1. Chapter 12: Gravimetric Methods of Analysis CHE 321: Quantitative Chemical Analysis Dr. Jerome Williams, Ph.D. Saint Leo University

2. Overview Gravimetric Analysis Precipitating Agents Applications of Gravimetric Methods

3. Gravimetric Analysis Formation and growth of crystals are very important in analytical chemistry and other areas of science.

4. Gravimetric Analysis Gravimetric methods are based on determining mass of a pure compound to which the analyte is chemically related. Types of analysis – Precipitation gravimetryVolatilization gravimetry – Gravimetric TitrimetryElectrogravimetry – Atomic Mass Spectrometry

5. Gravimetric Analysis Precipitation gravimetry: – A precipitating agent should react specifically or at least selectively with the analyte. – Characteristics of ideal precipitating agent 1. Easily filtered & washed free of contaminants 2. Low solubility to minimize loss of sample 3. Unreactive with atmosphere. 4. Known chemical composition after dried or ignited

6. Gravimetric Analysis Particle Size & Filterability of Precipitates: – Larger particles generally more desirable. – Factors that determine Particle Size: 1. Colloidal vs. Crystalline suspensions 2. Relative supersaturation 3. Mechanism: Nucleation & Particle Growth

7. Figure 12-5 p289

8. Figure 12-6 p290

9. Table 12-1 p290

10. Table 12-2 p294

11. Table 12-3 p295

12. p295

15. p296

21. Table 12-4 p297

22. Figure 12-8 p298