Gravimetric analysis is a collection of quantitative analysis laboratory techniques based on the measurement of an analyte's mass. One example of a gravimetric analysis technique can be used to determine the amount of an ion in a solution by dissolving a known amount of a compound containing the ion in a solvent to separate the ion from its. Gravimetric Analysis A simple example is the dimension of solids suspended in a water pattern: An identified quantity of water is filtered, and the gathered solids are weighed. In general, the analyte have got to first be transformed to a high-quality by precipitation with a correct reagent. Oct 17, 2016  The most important lesson from 83,000 brain scans Daniel Amen TEDxOrangeCoast - Duration: 14:37. TEDx Talks Recommended for you. Oct 17, 2016 The most important lesson from 83,000 brain scans Daniel Amen TEDxOrangeCoast - Duration: 14:37. TEDx Talks Recommended for you. What is Gravimetric Analysis? Gravimetric analysis is a method in analytical chemistry to determine the quantity of analyte based on the mass of a solid. Example: Measuring the solids suspended in the water sample – Once a known volume of water is filtered, the collected solids are weighed. Gravimetric analysis describes a set of methods used in analytical chemistry for the quantitative determination of an analyte (the ion being analyzed) based on its mass. The principle behind this type of analysis is that once an ion's mass has been determined as a unique compound, that known measurement can then be used. Because the release of a volatile species is an essential part of these methods, we classify them collectively as volatilization gravimetric methods of analysis. 8.4: Particulate Gravimetry Precipitation and volatilization gravimetric methods require that the analyte, or some other species in the sample, participates in a chemical reaction.

• Role Of Dmg In Gravimetric Analysis
• Use Of Dmg In Gravimetric Analysis System

Thermogravimetric analysis or thermal gravimetric analysis (TGA) is a method of thermal analysis in which the mass of a sample is measured over time as the temperature changes. This measurement provides information about physical phenomena, such as phase transitions, absorption, adsorption and desorption; as well as chemical phenomena including chemisorptions, thermal decomposition, and solid-gas reactions (e.g., oxidation or reduction).^[1]

Thermogravimetric analyzer[edit]

Thermogravimetric analysis (TGA) is conducted on an instrument referred to as a thermogravimetric analyzer. A thermogravimetric analyzer continuously measures mass while the temperature of a sample is changed over time. Mass, temperature, and time are considered base measurements in thermogravimetric analysis while many additional measures may be derived from these three base measurements.

A typical thermogravimetric analyzer consists of a precision balance with a sample pan located inside a furnace with a programmable control temperature. The temperature is generally increased at constant rate (or for some applications the temperature is controlled for a constant mass loss) to incur a thermal reaction. The thermal reaction may occur under a variety of atmospheres including: ambient air, vacuum, inert gas, oxidizing/reducing gases, corrosive gases, carburizing gases, vapors of liquids or 'self-generated atmosphere'; as well as a variety of pressures including: a high vacuum, high pressure, constant pressure, or a controlled pressure.

The thermogravimetric data collected from a thermal reaction is compiled into a plot of mass or percentage of initial mass on the y axis versus either temperature or time on the x-axis. This plot, which is often smoothed, is referred to as a TGA curve. The first derivative of the TGA curve (the DTG curve) may be plotted to determine inflection points useful for in-depth interpretations as well as differential thermal analysis.

A TGA can be used for materials characterization through analysis of characteristic decomposition patterns. It is an especially useful technique for the study of polymeric materials, including thermoplastics, thermosets, elastomers, composites, plastic films, fibers, coatings, paints, and fuels.

Type of TGA:

There are three types of thermogravimetry.

1. Isothermal or static thermogravimetry- In this technique, the sample weight is recorded as a function of time at constant temperature.
2. Quasistatic thermogravimetry- In this technique, the sample is heated to a constant weight each of series of increasing temperatures.
3. Dynamic thermogravimetry- In this technique the sample is heated in an environment whose temperature is changed in a linear manner.

Applications[edit]

Thermal stability[edit]

TGA can be used to evaluate the thermal stability of a material. In a desired temperature range, if a species is thermally stable, there will be no observed mass change. Negligible mass loss corresponds to little or no slope in the TGA trace. TGA also gives the upper use temperature of a material. Beyond this temperature the material will begin to degrade.

TGA is used in the analysis of polymers. Polymers usually melt before they decompose, thus TGA is mainly used to investigate the thermal stability of polymers. Most polymers melt or degrade before 200 °C. However, there is a class of thermally stable polymers that are able to withstand temperatures of at least 300 °C in air and 500 °C in inert gases without structural changes or strength loss, which can be analyzed by TGA.^[2][3][4]

Oxidation and combustion[edit]

The simplest materials characterization is the residue remaining after a reaction. For example, a combustion reaction could be tested by loading a sample into a thermogravimetric analyzer at normal conditions. The thermogravimetric analyzer would ion combustion the sample by heating it beyond the ignition temperature of a sample. The resultant TGA curve plotted with the y axis as percentage of initial mass would show the residue at the final point of the curve.

Oxidative mass losses are the most common observable losses in TGA.^[5]

Studying the resistance to oxidation in copper alloys is very important. For example, NASA (National Aeronautics and Space Administration) is conducting research on advanced copper alloys for their possible use in combustion engines. However, oxidative degradation can occur in these alloys as copper oxides form in atmospheres that are rich in oxygen. Resistance to oxidation is very important because NASA wants to be able to reuse shuttle materials. TGA can be used to study the static oxidation of materials such as these for practical use.

Combustion during TG analysis is identifiable by distinct traces made in the TGA thermograms produced. One interesting example occurs with samples of as-produced unpurified carbon nanotubes that have a large amount of metal catalyst present. Due to combustion, a TGA trace can deviate from the normal form of a well-behaved function. This phenomenon arises from a rapid temperature change. When the weight and temperature are plotted versus time, a dramatic slope change in the first derivative plot is concurrent with the mass loss of the sample and the sudden increase in temperature seen by the thermocouple. The mass loss could be the result of particles of smoke released from burning caused by inconsistencies in the material itself, beyond the oxidation of carbon due to poorly controlled weight loss.

Thermogravimetric kinetics[edit]

Thermogravimetric kinetics may be explored for insight into the reaction mechanisms of thermal (catalytic or non-catalytic) decomposition involved in the pyrolysis and combustion processes of different materials.^{[6][7][8][9][10][11][12]}

Activation energies of the decomposition process can be calculated using Kissinger method.^[13]

Though a constant heating rate is more common, a constant mass loss rate can illuminate specific reaction kinetics. For example, the kinetic parameters of the carbonization of polyvinyl butyral were found using a constant mass loss rate of 0.2 wt %/min.^[14]

Operation in combination with instruments[edit]

The TGA instrument continuously weighs a sample as it is heated to temperatures of up to 2000 °C for coupling with FTIR and mass spectrometry gas analysis. As the temperature increases, various components of the sample are decomposed and the weight percentage of each resulting mass change can be measured.

Thermogravimetric analysis is often combined with other process or used in conjunction with other analytical methods. For example, a TGA is sometimes attached in line with a mass spectrometer.

Types of Thermal gravimetric analysis:

1) Isothermal or Static Thermogravimetry: In this technique, the sample weight is recorded as function of time at constant temperature.

2) Quasistatic Thermogravimetry: In this technique the sample is heated to a constant weight at each of increasing temperatures.

3) Dynamic Thermogravimetry: In this technique the sample is heated in an environment whose temperature is changed in linear manner.

References[edit]

1. ^Coats, A. W.; Redfern, J. P. (1963). 'Thermogravimetric Analysis: A Review'. Analyst. 88 (1053): 906–924. Bibcode:1963Ana..88.906C. doi:10.1039/AN9638800906.
2. ^Liu, X.; Yu, W. (2006). 'Evaluating the Thermal Stability of High Performance Fibers by TGA'. Journal of Applied Polymer Science. 99 (3): 937–944. doi:10.1002/app.22305.
3. ^Marvel, C. S. (1972). 'Synthesis of Thermally Stable Polymers'. Ft. Belvoir: Defense Technical Information Center.
4. ^Tao, Z.; Jin, J.; Yang, S.; Hu, D.; Li, G.; Jiang, J. (2009). 'Synthesis and Characterization of Fluorinated PBO with High Thermal Stability and Low Dielectric Constant'. Journal of Macromolecular Science, Part B. 48 (6): 1114–1124. Bibcode:2009JMSB..48.1114Z. doi:10.1080/00222340903041244.
5. ^Voitovich, V. B.; Lavrenko, V. A.; Voitovich, R. F.; Golovko, E. I. (1994). 'The Effect of Purity on High-Temperature Oxidation of Zirconium'. Oxidation of Metals. 42 (3–4): 223–237. doi:10.1007/BF01052024.
6. ^Reyes-Labarta, J.A.; Marcilla, A. (2012). 'Thermal Treatment and Degradation of Crosslinked Ethylene Vinyl Acetate-Polyethylene-Azodicarbonamide-ZnO Foams. Complete Kinetic Modelling and Analysis'. Industrial & Engineering Chemistry Research. 51 (28): 9515–9530. doi:10.1021/ie3006935.
7. ^Reyes-Labarta, J.A.; Marcilla, A. (2008). 'Kinetic Study of the Decompositions Involved in the Thermal Degradation of Commercial Azodicarbonamide'(PDF). Journal of Applied Polymer Science. 107 (1): 339–346. doi:10.1002/app.26922. hdl:10045/24682.
8. ^Marcilla, A.; Gómez, A.; Reyes, J.A. (2001). 'MCM-41 Catalytic Pyrolysis of Ethylene-Vinyl Acetate Copolymers. Kinetic Model'. Polymer. 42 (19): 8103–8111. doi:10.1016/S0032-3861(01)00277-4.
9. ^Marcilla, A.; Gómez, A.; Reyes-Labarta, J.A.; Giner, A. (2003). 'Catalytic pyrolysis of polypropylene using MCM-41. Kinetic model'. Polymer Degradation and Stability. 80 (2): 233–240. doi:10.1016/S0141-3910(02)00403-2.
10. ^Marcilla, A.; Gómez, A.; Reyes-Labarta, J.A.; Giner, A.; Hernández, F. (2003). 'Kinetic study of polypropylene pyrolysis using ZSM-5 and an equilibrium fluid catalytic cracking catalyst'. Journal of Analytical and Applied Pyrolysis. 68-63: 467–480. doi:10.1016/S0165-2370(03)00036-6.
11. ^Conesa, J.A.; Caballero, J.A.; Reyes-Labarta, J.A. (2004). 'Artificial Neural Network for Modelling Thermal Decompositions'. Journal of Analytical and Applied Pyrolysis. 71: 343–352. doi:10.1016/S0165-2370(03)00093-7.
12. ^Reyes, J.A.; Conesa, J.A.; Marcilla, A. (2001). 'Pyrolysis and combustion of polycoated cartons recycling. kinetic model and ms analysis'. Journal of Analytical and Applied Pyrolysis. 58-59: 747–763. doi:10.1016/S0165-2370(00)00123-6.
13. ^Janeta, Mateusz; Szafert, Sławomir (2017-10-01). 'Synthesis, characterization and thermal properties of T8 type amido-POSS with p-halophenyl end-group'. Journal of Organometallic Chemistry. Organometallic Chemistry: from Stereochemistry to Catalysis to Nanochemistry honoring Professor John Gladysz's 65 birthday. 847 (Supplement C): 173–183. doi:10.1016/j.jorganchem.2017.05.044.
14. ^Tikhonov, N. A.; Arkhangelsky, I. V.; Belyaev, S. S.; Matveev, A. T. (2009). 'Carbonization of polymeric nonwoven materials'. Thermochimica Acta. 486 (1–2): 66–70. doi:10.1016/j.tca.2008.12.020.

Role Of Dmg In Gravimetric Analysis

Table of Content

Abstract

The main objective of this experiment is to determine the concentration of nickel (II) ion in a nickel sample solution of unknown concentration. Gravimetric method is used whereby dimethylglyoxime (1% in alcohol) is added to precipitate the analyte which is later separated from the solution and dried. The concentration of the sample solution has been calculated as 0.109 mg/mL.

• Introduction

In this lab, you will be precipitating nickel (Ni2+) from an unknown Nickel ore. You will need to determine the % of nickel in the unknown which you will report on your unknown card and your lab report. Accuracy will play a large part of your grade so do every step CAREFULLY!

Nickel is precipitated with an organic precipitating agent termed dimethylglyoxime (DMG) as shown below. Organic reagents often react with more than one metal ion, therefore, adequate specification can be achieved with concentration and pH. DMG forms a chelating complex with the metal ion and forms a bright red precipitate Ni(C4H7N2O2)2 in a slightly basic solution of 1:1 aqueous ammonia. The precipitate is washed with a 30% ethanol solution and weighed (constant weight) after drying the frits in the oven at 110EC for 2 hours.

• Background Information of Method

The gravimetric method used in this experiment is among the most accurate methods but time-consuming. Overall, this method includes precipitation of the analyte in aqueous solution which is then separated from the mother liquor, washed, heated to constant weight and weighed as compound of definite composition.

Technique used

Gravimetric analysis is one of the most accurate analytical methods available. It is concerned with the determination of a substance by the process of weighing. The element or radical to be determined is converted into a stable compound of definite composition and the mass of the compound is determined accurately. From this, the mass of element or radical is calculated.

The gravimetric analysis involves

a) precipitation

b) filtration

c) washing of the precipitate and

Feb 14, 2019  Programs used to perform the conversion from exe file to dmg format. It looks like that the exe to dmg conversion is often sought by users that want to convert a Windows installer (usually.exe) to a Mac installer (often saved as.dmg or.app), so they can install Windows app. Exe to dmg converter free download.

d) drying, ignition and weighing of the precipitate.

• Rationale / Purpose of Experiment

This experiment aims to determine the concentration of the nickel (II) ion (Ni²⁺) in a sample solution that contains it.

• Background Information of Analyte

The analyte in this experiment is Ni²⁺. As an element, it is one of the transition metals alongside copper, zinc, iron, manganese, etc. In ionic form, it usually possesses a charge of +2 and gives the solution containing it a green colour. When in contact with basic chemicals, such as aqueous sodium hydroxide (NaOH) and ammonia, it precipitates into a green nickel salt compound; this means nickel (II) solution is acidic. In this experiment, it comes in contact with dimethylglyoxime (DMG, C₄H₆(NOH)₂) and precipitated as nickel dimethylglyoximate (Ni(DMG)₂) in red.

• Materials and Methods
  • Apparatus

Volumetric flask (100 mL), beaker (400 mL), labelling tape, pipette (20 mL), measuring cylinder, microwave oven, thermometer, dropper, electronic weigh, glass rod, basin, sintered glass crucibles, desiccator, tongs, blue litmus paper, aspirator, side-arm filtering flask, retort stand, retort clamps.

• Chemicals and Reagents

Nickel (Ni²⁺) sample solution, distilled water, dimethylglyoxime (DMG, 1% in alcohol), nitric acid (HNO₃, 6 M), urea, oxalic acid, dilute ammonium hydroxide (NH₄OH).

• Experimental Procedures

A sample of nickel solution in a 100 mL volumetric flask is obtained and diluted to the mark with distilled water. The flask is shaken to mix the solution thoroughly and three aliquot samples (20 mL) are transferred into separate 400 mL beakers using a pipette. Each replicate is labelled as 1, 2 and 3 respectively and added distilled water (approximately 150 mL) before being heated to around 80°C in a microwave oven. DMG (10 mL) is added slowly to each replicate which their acidity are later checked with blue litmus paper. HNO₃ (6 M) is added dropwise if any of the replicates is not acidic. Urea (3 g) is weighed and added to each replicate and stirred. The mixture is heated to boil for 3 minutes and cooled down to room temperature in a water-filled basin. Each replicate containing precipitate is added a few drops of dilute NH₄OH. If the drop does not form red coloration upon mixing with the solution, precipitation is considered complete.

Three clean sintered glass crucibles, labelled 1, 2 and 3 respectively, are placed in a dessicator using tongs and weighed separately. The crucibles are then attached to the mouth of filtering flasks which are connected to the aspirator. The supernatant liquid (100 mL) of the mixture is decanted through the respective crucibles and the mixture in each replicate is stirred before being filtered through the crucibles using suction (vacuum filtration) for about 10 minutes. All the red precipitate is made sure to have been transferred into the crucible. The precipitate is washed with a few portions of distilled water (10 mL) before being dried in the oven until constant weight. When the experiment is completed, the crucibles are washed and rinsed in oxalic acid to remove unwashed precipitate.

• Results and Discussion

Overall, the experiment was conducted without any unfortunate incidents. A few errors occurred during the conduct of experiment, which will be explained further in the discussion section….CONTINUED

IMPORTANT!! Purchase to download the entire lab report below (11pages)

Use Of Dmg In Gravimetric Analysis System