scholarly journals Solubility and Crystallization of Piroxicam from Different Solvents in Evaporative and Cooling Crystallization

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1552
Author(s):  
Iben Ostergaard ◽  
Haiyan Qu
Keyword(s):  
Room Temperature ◽  
Evaporation Rate ◽  
Solute Concentration ◽  
Polymorphic Form ◽  
Stable Form ◽  
Stochastic Nature ◽  
Cooling Crystallization ◽  
Evaporative Crystallization ◽  
Polymorphic System ◽  
Simple Link

In this work, the solubility of a non-steroidal anti-inflammatory drug (NSAID), piroxicam, is investigated. The polymorphic form II, which is the most stable form at room temperature, was investigated in seven different solvents with various polarities. It has been found that the solubility of piroxicam in the solvents is in the following order: chloroform > dichloromethane > acetone > ethyl acetate > acetonitrile > acetic acid > methanol > hexane. Crystallization of piroxicam from different solvents has been performed with evaporative crystallization and cooling crystallization; the effects of solvent evaporation rate and solute concentration have also been studied. Both form I and form II could be produced in cooling and evaporative crystallization, and no simple link can be identified between the operating parameters and the polymorphic outcome. Results obtained in the present work showed the stochastic nature of the nucleation of different polymorphs as well as the complexity of the crystallization of a polymorphic system.

Investigations on the polymorphism and pseudopolymorphism of clobetasone butyrate

2011 ◽  
Vol 76 (5) ◽  
pp. 553-566
Author(s):  
Christian Näther ◽  
Inke Jeß
Keyword(s):  
Room Temperature ◽  
Polymorphic Form ◽  
Stable Form ◽  
Scanning Calorimetry ◽  
Amorphous Form ◽  
Space Group ◽  
Dsc Measurements ◽  
Independent Molecules ◽  
Solvent Molecules ◽  
Similar Conformation

Clobetasone butyrate was investigated for polymorphism and pseudopolymorphism. Solvent mediated conversion experiments reveal that the commercially available form I represent the thermodynamically most stable form at room temperature and DSC measurements shows that it should also be the most stable form until melting. Form I crystallizes in space groupP212121with three crystallographically independent molecules of similar conformation. From methanol an additional pseudo polymorphic form was discovered. In the crystal structure (space groupP212121) the solvent molecules are connected to the clobetasone butyrate molecules by O–H···O hydrogen bonding. Investigations of the solvate using thermogravimetry, differential thermoanalysis as well as differential scanning calorimetry proves, that on solvent removal an amorphous form is obtained that crystallizes into form I on further heating.

Room-temperature NaI/H2O compression icing: solute–solute interactions

2017 ◽  
Vol 19 (39) ◽  
pp. 26645-26650 ◽  
Author(s):  
Qingxin Zeng ◽  
Chuang Yao ◽  
Kai Wang ◽  
Chang Q. Sun ◽  
Bo Zou
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Bond Energy ◽  
Room Temperature ◽  
Solute Concentration ◽  
Solute Interaction ◽  
Solute Interactions

H–O bond energy governs the PCx for Na/H2O liquid–VI–VII phase transition. Solute concentration affects the path of phase transitions differently with the solute type. Solute–solute interaction lessens the PC2 sensitivity to compression. The PC1 goes along the liquid–VI boundary till the triple phase joint.

Critical concentration of Mg addition for plastic instabilities in Al–Mg alloys

2000 ◽  
Vol 15 (5) ◽  
pp. 1037-1040 ◽  
Author(s):  
N. Q. Chinh ◽  
F. Csikor ◽  
Zs. Kovács ◽  
J. Lendvai
Keyword(s):  
Room Temperature ◽  
Loading Rate ◽  
Critical Concentration ◽  
Solute Concentration ◽  
Mg Alloys ◽  
Depth Sensing ◽  
Solute Content ◽  
Mg Addition ◽  
Constant Loading Rate ◽  
Al Mg Alloys

Plastic instabilities were investigated by the depth-sensing microhardness test in binary high-purity Al–Mg alloys with different Mg contents. During the tests the applied load was increased from 0 to 2000 mN at constant loading rate. The instabilities appeared as characteristic steps in the load–depth curves during indentation. It was shown that the occurrence and development of the plastic instabilities depend strongly on the solute content. Furthermore, the plastic instabilities occurred only when the solute concentration was larger than a critical value, C0. From room-temperature tests on Al–Mg alloys, C0 was found to be 0.86 wt% Mg. The critical concentration, which is necessary to get plastic instabilities, was also interpreted theoretically.

scholarly journals Occurrence of polymorphism in famotidine raw materials

2014 ◽  
Vol 70 (a1) ◽  
pp. C1563-C1563
Author(s):  
Marilene Ângelo ◽  
Jennifer Jacon ◽  
Olimpia Maria Santos ◽  
Edith Cristina Cazedey ◽  
Rudy Bonfilio ◽  
...  
Keyword(s):  
Raw Materials ◽  
Polymorphic Form ◽  
Raw Material ◽  
Stable Form ◽  
Reference Standard ◽  
H2 Receptor Antagonist ◽  
Scanning Calorimetry ◽  
Histamine H2 Receptor ◽  
Ulcer Disease ◽  
And Control

Polymorphs are compounds with the same chemical composition, however the molecules are arranged in at least two different ways in the solid state. Famotidine is a histamine H2-receptor antagonist inhibitor of gastric secretion and widely used in gastric and duodenal ulcer disease. Two polymorphs are described for famotidine, A and B. The polymorph A is the most thermodynamically stable form and polymorph B is the kinetically favored form being marketed because it presents greater pharmacological activity. The aim of this study was to evaluate the occurrence of famotidine polymorphs in five raw materials acquired from different suppliers. The reference standard (USP) was also analyzed. All samples were characterized by powder X-ray diffraction (PXRD), infrared spectrophotometry (IR-ATR) and differential scanning calorimetry (DSC). PXRD analysis enables us to identify form B in five raw material samples and in the reference standard (USP). However, one of the raw materials additionally shows the presence of polymorphic form A. The DSC and IR-ATR techniques were essential to identify the polymorphic forms of famotidine confirming the results obtained by PXRD. Since the presence of polymorphs can compromise the effectiveness and safety of medicines and there is no official methodology of analysis and control of polymorphism in famotidine raw materials, the polymorphic contamination found in this study are being further analyzed and their physicochemical properties are being evaluated.

scholarly journals Influence of Magnetic Field on Evaporation Rate and Surface Tension of Water

2018 ◽  
Vol 2 (4) ◽  
pp. 68 ◽  
Author(s):  
Emil Chibowski ◽  
Aleksandra Szcześ ◽  
Lucyna Hołysz
Keyword(s):  
Magnetic Field ◽  
Surface Tension ◽  
Hydrogen Bonds ◽  
Room Temperature ◽  
Evaporation Rate ◽  
Water Evaporation ◽  
Water Molecules ◽  
Surface Tension Data ◽  
Ring Magnet ◽  
The Magnetic Field

Using neodymium ring magnets (0.5–0.65 T), the experiments on the magnetic field (MF) effects on water evaporation rate and surface tension were performed at room temperature (22–24 °C). In accordance with the literature data, the enhanced evaporation rates were observed in the experiments conducted in a period of several days or weeks. However, the evaporated amounts of water (up to 440 mg over 150 min) in particular experiments differed. The evaporated amounts depended partially on which pole of the ring magnet was directed up. The relatively strong MF (0.65 T) caused a slight decrease in surface tension (−2.11 mN/m) which lasted longer than 60 min and the memory effect vanished slowly. The surface tension data reduced by the MF action are reported in the literature, although contrary results can be also found. The observed effects can be explained based on literature data of molecular simulations and the suggestion that MF affects the hydrogen bonds of intra- and inter-clusters of water molecules, possibly even causing breakage some of them. The Lorentz force influence is also considered. These mechanisms are discussed in the paper.

Natural Convection in Evaporating Minute Drops

1982 ◽  
Vol 104 (4) ◽  
pp. 656-662 ◽  
Author(s):  
Nengli Zhang ◽  
Wen-Jei Yang
Keyword(s):  
Room Temperature ◽  
Evaporation Rate ◽  
Flow Structures ◽  
Interfacial Flow ◽  
Flat Plates ◽  
Liquid Drops ◽  
Ripple Formation ◽  
Air Interface ◽  
Flow Map ◽  
Interface Type

Interfacial flow structures in small liquid drops evaporating on flat plates are cinematographically investigated using the methods of direct photography and laser shadowgraphy. Various liquids of relatively low boiling point were evaporated on glass and copper plates at room temperature. The laser shadowgraph records the flow patterns simultaneously at both the liquid-air interface and the liquid-solid interface, from which the evaporation rate is determined. It reveals the existence of three distinct flow structures at the liquid air interface: stable, substable, and unstable. An interfacial flow map is constructed. The direct photography is employed to study the morphology during the entire process of the unstable-interface type evaporation. The mechanism of ripple formation which enhances the evaporation rate is found to be caused by hydrophilicity of the liquid.

scholarly journals A water lily–inspired hierarchical design for stable and efficient solar evaporation of high-salinity brine

2019 ◽  
Vol 5 (7) ◽  
pp. eaaw7013 ◽  
Author(s):  
Ning Xu ◽  
Jinlei Li ◽  
Yang Wang ◽  
Chang Fang ◽  
Xiuqiang Li ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Evaporation Rate ◽  
High Salinity ◽  
Energy Conversion Efficiency ◽  
Solute Concentration ◽  
High Energy ◽  
High Rate ◽  
Water Lily ◽  
Solar Absorbers ◽  
Metal Recycling

In recent years, interfacial solar vapor generation has shown great potential in realizing desalination and wastewater treatment with high energy conversion efficiency. However, high evaporation rate cannot be maintained because of the seemingly unavoidable fouling or salt accumulation on the solar absorbers. The degradation accelerates as the solute concentration increases. Here, we demonstrate a water lily–inspired hierarchical structure that enables efficient evaporation (~80% solar-to-vapor efficiency) out of high-salinity brine [10 weight % (wt %)] and wastewater containing heavy metal ions (30 wt %). More notably, neither decrease in evaporation rate nor fouling on absorbers was observed during the entire evaporation process until water and solute were completely separated. With the capabilities of stable and high-rate evaporation out of high-salinity brine and the effective separation of solute from water, it is expected that this technology can have direct implications in various fields such as wastewater treatment, sea-salt production, and metal recycling.

Large Heat Transport Due to Spontaneous Gas Oscillation Induced in a Tube With Steep Temperature Gradients

1983 ◽  
Vol 105 (4) ◽  
pp. 889-894 ◽  
Author(s):  
T. Yazaki ◽  
A. Tominaga ◽  
Y. Narahara
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Helium ◽  
Heat Conductivity ◽  
Room Temperature ◽  
Evaporation Rate ◽  
Experimental Studies ◽  
Temperature Gradients ◽  
Pressure Amplitude ◽  
Large Heat

This paper describes experimental studies of heat transfer due to the oscillations of gas columns that are spontaneously induced in a tube with steep temperature gradients. The tube (∼3 m in length) is closed at both ends and bent into U-shaped form at the midpoint. The temperature distribution along the tube is step-functional and symmetrical with respect to the midpoint. The warm part (closed-end sides) is maintained at room temperature and the cold one is immersed in liquid helium (4.2 K). The heat transported from the warm part to the cold is estimated from the evaporation rate of liquid helium. The heat flux by the oscillations is proportional to the square of the pressure amplitude, and the effective heat conductivity can be several orders of magnitude larger than the molecular heat conductivity of gas. The experimental results are compared with the theory of the second-order heat flux proposed by Rott and are found to be in satisfactory agreement with this.

The Phase Relationship Between the Pyrazinamide Polymorphs α and γ

2019 ◽  
Author(s):  
Kangli Li ◽  
Gabin Gbabode ◽  
Maria Barrio ◽  
Josep-Lluis Tamarit ◽  
Marine Vergé-Depré ◽  
...  
Keyword(s):  
Room Temperature ◽  
Phase Relationship ◽  
Pharmaceutical Formulations ◽  
Equilibrium Temperature ◽  
Topological Pressure ◽  
Temperature Phase ◽  
Stable Form ◽  
Vapor Pressures ◽  
Equilibrium Conditions ◽  
Metastable Forms

<div> <div> <div> <p>Pyrazinamide is an active pharmaceutical compound for the treatment of tuberculosis. It possesses at least four crystalline polymorphs. Polymorphism may cause solubility problems as the case of ritonavir has clearly demonstrated; however, polymorphs also provide opportunities to improve pharmaceutical formulations, in particular if the stable form is not very soluble. The four polymorphs of pyrazinamide constitute a rich system to investigate the usefulness of metastable forms and their stabilization. However, despite the existence of a number of papers on the polymorphism of pyrazinamide, well-defined equilibrium conditions between the polymorphs appear to be lacking. This paper focusses on the phase behavior of the so-called a and g polymorphs of pyrazinamide, its liquid phase and vapor phase. The melting points and enthalpies of both solid phases have been determined. The equilibrium temperature between a and g was experimentally found at 392(1) K. Moreover, vapor pressures and solubilities of both phases have been determined, clearly indicating that form a is the more stable form at room temperature. High-pressure thermal analysis and the topological pressure-temperature phase diagram demonstrate that the g form is stabilized by pressure and becomes stable at room temperature under a pressure of 260 MPa. </p> </div> </div> </div>

The preparation and some properties of transparent conducting ZnO for use in solar cells

1982 ◽  
Vol 60 (10) ◽  
pp. 1387-1390 ◽  
Author(s):  
J. H. Morgan ◽  
D. E. Brodie
Keyword(s):  
Solar Cells ◽  
Glow Discharge ◽  
Room Temperature ◽  
Evaporation Rate ◽  
Dc Glow Discharge ◽  
Electron Carrier ◽  
Glass Substrates ◽  
Transparent Conducting Films ◽  
Transparent Conducting ◽  
Evaporation Technique

The fabrication of transparent conducting films of ZnO is described. These films are deposited on room temperature glass substrates using an enhanced reactive evaporation technique in which the power in a dc glow discharge, the oxygen pressure, and the zinc evaporation rate are controlled separately. Each of these parameters is adjusted to optimize the required film property.Films with ρ = 0.0014 Ω cm and an absorption of ~ 1% at 550 nm and 40 Ω/ have been prepared with no annealing. The electron carrier densities are ~ 1.3 × 1020 cm−3 and the mobilities are ~ 34 cm2/(Vs) with a variation of less than ~ 15% between −120 and +150 °C.

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