Unusual temperature-sensitive protonation behaviour of 4-(dimethylamino)pyridine

The kinetics of the formation and dissociation of Cu(II) complexes of adenosine have been determined in acidic and basic medium. In acidic medium, the complex is formed between the Cu(II) and the adenine base and the kinetic parameters have been obtained in this case using a temperature jump method. In basic medium, only the dissociation of the complexes could be studied by a stopped-flow method, by addition of EDTA or strong acid solutions. In these complexes, Cu(II) is bridged with ribose hydroxyls. Finally, D-ribose has also been studied for comparison in the same conditions. The mechanism of these reactions is discussed.

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The utilization demineralized rice husk waste for biofuel source via pyrolysis: thermogravimetric analysis and kinetic study

MATEC Web of Conferences ◽

10.1051/matecconf/201928005019 ◽

2019 ◽

Vol 280 ◽

pp. 05019

Author(s):

Hesti Wijayanti ◽

Iryanti Fatyasari Nata ◽

Rinny Jelita

Keyword(s):

Nitric Acid ◽

Thermogravimetric Analysis ◽

Acid Solution ◽

Rice Husk ◽

Nitric Acid Solution ◽

Agricultural Waste ◽

Solution Treatment ◽

Strong Acid ◽

Raw Material ◽

Acid Solutions

Rice husk is considered as agricultural waste that causes environmental problem during its handling. In this study, rice husk was treated with acid (citric acid and nitric acid) solutions prior used as raw material for producing biofuel and chemicals via pyrolysis. The pyrolysis behaviors of rice husk treated with water and acid solutions have been investigated through thermogravimetric analysis from room temperature to 600 oC at the heating rate of 10oC/min under 50 ml/min nitrogen flow. Demineralization treatment using strong acid (nitric acid) solution showed more impacts to the rice husk in thermogravimetric analysis, i.e. lower ash content, less minerals content and thermal stability increased. One step model kinetic resulted the lowest activation energy (12.8709 kJ/mol) occured at the 5% nitric acid solution treatment. Excellent agreement between the experimental data and model predictions was found with 8.63% of the relative error. In other words, demineralization using 5% nitric acid solution would improve rice husk performance during its pyrolysis reaction for producing biofuel.

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Determination of formation constants of molybdophosphates in strong acid solutions

Analytical Chemistry ◽

10.1021/ac00243a010 ◽

1982 ◽

Vol 54 (6) ◽

pp. 879-884 ◽

Cited By ~ 19

Author(s):

C. C. Kircher ◽

S. R. Crouch

Keyword(s):

Strong Acid ◽

Formation Constants ◽

Acid Solutions

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Extraction of Silica from Palm Ash Using Citric Acid Leaching Treatment: Preliminary Result

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.795.701 ◽

2013 ◽

Vol 795 ◽

pp. 701-706 ◽

Cited By ~ 3

Author(s):

Che Pa Faizul ◽

C. Abdullah ◽

B. Fazlul

Keyword(s):

Citric Acid ◽

Rice Husk ◽

Acid Leaching ◽

Strong Acid ◽

Agricultural Wastes ◽

Raw Material ◽

Solution Temperature ◽

Acid Solutions ◽

Silica Materials ◽

Metallic Impurities

Large quantities of agricultural wastes such as palm ash and rice husk are found throughout Malaysia, have a possibility to be used as a usefully renewable source for production of energy and silica (SiO2). Extensive researches have been carried out to extract silica from agricultural wastes such as rice husk, due to silica as a useful raw material for industrial application. In the previous studies, the strong acid leaching treatment was carried out to remove metallic impurities and organics contained in rice husk. Since leaching treatment is a proper route to extract the silica, sulphuric acid (H2SO4), hydrochloric acid (HCl) and nitric acid (HNO3) solutions are currently used in leaching treatment to prepare silica materials [. A strong acid leaching treatment, however, is significantly hazardous to the environment and people. In this study, the weaker acid, citric acid solutions were used to replace strong acid in leaching processes. Preliminary results showed that silica can be extracted from palm ash using citric acid leaching treatment under the optimum extracting conditions with 70°C of solution temperature, 60 minutes of reaction time and concentration of citric acid of more than 2%. The purity of silica extracted is more than 90%.

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Change of Calibration Parameters in Frequently Used Vials in Benzene Scintillation Counting

Radiocarbon ◽

10.1017/s0033822200031271 ◽

1995 ◽

Vol 37 (2) ◽

pp. 737-742 ◽

Cited By ~ 3

Author(s):

Herbert Haas

Keyword(s):

Strong Acid ◽

Scintillation Counting ◽

Calibration Data ◽

Acid Solutions ◽

Calibration Parameters ◽

Made In

Scintillation counting vials used for counting synthesized benzene accumulate an inside coating which is insoluble in benzene. This coating reduces the photon transfer from the vial and lowers its observed background. Age calculations that include calibration data collected with other vials may be inaccurate if this effect is not considered. Frequent cleaning of the counting vials with strong acid solutions keeps the coating from accumulating.A sample counting vial cleaned only with photospectrometric grade benzene between 67 different sample benzene fillings made in a 20-month period showed, during counting, an efficiency lowered by 2.8% and a background lowered by 8.7%. Age calculations for a 10 ka old sample made with calibration data from “matched” vials would yield a result too old by 515 yr.

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