Fume cupboards positioning

Next day, hang the paper from the edge of the fume-cupboard window in the full draught of the fan to dry, and immediately mark the position of the solvent front. 

The top of the bench should always be kept clean and dry this can easily be done if a wet and a dry rag are kept at hand. Apparatus not immediately required (a) should be kept as far as possible in a cupboard beneath the bench if it must be placed on the bench, it should be arranged in a neat and orderly manner. All apparatus should be washed immediately after use and placed in a position to drain at the first opportunity, the apparatus should be dried. It must be emphasised that as a general rule a deposit of dirt or tar is more easily removed when it is freshly formed a suitable cleaning agent can usually be found while one still remembers the nature of the material or the circumstances attending its formation. It is hardly necessary to add that sohd waste and filter papers must not be thrown into the sink, and that all operations requiring the handhng of unpleasant and noxious materials sliould be carried out in the fume cupboard ( hood ). 

Fume cupboards are widely used in chemistry laboratories, both in schools and in industry, to control moderately dangerous contaminants generated by small-scale processes. The releases usually have low momentum and ideally the cupboard should be used with the sash in the closed position. 

Variable Air Volume Fume Cupboards This type of cupboard incorporates a variable air volume (VAV) controller that regulates the amount of air exhausted from the cupboard such that the face velocity remains essentially constant irrespective of the sash position. A sensor detects either the sash position, the pressure differential l>etween the fume cupboard interior and the room, or the vekxity at some point in the cupboard. This information is used to control either the exhaust fan speed or the position of a control damper. The supply air volume flow rate into the laboratory or workspace should also be regulated. It should be remembered that with the sash in the closed position the amount of air to dilute contaminants in both the fume cupboard and the laboratory is reduced and that there could, for example, be difficulty in reducing contaminant levels below the lower exphasive level. 

A fume cupboard should not be positioned where the only escape route from the area would necessitate passing directly in front of the fume cupboard. Siting with respect to makeup air grills should be considered carefully (see above on drafts and cross-flows) and a minimum separation distance of 1500 mm is recommended. ... 

Preparation of Amorphous Boron from Boric Acid Anhydride. (Each student performs only one of the experiments for preparing amorphous boron.) Put 2 g of boric acid anhydride into an iron crucible or onto an iron plate and roast it if the boric acid anhydride contains moisture, then when it is heated with magnesium an explosion may occur ). Triturate the boric acid anhydride as rapidly as possible (why ) in 4 mortar, weigh 1 g and mix it with 2 g of a magnesium powder. Place the mixture into a refractory test tube and fasten it in an inclined position in a clamp of a stand in a fume cupboard . First carefully heat the test tube with the mixture with the flame of a burner, and then strongly heat the bottom part of the tube. What do you observe ... 

For this, the plate is placed in a level position ( ) in the fume cupboard until the odor of the solvent has disappeared. The plate can sometimes be carefully blown with compressed air, but care must be taken to avoid blowing the solvent across it, as this could lead to an undesired chromatographic effect. With powerful solvent systems containing water or acids, drying with warm air is usually necessary, and the last residues of sol-... 

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