小说阅读鉴赏技巧Novel reading appreciation skillsWord下载.docx

1、2 、 study the use of capillary and charging method.With Sarkozy tube 3, to determine the melting point.Experimental principle: the melting point of a substance is the temperature at which the solid-liquid two-phase vapor pressure is equal at a given pressure, that is, the temperature at which the so

2、lid phase coexists with the liquid phase. Pure solid organic compounds usually have a fixed melting point, which is under a certain pressure and heated to near the melting point, the change of solid-liquid two-phase between very sensitive, from the beginning to melt completely melted, the temperatur

3、e change is generally not more than 0.5 to 1 DEG C. Substances containing impurities tend to have lower melting points than pure ones, and the melting process has a greater temperature change. This is of great value in the identification of pure solid organic compounds, and the purity of the compoun

4、ds can be qualitatively determined according to the length of the melting process.Experimental procedure:（1） preparation of melting point tubes1. drawn capillary. With the sample loaded capillary, and its diameter is 1 1.2mm, 40 50mmlong if Sarkozy melting point tube, a length of about 70 75mm. The

5、best wear out tube or pipe for capillary tube drawing 10mm thin glass. To draw the capillary before, should put the tube （or glass tube） with chromic acid and distilled water washed and dried, because cannot be pulled into a capillary cleaning.Methods: hands to draw the capillary glass tube, rotary

6、heating in strong oxidizing flame, which fully burning soft dark cherry red. The glass tube moves away from the flame, and then began to slow, fast and elongated, reciprocating rotating glass tube, until pulled into an outer diameter of 1 to 1.2mm of the capillary, trombone, pay close attention to t

7、he thickness of the capillary. The drawn capillary tube is cut at two times the required length, and the ends are fused at the edge of the small flame to close （the closed tube bottom is thin） so as not to leave dust in storage. When the utility model is used, the capillary pipe is cut off in the mi

8、ddle, and then two melting points pipes are formed.2. loading of sample0.1 0.2g dry powder on the surface of sample dish into a small pile of pile, the melting point of the open end of the tube inserted in the sample, take a small amount of powder. The melting point of pipe erected on the desktop at

9、 a few （melting point tube must fall direction perpendicular to the desktop, or melting point tubes are easy to fracture）, the sample into the bottom of the tube. Repeat the material several times. The melting point of pipe from a length of about 40 50cm high glass tube fell into the dish, repeated

10、several times, so that the sample at the end of the pipe tightly together. The sample must be uniform and strong. The sample height is about 2 3mm.3. instrumentationFigure C-3-1, figure C-3-2Sarkozy will clamp the iron, pour in the liquid bath bath for easy heat conduction, high level side tube abou

11、t 0.5cm. The thermometer with a notched single hole cork fixed on Sarkozy tube. Then use the thermometer mercury ball dipped in a small amount of bath, will be installed to the melting point of the sample tube carefully wetting, adhesion on the thermometer side, can also use the latex tube is made o

12、f a thin shear rubber ring is fixed on the thermometer and the central tube in the sample melting point thermometer mercury ball. The rubber ring is higher than the profit level and the rubber bath bath, in order to avoid contact. The thermometer into the Sarkozy tube in the middle depth of mercury

13、ball just at the midpoint of the two sides of the pipe line at Sarkozy prevail.The thermal conductivity of liquid bath, usually with concentrated sulfuric acid, glycerol and liquid paraffin. Which option is selected depends on the required temperature two. If the temperature is below 140, it is bett

14、er to use liquid paraffin or glycerin. Medicinal liquid paraffin can be heated to 220 degrees, still does not change color. The need to be heated to 140 degrees above, but also by concentrated sulfuric acid, hot concentrated sulphuric acid is very corrosive, if used improperly, concentrated sulfuric

15、 acid spilled easily hurt. Therefore, when measuring the melting point, wear goggles.The temperature exceeds 250 degrees, and the concentrated sulfuric acid gives off white smoke, which hinders the reading of temperature. In this case, potassium sulfate can be added to the concentrated sulfuric acid

16、 to heat it to a saturated solution,Then the measurements were made.The use of concentrated sulfuric acid in a hot bath, sometimes due to organic matter falls into acid and black, interfere with the observation of the sample melting process. In this case, some potassium nitrate crystals can be added

17、 to remove organic matter.4. determination methodIn order to accurately determine the melting point, the heating time, especially in the heating to the melting point close to the sample, must make the temperature rise slowly and evenly. For each sample, at least for two times. For the first time, th

18、e temperature can be increased rapidly, and the temperature can be increased by 5 degrees per minute. Thus an approximate melting point can be obtained. Then took a hot bath to cool down, change a loaded sample tube made of second determination of melting point.Second melting point determination, at

19、 the beginning （starting fast rise Wenk per minute rise 10 degrees, later reduced to 5 DEG C）, when the temperature in order to approximate the low melting point of about 10 DEG C, then a small flame, so that the temperature rise slowly and evenly （every 1 DEG C）, material changes in test tube obser

20、ve the melting point, melting point tube record has just appeared in small droplets of liquid and sample exactly the two melting temperature readings. The more pure the material, the smaller the difference between the two temperatures. If the temperature is too high, the range of the melting point i

21、s not correct.When recording the melting point, the temperature at which the initial melting and the full melting are recorded, such as 123125 degrees centigrade, must not be recorded only for the average of the two temperatures, such as 124 degrees centigrade.After the experiment, the thermometer i

22、s removed, placed in the asbestos net make its natural cooling to room temperature, using waste paper to wipe bath, and then rinse with water. If the thermometer is removed from the hot bath immediately after washing, thermometer will by sudden rupture. Bath liquid cooling and then fell back to the

23、bottle.5. calibration of thermometerWhen the melting point is measured by the above method, there is a certain deviation between the melting point readings of the thermometer and the true melting point. This may be due to the error of the thermometer. For example, the capillary hole in a general the

24、rmometer is not necessarily very uniform, and sometimes the calibration is not very accurate. Secondly, there are two kinds of thermometer, full immersion and semi immersion. Full immersion scale thermometers are evenly heated in the mercury thermometer line under the condition of it, and the heatin

25、g in measuring the melting point of only part of the mercury line, thus exposing the mercury line temperature is of course all heating is low. In addition, after long-term use of thermometer, glass may also occur volume deformation, so that the calibration is not allowed. In order to correct the the

26、rmometer, a standard thermometer can be used, and the melting point of pure organic compounds is usually used as a standard for correction. The error can be removed by correcting the thermometer by this method. The correction as long as the choice of a number of pure compounds of known point as the

27、standard, determination of their melting point, to observe the melting point and melting point known as abscissa, the difference of the longitudinal coordinate, drawing curves, at any temperature readings can be read directly from the curve.The melting point of a standard sample is as follows, and c

28、an be chosen when calibrated.Melting point （temperature） of sample, melting point （DEG C）Water ice 0 urea 132Alpha naphthylamine 503, 5 - two nitrobenzo 204205Two aniline, 53, two, acetophenone two, 95Two chlorobenzene, 53 alpha naphthol 96Benzoic acid, phenyl ester 70, two phenyl hydroxy acetic aci

29、d 150Naphthalene 80 salicylic acid 159Two nitrobenzene, 90 anthracene, 216114 phenolphthalein acetanilide 215Benzoic acid 122 anthraquinone 286Adipic acid 132The best measure zero with a mixture of distilled water and pure water, distilled water 20ml placed in a 15X2.5cm tube, the tube immersed in i

30、ce cold distilled water bath to the part of the ice, with a glass rod to stir the ice water mixture will be removed from the ice bath tube, then the temperature gauge is inserted into the ice the water, gently stir the mixture, after constant temperature readings （23min）.Thinking question1. what is

31、the melting point? What is the melting process?2. what is the melting process of pure and impure materials?3. what problems should be paid attention to in capillary loading sample?Why should the 4. Sarkozy nozzle of the rubber plug slot?5. how high is the sample height in the capillary?6. when measu

32、ring the melting point, why should a small fire heating?7. if the sample tube of the first test can be used for second melting point measurements, why?8. what will happen if you encounter the following melting point?（1） the melting point tube is not clean.（2） the wall of melting point tube is too thick.（3） the sample is