【正文】 。 they can be left to the third part.
3) The summary of a novel or a play is usually written in the present tense, while that of nonfiction, in the tense of the original work: for example, the past tense should be used for a history, and the present for a scientific work.
4) Comments on and evaluation of the book from the third and most important part of a book report. In this part the writer expresses his or her own views on the book, names its merits and demerits, and discusses its relevance to the present time. The discussion should center on the content of the book, but the author’s style and techniques of presentation, if interesting, can also be touched upon.此資料由網(wǎng)絡(luò)收集而來，如有侵權(quán)請告知上傳者立即刪除。
4. 報告字數(shù)為10001500字。 pipette.
Part 3 The procedure
operating procedure for AAS
(1) inspect major ponents to ensure operating normal.
(2) Install required hollow cathode lamp. Select “T” 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.
(7) Turn on air pressor and acetylene gas and ignite flame. Adjust the flame appropriately and preheat the burner.
(8) Inject distilled water into the flame and continue to preheat the burner. Inject distilled water into the flame after each sample.
(9) Select “E”, inject blank solution into the flame and adjust the meter to zero.
(10) Optimize analysis conditions and measure standard solution and samples.
(11) After pletion of measurement, turn off acetylene gas valve and then air pressor, cut off gas supply a moment later.
(12) Select “T” 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 (10μg/ml) is obtained by diluting 10 ml of Cu standard stock solution to 100 ml with
redistilled water.
(4) Plotting of the standard curve
0 ml, 1 ml, 2 ml, 3 ml, 4 ml and 5 ml of Cu standard solution