The Characteristics of Qualitative Filter Paper and Its Functions in Lab

Qualitative analysis filter paper is relative to quantitative analysis filter paper and chromatographic qualitative analysis filter paper. The amount of ash produced by the qualitative filter paper after ashing does not exceed 0.13%. Qualitative filter paper is frequently used in the separation of sediments, clarification of liquids, and qualitative analysis. From chemical product filtration, and electroplating industry filtration to coarse filtration and fine filtration of Chinese patent medicine, etc., the grades of filtration products vary greatly. In many different industries, we often use this kind of filter paper in many daily analysis usages.

Characteristics of filter paper

To determine or identify particulate constituents of a mixture irrespective of the amount present, qualitative filter papers are often used in the separating process which requires high purity and consistent performance. They are recommended to use in analytical methods by definition, and we can find different types to meet our needs, such as ash-less qualitative filter paper, and hardened low-ash filter paper.

Often used in several test methods, the ash-less qualitative filter paper is perfect in many standardized test methods, such as gravimetric analysis and sample preparations. Standard ash-less qualitative filter paper does not contain any agents of reinforcement. With intermediate ash content, hardened low-ash filter papers (ash 0.015%) achieve the gravimetric analysis and typical sample preparations in the analysis where the instrumental techniques are involved.

The success of filtration in the lab depends on the right choice of filter paper. When you select qualitative filter papers in a wide range of grades for particular filtration, you may concern about the specifications such as particle retention, product appearance, filtration speed, ash content, basis weight, and wet burst.

The finished qualitative filter paper has a relatively flat surface, uniform texture, high resolution, good results reproducibility, strong load capacity, good diffusion effect, very few impurities, and low background interference. It is suitable for color layer analysis. It is mainly used by units and scientific research institutions that require high precision in experiments. It can also be further processed into testing paper for high-precision testing. Its composition is high-quality pure cotton cellulose without any additives; it is specially designed for high-end users, with stable filtration performance and good uniformity, which is very important for chemical analysis.

Functions in lab filter paper

In addition to filtering, qualitative filter paper has other functions. Please allow HAWACH to introduce the role of filter paper in the experiment.

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 surface of the water, use tweezers to take a grain of metal sodium the size of a soybean, and absorb the kerosene. Place it on wet filter paper and cover a large beaker at the same time.

Since sodium stays on the filter paper and cannot swim, its reaction heat is easy to accumulate, so it can be seen that 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.

Operation of filter paper

(1) Take a piece of filter paper, put it into the 75% cold sulfuric acid prepared above, immerse it in the acid solution with a glass rod, and soak for about 60-90 seconds (depending on the temperature, the time is shorter when the temperature is higher).
(2) Take out the softened filter paper with a glass rod, rinse it in clean water first, and then immerse it in a dilute ammonia solution to wash for a while to neutralize the acid on the filter paper. At this time, the filter paper has become firmer. After taking it out, place it on a clean glass plate and let it dry naturally. The resulting “parchment paper” is as white and firm as sheepskin.
(3) If it is not dried, it can also be used directly in experiments on semi-permeable membranes. Its experimental effect has a lot to do with the production process of parchment paper (temperature, sulfuric acid concentration, soaking time, etc.).

Instruction of filter paper

(1) The sulfuric acid of the leaching filter paper must be cooled to room temperature, otherwise, the filter paper 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) The filter paper can only be soaked one by one, and must not be soaked overlappingly or folded during soaking.