There are many ways of retracting filter paper, usually using the four-fold method. The key point is to make the retracted filter paper fit and close to the inner cavity of the Buchner funnel. When retracting, the hand should be cleaned, and the taper of the retracted filter paper should be consistent with that of the Buchner funnel; after folding, one half of the filter paper is multi-layer, and the other half is layer by layer. Tear off a piece of the outer double-layer corner of the other side of the multi-layer, so that the filter paper can fit the Buchner funnel wall better when the tap water is wet.
The size of filter paper should be less than 1cm above and below the edge of the Brinell funnel. After putting the treated filter paper into the display bucket, press it tightly with your hands to make it close, and then put a small amount of water on the filter paper with a washing bottle to make it wet. If the telescopic cone angle is suitable, there should be no bubbles between the filter paper and the wall of the Buchner funnel after introducing water, and a water column can be generated in the neck of the Buchner funnel so that the force of the water column can accelerate the filtration rate. If there are bubbles, they should be removed. The liquid level of filter material poured in is usually one-third of the filter paper.
In the test, the filter paper is often used together with the filtering Brucella funnel and Brucella funnel. Before application, the filter paper should be folded into a suitable shape. The common folding method is to fold the filter paper into a similar flower shape. The higher the folding level of the filter paper is, the higher the total surface area can be shown, and the better the filtering effect is. However, it is not necessary to fold too much to cause the filter paper to crack. Put the glass rod on the double-layer filter paper and keep it well proportioned to prevent the filter paper from being damaged.
Operation process:
1. Fold up the filter paper 2 times and fold it into a 95 ° center angle.
2. Press the folded filter paper to one side and open it one layer at a time to form a funnel.
3. Put the funnel-shaped filter paper into the Brinell funnel. The edge of the filter paper should be smaller than the edge of the Brinell funnel. Pour some cold water into the mouth of the Brinell funnel to make the wet filter paper close to the inner cavity of the Brinell funnel. Then throw away the remaining cold water for use.
4. Place the Brucella funnel with filter paper on the road of Brucella funnel for filtering (such as the ring on the iron platform), send the measuring cup or test tube baby receiving the filter solution under the Brucella funnel neck, and make the front of the Brucella funnel neck lean against the inner wall of the receiving vessel.
5. When introducing the liquid that must be filtered into the Buchner funnel, hold the liquid measuring cup in the left hand and the glass rod in the right hand. The bottom of the glass rod is close to the low side of the Buchner funnel so that the cup mouth is close to the glass rod. When the filtered liquid is discharged along with the cup mouth, it will be injected into the Buchner funnel along with the inclination of the glass rod. The liquid level flowing into the Buchner funnel should not exceed the level of the filter paper in the Buchner funnel Aspect ratio.
6. When the liquid passes through the filter paper and flows down the neck of the Buchner funnel, check whether the liquid flows down the wall of the cup and to the bottom of the cup.
Otherwise, the measuring cup should be moved or the Buchner funnel should be rotated to make the front of the Buchner funnel firmly adhere to the wall of the measuring cup so that the liquid can flow down slowly along the inner cavity of the measuring cup.