4.3
표본: 여과
여과는 현탁액을 다공성 매질에 통과시켜 유체에서 고체를 분리하는 물리적 분리 공정입니다. 여과하는 동안 고체는 다공성 매질에 수집되고 집합적으로 여과액이라고도 알려진 액체는 통과합니다. 여과 매체는 여과 목적, 수량, 침전물의 성질에 따라 선택됩니다. 적합한 여과 매체…
여과는 여과 매체를 사용하여 유체에서 고체를 물리적으로 분리하는 것입니다.
여과 매체는 여과의 목적, 양 및 고체의 입자 크기에 따라 선택됩니다.
일반적으로 여과 효율은 입자 크기에 따라 증가합니다.
간단한 여과에서, 침전물은 먼저 침전되도록 허용되고, 모액은 유리 막대의 아래 여과지가 장착된 깔때기로 기울어집니다.
그런 다음 침전물은 고무 경찰관을 사용하여 여과지로 이송됩니다.
계량이 필요한 경우 침전물을 회수하기 위해 무회분 여과지를 점화할 수 있습니다.
또는 진공 펌프에 연결할 수 있는 사이드암이 있는 Buchner 플라스크에 고정된 소결 유리 깔때기를 사용하여 침전물을 가두는 데 사용합니다.
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Q1: What is filtration and how does it separate solids from liquids?
Filtration is a physical separation process that passes a suspension through a porous medium to separate solids from fluids. Solids collect on the porous medium while liquids, called the filtrate, pass through. The filtration medium is selected based on the filtration purpose, quantity, and nature of the precipitate to ensure effective separation.
Q2: How does particle size affect filtration efficiency?
Filtration efficiency increases with particle size. Larger particles are retained more effectively on the filtration medium, while smaller particles may pass through more easily. The choice of filtration medium depends on the particle size of the solid being separated to optimize efficiency.
Q3: What are the key properties of a suitable filtering medium?
A suitable filtering medium must be inert, mechanically strong, nonabsorbent toward dissolved materials, and permissive toward rapid filtration. These criteria ensure the medium does not react with the sample, maintains structural integrity during use, and allows efficient liquid passage while retaining solids.
Q4: Why is ashless filter paper preferred in gravimetric analysis?
Ashless filter paper is preferred because regular filter paper is hygroscopic and can absorb moisture, affecting mass measurements. Ashless filter paper can be ignited to recover the precipitate without leaving residue, making it ideal for gravimetric procedures that require accurate weighing of collected solids.
Q5: What is the difference between simple filtration and suction filtration?
Simple filtration uses gravity to pass liquid through filter paper in a funnel, with the precipitate settling first and mother liquor decanted. Suction filtration uses a Buchner flask connected to a vacuum pump with a sintered-glass funnel to trap the precipitate more rapidly and efficiently.
Q6: How do you recover and weigh solids collected in a crucible during suction filtration?
The solid is transferred to a glass or silica crucible containing a porous glass disc, then fitted into a Buchner flask for suction filtration. After filtration, the crucible is dried and weighed directly. The weight difference of the crucible before and after filtration gives the mass of the collected solid.
Q7: What is the purpose of using a rubber policeman during filtration?
A rubber policeman is used to dislodge any solid that adheres to the glass rod or beaker during the filtration process. This ensures complete transfer of the precipitate to the filter paper, preventing loss of sample and improving the accuracy of separation and subsequent gravimetric analysis. Filtration often precedes precipitation and co-precipitation procedures.