oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

3 ( 1 )

2019 ( 74 )

2018 ( 1151 )

2017 ( 1208 )

Custom range...

Search Results: 1 - 10 of 40938 matches for " chloride analysis "
All listed articles are free for downloading (OA Articles)
Page 1 /40938
Display every page Item
Gran method for end point anticipation in monosegmented flow titration
Aquino, Emerson V;Pasquini, Celio;Rohwedder, Jarbas J. R;Raimundo Jr, Ivo M;Montenegro, M. Concei??o B. S. M;Araújo, Alberto N;
Journal of the Brazilian Chemical Society , 2004, DOI: 10.1590/S0103-50532004000100017
Abstract: an automatic potentiometric monosegmented flow titration procedure based on gran linearisation approach has been developed. the controlling program can estimate the end point of the titration after the addition of three or four aliquots of titrant. alternatively, the end point can be determined by the second derivative procedure. in this case, additional volumes of titrant are added until the vicinity of the end point and three points before and after the stoichiometric point are used for end point calculation. the performance of the system was assessed by the determination of chloride in isotonic beverages and parenteral solutions. the system employs a tubular ag2s/agcl indicator electrode. a typical titration, performed according to the iupac definition, requires only 60 ml of sample and about the same volume of titrant (agno3) solution. a complete titration can be carried out in 1 - 5 min. the accuracy and precision (relative standard deviation of ten replicates) are 2% and 1% for the gran and 1% and 0.5% for the gran/derivative end point determination procedures, respectively. the proposed system reduces the time to perform a titration, ensuring low sample and reagent consumption, and full automatic sampling and titrant addition in a calibration-free titration protocol.
Another Base, Another Solvent? Desalinating Iron Finds with Tetramethylammonium Hydroxide Solution
Charlotte Friederike Kuhn,Christian Heinrich Wunderlich,Gerhard Eggert,Thomas Schleid
E-Preservation Science , 2011,
Abstract: The desalination processes commonly applied to improve the corrosion stability of archaeological iron artifacts are based on immersion treatments in aqueous sodium hydroxide solutions. Faster and more efficient chloride extraction in solutions based on organic solvents with a lower surface tension can be expected. Furthermore, the danger of new corrosion forming during the subsequent washing out of residual chemicals from the desalinating solution could be minimised, if organic solvents would replace the water, commonly used for this process. Only alkali metal hydroxide (LiOH and NaOH) solutions in organic solvents have been tested so far. Their comparatively low chloride extraction efficiency was ascribed to the low solubility of the alkali metal hydroxides and the corresponding chlorides in the solvents used. Tetramethylammonium hydroxide (TMAH) is readily soluble in alcohols and has been tested in aqueous and/or methanolic solutions as an alternative. Neither improved overall chloride extraction efficiency, nor a higher chloride extraction rate could be observed using methanolic solutions. However, aqueous TMAH showed a trend towards higher overall chloride extraction efficiency than the common alkaline treatments. These results could be explained by the different solubility of corrosion products, in particular akaganéite, β-FeO(OH), in the tested solutions.
Gran method for end point anticipation in monosegmented flow titration
Aquino Emerson V,Pasquini Celio,Rohwedder Jarbas J. R,Raimundo Jr Ivo M
Journal of the Brazilian Chemical Society , 2004,
Abstract: An automatic potentiometric monosegmented flow titration procedure based on Gran linearisation approach has been developed. The controlling program can estimate the end point of the titration after the addition of three or four aliquots of titrant. Alternatively, the end point can be determined by the second derivative procedure. In this case, additional volumes of titrant are added until the vicinity of the end point and three points before and after the stoichiometric point are used for end point calculation. The performance of the system was assessed by the determination of chloride in isotonic beverages and parenteral solutions. The system employs a tubular Ag2S/AgCl indicator electrode. A typical titration, performed according to the IUPAC definition, requires only 60 mL of sample and about the same volume of titrant (AgNO3) solution. A complete titration can be carried out in 1 - 5 min. The accuracy and precision (relative standard deviation of ten replicates) are 2% and 1% for the Gran and 1% and 0.5% for the Gran/derivative end point determination procedures, respectively. The proposed system reduces the time to perform a titration, ensuring low sample and reagent consumption, and full automatic sampling and titrant addition in a calibration-free titration protocol.
Validation of spot-testing kits to determine iodine content in salt
Pandav,Chandrakant S.; Arora,Narendra K.; Krishnan,Anand; Sankar,Rajan; Pandav,Smita; Karmarkar,Madhu G.;
Bulletin of the World Health Organization , 2000, DOI: 10.1590/S0042-96862000000800007
Abstract: iodine deficiency disorders are a major public health problem, and salt iodization is the most widely practised intervention for their elimination. for the intervention to be successful and sustainable, it is vital to monitor the iodine content of salt regularly. iodometric titration, the traditional method for measuring iodine content, has problems related to accessibility and cost. the newer spot-testing kits are inexpensive, require minimal training, and provide immediate results. using data from surveys to assess the availability of iodized salt in two states in india, madhya pradesh and the national capital territory of delhi, we tested the suitability of such a kit in field situations. salt samples from delhi were collected from 30 schools, chosen using the expanded programme on immunization (epi) cluster sampling technique. a single observer made the measurement for iodine content using the kit. salt samples from madhya pradesh were from 30 rural and 30 urban clusters, identified by using census data and the epi cluster sampling technique. in each cluster, salt samples were collected from 10 randomly selected households and all retailers. the 15 investigators performing the survey estimated the iodine content of salt samples in the field using the kit. all the samples were brought to the central laboratory in delhi, where iodine content was estimated using iodometric titration as a reference method. the agreement between the kit and titration values decreased as the number of observers increased. although sensitivity was not much affected by the increase in the number of observers (93.3% for a single observer and 93.9% for multiple observers), specificity decreased sharply (90.4% for a single observer and 40.4% for multiple observers). due to the low specificity and resulting high numbers of false-positives for the kit when used by multiple observers (??real-life situations??), kits were likely to consistently overestimate the availability of iodized salt. th
Influência de pré-influência de pré-tratamentos sobre a desidrata??o osmótica de carambolas
Shigematsu, Elke;Eik, Nenis Maria;Kimura, Mieko;Mauro, Maria Aparecida;
Ciência e Tecnologia de Alimentos , 2005, DOI: 10.1590/S0101-20612005000300024
Abstract: osmotic dehydration (od) of star fruit (averrhoa carambola l.) in sucrose solution was studied, aiming at optimizing the process. at a first set of trials, edible coating (pectin or pectin+starch) was applied on the slices followed by od (50%, w/w, 27°c). on a second set of trials, the coatings partial drying in the oven, before od, was also assessed. at a third set of trials, the addition of the cacl2 in the osmotic solution itself was tested. the pectin based and pectin+starch based coatings, moist or oven-dried before the osmotic dehydration, were not viable on the process efficiency improvement (maximum water loss/solute gain) due to the high moisture retention and the easy sucrose impregnation of them. the vegetal tissue, uncoated, restrained more of the solute transfer and allowed a higher water output. the use of 0.04m cacl2 concentration in the sucrose osmotic solution itself improved the process efficiency slightly in relation to the solution without salt. these pre-treatments also yielded positive results on the sensorial evaluation of the air-dried (60 and 70°c) star fruit slices, in comparison with the non-treated fruit, and the best temperature was 60°c
Nitrogênio e potássio via fertirriga??o e aduba??o convencional-estado nutricional das bananeiras e produ??o de frutos
Teixeira, Luiz Ant?nio Junqueira;Natale, William;Martins, Ant?nio Lúcio Mello;
Revista Brasileira de Fruticultura , 2007, DOI: 10.1590/S0100-29452007000100032
Abstract: a field experiment was carried out in pindorama (sao paulo state, brazil) with the objective of investigating the effects of n and k application through fertirrigation and conventional fertilization on banana plants during two crop cycles. plant growth, nutrition status and fruit production were evaluated. the fertilization caused a reduction in the productive cycle. fertilizers applied by fertirrigation or conventional fertilization changed the n and k leaf content. the fruit production varied in function of the treatment in the two cultivated cycles. fruit production (t ha 1 year 1) obtained with application of 80% of n and k doses by fertirrigation was comparable to fruit production with 100% of fertilizer rate applied by conventional fertlization.
Nitrogênio e potássio em bananeira via fertirriga??o e aduba??o convencional-atributos químicos do solo
Teixeira, Luiz Ant?nio Junqueira;Natale, William;Bettiol Neto, José Emílio;Martins, Antonio Lúcio Mello;
Revista Brasileira de Fruticultura , 2007, DOI: 10.1590/S0100-29452007000100031
Abstract: a field experiment was carried out in pindorama (sao paulo state, brazil) in which it was evaluated the effects of n and k application through fertirrigation and conventional fertilization on soil chemical properties in a banana plantation, during two cycles of production. nutrient (p, k, ca and mg) availability and movement in soil profile and some chemical properties (organic matter, ph and base saturation) were evaluated through samples carried out in the experiment implantation and at the end of the first and second production cycles. the most important treatment effects were on soil ph and on exchangeable k. fertilizers, applied by fertirrigation or conventional fertilization, increased soil ph specially in soil layer depth of 0 to 20 cm. it was observed that the impact of ph soil fertilization via fertirrigation was proportional to fertilizer rate. the conventional fertilization also caused a ph decrease on soil, and it was more intense near the plants, reflecting the effect of fertilizer local application. the application of solid fertilizer on the soil surface determined a significant accumulation of exchangeable k on layers until the depth of 20 cm and in the region nearer the plant pseudo-stem . the effects of fertirrigation on soil chemical properties were more diffuse because fertilizers were spread in a larger area than the application of conventional fertilization.
Hipertens?o arterial e consumo de sal em popula??o urbana
Bisi Molina,Maria del Carmen; Cunha,Roberto de Sá; Herkenhoff,Luis Fernando; Mill,José Geraldo;
Revista de Saúde Pública , 2003, DOI: 10.1590/S0034-89102003000600009
Abstract: objective: to evaluate the salt intake and urinary na+/k+ ratio in a randomized sample from an ethnically mixed urban population. methods: a randomized residential sample of 2,268 individuals aged 25-64 in vitória, es, was selected, of whom 1,663 (73.3%) reported to the hospital for standardized tests. salt, na+ and k+ intake was estimated from 12-hour urine excretion (7 p.m. to 7 a.m.) and from the monthly salt consumption at home reported in the interview. clinic arterial pressure was measured twice under standard conditions by two trained investigators, using mercury sphygmomanometry. the student t and tukey tests were utilized for statistical analysis. results: urinary na+ excretion was higher in men and individuals of lower socioeconomic level (p<0.000). no difference between ethnic groups was observed. k+ excretion was unrelated to socioeconomic level and ethnicity, but was significantly higher among men (25±18 vs. 22±18 meq/12h; p=0.002). positive linear correlation was observed between urinary na+ excretion and systolic (r=0.15) and diastolic (r=0.19) arterial pressure. hypertensive individuals showed higher urinary na+ excretion and na+/k+ ratio than normotensive individuals. reported salt intake was around 50% of the intake estimated from 12-hour urine collection (around 45% of 24-hour urinary excretion). conclusions: salt intake is strongly influenced by socioeconomic level and may partially explain the higher prevalence of hypertension in lower socioeconomic classes.
SCC of Stainless Steel Furnace Tubes in a Heating Furnace
ZHU Ziyong ZHOU Xiangyang GU Jianfan KE Wei Corrosion Science Laboratory,Academia Sinica,Shenyang,China,
朱自勇
,周向阳,顾建繁,柯伟

材料科学技术学报 , 1992,
Abstract: Some furnace tubes made of the austenitic stainless steel 1Cr18Ni9Ti for heating crude oil ex- hibited leakage and were on fire in a refinery.Cor- rosion failure analysis was conducted to explore the cause of failure.Macro-and microexamination in- dicated the failure to be stress corrosion cracking by chloride and sulphide with cracks initiating on the inner surface in weld or heat affected zone.Veri- fying tests demonstrated that the cracks occurred during operating period.The cause of failure was related to the critical situation of the refinery:lack of desalination equipment,lots of steam with liquid film on inside tube walls owing to mixing crude oil with a great amount of water,increasing decompo- sition of inorganic salts and lowering the tempera- ture in furnace tubes.
PREPARATION AND CHARACTERIZATION OF COMPOSITES COMPRISING MODIFIED HARDWOOD AND WOOD POLYMERS/POLY(VINYL CHLORIDE)
Ruxanda Bod?rl?u,Carmen Alice Teac?,Iuliana Spiridon
BioResources , 2000,
Abstract: Chemical modification of hardwood sawdust from ash-tree species was carried out with a solution of maleic anhydride in acetone. Wood polymers, lignin, and cellulose were isolated from the wood sawdust and modified by the same method. Samples were characterized by Fourier transform infrared spectroscopy (FTIR), providing evidence that maleic anhydride esterifies the free hydroxyl groups of the wood polymer components. Composites comprising chemically modified wood sawdust and wood polymers (cellulose, lignin)-as variable weight percentages-, and poly (vinyl chloride) were obtained and further characterized by using FTIR spectroscopy and scanning electron microscopy (SEM). The thermal behavior of composites was investigated by using the thermogravimetric analysis (TGA). In all cases, thermal properties were affected by fillers addition.
Page 1 /40938
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.