Manual of basic techniques for a health laboratory - libdoc.who.int

66 Manual of basic techniques for a health laboratory●●●●●●●●Keep the mechanical stage clean.Do not dismantle the optical components, as this may cause misalignment. Theoptical surfaces should be cleaned with lens cleaning tissue or soft tissuepaper.Never put the microscope away with immersion oil on the objective. Removeany oil daily. Mild soap solution is suitable for most cleaning.Use organic solvents only in accordance with the manufacturer’s recommendations.Never carry the microscope by the limb with one hand; use both hands, oneunder the foot, the other holding the limb.When changing a bulb, avoid touching the glass with your fingers, as fingerprintsreduce the intensity of illumination.To maximize the lifespan of bulbs, adjust the voltage with a dimmer switch togive the lowest required light intensity.If the mains voltage fluctuates excessively, use a voltage stabilizer.Additional precautions to be taken in hot climatesDry climatesIn hot, dry climates the main problem is dust. Fine particles work their way into thethreads of the screws and under the lenses. This can be avoided as follows:● Always keep the microscope under an airtight plastic cover when not in use.● At the end of the day’s work, clean the microscope thoroughly by blowing airover it with a rubber bulb.● Finish cleaning the lenses with a soft camel-hair brush, a fine paintbrush or ablower. If dust particles remain on the surface of the objective, clean it withspecial lens tissue paper.Humid climatesIn hot, humid climates and during the wet season in hot, dry climates, fungi maygrow on the microscope, particularly on the surface of the lenses, in the grooves ofthe screws and under the paint, and the instrument will soon be useless. This canbe prevented as described below.Always keep the microscope under an airtight plastic cover when not in use, togetherwith a dish filled with blue silica to dry the air under the cover. (The silicawill turn red when it has lost its capacity to absorb moisture from the air. It can besimply regenerated by heating in a hot-air oven or over a fire.) The microscopemust be cleaned daily to get rid of dust.These procedures must be carried out regularly, and are essential in conjunctionwith repair and maintenance procedures.3.2 Weighing: use of laboratory balancesBalances may be either electrically or manually operated. All types should be positionedon a firm level bench away from vibrations, draughts and direct sunlight.The balance is used to weigh chemicals for production of reagents, and cleanlinessis essential if accurate results are to be obtained:● Remove dust by blowing or using a soft brush.● Remove stains or chemicals using a soft brush.● Use a plastic weigh boat or filter-paper to weigh chemicals on the balance; neverplace chemicals directly on to the pan.