Ashless Quantitative Filter Paper: How to Use Filter Paper for Experiments
In addition to filtering, filter paper is often used in other experiments, such as using filter paper to absorb kerosene on the surface of potassium and sodium, using filter paper as a carrier for flame reaction, using filter paper for laminated galvanic cell experiments, and using filter paper for various spray color reactions, etc. Here HAWACH introduces two innovative and representative examples. Also welcome to share more with HAWACH team.
1. The reaction of sodium and water
1.1 Operation
Take a petri dish, fill it with water that accounts for 1/2 of its volume, add a few drops of phenolphthalein solution, cut around filter paper, and carefully stick it on the water surface. Take a grain of metal sodium the size of soybean with tweezers, and place it on wet filter paper after absorbing kerosene. Then cover it with a large beaker. The reaction heat is easy to accumulate due to the sodium staying on the filter paper without movement.
Therefore, we can see the sodium melts into a ball on the filter paper first, and ignites after a while, emitting a yellow flame, and producing a large amount of white smoke (the product is light yellow sodium peroxide, the color of the smoke is almost white when actually observed), and the aqueous solution under the filter paper gradually turns red.
1.2 Description
(1) The filter paper cannot sink in water, but only float on the water surface, otherwise, the sodium will not ignite.
(2) The above method can also be used for the reaction between potassium metal and water.
(3) When sodium reacts on wet filter paper, there is no phenomenon of sodium particles moving around and solution splashing, which shows that changes in reaction conditions will cause changes in experimental phenomena.
(4) The advantages of this experiment are: not only can see the various phenomena of sodium and water reaction, but also can observe the experimental phenomenon of sodium burning in the air; the safety of the experiment is improved, and there is no pollution.
2. Making “Parchment Paper”
2.1 Principle
Taking advantage of the characteristics of cellulose being soluble in concentrated sulfuric acid and undergoing hydrolysis reaction, the filter paper of pure cellulose is immersed in a certain concentration of sulfuric acid to partially dissolve and hydrolyze the surface of the filter paper and form a thin layer of viscous material. Stop the reaction at this time and wash with a large amount of water to make the viscous layer evenly attached to the surface of the filter paper, making the pores of the filter paper smaller. The treated filter paper can be used for experiments on semi-permeable membranes. Because part of the cellulose on the surface of the filter paper changes the original loose structure in the process of dissolving in acid, its firmness is significantly increased after washing with water. According to tests, its tensile strength can reach 28 times that of the original filter paper. Because of its white color, it is called “parchment”.
2.2 Preparation
(1) Slowly pour two parts (volume) of concentrated sulfuric acid into one part of water, stir it evenly, and allow it to cool to room temperature. At this time, the concentration of sulfuric acid obtained is about 75%. The concentration in winter can be slightly higher than this value, and in summer it should be slightly lower than this value.
(2) Take a water tank and pour about half of the water, and then pour a small amount of ammonia.
(3) Prepare some quantitative filter paper and glass rods.
2.3 Operation
(1) Prepare 75% cold sulfuric acid to immerse a piece of filter paper, take a glass rod to soak it for about 60-90 seconds. The soak time replies to the temperature, the shorter time, the higher temperature.
(2) Use a glass rod to take out the softened filter paper. Firstly, rinse it in clean water and then neutralize the acid on the filter paper by immersing it into a dilute ammonia solution to wash for a while. After the filter paper becomes firmer, take it out, put it into a clean glass plate and dry it naturally. Then we can get white and firm “parchment paper”.
(3) Its experimental effect has a lot to do with the production process of parchment paper (temperature, sulfuric acid concentration, soaking time, etc.).
2.4 Description
(1) Cool the sulfuric acid of the leaching filter paper to room temperature. If not, it will be completely dissolved or even carbonized.
(2) If you want to do a dialysis experiment, you must use high-quality quantitative filter paper (ash-free filter paper), and control the soaking conditions.
(3) Soak the filter paper one by one, and please note soaking overlappingly folded is not allowed.
