【正文】 talk little. and they prefer to listening to teachers rather than198。163。206。209。184。176。(3)get familiar with the application of atomic absorption spectrometry.1. 2the principlesatomic absorption spectrometry (aas) is a technique for measuring quantities of chemical elements present in environmental samples by measuring the absorbed radiation by the chemical element of interest. this is done by reading the spectra produced when the sample is excited by radiation. the atoms absorb ultraviolet or visible light and make transitions to higher energy levels .the concentration is calculated based on the beerlambert law. absorbance is directly proportional to the concentration of the analyte absorbed for the existing set of conditions. the concentration is usually determined from a calibration curve, obtained using standards of known concentration. calibration curve method: prepare standard solutions of at least three different concentrations, measure the absorbance of these standard solutions, and prepare a calibration curve from the values obtained. then measure the absorbance of the test solution adjusted in concentration to a measurable range, and determine the concentration of the element from the calibration curve.part 2 the materials and apparatuspart 3 the procedure operating procedure for aas(2) install required hollow cathode lamp. select 161。 before turning to the power and hollow cathode lamp. then select appropriate la mp current and preheat for 30min.(3) make sure electrical meter to point to zero and then turn on highvoltage power.(4) select appropriate slit width.(5) rotate monochromator and select required wavelength. if the power meter is too high or low, adjust negative high voltage until the meter reads full scale.(6) adjust light point and wavelength so that the meter represents the maximum value.(8) inject distilled water into the flame and continue to preheat the burner. inject distilled water into the flame after each sample.(9) select 161。, inject blank solution into the flame and adjust the meter to zero.(10) optimize analysis conditions and measure standard solution and samples.(12) select 161。 before turning off high voltage power, decrease lamp current and then turn off the lamp. at the same time, all buttons should be on original positions.(13) check the equipment before leaving the laboratory. determination of soil samples(1) preparation of extracting solution ( mol/l edta solution) g of edta is dissolved with water in a beaker (500 ml). the ph is adjusted to using dilute ammonia. the mixture is transferred into a volumetric flask (1000ml), dilute to the mark and mixed well.(2) treatment of soil samples g of airdried soil (60 100 mesh) is put into an erlenmeyer flask with stopper (100 ml). ml of edta solution is added. the mixture is shaken for 1h and then filtered. the filtrate is preserved for analysis.(3) preparation of cu standard stock solution g of cu is dissolved in 15 ml of (1:1) nitric acid solution. the mixture is transferred into a volumetric flask (1000 ml) and diluted to the mark with redistilled water. the concentration of the stock standard solution is 100g/ml. (the concentration should be calculated according to the mass of cu).the working cu standard solution (10166。g/ml) are added respectively to 6 volumetric flask (10 ml) with 1 ml of 5 mol/l hydrochloric acid. the mixture is diluted with redistilled water and mixed well to give 0166。g/ml,166。g/ml, 166。g/ml of cu, respectively. the absorbance is measured at wavelengths of 3247 ?. the standard curve is constructed by plotting absorbance vs. concentration.(5) determination of samplesthe sample solution is analyzed using the same procedure and conditions as for the standard curve. the concentration of cu is obtained from the standard curve based on the absorbance.part 4 the results the raw data aas standard curve calculationthe absorbance of sample is .according to the formula above :y=+,r2=the concentration of cu in the sample is:part 5 discussionin this experiment, we use the aas to determine cu in soil. i learn how to operate the aas and the limitation. in the experimental process, standard solution was prepared in strict accordance with the experimental requirements and i learn how to deal with the data. finally we get the standard curve, then, the sample concentration is calculated according to the absorbance of the sample.ultimately, we get the linear formula is y = + and r2=. from according to the formula and the absorbance of cu in the sample is , we draw the concentration of cu in the sample is 166。ll do an experiment, we must prepare our prelab by ourselves and translate it into chinese .only do like this, we can understand the experiment well. secondly we should prefer to solute the problems in the experiment rather than ask for ta. finally, everyone should understand his own task in the 163。211。206。177。241。233。168。196。amp。254。211。211。169。161。211。169。161。169。196。170。162。169。216。202。254。172。214。211。169。196。169。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。173。168。187。169。 differences163。186。 203。163。185。180。163。211。214。211。186。191。179。208。202。172。202。184。243。172。210。180。195。177。161。161。210。207。210。208。210。200。213。196。211。188。214。191。208。194。213。163。206。188。188。213。209。161。161。161。161。161。161。.................... ..................................................................................................................................................................................................................................................................................................................................................................................................... 163。206。210。182。210。163。188。163。203。203。163。180。209。163。210。206。163。177。203。203。163。195。1163。206。210。196。186。188。211。211。213。207。211。185。180。163。211。214。211。186。191。2163。213。161。191。208。213。196。163。210。200。185。180。188。210。161。times new roman208。186。180。190。163。194。210。193。163。161。161。161。161。161。161。161。161。161。..i abstract (in english)161。161。161。161。161。161。161。161。161。161。ii abstract (in chinese)...161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。.161。..161。1 163。188。204。times new roman203。163。180。161。161。211。194。188。163。195。194。197。163。205。ii. the characteristics of idioms161。161。161。161。161。161。161。161。182。177。163。186。178。180。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。..4a. differences between literal translation and free translation .......41. 163。188。204。times new roman203。163。188。163。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。161。203。177。163。186。178。180。............................................6b. .........................................................................................................6c. .........................................................................................................6d. .........................................................................................................7 iv. different cultures in china and western countries 161。161。161。206。211。191。177。181。188。189。217。231。175。202。249。219。177。226。204。235。191。230。219。167。239。175。167。171。182。167。188。180。211。202。191。207。188。196。192。180。:198。205。163。 187。194。c163。177。g163。214。n163。191。j163。206。206。d163。184。r163。188。172。163。 202。191。db163。203。179。163。 181。171。1