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Filter paper (Laboratory Use)
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.
|
Type |
Qualitative filter paper |
Quantitative filter paper |
|
Applications |
Mainly used for rough separating of solid impurities, such as particles, precipitates, and colloids |
Mainly used for precise weighing and separating of trace solid substances, such as trace ions, heavy metal ions, etc. |
|
Accuracy |
Low accuracy and can tolerate certain errors |
High accuracy |
|
Material |
Generally made from cellulose or mixed cellulose |
Generally made of high-purity cellulose, with more stable chemical properties |
|
Size |
Larger size |
Smaller size to meet the separating and weighing requirements of trace substances |
Quantitative analysis filter paper:
During the manufacturing process of quantitative analysis filter paper, the pulp is treated with hydrochloric acid and hydrofluoric 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 analysis.
Quantitative 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 a thickness of 60cm × 60cm, 30cm × 30cm, etc.
Qualitative analysis of filter paper:
Qualitative analysis filter paper generally has a large amount of residual ash, which is only used for general qualitative analysis and for filtration precipitation or suspension in solution, and cannot be used for quality analysis.
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.
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.
|
Funnel |
Filter paper |
|
30 |
55 |
|
45 |
90 |
|
50 |
90 |
|
55 |
110 |
|
60 |
110 |
|
65 |
125 |
|
70 |
125 |
|
75 |
150 |
|
100 |
185 |
|
120 |
240 |
|
150 |
285 or 300 |
|
180 |
360 |
|
210 |
400 |
|
250 |
500 |
|
300 |
600 |
Precautions when using filter paper:
● Treatment method for filter paper
If handled with pointed tweezers, it may damage the filter paper. Please use tweezers with a flat front end to handle the filter paper.
If using glass filter paper, please do not fold it as it is made of fiberglass material.
● Setting of filter paper
The side of the product packaging marked with the product name is the front of the filter paper.
Please set the front of the filter paper to the top (the side that comes into contact with the fluid before filtering).
If set in the opposite position (with the back of the filter paper set above), the filtering life may be shortened.
● 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.
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