英文实验报告

Qualitative determination of the elements of organic

compounds

Part1 The purposes

1 Learn the principles of the analysis of elements.

1 Master the inspection method of common elements.

Part2 The principles

2.1 The inspection of hydrogen and carbon

Ba(OH)2+CO2→BaCO3↓+H2O

Observe the test tube wall with or without water drop.

2.2 The inspection of sulfur and nitrogen

3NaCNS+FeCl3→Fe(CNS)3 (sanguineous)+3NaCl

2.2.1 The inspection of nitrogen

FeSO4+6NaCN→Na4[Fe(CN)6]+Na2SO4

3Na4[Fe(CN)6]+4FeCl3→Fe4[Fe(CN)6]3↓(blue)+12NaCl

2.2.2 The inspection of sulfur

2.2.2.1 Na2S+2HAc→H2S↑+2NaAc

H2S+Pb(Ac)2→PbS↓+2HAc

2.2.2.2Na2S+Na2Fe(CN)5NO→Na4Fe(CN)(NOS)(claret-colored)

2.3 The inspection of halogen

NaX+AgNO3→AgX↓+NaNO3

2I-+Cl2→2Cl-+I2(A purple color appears in CCl4 layer.)

I2+5Cl2+6H2O→2IO3-+12H++10Cl-(The purple color in CCl4layer fades.)

2Br-+Cl2→2Cl-+Br2(A brown color appears in CCl4 layer.)

Part3 The materials and apparatus

sucrose solution; copper(II) oxide; barium hydroxide; sodium; 10% acetic acid; lead acetate test paper; sodium nitroprusside; 10% sodium hydroxide; iron(II) sulfate; iron(III) chloride; 10% sulfuric acid; diluted hydrochloric acid; 5% silver nitrate; diluted sulfuric acid; carbon tetrachloride; Saturated chlorine water; Saturated chlorine water;

0.1% ammonium hydroxide; concentrated sulfuric acid; 0.5% sodium persulfate.

Part4 The procedures, phenomena and conclusions

Part5 The result

According to the phenomena, we can learn the compound contains hydrogen, carbon, sulfur, nitrogen, chlorine and bromine.

Part6 Discussion

6.1 Q: What's the meaning of the qualitative determination of the elements? Why use the sodium-fusion method to inspect nitrogen and sulfur?

A: It can identify a particular element of organic compounds that determine qualitatively the elements of organic compounds. It can help us to select the ways and methods to identify elements of unknown specimen deeply, and the qualitative determination of the elements is the preparation of quantitative analysis. Inspection of nitrogen and sulfur with sodium (or potassium)-fusion method makes the nitrogen and sulfur of organic compounds into soluble inorganic compounds, then separate and inspect CN-, S2- and so on.

6.2 Q: How to deal with the tiny sodium that sticks to the filter paper, when we cut the sodium on the filter paper?

A: The tiny sodium that sticks to the filter paper can be dealt with by ethyl alcohol, you must not cast it into the tank, disposal bottle and dustbin.

6.3 Q: What gas emission is likely to be when we identify the halogen, if specimen containing sulfur and nitrogen, while, deal with them by nitric acid and boiling? How to solve correctly?

A: It is the gas of hydrogen sulfide and formonitrile when we identify the halogen, if specimen containing sulfur and nitrogen, while, deal with them by nitric acid and boiling. The acidic solution must be boiled for several minutes in fuming cupboard to remove the gas of hydrogen sulfide and formonitrile.