A cork borer is often used in a Biology or Chemistry laboratory. It is a metal tool used for cutting a hole in a rubber or cork stopper to insert the glass tubing. Usually, the cork borers are available in a nested size set including with a solid pin, used to push the removed cork or rubber out of the borer. In general, the individual borer is called a hollow tube, tapered at the edge, with some handle on the other end.
Cork borer sharpener is a separate device used to hone the cutting edge to slice the cork more easily.
These cork borers are also used for tree ring analysis (dendrochronology), taking samples from living trees, and taking samples for experiments when a constant diameter is required. For example, a cork borer is used to maintain a constant surface area when testing the potato's water potential.
A cork borer can also be used to punch holes on an agar plate and perform well diffusion assays to study bioactivity in microbiology.
Let us observe the process of boring a Cork.
In the chemical laboratory, the student must carry out simple operations such as cutting a glass tube, bending a glass tube, boring a cork, and the complex process of analyzing substances both qualitatively and quantitatively. Thus, a general acquaintance with such operations becomes obvious before taking up the actual experiments. As most of these processes involved heating, and hence, knowledge of using a burner is essential.
To know the basic techniques on boring a cork and fitting the glass tubes.
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Let us discuss how the process goes through.
A cork becomes harder over time and trying to bore a cork, which hardens results in the formation of cracks. To soften the cork, we are required to wet the cork in water. Once the cork gets flexible, press it in a cork presser, which is a mechanical device. In another way, we can wrap the wet cork in a piece of paper and place it under the shoe, and press it. Now, we have softened cork.
Place the cork on a flat surface area or a table with its narrow end facing up.
To ensure that we get a straight hole, mark the borer position on both sides of the cork.
If the cork that we have taken is a rubber one, we can apply some glycerine on the borer. The reason we do this is because glycerine acts as a lubricant on the hard rubber cork.
Now, hold the cork with the left hand tightly, and by applying force, start the boring process with a twisting motion. You should make sure the borer throughout remains vertical.
Take the borer out and reverse the cork when half of the cork has been bored. Now, start boring from the reversed or opposite side till a hole is obtained.
Finally, now, we can remove the borer.
Now, we will fit the glass tube into the hole bored in the cork.
Then, dip the end of the cork through which the tube will be inserted in water. Perform the same with the end of the tube that is to be used. This process ensures the easy insertion of the tube into the cork.
Hold the cork with the help of one hand and the tube with the other.
Then, hold the tube close to the wet end and insert it into the cork's borehole using a rotatory motion.
Note: To fit up a wash bottle, it is essential to bore two holes in the cork. The two holes are bored similarly as done for a single hole, but we should consider the precaution that the two holes should not be very close to each other. If there is a minimal distance, then the thin cork layer may result in a break.
Let us look at the necessary precautions that are to be followed while performing the procedure:
Select diameter bores slightly smaller in size to that of the tube to be inserted in the hole.
Create a mark on both sides of the cork.
For obtaining a smooth hole, drill half the hole from one side and the other half from the cork's other side.
Since the rubber is a hard material, usually, the end of the tube inserted is dipped in glycerine or caustic soda solution before fitting it in the hole.
The glass tube should be rotated to ensure uniform heating while heating.
Do not bend the glass tubing by force ever. The tubing may break if we did so.
1. Explain the cleaning of Glass Apparatus?
We can get accurate results if the glass apparatus is properly cleaned before it is used. In general, water is used for cleaning, whereas, sometimes, if the apparatus has dirt, grease, spots, the water alone does not serve the purpose. It should be rinsed with the concentrated HCl or concentrated HNO3.
Then we should wash it with the running water under the tap. Chromic acid prepared by dissolving 5 gms of K2Cr2O7 in 100 gms of sulphuric acid is best for removing dirt and grease. Now, leave the apparatus in the chromic acid and after that, clean it in running water. Do not touch the chromic acid as the concentrated H2SO4 is corrosive.
2. What is the basic laboratory technique of a Soda-Lime Glass?
The laboratory apparatus to carry out the reactions, in general, is made up of glass. It is because the glass is resistant to the action of most of the chemicals. In general, we use two types of glass for making apparatus for laboratory work. These are the soda-lime glass and borosilicate glass.
Let us look at the Soda-Lime Glass now
Soda-lime glass is made by heating soda, silica, and limestone softens readily at about a temperature of 300-400°C in the burner flame. Thus, heating glass tubings made of soda-lime glass softens easily and can be bent. The coefficient of soda glass expansion is very high, and therefore, on sudden heating and cooling, it may break. To avoid such breaking, it should be heated and gradually cooled. Annealing by mild reheating and uniform cooling prevents the breakage. Such glass should not be kept on the cold surface while it is hot since a sudden cooling may break it.