Dnyanasadhana College, Thane. hhh Department of Chemistry T.Y.B.Sc. Analytical Chemistry Paper-IV Sem-VI Thermogravimetric analysis Dr.Bhagure G.R.

Contents 4.1.2 Thermogravimetric methods of analysis: Instrumentation basic components of thermobalance block diagram(balance,furnace, temperature measurement and control, recorder), Thermogram (TG curve)Factors affecting TG curve Instrumental factors (Furnace heating rate, furnace atmosphere ,geometry of the sample holder) and Sample characteristics (effect of sample mass, effect of sample particle size and effect of heat of reaction), Applications of TGA TGA of CaC2O4 .H2O and CuSO4.5H2O Determination of Drying temperature range and ignition temperature.

Physical Changes Chemical Changes Substance Heated Thermogravimetric analysis

Weight No loss in weight Loss in weight Time / Temperature Thermogram

TGA – Principle of Operation Thermogravimetry (TG) determines the mass change of a sample as a function of temperature or time. A good tool for: Quality Control And Assurance Failure Analysis Of Complex Polymer Mixtures And Blends. Study of a variety of chemical processes accompanied by mass changes.

Thermal Methods of Analysis Properties are measured as a function of temperature, time, or both Heat flow – direction and magnitude Mass change – loss / gain Mechanical properties Sheer Strain Dynamic loading Gas evolution CHM 342

INSTRUMENTATION: The instrument used in thermogravimetry (TG) is called a thermobalance. It consists of several basic components in order to provide the flexibility necessary for the production of useful analytical data in the form of TGA Curve as shown in Fig.1. Basic components of a typical thermobalance are listed below; i) Balance ii) Furnace: heating device iii) Unit for temperature measurement and control (Programmer) iv) Recorder: automatic recording unit for the mass and temperature changes These components may be represented by simple block diagram as in Fig.2  

INSTRUMENTATION Thermo balance Furnace: heating device Sample Holder Recording Balance and Balance Control Furnace: heating device Furnace temperature Programmer Sample Holder Atmospheric Control Recorder: automatic recording unit for the mass and temperature changes

Characteristic of good Thermobalance Weight change of sample should be recorded continuously. Furnace should reach maximum desired temperature. Heating rate should be linear and reproducible Sample holder should be in hot zone Provision to vary the heating rate in furnace Balance mechanism should be protected from furnace and corrosive gases. Recording of tem and wt to an accuracy of 0.01g. Balance should be sensitive

Factors affecting on Thermobalance Instrumental factors Sample Characteristics

Sample holder Geometry Instrumental factors Heating rate Furnanace atmosphere Static Air Dynamic Air Inert Atmosphere Sample holder Geometry

Sample Characteristics Weight of sample Large amount sample Small amount Sample Particle size of sample Smaller or greater particle size Compactness of sample Loose or compressed sample

Application of Thermogravimetry

Copper sulphate pentahydrate Percentage Wt. Loss B Temperature

Decomposition of Copper sulphate pentahydrate Reaction Temperature CuS04.5H20CuS04.H20 + 4 H20 363-423K CuS04.H20 CuS04 +H20 473-548 K CuS04 Cu0+ S02+1/2 02 971-1173K 2Cu0  + Cu20+ ½ 02 1273-1373

Thermogravimetric Analysis (TGA) A technique that permits the continuous weighing of a sample as a function of temperature and/or as a function of time at a desired temperature

Applications To measure a property of interest, such as specific heat, latent heat or heat of reaction To fingerprint a particular material or substance To assess high temperature stability of materials To detect phase transformations Fundamental studies of reaction kinetics

TGA Applications: Inorganic

TGA Applications: Organics Identification of polymers and pharmaceutical agents Thermal stability of synthetic and natural polymers and other organics Analysis of polymer-matrix composites Kinetics and mechanism of solid organics – gas reactions Residual solvent determinations

TGA Applications: Organics Determination of purity and thermal stability of Primary and secondary standards used in titrimetry. Determination of correct drying temperature of substance. Determination of composition of complex mixtures. Thermal decomposition of inorganic and Inorganic polymeric substances. Solid state reactions Roasting and calcining of minerals . Identification of polymers and pharmaceutical agents Thermal stability of synthetic and natural polymers and other organics Analysis of polymer-matrix composites Kinetics and mechanism of solid organics – gas reactions Residual solvent determinations

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