Практикалық сабақтарының тақырыптары мен мазмұны Practical assignment №1
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chemistry (1)
- Бұл бет үшін навигация:
- NOTES AND COMMENTARY should be such as will allow
- GAS ANALYSIS
| NOTES AND COMMENTARY
1. are spread down … into layers - оседают пластами 2. provided - при условии, что 3. was engaged in - занимался CHROMATOGRAPHY TECHNIQUES The techniques of carrying out a chromatographic investigation are very simple. The basic apparatus is the adsorption column. The adsorption column may be constructed of soft glass or in special cases of quartz. The diameter аnd length of the column are determined by the quantity of material to be absorbed. No universal adsorbent has been found. A good adsorbent should satisfy the following criteria: it should hold relatively large quantities of the materials to be resolved; the resolved materials must be eluted from the adsorbent by polar solvents; the size of the particles of adsorbent should be such as will allow rapid and uniform percolation; the adsorbents must not react with either the materials to be resolved nor the materials to be used as solvent or color developer; the adsorbent should not be porous and should, if possible, be colorless. The chromatograph is made as follows: a solution of the material to be adsorbed is poured into the adsorption column and allowed to percolate through the adsorbent. The column is washed with additional portions of the original solvent from which the compound was adsorbed. The sides of the column are washed with small portions of the solvent and then larger quantities are added to the column. The passage of the solvent through the column causes the adsorbed materials to move at different rates and thus produce the chromatogram. NOTES AND COMMENTARY should be such as will allow - должен бы быть таким, чтобы позволить rapid and uniform percolation - быстрое и равномерное просачивание PAPER CHROMATOGRAPHY, APPLICATIONS AND PROCEDURE In paper chromatography-the absorption column is replaced by strips of paper. The absorbent or ion exchanger is precipitated into the pores of the paper. One end of prepared paper is dipped into distilled water and allowed to stand until the water has climbed about a centimeter along the paper. It is then removed and dipped into a solution of the materials to be separated. After the unknown solution has climbed about 2 cm, the paper is removed from the unknown solution and returned to the distilled water. After the water has climbed to about 12 to 16 cm, the strip is removed and dried between filter paper. Brushing the dried paper strip with the proper developing agent will produce bands similar to those produced in the adsorption column. Numerous studies have been made of the paper-strip method for separating cations, anions and metal complexes. The procedure is similar to that of column chromatography. The paper-strip method has the advantage that the developing reagent does not pass through the adsorbent as it is required in column chromatography. The strip method requires a minimum of test solution, about 0.1 mm, several developers may be applied to the same strip. The paper-strip method has been applied to quantitative determination of the inorganic cations and to many organic materials. GAS ANALYSIS Special techniques are usually employed in the analysis of the gases. Since analysis of a gas, or gas mixture usually involves the measurement of a volume and only very rarely the weighing of a sample, the results are most frequently reported in per cent by volume rather than per cent by weight. It must be remembered that the volume of a gas is greatly dependent upon both the temperature and the pressure and it is necessary to adjust each measurement to standard conditions of temperature and pressure. It is obvious then that these conditions must remain constant over the course of the analysis. жүктеу/скачать 64,23 Kb. Достарыңызбен бөлісу:
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