Ten common troubleshooting methods in the lab

In the laboratory, there are often some unexpected "small troubles". For example, the stopper can not be opened, the dirt on the instrument is difficult to remove, and the emulsification occurs during liquid separation. If you can take the appropriate methods or techniques to deal with them, these troubles will be solved.

1. Opening the fixed glass grinding ring When the grinding part of the glass instrument cannot be opened due to sticking, the following methods can be used.
(1) Tap the wood to gently tap the side of the grinding part to make it loose and loose due to vibration. For the fixed reagent bottle, the grinding plug of the separatory funnel, etc., the plug and the bottle mouth of the instrument can be stuck at the corners of the test bench or the wooden table, and then the wood is lightly inclined at an angle of about 70° to the axis of the instrument. Tap gently and rotate the instrument intermittently. Repeat this operation several times to open the grind that is not severely fixed.
(2) Heating a somewhat fixed grinding mouth, which is inconvenient to tap or knock, and the outer layer of the fixing portion is heated to be thermally expanded to be detached from the inner layer. For example, use a hot damp cloth to "hot pack" the sticky place, use a hair dryer or swim the flame to bake the grind, etc.
(3) Infiltration Some grinding joints are firmly adhered due to drug erosion, or are valuable instruments with complicated structure. It is not suitable for tapping and heating. It can be opened by soaking in water or dilute hydrochloric acid for several hours. If the instrument is used urgently, an organic solvent with strong penetrability (such as benzene, ethyl acetate, petroleum ether and sodium dioctyl sulfosuccinate) may be added to the gap between the grinding ports to make it infiltrated into the stick. The fixed parts are thus separated from each other.

2. Open the screw cap that is fastened When the screw cap is not open, use a hair dryer or a small flame to bake around the cap to expand it, and then use it to wrap the cap and unscrew it.
If the bottle is filled with heat or flammable materials, take a strong rope, one end on a fixed object (such as door and window handles), then turn the rope clockwise on the bottle cap, then hand in hand At the other end of the rope, holding the bottle in one hand and pushing it forward can open the cap.

3. Remove the thermometer that is bonded by the rubber plug. When the thermometer or glass tube is stuck with the rubber plug or hose and it is difficult to remove it, insert the thermometer (or glass tube) and the rubber stopper (or hose) with the tip of the small screwdriver or the blade. In between, make a gap, and then drop a few drops of water, so operate and expand around the thermometer (or glass tube), while gradually deepening, will soon be taken out. You can also use a drill that just fits into the thermometer (or glass tube), put a little glycerin or water on it, put it in from one end of the thermometer, gently push it while pushing it, and when it is difficult to turn it, pull it out and put it on it. Lubricant, continue to rotate, and after repeated several times, the thermometer (or glass tube) can be taken out.

4. Clearing special dirt on the instrument When reflowing or concentrating the solution, crystals are often deposited on the inner wall of the flask above the liquid surface, and the adhesion is firm. Not only can it continue to participate in the reaction, but it sometimes decomposes due to poor thermal stability. In this case, the flask can be gently shaken, and the internal solution is impregnated with crystals to dissolve. If the apparatus is not restricted in activity and the flask cannot be shaken, a cold wet cloth may be applied to the upper portion of the flask to dissolve the precipitated crystals when the solvent condenses down the wall.

5. When the crystal precipitated on the inner wall of the dissolving flask is refluxed or concentrated, the crystal is often precipitated on the inner wall of the flask above the liquid surface, and the adhesion is firm, and not only cannot continue to participate in the reaction, but also gradually decomposes due to poor thermal stability. . In this case, the flask can be gently shaken, and the internal solution is impregnated with crystals to dissolve. If the apparatus is not restricted in activity and the flask cannot be shaken, a cold wet cloth may be applied to the upper portion of the flask to dissolve the precipitated crystals when the solvent condenses down the wall.

6. Packing up the spilled mercury commonly used in the laboratory is a mercury-filled pressure gauge and a mercury thermometer. If the operation is improper or the thermometer is damaged, a “spraying accident” will occur. Mercury vapor is extremely harmful to the human body, and it is necessary to promptly and thoroughly clean up the spilled mercury, and it must not be allowed to be lost. There are many cleaning methods, which can be selected according to different situations.
(1) Absorb a small amount of mercury, and use a common dropper to suck up the mercury beads one by one and collect them in a container. If the amount of mercury is large or spilled in the gap of the groove, the suction filter bottle can be connected to a 75° glass elbow through a rubber plug, and a “decompression aspirator” can be made to pass the mercury particles through the negative pressure. The glass tube is sucked into the filter bottle. The connection between the suction filter bottle and the pressure reducing pump can be slightly longer to prevent mercury from being drawn into the pump.
(2) Adhesion of mercury spilled on the table top (or the ground), if it has been dispersed into fine particles, it can be adhered with tape paper, then immersed in water and brushed into the container with a brush. This method is simple and easy to perform.
(3) The melting point of frozen mercury is -38.87 °C. If the sprinkled mercury is covered with an appropriate amount of dry ice-acetone mixture, the mercury will be frozen into a solid and lose fluidity within a few seconds, which is easier to clean.
(4) Conversion For the trace mercury that is scattered in the corner and difficult to be collected by the above method, the sulfur powder can be used to cover the area where the mercury particles are lost, and the mercury and sulfur are combined to form mercury sulfide with less toxicity, and then removed.

7. Elimination of emulsification When using a separatory funnel for extraction and washing operations, especially when the organic matter is washed with an alkali solution, it is often difficult to separate due to emulsification without delamination. If the degree of emulsification is not serious, the separatory funnel can be slowly rotated in the horizontal direction and then left to stand for a while to eliminate the foam at the interface and promote delamination. If it is still not layered, add a proper amount of water, then shake it horizontally or place it overnight to separate the clear interface.
If the density of the solvent is close to that of water, it is easy to emulsify with water during extraction or washing. At this time, an appropriate amount of *** can be added thereto to lower the density of the organic phase, thereby facilitating delamination.
For an emulsion formed by a slightly soluble ester of water and water, it can be stratified by adding a small amount of an inorganic salt such as sodium chloride or ammonium sulfate.

8. Rapid drying instrument When it is urgent to use a dry instrument in the experiment, and it is too late to dry by conventional methods, the inner wall of the instrument can be washed twice with a small amount of absolute ethanol, then rinsed once with a small amount of acetone to remove residual ethanol, and then used with a hair dryer. Drying can be achieved by blowing a few moments.

9. Stabilizing the flask in the water bath When cooling the material in the conical flask with cold water or ice bath, the flask will float due to the small amount of material and the buoyancy of the bath, which will affect the cooling effect. Sometimes the flask will be poured into the bath. ACCIDENT. If a circle of moderate length is used to make a circle smaller than the bottom diameter of the conical flask, the flask is placed in the flask and the flask is immersed in the bath. If the container used is a beaker, the circle can be placed over the beaker and the wire is hung on the mouth of the beaker to stabilize it and achieve sufficient cooling.

10. Making a simple constant temperature cooling bath When some experiments require the temperature of the constant temperature bath to be kept below room temperature, cooling with cold water or ice bath often does not achieve satisfactory results. At this time, you can make a simple constant temperature cooling tank: use a larger carton (reagent or instrument box) as the outer tank, put the thermostatic bath into the carton as the inner tank, and put a proper amount of dry ice between the inner and outer tanks. Then use foam plastic as insulation material to fill the gap and cover the upper part. The amount of dry ice can be adjusted according to the temperature and time required for the experiment. This cooling tank is easy to manufacture and has a good heat preservation effect.
When a special stain is adhered to a glass instrument and it is difficult to remove it by a general washing method, the nature of the soil should be distinguished first and then treated in a targeted manner.
For acidic soils that are insoluble in water, such as organic acids, phenolic deposits, etc., they can be washed with lye and then cleaned; for alkaline soils that are insoluble in water, such as metal oxides, scales, etc., they can be washed with hydrochloric acid; if The potassium permanganate deposit can be washed with sodium sulfite or oxalic acid solution; the manganese dioxide deposit can be dissolved by concentrated hydrochloric acid; when iodine is used, it can be soaked with potassium iodide solution; the silver nitrate stain can be washed with sodium thiosulfate solution and then washed; The silver (or copper) adhered by the silver mirror (or copper mirror) can be dissolved by adding dilute nitric acid to the micro-heat; the tar or resinous dirt can be immersed in an organic solvent such as benzene or ester, and then washed by an ordinary method. . For glass instruments that cannot be cleaned by the above methods, the edges of the dirt can be wetted with dilute hydrofluoric acid, and the dirt will fall off along with the thin layer of the etched glass, and then washed with water. Although the glass is corroded, the damage is small and generally does not affect the continued use.