Polyvinyl-alcohol oxidase

Transcription

Viscosity Measurement All fluids (liquids and gases) exhibit a characteristic property of flowing under an applied force, which could be even the force of their own weight; the ease which they flow differs from liquid to liquid. The property of resistance to flow when a stress is applied to a liquid is called its viscosity. Or internal friction present between two layers of a liquid which resists the flow of liquid is commonly known as Viscosity. Here, our aim is to find the absolute viscosity and the unknown composition of a given mixture. Apparatus: Wash bottle, stop watch, viscometer (Ostwald’s), unknown liquid, pyknometer or R.D bottle, and pipette, weighing balance. Ostwald’s viscometer is a traditional viscometer to measure the viscosity of a liquid. It is a U-shaped glass tube. In one arm, the bulb A is connected with a fine capillary. The lower end of capillary is connected with a U-tube provided with a bulb B in the second arm. The bulb is necessary to maintain the hydrostatic pressure during flow of liquid. Through the capillary tube, the liquid flows with measurable speed. There are two marks C and D above and below the bulb A. The liquid flows under its own weight. The density of the liquid is determined either by pyknometer or by R.D bottle. Procedure Clean the viscometer with chromic acid and then wash thoroughly with distilled water. It is then washed with alcohol or acetone and dried. A sufficient volume of distilled water is introduced by pipette in bulb B so that the bend portion of tube and half or a little more than half of bulb B are filled up. Clamp the viscometer in quite vertical position. Using the pippet pump, suck up water until it rises above the upper mark C and allows it to flow under its own weight. The time of flow of water from C to D is counted by starting the stop watch as the meniscus just reaches upper mark C and stopping the watch as the meniscus just passes the lower mark D. Take at least 3 or 4 readings with water and then take the mean of them. Now remove the water from viscometer and dry it. Introduce in bulb B the same volume of liquid and measure the time of flow of liquid as before. Take at least 3 or 4 readings and then take the mean value. Now, wash and dry the pyknometer (or R.D. bottle) and then weight it empty. Then fill it with distilled water and weigh. Remove water and dry. Then fill it with experimental liquid and weigh. Note the room temperature. Similarly the unknown composition of given mixture can also be found. The absolute viscosity of a given liquid can be found out by plotting a graph, time of flow in sec Vs composition of the given mixture.