• Korean Journal of Soil Science and Fertilizer
• /
• v.29 no.4
• /
• pp.321-327
• /
• 1996

A back titration method was suggested to determine the exchangeable acidity of soil originated from exchangeable aluminum and adsorbed hydrogen ion in relation to minimizing its titration error. In this method. soils are treated by neutral salt solution whose concentration is the same as soil solution suspended by distilled water. And then. its pH is adjusted at 3, using 1 N HCl solution and back-titrated by 0.1 N NaOH solution containing 1 N NaCl. The results of the suggested back-titration showed the possibility of practical application with linear relationship to that of standard method.

• Journal of the Korean Chemical Society
• /
• v.55 no.4
• /
• pp.620-625
• /
• 2011

A simple, rapid potentiometric back titration of Isoniazid (INH) in the presence of Rifampicin (RIF) in tablets and syrups is described. The method is based on the oxidation of INH by a known excess of copper (II) ion and the back titration of unreacted copper (II) ion potentiometrically with ascorbic acid using a lab-made Copper Based Mercury Film Electrode (CBMFE). The titration conditions have been optimized for the determination of 1.0-10.0 mg of INH in pure and dosage forms. The precision and accuracy of the method have been assessed by the application of lack-of-fit test and other statistical methods. Interference was not caused by RIF and other excipients present in dosage forms. Application of the method for INH assay in tablets and syrups was validated by comparison of the results of proposed method with that of the British Pharmacopoeia (BP) method using F- and t- statistical tests of significance.

• Macromolecular Research
• /
• v.15 no.6
• /
• pp.587-594
• /
• 2007

Well defined amphiphilic diblock copolymers of poly(styrene-b-vinylbenzylphosphonic acid) (PS-b-PVBPA) were prepared by controlled radical polymerization technique, two-step hydrolysis reactions using trime-thylsilyl bromide from the corresponding phosphonic ethyl ester. By indirect, backward pH titration of the block copolymer, a good titration curve of a dibasic acid was observed. The IEC values obtained from both backward pH titration and volumetric back titration were almost identical. Thermal gravimetric analysis (TGA) of the phosphonic acid containing block copolymer showed a high thermal stability up to $400^{\circ}C$.

• Korean Journal of Soil Science and Fertilizer
• /
• v.29 no.4
• /
• pp.328-335
• /
• 1996

Using literature data on back titration curves of some typical Korean soils and minerals we calculated the distribution functions of aparent surface dissociation constants for these materials using site heterogeneity approach. The studied materials exhibited broad range of apparent surface dissociation constants. The dominant surface sites for all samples appeared to be very weakly acidic. However, the relative amounts of surface sites differed among particular materials.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
• /
• v.2 no.2
• /
• pp.139-148
• /
• 1998

The charge densities of humic acid and humic extract have been determined by back titration using spectrophotometry as the method of end point detection and several cationic polymers of different charge density(copolymers of acylamide and dimethylaminoethylacrylate and polydiallyidimethylammonium chloride, PDDA), and a cationic indicator o-toluidine blue(o-Tb). The charge densities of humic acid and humic extract obtained depend on the charge densities of cationic polymers used. When the polymers of lower charge density are used, lower apparent charge density values are obtained, but for polymers of high charge density(above 2.5 meq/g), the measured values are almost identical, but also are nearly the same as that obtained for PDDA which has a high charge density(about 6 meq/g). For polymers of lower charge density, it is considered that the optimum dosage does not correspond to 1 :1 charge neutralization between anionic and cationic groups. Polymers of high charge density should be used in order to achieve a complete charge neutralization. As humic acid and humic extract are dissociable acids, their ionization is heavily pH dependent and so higher charge density values are obtaines with increasing pH.

• Macromolecular Research
• /
• v.14 no.5
• /
• pp.504-509
• /
• 2006

Poly(vinyl phosphate-b-styrene) (PVPP-b-PS) block copolymers were synthesized successfully from poly(vinyl alcohol-b-styrene) (PVA-b-PS) by reaction with phosphorus oxychloride and subsequent hydrolysis. The obtained block copolymers were slightly crosslinked, and were characterized by various analytical techniques. The total phosphorus content and the ratio of the differently bound phosphorus were obtained by both solid-state $^{31}P$ NMR and pH titration, but the results differed slightly. Characterization by energy dispersion X-ray analysis (EDS) or Rutherford back scattering (RBS), on the other hand, determined the total phosphorus contents, but the results were quite different from those by solid-state $^{31}P$ NMR.

• YAKHAK HOEJI
• /
• v.5 no.1
• /
• pp.16-19
• /
• 1960

Quantitative determination of Arsenic acid by precipitation of Arsenic acid as ZnNH$_{4}$AsO$_{4}$ and titration of Zn in the precipitate by EDTA has been investigated. Conclusion are as follows; 1) ZnNH$_{4}$AsO$_{4}$ was Soluble in NH$_{4}$Cl-NH$_{4}$OH buffer solution of pH lo and back-titration was unnecessary as in the case of MGNH$_{4}$AsO$_{4}$. 2) The end point was clear whether AsO$_{4}$$^{-3}$ present or not. 3) More simple and rapid method than that of Gravi metric method. 4) Could be determined within 0.3% error.

• Journal of the Korean Chemical Society
• /
• v.56 no.5
• /
• pp.563-570
• /
• 2012

Solid acid Mo(VI)/$ZrO_2$ with 2-10% Mo(VI) was coated on honeycomb monoliths by impregnation method. These catalytic materials were characterized by BET, $NH_3$-TPD/n-butylamine back titration, PXRD and SEM techniques. Phenyl salicylate (Salol) was synthesized via transesterification of methyl salicylate and phenol over these catalytic materials. An excellent yield (91.0%) of salol was obtained under specific reaction conditions. The effect of poisoning of acid sites of the catalytic material by adsorbing different bases and its effect on total surface acidity, powder XRD phases and catalytic activity was studied. A triangular correlation between the surface acidity, powder XRD phases and catalytic activity of Mo(VI)/$ZrO_2$ was observed. The thermally regenerated catalytic material was reused repeatedly with a consistent high yield of salol.

• The Korean Journal of Pharmacology
• /
• v.17 no.1 s.28
• /
• pp.27-32
• /
• 1981

It has been known that ethanol stimulates the secretion of gastric acid regardless of its route of administration. Recently, however, some studies have challenged this view and claimed that ethanol inhibits the gastric acid secretion. This study was undertaken to investigate the effects of ethanol on the gastric acid secretion in anesthetized rat in respect to the route of administration and the concentration of alcohol. Normal saline (pH adjusted to 6.0) was used as standard perfusion solution and ethanol was mixed as 0.8, 1.7, 5, 10 and 20%. Four ml of perfusion fluid was given into stomach via gastric tube and drained from duodenal tube every 5 min. Acid secretion was measured by back titration to pH 6.0 with N/20 NaOH and expressed as ${\mu}Eq/5$ min. Low concentration of ethanol up to 1.7% in perfusion solution caused little changes in acid secretion, but moderate concentration such as perfusion of 5% or 10% ethanol solution inhibited both the basal and histamine-induced gastric secretion. Moreover, loss of perfused acid was seen by 20% ethanol, which means back diffusion of hydrogen ions into the gastric mucosa. However, intravenous administration of ethanol, maintained at the level of 0.1% alcohol in blood, caused significant stimulation of gastric acid. We, therefore, conclude that in anesthetized rat ethanol has dual effects on acid secretion, i.e., inhibiting and enhancing by oral and intravenous administration, respectively, but further investigation is necessary to clarify these effects.

• Membrane Journal
• /
• v.9 no.3
• /
• pp.170-177
• /
• 1999

Asymmetric membranes for pervaporation were prepared with poly sulfone and sulfonated poly sulfone in order to separate water from 90% by weight butanol solution. Chlorosulfonic acid was reacted with trimethylchlorosilane for using as a sulfonating agent. The prepared polymers were characterized with FT-IR and $^1H$-NMR. The thermal properties of the polymers were examined with DSC and TGA. Back titration method was used for the evaluation of the degree of sulfonation or the ion ex¬change capacity. N-methyl-2-pyrrolidone (NMP) and diethyleneglycol dimethyl ether (DGDE) cosolvent were used for the preparation of asymmetric membranes. The cross section and skin layer of the mem¬branes were examined with scanning electron michroscopy to investigate membrane structure formed with cosolvent composition in the casting solution. In this article, the selectivity of the dense films were not different from each other so much. However, the permeation rates were significantly increased as much as 80 times compared to that of dense film.