Experiment 6 Objective: Report the effect of temperature on viscosity of the given sample on Engler viscometer Apparatus : Engler Viscometer, Thermometer, Flask, Stop Watch, etc.

TheoryIntroduction

This equipment is used to study the variation of viscosity with respect to temperature. Because viscosity is used for various design calculations in chemical engineering. Englersviscometer which isefflux tube wasdeveloped inGermany. The method is basically empirical but it is possible to relate efflux time to absolute viscosity using charts/tables developed by Asphalt institute for this purpose.ViscosityThe viscosity is an important fluid property when analyzing liquid behavior and fluid motion near solid boundaries. Viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress. The shear resistance in a fluid is caused by intermolecular friction exerted when layers of fluid attempt to slide by one another.There are two related measures of fluid viscosity dynamic(or absolute) kinematicKinematic viscosity isthe ratio of- absolute (or dynamic) viscosity to density- a quantity in which no force is involved. Kinematic viscosity can be obtained by dividing the absolute viscosity of a fluid with the fluid mass density. = / (2)Where; = kinematic viscosity (m2/s) = absolute or dynamic viscosity (N s/m2) = density (kg/m3)In the SI-system the theoretical unit of kinematic viscosity ism2/s- orStoke (St)where 1 St (Stokes) = 10-4m2/s = 1 cm2/sSince theStokeis a large unit it is often divided by100into the smaller unitCentistoke (cSt)- where 1 St = 100 cSt 1 cSt (centistoke) = 10-6m2/s = 1 mm2/sDegree EnglerDegree Engleris used in Great Britain as a scale to measure kinematic viscosity. Unlike theSayboltandRedwoodscales, theEnglerscale is based on comparing the flow of the substance being tested to the flow of another substance - water. Viscosity inEnglerdegrees is the ratio of the time of a flow of 200 cubic centimetersof the fluid whose viscosity is being measured- to the time of flow of200 cubic centimetersof water at the same temperature (usually20oCbut sometimes50oC or 100oC) in a standardizedEnglerviscosity meter. AninstrumentusedinthemeasurementofthedegreeEngler,ameasureofviscosity;thekinematicviscosityinstokesforthisinstrumentisobtainedfromtheequation=0.00147t 3.74/t,wheretistheeffluxtimeinseconds.Figure 1 Engler Viscometer

Applications of ViscosityThe following are examples of how viscosity measurements are used: FoodViscosity measurements are used in the food industry to maximize production efficiency and cost effectiveness. It affects the rate at which a product travels through a pipe, how long it takes to set or dry, and the time it takes to dispense the fluid into packaging. The production process has to be designed with the viscosity of the product in mind, making sure that pipes are angled to optimize flow, or that dispensers provide the right amount of force to induce flow, but not so much that the packaging will overfill.Viscosity is also a characteristic of the texture of food.The products viscosity must be measured and monitored during production to ensure that each batch is consistent and will go through the production process efficiently. AdhesivesTo choose the right viscosity for an adhesive, consider how the adhesive must flow, or not flow, on a part after the adhesive is applied. Low-viscosity adhesives will flow more readily than high-viscosity ones, so if you want an adhesive to stay exactly where you put it after dispensing rather than spread out a high-viscosity adhesive is ideal. Other Industries Petroleum:Viscosity measurements project the effectiveness of lubricating oil and determines design elements of pipelines. Concrete:Viscosity determines the self-leveling and pumping behavior of a mix. Cosmetics:Viscosity should be considered when designing the feel and flow of cosmetic products.Procedure:Thoroughly clean and dry the viscometer. Insert the stopper and fill the water bath with water. Heat the outer bath some degree above the test temperature. Pour the sample into the cup till it exactly reaches the top of the measuring point. Level the instrument and place 100 mL flask below to jet. Place the lid and inner thermometer in position and maintain the required temperature of the bath with frequent agitation. Maintain this continuously for three minutes by rotating cover. When these conditions have been maintained, withdraw the sample from effuse tube. Start the timer and note the time for filling 100 mL flask. Repeat the procedure and take at least six readings. Draw a graph between time and temperature.

Results: Temperature ( 0 C )Time(Engler Seconds)

20.642

24.640

29.139

34.134

40.130

Comments:The graph is a somewhat smooth line which depicts a non-linear decreasing trend. The results seem reliable within experimental error.

Experiment 7 Objective: To determine the flash point of a given sample of petroleum product by Pensky Martens apparatus ". Apparatus: Pensky Martens apparatus, beaker, thermometer.

Figure 2 Pensky Marten's closed cup apparatus

Related theoryIntroductionThis apparatus is used to measure the flash point of an oil sample in close environment. In thePenskyMartens closed-cup flash-point test, abrasstest cup is filled with a test specimen and fitted with a cover. The sample is heated and stirred at specified rates depending on the material that is being tested. Anignitionsource is directed into the cup at regular intervals with simultaneous interruption of stirring until a flash that spreads throughout the inside of the cup is seen. The correspondingtemperature is itsflash point.PenskyMartens closed cup is sealed with a lid through which the ignition source can be introduced periodically. The vapour above the liquid is assumed to be in reasonable equilibrium with the liquid. Closed cup testers give lower values for the flashpoint than open-cup testers(typically 510 K) and are a better approximation to the temperature at which the vapour pressure reaches the "lower flammable limit" (LFL).Flash PointTheflash pointof avolatilematerial is the lowesttemperatureat which it canvaporizeto form an ignitable mixture in air. Measuring a flash point requires an ignition source. At the flash point, the vapor may cease to burn when the ignition source is removed.Significance and Uses of flash Point The flash point is one measure of the tendency of the test specimen to form a flammable mixture with air under controlled laboratory conditions. It is only one of a number of properties that should be considered in assessing the overall flammability hazard of a material. Flash point can indicate the possible presence of highly volatile and flammable materials in a relatively nonvolatile or nonflammable material. For example, an abnormally low flash point on a test specimen of engine oil can indicate gasoline contamination. Flash point is used in shipping and safety regulations to define flammable and combustible materials. Using flash point substances are classified into different groups and are kept in mind during manufacture, storage and transport.

ProcedureClean the oil cup and dry, taking care that no traces of any low flash solvent used in cleaning remains in the cup. Pour the lid in position and insert level indicated by the filling mark, then place the lid in position and insert the thermometer in the holder. Set the cup in air bath, apply heat at the rate of 9-11 F per minute and adjust the stirrer to rotate at the rate of one to two revolutions per second. Starting at the temperature of at least 60 F apply the test flame at temperature intervals of 2 F if flash point is above 220 F, in such a manner that flame must be lowered in one half second. Leave it in this position for one second and then quickly raise it up (While the test flame is being applied stirring is stopped). Continue the procedure till flash point is obtained. Then cool the apparatus and refill with fresh oil and check the flash point by decreasing the range of temperature and get an accurate reading.ResultThe flash point obtained is 56O C.CommentsThe flash point is low hence the substance may be volatile. By consulting literature, the flash point may correspond to that of diesel oil. Experiment 3 Objective: To determine flash point and fire point of an oil using "Cleveland open cup flash point apparatus" and determine the sample of oil. Apparatus: Tripod stand with burner, Thermometer, Sand bath, cup containing oil, glass lid, test flash.

Related theoryIntroductionThis apparatus is used to measure the flash point and fire point of an oil sample in an open environment. This apparatus consists of the test cup, heating plate, test flame applicator, heater, and supports Figure 3 Cleveland open cup apparatus

The flash point of a flammable liquid is the lowest temperature at which it can form an ignitable mixture in air. The fire point is defined as the temperature at which the vapor continues to burn after being ignited. These are important temperatures in fuel storing. The main difference between this open cup apparatus and closed cup apparatus is that in this apparatus, the vapors are allowed to escape while in closed cup it is undesirable for the vapors to escape because every time that happens the flash point rises.Flash PointTheflash pointof avolatilematerial is the lowesttemperatureat which it canvaporizeto form an ignitable mixture in air. Measuring a flash point requires an ignition source. At the flash point, the vapor may cease to burn when the ignition source is removed.Fire point

Fire point is the lowest temperature corrected to a barometric pressure of 101.3 kPa (760mm Hg), at which application of an ignition source causes the vapors of a test specimen of the sample to ignite and sustain burning for a minimum of 5 s under specified conditions.

ScopeThese test methods cover the determination of the flash point and fire point of petroleum products by a manual Cleveland open cup apparatus.

This test method is applicable to all petroleum products with flash points above 79 deg. C and below 400 deg. C except fuel oils.

Significance and Uses of Flash Point and Fire Point The flash point is one measure of the tendency of the test specimen to form a flammable mixture with air under controlled laboratory conditions. It is only one of a number of properties that should be considered in assessing the overall flammability hazard of a material. Flash point can indicate the possible presence of highly volatile and flammable materials in a relatively nonvolatile or nonflammable material. For example, an abnormally low flash point on a test specimen of engine oil can indicate gasoline contamination. Flash point is used in shipping and safety regulations to define flammable and combustible materials. Using flash point substances are classified into different groups and are kept in mind during manufacture, storage and transport. The fire point is a general indication of fire hazard. Fire point shows the tendency of a specimen to support combustion.

ProcedureApparatus was setup and burner and test fire was set and checked. Oil in an open cup was placed on a sand bath. Initial temperature of oil was noted. Thermometer was dipped in oil and burner was lighted to heat oil uniformly via sand bath. Test fire of small diameter (1 inch) was established. Test fire was brought over oil to check flash point after every 3O C rise in temperature. After flash point was determined, test fire was brought over oil vapours more frequently after every 2 degree rise in temperature to check the fire point. When oil caught fire, the lid was put on the cup to block the supply of oxygen and extinguish the fire. The temperature for fire point was noted.ResultThe flash point obtained is 76o C and the fire point obtained is 86o C.CommentsThe flash and fire point corresponds to that of diesel oil.

Experiment 4Objective: to find out the softening point of pitch bituminousApparatus: Bituminous, Beaker, Kerosene oil, iron ball, thermometer, two square shouldered brass rings, pouring plate, a flat smooth brass plate, balls-two steel balls, ring holder and assembly.Theory:In this method the determination of softening point of bitumen in the range from 30 to 157 deg. C. Two horizontal disks of bitumen cast in shouldered brass rings are heated at a controlled rate in a liquid bath while each supports a steel ball. The softening point is reported as the mean of the temperatures at which the two disks soften enough to allow each ball enveloped in bitumen to fall a distance of 25mm.Reagents and materials:1. Bath liquid which can be used2. Freshly boiled distilled water to avoid trapping air bubbles on the surface of the specimen which may affect the results.3. USP glycerin4. Ethylene Glycol5. Release agents; to prevent adhesion of bitumen to the pouring plate when casting disks the surface of brass pouring plate may be thinly coated just before use with silicone oil or grease, a mixture of glycerin and dextrin, talc or china clay.Procedure:Select any one of the following bath liquids and thermometer appropriate for expected softening point.1. Distilled water; used for softening points between 30 deg. C and 80 deg. C.2. Glycerin; used for 80 deg. C up to 157 deg. C.3. Ethylene glycol; all softening 30- 110 deg. C. Assemble the apparatus in the laboratory hood with the specimen rings ball centering guides and thermometer in position. Place the bath in ice water if necessary or gently heat to establish and maintain the starting bath temperature for 15 min with the apparatus in place. Heat the bath so that temperature rises at a uniform rate of 5 deg. C. Record for each ring and ball the temperature indicated by the thermometer at a uniform rate of 5 deg.C Record for each ring and ball the temperature indicated by the thermometer at the first instant the bitumen surrounding the ball touches the bottom plateCalculations:From the experiment the softening point of bituminous comes out to be 64 C. The softening point determined in a water bath will be lower than the determined in a glycerin bath.Significance and Uses: Bituminous are viscous elastic materials without sharply defined melting points they gradually become softer and less viscous as the temperature rises. The softening point is useful in the classification of bitumen, as one element in establishing the uniformity of sources of supply and is indicative of the tendency of the materials to flow at elevated temperatures encountered in service.

Experiment 5Objective: to report the effect of the temperature on the viscosity of given sample by redwood viscometerApparatus: 1. Redwood viscometer 2. Thermometer3. 5 ml flask4. Stop watch5. Tissue paperProcedureClean and dry the oil cup thoroughly, soft tissue paper should be used for rubbing the interior of the cut. Set the apparatus and level it. Heat the bath few degrees above the test temperatures and pour sample into the oil cup. Adjust the temperature to the required point, while the temperature is being adjusted stir the bath by rotating the stirrer continuously and the oil gently by the thermometer.After the oil temperature has become steady at the required valve, adjust the level of the oil at the gauge point then cover the il cup with the lid and start the test.Place a clean dry 50 ml flask below jet at the distance of few millimeter. Lift the vlave and start stop watch as the oil reaches graduation mark at the neck of the flask stop the watch and record the temp. Repeat the procedure and take few readings.Observations and calculationsFor 50 ml volumeTemperature (deg. C)Time (s)

2177

2652

3143

3631

4128

4620

5118

5616

Precautions The oil should be fitted thoroughly to remove the solid particles that may clog the jet.The receiving flask should be placed in such a manner that the oil stream from jet strikes the neck of receiving flask and will not cause any foaming. After each reading the oil should be completely drained.Significance & usesViscosity is the property of the lubricating oil that determines its ability to lubricate and through its film strength it is used denoting the effect of temperature changes and for determining the presence of contaminants in used oil during service.