High Quality Filter Paper for Laboratory Use Quantitative and Qualitative Analysis

Filter paper is a type of paper with good filtration performance, which is loose and has strong absorption performance for liquids. Filter paper is commonly used as a filtering medium in laboratory analysis to separate the solution from the solid. At present, there are three main types of filter paper: quantitative analysis filter paper, qualitative analysis filter paper, and chromatography qualitative analysis filter paper.
The concepts of quantitative filter paper and qualitative filter paper are both unique to cellulose filter paper and are not applicable to other types of filter paper such as glass microfiber filter paper.

Qualitative filter paper is used for qualitative chemical analysis and corresponding filtration separation, and is generally used for filtering solutions, conducting qualitative experiments on chlorides, sulfates, etc. that do not require numerical calculations; Quantitative filter paper is used for precision calculation of numerical values, such as determining residues, insoluble substances, etc. Generally, after filtration, quantitative filter paper also needs to be processed in a high-temperature furnace.

The types and specifications of qualitative analysis filter paper are basically the same as those of quantitative analysis filter paper, with three types: fast, medium, and slow. When filtering sedimentation, attention should be paid to:1. Generally, natural filtration is used to separate liquid and solid by utilizing the filter paper body and the ability to intercept solid particles.2. Due to the small mechanical strength and toughness of the filter paper, it is recommended to minimize the use of suction filtration. If the filtration speed must be accelerated to prevent filtration failure due to filtration, 2-3 layers of filter paper can be stacked in the funnel according to the suction force during air pump filtration. When using vacuum filtration, a layer of dense filter cloth should be placed on the funnel first, and then filter paper should be placed on top of it for filtration.3. It is best not to filter hot concentrated sulfuric acid or nitric acid with filter paper.

Quantitative analysis of filter paper.During the manufacturing process of quantitative analysis filter paper, the pulp is treated with hydrochloric acid, and washed with distilled water to remove most of the impurities in the paper fibers. Therefore, the residual ash after burning is very small, which has almost no impact on the analysis results and is suitable for precise quantitative analysisQuantitative analysis of filter paper, divided into three categories: fast, medium, and slow. There are two types of filter paper shapes: circular and square. The specifications of circular filter paper are divided into several types according to diameter, including 9cm, 11cm, 12.5cm, 15cm, 18cm, etc. The square quantitative filter paper has the size of 60cm × 60cm, 30cm × 30cm, etc.

Size selection of circular filter paper.

The size (diameter) of the circular filter paper should be selected according to the diameter of the funnel used (diameter of the opening), as shown in the table below.

Size of filter paper.

The filter paper can expand by a maximum of 0.7% in size based on changes in humidity. In addition, after soaking in water, it can increase by up to 4%.

Therefore, the size of the filter paper should be selected based on the size of the filter paper setting part and the changes in the size of the filter paper.

4 Fold.

Used for the purpose of recovering sediment.

★ Fold the circular filter paper in half along the centerline as shown in Figure 1.

★ As shown in Figure 2, the right angle is slightly tilted and folded in half.

★ Before placing the filter paper on the funnel, slightly tear off one end of the filter paper as shown in Figure 3.

★ In this way, the fit between the funnel and filter paper will be better.

★ Spread the larger side into a cone and place it on the funnel.

In addition, when using, the filter paper should be lower than the funnel. When filtering, slowly soak the original solution to make it tightly adhere to the funnel. Then, use glass rods and other tools to transfer the sample while pouring it in.

Folding method with multiple folds. 

Use when there are a large number of samples and only the filtrate is needed to accelerate the filtration rate.
★ If the filter paper is folded multiple times, sometimes the center part can easily crack, so when making a crease, do not press hard on the center part. Slowly fold down from the edge to make the center part slightly full and round.
★ If the unfolded part of the center part is too large, the contact surface with the bottom of the funnel will be reduced, which can also easily cause cracking. Please be careful.
★ If two or more filter papers are overlapped and folded, it is also possible to damage the center part. Please fold each paper one by one.
1) Fold the filter paper in half along the centerline (a-b) of (Figure 4), and then fold it into four folds (c-o), as shown in (Figure 1). At this time, do not use force to fold the center part.
2) After folding twice, return to the creased state of (a-b).
3) Then fold the part (d, e) in half. Do not forcefully fold the center part.
4) Fold a and d, d and c, b and e, e and c in half in the same way, and do not use force to fold the center part during operation.
5) After folding, open the filter paper and adjust and press it separately.

Q1. How can I choose the suitable one?