing 0.02 n HCl and an autotitrator. When 23 samples of ground beef from retail stores were tested, an average of 1.32 ml of acid was required for titration of 1 g of fresh beef to p H 5.00, whereas 2.58 ml was required for the same meat at the onset of spoilage. Preliminary data indicate that beef which requires more than 2 ml of 0.02 n HCl/g to lower its p H to 5.00 under the conditions of the test is in some state of incipient spoilage. The statistical correlation between titration values, log bacterial numbers, and extract-release volume was high ( P < 0.001). The technique is simple to execute and is highly reproducible, and duplicate samples can be run within 15 min.

Use of a Titrimetric Method to Assess the Bacterial Spoilage of Fresh Beef 1

A new method of determining bacterial spoilage in fresh beef is presented. The technique is based upon the fact that as beef undergoes refrigerator spoilage, there is a gradual increase in the production of alkaline substances by the spoilage flora. The level of these substances was measured by titrating meat homogenates to a pH 5.00 end point, employing 0.02 n HCl and an autotitrator. When 23 samples of ground beef from retail stores were tested, an average of 1.32 ml of acid was required for titration of 1 g of fresh beef to pH 5.00, whereas 2.58 ml was required for the same meat at the onset of spoilage. Preliminary data indicate that beef which requires more than 2 ml of 0.02 n HCl/g to lower its pH to 5.00 under the conditions of the test is in some state of incipient spoilage. The statistical correlation between titration values, log bacterial numbers, and extract-release volume was high (P < 0.001). The technique is simple to execute and is highly reproducible, and duplicate samples can be run within 15 min.

A 200 ml Solution Calorimeter with Semiautomatic Adiabatic Control

This adiabatic solution calorimeter was designed specifically for thermochemical studies of the less familiar oxidation states of the rare earths. It has been used in the determination of the heats of solution of Pr, Eu, EuCl2, and Pr(NO3)3 in acids. Currently, it is being employed in the determination of the heats of formation of the various stable, nonstoichiometric oxides of Pr. Close control of adiabatic conditions is maintained automatically throughout a run; manual manipulations are held to a minimum. The calorimeter holds about 200 ml of acid or water into which a solid sample is dissolved at the appropriate time. The temperature of the adiabatic shield which surrounds the calorimeter automatically increases at nearly the same rate as that of the calorimeter itself, and the increment of temperature is measured with a platinum resistance thermometer. The heat generated by a chemical reaction is calculated from a comparison of this rise in temperature to that caused by a calibrated quantity of electrical heat. Included in this paper are (1) a complete description of the apparatus, including figures; (2) a table giving results of some calorimetric experiments; and (3) a summary of the characteristics of the calorimeter.

Differential staining of aborted and nonaborted pollen.

A single staining solution was made by compounding it in the following order (dyes were from British Drug Houses): ethanol, 10 ml; 1% malachite green in 95% ethanol, 1 ml; distilled water, 50 ml; glycerol 25 ml; phenol, 5 gm; chloral hydrate, 5 gm; acid fuchsin 1% in water, 5 ml; orange G, 1% in water 0.5 ml; and glacial acetic acid, 1–4 ml. For best results in differentiation to give green pollen walls and red protoplasm, the staining solution should be acidified with glacial acetic acid. The amount of acid to be added depends upon thickness of the pollen walls: for very thin-walled pollen, 1 ml; for moderately thin walls, 2 ml; and for thick-walled or spiny-walled pollen, 3 ml of acid. For pollen inside non-dehiscent anthers, 4 ml of acid should be used. Staining is hastened by flaming the slide (for loose thin-walled pollen) or by immersing thick-walled pollen or anthers for 24–48 hr at 50 C. In the typical stain, aborted pollen grains are green; nonaborted, red. The method is useful for pollen inside nondehiscent anthers if these are small and not too deeply coloured naturally. The stain is very durable, especially if the coverslips are sealed with param wax. The staining solution will keep well for about a month. It is useful both for angiosperms and gymnosperm microgametes.