Практикалық сабақтарының тақырыптары мен мазмұны Practical assignment №1
SPEAKING. Make up a description of any element you like
жүктеу/скачать 64,23 Kb.
|
chemistry (1)
- Бұл бет үшін навигация:
- METHODS OF ANALYSIS
- METHODS OF SEPARATION
| SPEAKING. Make up a description of any element you like
PROJECT WORK. “Technical Description” RENDERING AND ANNOTATION CHECKLIST UNIT 6. ANALYTICAL CHEMISTRY STARTING UP READING METHODS OF ANALYSIS The analysis of a complex material usually involves four steps, sampling, dissolving the sample, separating mutually interfering substances, and determining the constituents of interest. The first step, sampling can be a significant problem, particularly in industrial applications. Sampling is complete when the subdivision is small enough to permit analysis. The second step is the dissolving of a sample. If we know the nature of the sample we use a suitable reagent. I/Gravimetric methods involve a weighing operation as the final measurement. Gravimetric analysis have been developed for almost everything from A(luminium) to Z(irconium). Gravimetric procedures may be done in various ways: by precipitating, by dissolving, by removing as a volatile compound. Volumetric methods involve measurement of that volume of a solution of known concentration which reacts with a known amount of the sample. Such a solution is called a standard solution. Volumetric techniques are now applicable to most of the elements and to many specific inorganic and organic compounds. They are widely used in all phases of chemistry, in medicine, and in many allied sciences. Physico-chemical methods depend upon the measurement of physical properties other than mass and volume. Such methods are important when the simpler methods of analysis are inadequate. METHODS OF SEPARATION Methods of separating a solid and a liquid are built around two processes, filtration and centrifugation. Filtration is the process of passing the suspension of solid and liquified through a porous barrier which will trap the solid. The barrier may be filter paper, sintered glass, asbestos matting, glass wool and others. Centrifugation is mechanized setting (or floating) and depends upon the differencebetween the densities of the solid and the solution. Gravitational setting is usually inadequate. A centrifuge can be used to enhance the gravitational force moving the particles. Most centrifuges operate at hundreds of revolutions per minute. Extremely difficult separations require speeds of tens of thousands of revolutions perminute. жүктеу/скачать 64,23 Kb. Достарыңызбен бөлісу:
|