Graduated Cylinders & Test Tubes

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Graduated Cylinders & Test Tubes

A graduated cylinder is a relatively narrow glass cylinder, manufactured from chemically resistant borosilicate glass, explicitly used for measuring a liquid’s volume. Generally graduated cylinders are not used for high-quality volumetric work. The tolerance and resistance of graduated cylinders are considerably higher than that of the volumetric flasks. Our graduated cylinders provide increased mechanical strength to avoid breakage and cracking. Measurements on the graduated cylinders are taken by viewing the lower meniscus at the eye-level (the lowest point of the convex dip in the cylinder).

To fill a graduated cylinder following protocol should be followed:

  1. Clean and dry the cylinder before filling.
  2. Transfer the liquid to be measured into the cylinder with the help of a pipette, burette, or any other laboratory instrument in a steady stream. Do not splash.
  3. Stop filling when the calibration line is achieved for a few minutes and let the liquid drain from the walls of the container.
  4. Draw out the excess fluid by using a pipette if the calibration line is crossed. While pipetting out the excess liquid, make sure that the surface tension in the tip of the pipette is sufficient.
  5. Cover the cylinder to prevent evaporation or contamination.

To empty a filled graduated cylinder follow the following protocol:

  1. Incline the cylinder gradually to pour out a steady stream of liquid of the spout. Do not splash.
  2. Keep inclining until the cylinder is vertical and hold it for about half a minute.
  3. To empty the cylinder touch the drop at the tip of the spout to the wall of the receiving container.
  4. Do not remove the cylinder vertically.

Glass Test Tubes

A test tube is a thin glass vessel with a rounded bottom designed to hold small quantities of chemicals and feature a flared lip to make pouring easier. Test tubes can hold liquid or solid chemicals and can be used to contain small chemical reactions. The slimness of the test tube efficiently reduces the spread of any vapors that may be produced by the reaction. Also, a test tube allows the user to heat the sample on the flame.

Uses of Glass Culture Tubes

  • The glass culture tubes are commonly used in chemistry labs to handle chemicals, especially for qualitative experiments and assays. Their round bottom and vertical sides reduce fluid and mass loss while pouring. Also, the round bottom makes it easier to wash out, and allow convenient monitoring of the contents.
  • Test tubes are useful vessels for heating small amounts of liquids or solids on a Bunsen burner. Its neck usually holds the tube with a clamp or tongs. By slightly inclining the tube, the bottom can be heated to hundreds of degrees in the flame, while the neck remains relatively cold, allowing vapors to condense on its walls.
  • A water-filled test tube and upturned tube in a water-filled beaker are used to capture gases in electrolysis.
  • A test tube with a stopper can also be used for temporary storage of chemical or biological samples.
  • In clinical medicine, air-removed, sterile test tubes are used for the collection and holding of physiological fluid samples such as blood, urine, pus, and synovial fluid.

Thermometers

A thermometer is a commonly used laboratory instrument to measure and show temperature with high accuracy. As the temperature ranges and conditions of a system can vary, a variety of materials have been incorporated into different types of thermometers.

Types of Thermometers

  • Liquid-in-glass thermometer

The volume of the material is measured by the liquid-in-glass thermometers. As the volume of liquid increases with an increase in heat.

  • Gas or vapor at constant volume

This type of thermometer measures the pressure change as the pressure of a gas increases with increase in temperature.

  • Dilatometer (or bimetal coil)

It measures the length change of the metals. As heat rises, the length of one metal expands more than the length of the other metal.

  • Platinum wire

It measures the electric resistance of the material as the electrical resistance of the wire increases with the temperature.

  • Thermocouple

It measures the thermal electromotive force as the thermal electromotive force has a direct relation with the heat.

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