When carrying out vacuum filtration which of the following isNOT necessary
A: Clamping the Buchner flask
B: Breaking the seal before turning off the vacuum
C: Folding the filter pape
D: Wetting the filter paper before you start
A: Clamping the Buchner flask
B: Breaking the seal before turning off the vacuum
C: Folding the filter pape
D: Wetting the filter paper before you start
举一反三
- When taking cold tone portrait photo in lighting room, we can make photo in cold tone by ______. A: putting white light filter paper before lamp. B: putting blue colour filter before lamp C: lowering the temperature of light D: highering the temperature of light
- Which of the following titles best describes the passage as a whole A: The Vacuum: Its Fluctuations and Decay. B: The Vacuum: Its Creation and Instability. C: The Vacuum: A state of Absence. D: Particles That materialize in the Vacuum.
- Which sentence has the most formal style? A: Don't send anything off until you're told to do so. B: Please await instructions before dispatching items. C: Please wait for instructions before sending items off. D: When they tell you to send them off, you can start to do it.
- Before engaging the turning gear and turning the diesel engine, which of the following operation should be done except______.
- The consequences of uneven water distribution include ( ) A: "mud ball" or "mud cake" will form, which can cause a short-circuiting phenomenon during filtration B: the filter media may break during filtration and backwash periods C: backwash pipes may be destroyed D: The particles of the local support layer will move and mix with the filter media, and the filter media will run off under this situation if a large amount of uneven backwash water come through