Analytical Chemistry Experiment

Simple Distillation Method

Abstract

A quick fit set-up for simple distillation was been assembled carefully. 50ml of Pineapple wine was placed in a pear shaped flask and added with boiling chips. Making sure that water was flowing in a condenser, the wine sample was heated with a burner using one inch blue flame. Four distillate with recorded temperatures were collected. These distillates were kept for boiling point experiments…

Introduction

The boiling point of a pure organic liquid is a physical property of that liquid. It is defined as the temperature at which the vapor pressure of the liquid exactly equals the pressure exerted on it. Boiling points can be determined using the technique of simple distillation. Distillation is a technique that is used to purify a mixture of liquids or to obtain a boiling point of a pure liquid (in the case of this course). Essentially, the liquid is heated to boiling and the vapors condensed above the boiling liquid.

Distillation is a very old technique which is frequently used to purify compounds and to determine their boiling points. The boiling point is a useful molecular constant for the characterization and identification of pure compounds. Furthermore, the boiling point range is usually a good indicator of the purity of a liquid.

Distillation is a physical process used to separate mixtures that contain at least one liquid. Distillation works because each substance in the mixture has its own unique boiling point. So, as a mixture is heated, the temperature of the mixture rises until it reaches the temperature of the lowest boiling substance in the mixture. The lowest boiling substance boils away. Meanwhile, the other components of the mixture remain in their original phase (either solid or liquid) until the lowest boiling component has all boiled off. Only then does the temperature of the remaining mixture rise and other components are boiled off.

I. Review of Related Literature

Distillation often follows fermentation. Fermentation is used to produce alcoholic beverages. Grain is fermented to make beer, while grape juice is fermented to make wine. Beer and wine never contain more than around 12% alcohol, because any higher concentration kills the yeast that produce the alcohol. To make stronger drink, distillation is used. Wine, beer, or fermented brews made from corn, sugar cane, or potatoes can be purified by distillation. Since ethyl alcohol boils at only 83°C while water boils at 100°C, the alcohol will boil off, leaving the water behind. The alcohol vapors are then condensed and collected. Distillation can produce liquors that range from 40-95% ethyl alcohol.

The object of distillation is the separation of the alcohol from the other ingredients in the beer, mostly water. In making fuel alcohol it is necessary to get all of the alcohol and water separated if the alcohol is going to be mixed with gasoline, and most of the alcohol and water separated if the alcohol is going to be burned in a converted engine. As will be seen, the purer the alcohol, the harder it is to make.

The separation of the alcohol and water by distillation is made possible by the fact that alcohol boils at about 173 degrees F. and water at 212 degrees F. When the mixture of water and alcohol is boiled, vapors with a greater concentration of alcohol will be formed and liquid with a lesser concentration of alcohol will remain behind. However, because water and alcohol do not form what is called an “ideal” mixture, the separation cannot be done in one clean step.

Figure Simple Distillation

It illustrates a simple distillation apparatus using laboratory-type equipment. Note that the equipment consists basically of a container for the liquid to be distilled (still pot), a heat source, and a condenser to turn the distilled vapors back into liquid form. The thermometer is necessary to monitor the temperature of the vapors.

II. Methodology

1.)    Carefully assemble the quick-fit set-up.

2.)    Place 50ml of the liquid sample in the pear shaped flask. Add a few pieces of boiling chips.

3.)    Make sure the water is flowing through the condenser. Heat the sample with a burner, using a one-inch blue flame.

4.)    Collect the distillate in labeled test tubes, recording the temperature. Change the test tube after collecting 5 to 10 drops. Keep the distillate for the boiling point determination.

5.)    When done, cut off the heat source first, before closing the water valve.

6.)    Allow time for the set-up to cool before dismantling the glassware.

III. Discussions of Data and Interference from Results

The data below are from the collected fractions of distillates from the liquid sample. Every fraction contains 1mL of the distillate. We used a test tube containing 1mL of distilled water to compare it with our fraction to know if it contains the right amount of volume we wanted.

	Volume of fraction collected	Temperature	Flame test result
Fraction 1	1mL	°C	Not Tested
Fraction 2	1mL	°C
Fraction 3	1mL	°C
Fraction 4	1mL	°C

The first fraction we collected with 1mL of the distillate was at __°C, the second at __°C  third at __°C  and the last is at __°C . We didn’t tested the first fraction if it is flammable or not to know if the distillate was an ethanol or not since our instructor not ask to do it so. But as far as the temperature values are concerned since they are closed to the accepted values boiling ethyl alcohol, I can say that the product is an ethyl alcohol.

IV. Answers to Guide Questions

1.)    Where should the thermometer bulb in the distillation setup be placed and why?

The thermometer should be placed above the liquid sample where the vapor is passing. In this case, we can determine the temperature of the vapor and not the liquid sample.

2.)    How can one know that a component of liquid mixture has been completely vaporized and distilled over?

One can know that a component of liquid mixture has been completely vaporized and distilled over if, the vapor from the liquid sample turned to pure liquid.

3.)    What is the advantage of a fractional distillation over the simple distillation type?

The advantage of fractional distillation over the the simple distillation type is that, in fractional distillation, the separation of a mixture into its component parts, or fractions, such as in separating chemical compounds by their boiling point by heating them to a temperature at which several fractions of the compound will evaporate.

While in simple distillation, all the hot vapors produced are immediately channeled into a condenser which cools and condenses the vapors. Therefore, the distillate will not be pure, its composition will be identical to the composition of the vapors at the given temperature and pressure.

V. Bibliography

• Zubrick, James W. The Organic Chemistry Lab Survival Manual: A Student’s Guide to Techniques 6th Edition. New York: John Wiley & Sons Canada, Ltd.; 5th edition.

• S.W. Mathewson, “The Manual for the Home and Farm Production of Alcohol Fuel” http://journeytoforever.org/biofuel_library/ethanol_manual/manual11.html

• “Distillation”, http://en.wikipedia.org/wiki/distillation.html
• “Elements, Compounds and Mixtures”, http://www.gcsescience.com/distillation.html

Technorati Tags: Analytical Chemistry, Distillation, Experiment, Simple Distillation

Analytical Chemistry Experiment

Determination of the Boiling Point

Abstract

After the preparation of capillary tubes and through the adaptation of simplified Siwoloboff method, few drops of pineapple wine sample were placed in a centrifuge tube.  The capillary tube which is sealed end up was immersed in the sample.  The centrifuge tube is then attached to the bulb of the thermometer.  The tube - thermometer was placed in a oil bath added with few pieces of boiling chips, heated, and occasionally stirred in order to ensure uniform distribution of heat.  A close observation took place and at which the first bubble leaves the capillary tube, the temperature was recorded. Do two trials…

I. Introduction

Several factors enter into determining the boiling point, and the molar heat of vaporization, of a hydrocarbon. Hydrocarbons containing  more than 6 carbon atoms in a linear chain depend upon chain entanglement in addition to the factors that also play a role in hydrocarbons containing less than 6 carbon atoms in a linear chain. For the smaller hydrocarbons, the forces holding the liquid together are similar, primarily van der Waals interactions. However, in addition, the degree of non-ideality of the vapor phase, and the globular shape of the molecule. The more symmetric molecules tend to be more volatile.

The boiling point of a liquid is the temperature at which the liquid and vapor phases are in equilibrium with each other at a specified pressure. Therefore, the boiling point is the temperature at which the vapor pressure of the liquid is equal to the applied pressure on the liquid. The boiling point at a pressure of 1 atmosphere is called the normal boiling point.

II. Review of Related Literature

Siwoloboff Method

Principle

A sample is heated gradually in a tube which is immersed in a liquid bath. The sample tube is held in close contact with a thermometer and it contains a boiling capillary which is fused about 1 cm above its lower end. Upon approach of the boiling temperature bubbles emerge rapidly from the lower open end of the capillary. The boiling temperature is that temperature at which, on momentary cooling, the string of bubbles stops and liquid suddenly rises in the capillary.

Procedure

The bath liquid is chosen according to the expected boiling temperature of the test substance. Silicone oil can be used for temperatures up to 573 K. Liquid paraffin may only be used for

Temperatures up to 473 K. At first, the heating of the bath should be adjusted to a temperature rise of 3 K/min. The bath must be stirred. At about 10 K below the expected boiling temperature, the heating is reduced so that the temperature rise is less than 1 K/min. Upon approach of the boiling temperature, bubbles begin to emerge rapidly from the capillary. The boiling temperature is that temperature at which, at momentary cooling, the string of bubbles stops and fluid suddenly rises in the capillary

OECD Guidelines for the Testing of Chemicals 1995

III. Methodology

1.)    Prepare 2-3 capillary tubes, sealing one end with the use of a Bunsen burner.

2.)    Adapting the simplified Siwoloboff method, place a few drops of the sample in a centrifuge tube. A capillary tube, its sealed end up, is immersed in the sample. The centrifuge tube is then attached to the bulb of the thermometer.

3.)    The tube-thermometer is then placed in an oil bath. Add a few pieces of boiling chips to the bath.

4.)    Heat the oil bath with a small blue flame, occasionally stirring it, to ensure uniform distribution of heat.

5.)    Closely observe and record the temperature at which the first bubble leaves the inverted capillary tube. Then record the temperature when the liquid sample enters the tube, just as the last bubble leaves it. This is the so-called boiling point range.

6.)    Do a second trial repeating steps 2 to 5.

IV. Discussions of Data and Interference from Results

	T1/°C	T2/°C
Sample 1	72°C	80°C
Barometric Pressure	765 mmHg

The sample we used has the range 72°C  to 80°C in 765 mmHg, while the boiling point of ethanol in 760 mmHg is 78.5°C. We could not really tell whether the sample we used was pure for we are not in the atmospheric pressure.

V. Answers to Guide Questions

1. How closely did your corrected boiling point agree with the literature boiling point for the known compound? What are some possible errors in this experiment?

Boiling point of ethyl alcohol is about 78.5 °C and our boiling point ranges between 72 °C to 80 °C.

There are many possible sources of error in this experiment. It can be human error and instrumental error.

One of the causes of errors in determining the boiling point I found which can change our observed value is the barometric pressure. The literature boiling point of ethanol is about 78.5 °C in 760 mmHg while our boiling point was in 765 mmHg.

1. Which parameter gave the best correlation with experimental boiling point in the modeling experiment?

• Based on the experiment, I observed that the closer the atmospheric pressure to the normal pressure, which is 760 mmHg, the closer the value of the temperature to the normal temperature of ethanol. This is the factor that may affect the result of the experiment in the determination of Boiling Point.

1. Based on your modeling results, is boiling point dependent on thermodynamic stability?

• No, boiling point is not dependent on thermodynamic stability. The boiling point of a compound can only be determined by physical means.

1. For your particular set of compounds, what conclusions can you draw about how structural features affect boiling point?

• On how structural features affect boiling point, I therefore conclude that, the longer the chain of hydrocarbons is, the higher the boiling point of the compound.

VI. Bibliography

• Zubrick, James W. The Organic Chemistry Lab Survival Manual: A Student’s Guide to Techniques 6th Edition. New York: John Wiley & Sons Canada, Ltd.; 5th edition.

• http://en.wikipedia.org/wiki/Boiling_point

• “OECD Guidelined for the Testing of Chemicals 1995″ http://www.oecd.org/dataoecd.html

Technorati Tags: Boiling Point, Experiment, Siwoloboff Method

EXPERIMENT

VISCOSITY

Abstract

To measure the relative and absolute viscosities of distilled water, methanol, ethanol and propanol , Ostwald - Cannon- Fenske viscometer was standardized and used.  The group recorded the time required for the upper meniscus of the liquid samples to subsequently pass the two calibration marks of the viscometer at a specified temperatures (40, 50 and 60˚C ) and observed that as the temperature of the sample increases, the time necessary from one point to another decreases.  A pycnometer was then used to measure the density of the samples at 40, 50, 60 ˚C through ascertaining the volume of the apparatus and mass of the liquid.  Through the data we had gathered, relative viscosity can be computed using the formula (μ₁ /μ₂ ) = (ρ₁/ ρ₂) * (t₁/t₂) and found out that as the temperature of a liquid increases, its relative viscosity decreases…

I. Introduction

When two solid bodies in contact move relative to each other, a friction force develops at the contact surface in the direction opposite to motion.  To move a table on the floor, for example, we have to apply a force to the table in the horizontal direction large enough to overcome the friction force.  The magnitude of the fore needed to move the table depends on the friction of coefficient between the table and the floor.

The situation is similar when a fluid moves relative to a solid or when two fluids move relative to each other.  It appears that there is a property that represents the internal resistance of a fluid to motion or the “fluidity”, and that property is viscosity.

Viscosity is a measure of the resistance of a fluid to being deformed by either shear stress or extensional stress. It is commonly perceived as “thickness”, or resistance to flow. Viscosity describes a fluid’s internal resistance to flow and may be thought of as a measure of fluid friction.  There are actually two quantities that are called viscosity. The quantity defined above is sometimes called dynamic viscosity, absolute viscosity, or simple viscosity to distinguish it from the other quantity, but is usually just called viscosity. The other quantity called kinematic viscosity (represented by the symbol ν “nu”) is the ratio of the viscosity of a fluid to its density (Mott, R. L. 2006).

II. Review of Related Literature

Viscometer

An instrument used for measuring the viscosity and flow properties of fluids. A commonly used type (Brookfield) measures the force required to rotate a disc or hollow cup immersed in the specimen fluid at a predetermined speed.

Of the many types, some employ rising bubbles, falling or rolling balls, and cups with orifices through which the fluid flows by gravity. Instruments for measuring flow properties of highly viscous fluids and molten polymers are more often called plastometers or rheometers (J.M, C. a. 2006).

Units of Dynamic viscosity

Poise (symbol: P)

Named after the French physician Jean Louis Marie Poiseuille (1799 - 1869), this is the cgs unit of viscosity, equivalent to dyne-second per square centimetre. It is the viscosity of a fluid in which a tangential force of 1 dyne per square centimetre maintains a difference in velocity of 1 centimetre per second between two parallel planes 1 centimetre apart.

Even in relation to high-viscosity fluids, this unit is most usually encountered as the centipoise (cP), which is 0.01 poise. Many everyday fluids have viscosities between 0.5 and 1000 cP.

Some typical viscosities (cP at 20°C)
air	0.02	motor oil SAE 20	125
acetone	0.3	motor oil SAE 50	540
methanol	0.6	castor oil	986
water	1.0	glycerin	1490
ethanol	1.2	pancake syrup	2500
mercury	1.5	maple syrup	3200
linseed oil (raw)	28	treacle	20,000
corn oil	72	peanut butter	250,000
olive oil	84	window putty	100,000,000

Pascal-second (symbol: Pa·s)

This is the SI unit of viscosity, equivalent to newton-second per square metre (N·s m^-2). It is sometimes referred to as the poiseuille (symbol Pl).

One poise is exactly 0.1 Pa·s. One poiseuille is 10 poise or 1000 cP, while 1 cP = 1 mPa·s (one millipascal-second).

Table of equivalents
Dynamic viscosity	symbol	centipoise equivalent
1 kilogram-force second per square metre	kgf·s m-2	9 806.6501248
1 poundal second per square foot	pdl·s ft-2	1 488.164435
1 pound per foot hour	lb (ft·h)-1	0.4133789
1 pound per foot second	lb (ft·s)-1	1 488.1639328
1 pound-force second per square foot	lbf·s ft-2	47 880.2595148
1 pound-force second per square inch (reyn)	lbf·s in-2	6 894 757
1 slug per foot second	slug (ft·s)-1	47 880.25898

(White, F. M. 2008)

III. Methodology

APPARATUS/ MATERIALS

Ostwald - Cannon - Fenske viscometer

distilled water, methanol, ethanol, and propanol

Thermometer

Pycnometer

suction bulb

600 mL beaker

Brookfield viscometer

stopwatch

analytical balance

hot plate with stirrer

stirring rod

Iron stand

iron clamp

starch

PROCEDURE

A. Standardization of the Viscometer

1.        Before the viscometer is used, it must be carefully and thoroughly cleansed.  To ensure this, the tube should be filled some hours previous to the experiment with a detergent solution and then rinsed with distilled water several times by means of suction bulb, and then dried.  After cleaning, the viscometer is clamped vertically into a thermostat bath with all the bulbs immersed.  Enough water is then introduced into the viscometer to fill the large bulb.  The temperature of the water bath must be kept constant.  Constant stirring ensures the temperature uniformly set at room conditions.  Record this temperature.

2.       When the conditions are satisfactory, the liquids in the tube are then drawn through the capillary by gentle suction, to a point somewhat above the upper boundary mark above the upper bulb.  Allow it to run back to its own accord, recording the time required for the upper meniscus to successively pass the two calibration marks.

B. Determination of Relative Viscosities

1.       Prepare a sample of water and the three other liquids samples.  Determine the outflow time for each of these liquids, as directed under Part A and record the time of efflux.  Repeat at temperatures 40, 50 and 60 ˚C.  For every liquid, make three readings at each temperature.

2.       Determine the density of each liquid at 40, 50 and 60 ˚C using a pycnometer.  To do this, weigh the empty pycnometer and then, fill it to the brim with sample and gently cover with the lid.  The volume of the liquid is the volume marked on the pycnometer.  Make sure that there are no bubbles present inside.  Wipe the pycnometer dry on the outside.  Weigh the pycnometer containing the sample.

C. Determination of the Absolute Viscosities (optional)

1.       Prepare and heat to 95˚C about 400 mL of 5% starch - water (SW) mixture and continuously stir the mixture until homogenous.

2.       Transfer the starch - water sample to a smaller beaker and use the Brookfield viscometer for viscosity measurement (use the smallest spindle first). Make sure that spindle is submerged in the solution.  Record the temperature and at which the viscosity reading was taken.  Do this every 5 minutes for 30 minutes.  Repeat the procedure using another 2 spindles.  (WARNING:  Be careful, in removing and placing spindles. Ask the help of your lab instructor)

3.       Repeat steps 1 and 2 for 10 % and 15 %

IV. Data and Discussion

A. Standardization of the Viscometer

Table I: Average time of a liquid sample to pass the two calibration marks at a given temperature (40˚C, 50˚C & 60˚C)

Liquid Sample	AVERAGE TIME REQUIRED TO PASS  FROM THE CALIBRATION MARKS  AT A GIVEN TEMPERATURE
	@ 40˚C (s)	@ 50˚C (s)	@ 60˚C (s)
Distilled Water (H2O)	3.05	2.90	2.61
Methanol (CH3OH )	2.92	2.86	2.74
Ethanol (CH3CH2OH )	4.16	3.84	3.55
Propanol (CH3CH2CH2OH )	5.60	5.09	4.87

The data in the graph shows the relationship of temperature and time. Notice that as the temperature of liquid sample increases, the time necessary to flow decreases. The liquid sample that has fastest time to flow was methanol (purple line) (2.92 to 2.74), while propanol ( blue green line) said to be the slowest (from 5.60 secs to 4.87 secs)

Graph 1: Time vs Temperature of the Liquid samples

B. Determination of Relative Viscosities of Liquid Samples

Volume of Pycnometer = 24. 755 cm³
mass of pycnometer w/o liquid sample = 42.7 g
mass of pycnometer w/o liquid sample & thermometer = 31.4 g

Table II-A: Determination of Relative Viscosities of Distilled Water (H₂O) at a given temperature (40˚C, 50˚C & 60˚C)

Temperature	Mass of pycnometer w/ liq (g)	Density ( g / cm3 )	Relative Viscosities ( μ ) (cP)
Initial Temperature	55.9	-
@ 40˚C	55.6	0.9776	0.6529
@ 50˚C	55.7	0.9816	0.5468
@ 60˚C	55.7	0.9816	0.4665

• The data in the graph shows the relationship of viscosity and temperature of a distilled water at 40, 50 and 60˚C
• The graph tells us that as the temperature of the distilled water increases, its viscosity decreases (from 0.6529 @ 40˚C to 0.4665 @ 60 ˚C)

Table II-B: Determination of Relative Viscosities of Methanol (CH₃OH) at a given temperature (40˚C, 50˚C & 60˚C)

Temperature	Mass of pycnometer w/ liq (g)	Density ( g / cm3 )	Relative Viscosities ( μ ) (cP)
Initial Temperature	62.1	-
@ 40˚C	61.9	0.7756	0.4959
@ 50˚C	61.5	0.7594	0.4172
@ 60˚C	61.0	0.7392	0.3688

The data in the graph shows the relationship of viscosity and temperature of methanol at 40, 50 and 60˚C The graph tells us that as the temperature of the methanol increases, its viscosity decreases (from 0.4959 cP @ 40 ˚C to 0.3688 cP@ 60˚C) Methanol gathered the smallest value of viscosity compared to the other liquids.

Table II-C: Determination of Relative Viscosities of Ethanol (CH₃CH₂OH) at a given temperature (40˚C, 50˚C & 60˚C)

Temperature	Mass of pycnometer w/ liq (g)	Density ( g / cm3 )	Relative Viscosities( μ ) (cP)
Initial Temperature	62.8	-
@ 40˚C	62.4	0.7958	0.7249
@ 50˚C	62.0	0.7796	0.5750
@ 60˚C	61.8	0.7716	0.4988

The data in the graph shows the relationship of viscosity and temperature of ethane alcohol at 40, 50 and 60˚C The graph tells us that as the temperature of the methanol increases, its viscosity decreases (from 0.7249cP @ 40 ˚C to 0.4988 cP @ 60˚C) .

Table II-D: Determination of Relative Viscosities of Propanol (CH₃CH₂CH₂OH) at a given temperature (40˚C, 50˚C & 60˚C)

Temperature	Mass of pycnometer w/ liq (g)	Density ( g / cm3 )	Relative Viscosities ( μ ) (cP)
Initial Temperature	61.9	-
@ 40˚C	61.6	0.7635	0.9362
@ 50˚C	61.3	0.7514	0.7347
@ 60˚C	61.0	0.7392	0.6554

The data in the graph shows the relationship of viscosity and temperature of propanol at 40, 50 and 60˚C The graph tells us that as the temperature of the distilled water increases, its viscosity decreases from 0.9362cP @ 40 ˚C to 0.0.6554 cP @ 60˚C) Propanol gathered the highest value of viscosity compared to the other liquids

ANSWER TO THE FOLLOWING QUESTIONS

1.    What is the effect of trapped bubbles in the viscometer during the run on a) the measured time?  b) the relative viscosity? Explain your answer.

• Trapped bubbles in the viscometer cause great difficulty and large error in the experiment. Based on what we had encountered in the experiment, the effect of trapped bubbles is that its measured time is faster compare to time of a viscometer without bubbles. On the other hand, its effect on the relative viscosity is that it can make result smaller since time is directly proportional to viscosity, which means, the smaller the value of time is, the smaller the value of viscosity will be.

2.    How would you explain the difference in the viscosities of methanol, ethanol, and propanol relative to that of water?  What factors bring about such differences?

• Based on the experiment we performed, it shows that the viscosity of water is greater than the viscosities of the other three liquid samples. Density is the main factor that brings about such differences. Through the data we gathered, it is apparent that the density of water is greater than these three liquid by about 0 .2000 g/cm3. Since density is directly proportional to the viscosity, therefore, the smaller the density of a liquid is, its viscosity will also be small.

3.    Why is it necessary to measure the viscosity of a liquid (or a gas)?  Give practical examples where such physical property is needed.

• Measuring the viscosity of a liquid made a vital role to our daily lives. Suppose our blood, if its too thick then it can clot and cause a heart attack or stroke, or if it’s too thin can bleed from a small cut for hours. Doctors have to know the viscosity of our blood when performing operations. On the other hand as future Chemical Engineers, pretending that we are designing the distribution system of water from a water plant for a town. Given the average demand of water for the town for any given time, and we know the viscosity of water, what will be the flow? What pressure will the pipes be under? What size of pipes will be needed? Can the pipe withstand the pressure? Will the water flow smoothly? All these are influenced by the viscosity of water. It gets even more complicated in designing chemical plants, where a lot of different fluids other than water, with different viscosities, have to be considered.

4.    Why do you think does the Brookfield viscometer have different spindles of different sizes?  How does the size of the spindle relate to the viscosity measurement?  With the aide of illustrations, explain your answer.

• Brookfield Viscometer is used in determining the absolute viscosities (see part C of Methodology). Since the experiment is said to be optional, then we must perform the experiment first before answering the question.

V. Conclusion and Recommendation

After performing this experiment, I therefore conclude that viscosity varies with temperature. In general, the viscosity of a simple liquid decreases with increasing temperature (and vice versa). As temperature increases, the average speed of the molecules in a liquid increases and the amount of time they spend “in contact” with their nearest neighbors decreases (see graph 1). Thus, as temperature increases, the average intermolecular forces decrease. The exact manner in which the two quantities vary is nonlinear and changes suddenly when the liquid changes phase.  Viscosity is normally independent of pressure, this do not varies the value of viscosity. Since liquids are normally incompressible, an increase in pressure doesn’t really bring the molecules significantly closer together.

Since the group experiences unexpected hindrances while performing, I recommend that:

1.       Ostwald viscometer should be cleansed thoroughly before and after conducting the experiment.  Contamination may occur if the apparatus was not cleansed and this may greatly affect the values of the viscosity of the liquid sample.

To ensure that viscometer is clean, the tube should be filled some hours before the experiment with a detergent solution and rinsed with distilled water several times by means of suction bulb. Be sure that it is totally dried.

2.       The viscometer should vertically clamped to the iron stand. Tilted viscometer may affect the time spent of the liquid as well as the reading at which it passes the calibration marks.

3.       Water bath eats lots of time. Prior to set -up, group should start to warm the water. If the water is exceeds the required temperature, it can be cooled by adding enough tap water.  Constant temperature is a must in the experiment. Incorrect temperature reading will make large error in the results.

4.       The member who reads the liquid passes the calibration marks should be the one who should record the time, because he / she is the one who controls the release of air in the tube. It is easier that he / she record the time to avoid errors.

References:

J.M, C. a. (2006). Fluid Mechanics Fundamentals and Application. United Kingdom: Mc Graw - Hill. Viscosity. pg 46

Mott, R. L. (2006). Applied Fluid Mechanics 6th ed. Singapore: Pearson Prentice Hall. Viscosity of Fluids. pg 23-24

Serway, R.A. (1996). Physics for Scientists & Engineers, 4th Edition, Saunders College Publishing.

White, F. M. (2008). Fluid Mechanic 6th ed. New York: Mc Graw - Hill.Viscosity. pg 14

Technorati Tags: absolute viscosity, dynamic viscosity, ethanol, Experiment, kinematic viscosity, methanol, propanol, relative viscosity, viscometer, viscosity, water

§ Micro-study

§ Macro-study

§ Longitudinal (diachronic) study

§ Cross-sectional (synchronic) study

§ Pilot study

Technorati Tags: Qualitative Research, quantitative research, Research, research methods

Scientists develop prebiotic, low-fat sausages By Stephen Daniells

15/11/2007- Inulin, the prebiotic fibre associated with improved gut and bone health, can be used as a fat replacer in sausages to cut energy by over 20 per cent without affecting the flavour profile, suggests new research from Germany. Inulin is already extensively used as a fat and sugar replacer, but according to background information in the article, its use in sausages has only been the subject of very limited study. “Consumer demands for low-fat products, the precautionary principle in the new EC law to achieve the demanded high level of health protection, and market competition are all driving forces for the meat industry to launch new products,” wrote lead author Bernhard Nowak in the Journal of Food Science. “Therefore, in addition to dealing with traditional meat production problems such as hygiene and quality, it is also necessary to consider preventive, prebiotic aspects.” The researchers, from the University of Veterinary Medicine Hannover, and Leibniz University Hannover, investigated the feasibility of incorporating between three and 12 per cent inulin as a fat replacer into bologna-type sausages in order to reduce the energy content by nine to 48 per cent. “In our experiment, the added inulin was applied as a gel (inulin diluted with water 1:1), and added in gradually increasing amounts to replace some of the back fat in the bologna formula; thus fat reduction was achieved by really replacing fat and not by increasing the amount of muscle meat in the formula, as has been done in many other experiments,” they explained. Nowak and co-workers report that the highest inulin incorporation was associated with a 47.5 per cent reduction in energy, but at all levels of fat replacement negative physicochemical effects. These included a darker colour, increased hardness, and a reduction in ‘fracturability’. Subsequent re-formulation by the researchers to substitute citrate for the phosphate in the recipe led to significant reduction in these negative effects. The best results, in terms of both physicochemical properties and sensory attributes, were obtained for sausage formulations containing sic per cent inulin as a fat replacer. Such sausages offered 22 per cent less energy than normal sausages. The sensory attributes (texture, colour) were assessed by four trained tasters, and states to be comparable to the control sausages. Furthermore, the inulin sausages were found to be microbiologically stable for 23 days of storage. “It is possible to add up to six per cent inulin as a gel to bologna-type sausages with citrate in the formula and achieve a significant reduction of the energy content (22 per cent) without negatively affecting sensory quality,” wrote Nowak. The researchers do state that the production costs of the reduced fat sausages with the potentially prebiotic activity are higher than normal sausages. “However, these new and beneficial aspects of innovative products must be properly communicated to the consumer in an easily comprehensible manner and then the higher production costs of almost one-third to a standard sausage will be paid by many people,” they concluded. Source: Journal of Food Science Published on-line ahead of print, doi: “Energy Content, Sensory Properties, and Microbiological Shelf Life of German Bologna-Type Sausages Produced with Citrate or Phosphate and with Inulin as Fat Replacer” Authors: B. Nowak, T. von Mueffling, J. Grotheer, G. Klein, B.-M. Watkinson