LAB 4 PART B PARTICLE SIZE AND SHAPE ANALYSIS WITH MICROSCOPE

TITLE

Part B: Particle size and shape analysis with microscope

OBJECTIVES

The objective of this experiment are:

1.        To analyse and determine the shape and size of particles in various type of samples under microscope

2.        To observe and compare the size of particles of different samples.

DATE OF EXPERIMENT

16^th November 2015

INTRODUCTION

Particle is construed as small object of any size from macroscopic scale (10^-3 m) to the atomic scale (10^-10 m). Dimension (equivalent diameter of the particles) of particulates are important in achieving optimum production of efficacious medicine. Particle size analysis is the integral component of the effort to formulate and manufacture many pharmaceutical dosage forms. The analysis of particle size and shape is very important in pharmaceutical science field because the size and shape of particles will affects the bulk properties, product performance, processability, stability and appearance of the end product and eventually affects the absorption of active ingredients of drugs in the target tissues for treatment of diseases and thus alters the efficacy of drugs. It is hard and impractical to determine the fine particles more than a single dimension because fine particle have irregular and different number of faces, thus, solid particles are often considered as a sphere and the particles size can be characterized by determination of their diameter.

            There are many particle size analysis methods such as sieve method, microscope method, coulter counter, laser light scattering method, dynamic light scattering method and so on. The particle size analysis methods can be categorised into different categories based on several different criteria such as size range of analysis, wet or dry methods, manual or automatic methods and speed of analysis. 

In this experiment, microscope method is used to analyse the particle shape and size of different type of sample. Microscope method is an excellent technique enable to students or researchers to look at the particles directly. Under the microscope, shape and size of particles are no doubt can be seen clearly, but also the good or poor dispersion of particles, and presence of agglomeration can be determined. This is relatively cheap and it has it disadvantages such as not suitable for quality control due to skills in handling the samples and microscope as well as rapid operator fatigue or operator variability on the same sample. There are three types of microscope can be used in determining the shape and size of particles which are light microscope, transmission electron microscope (TEM) and scanning electron microscope  (SEM). Scanning electron microscopy is used when a three-dimensional particles is required. Generally, in using microscope method, the equivalent diameters of particles of different samples are determined for particle size analysis. There are three ways in measuring equivalent diameters, which are projected area diameter, d_a, projected perimeter diameter, d_p and Feret’s and Martin’s diameter.

Most powders contain particles with large number of different equivalent diameters. Particle size distribution can be broken down into different size ranges which can be presented in the form of histogram plotted from data obtained to define the size distribution and compare the characteristics of two or more powders consisting of particles with many different diameters. Histogram is useful in interpreting the particle size distribution, determination of the percentage of particles of equivalent diameters and comparing the different particle size distribution. The distribution plotted in histogram can be divided into three types which are normal distribution, skewness distribution and bimodal frequency distribution.

LISTS OF CHEMICALS

Five different type of sands with various size, 800 mic, 500 mic, 355 mic and 150 mic respectively, lactose powder and MCC powder

LISTS OF APPARATUS

Microscope, newspaper

  

PROCEDURE

1. Five different type of sands with various size, 800 mic, 500 mic, 355 mic and 150 mic respectively, lactose powder and MCC powder were prepared  in little amount in different plates

2. The various size sand was then put in very little amount on the slides under microscope to observe and analyze its particle size and shape with magnification of 10x.

3. The particles observed microscopically was then sketched and the general shape of the sand particle was determined.

4. Step 2 and step 3 were repeated by replacing various size sand with sands with 800 mic, 500 mic, 355 mic, 150 mic, lactos powder, and MCC powder respectively.

RESULTS
Sketching of the particles of different materials:

QUESTIONS

1.        Explain in brief the various statistical methods that you can use to measure the diameter of a particle.

          Among the statistical methods that can be used to measure the diameter of a particle are projected area diameter, projected perimeter diameter, Feret’s diameter and Martin’s diameter.

          Projected area diameter is the diameter of a circle having the same area as the particle viewed normally to the plane surface on which the particle is at rest in a stable position. Projected perimeter diameter is the diameter of a circle having the same circumference as the perimeter of the particle. These methods are independent of particle orientation as they take account of 2 dimensions of the particle only. Thus they are less accurate for asymmetrical particle.

          Feret’s diameter is the mean distance between 2 tangents on opposite sides of the particle. Martin’s diameter is the mean chord length of projected particle perimeter. These 2 methods take account of both the orientation and the shape of a particle.

2. State the best statistical method for each of the samples that you have analysed.

                 The best statistical method to be used are Feret’s diameter and Martin’s diameter. This is because both methods provide the average diameter on many different orientations of the particle to give a mean value for the diameter of each particle. Therefore, it gives a more accurate value of average diameter as compared to projected area diameter which does not take account of the orientation of the particle.

DISCUSSION

In this experiment, the characteristic of different particles were observed and studied including the size and the shape using a light microscope. Among the particles observed are sands with different size of 150 micron, 350 micron, 500 micron, 850 micron and various size, lactose and microcrystalline cellulose (MCC). Microscopy method is a technique used to characterize particle size, shape and volume distribution through the direct visualisation and measurements of small particles. Light microscope works according to the principle of passing the visible light transmitted or reflected from a sample through single or multiple lens to allow the magnification of the sample. In this experiment, 10x10 magnification is used throughout the experiment.

Through this experiment, it is found that the shapes and sizes of different particles are distinct from each other. All sand particles have irregular shapes as some of them have pointed edges and the size of sand particles increases in order of 150 micron, 350 micron, 500 micron and 850 micron. Sand particles of various size have different sizes of particles in it. As for MCC and lactose, both of these particles have a granular shape without any pointed edges like those in sand particles and their sizes are much smaller than the 150 micron sand particles. The difference between MCC and lactose is that MCC particles are acicular while lactose particles are fine rounded. The particles are dispersed evenly on the slide before observing to prevent the particles from sticking together and thus avoid agglomeration. During the observation of the particles, the shape and size of the particles are actually analysed in a two-dimensional image. Similar particles may appear to be different because they may have different orientation. However, it is assume that the particles are randomly oriented and viewed in their most stable orientation.

There are 4 main methods to analyse particle size, which are projected area diameter, projected perimeter diameter, Feret’s diameter and Martin’s diameter. Projected area diameter is the diameter of a circle having the same area as the particle viewed normally to the plane surface on which the particle is at rest in a stable position. Projected perimeter diameter is the diameter of a circle having the same circumference as the perimeter of the particle. These 2 methods are independent of particle orientation. Feret’s diameter is the mean distance between 2 parallel tangents on opposite sides of the particle. Martin’s diameter is the mean chord length of of a particle which divides the projected area. These 2 methods take account of both the orientation and the shape of a particle.

Precaution steps that were taken in this experiment includes the careful handling of the particles by using different spatulas for different particles to avoid mixing of particles. Besides, the experiment is carried out in a stale air condition to prevent the particles from dispersing everywhere. Goggles and mask were also worn to prevent the particles from entering our body.

CONCLUSION

            Different particles have different shapes and sizes. Microscopy is one of the methods to study particle shape and size through the direct observation of the particles. Diameter of a particle and be measured through projected area diameter, Feret’s diameter and Martin’s diameter. The characteristics of particles which includes the shape and the size is necessary to be understood to increase the efficacy of drugs through the formulation of drugs in the field of pharmaceutical industry.

REFERENCES

Florence, A. T. & Attwood, D. 2006. Physicochemical Principles of Pharmacy. Edisi ke-5. London: Pharmaceutical Press.

Martin, A. 2011. Physcial Pharmacy: Physical Chemistry Principles in Pharmaceutical Sciences. Edisi ke-6. Philadelphia: Lippincott Williams & Wilkins.

Cairns, D. 2008. Essentials of Pharmaceutical Chemistry. Edisi ke-3. United States of America: Pharmaceutical Press.

Chang, R. & Goldsby, K. A. 2014. Chemistry. Edisi ke-11. New York: McGraw- Hill Education.

LAB 4 PART A PARTICLE SIZE ANALYSIS USING SIEVING METHOD

TITLE

Part A: Particle Size analysis using Sieving Method

OBJECTIVES

To determine the particle size of lactose and microcrystalline cellulose (MCC).

To classify and differentiate the powder based on the diameter of the powder particles.

To identify the size distribution of lactose and microcrystalline cellulose (MCC)

DATE OF EXPERIMENT

16^th November 2015

INTRODUCTION

A test sieve is an instrument which is used for the measurement of particle size. In its most common form it consists of a woven wire screen, with square apertures, rigidly mounted in a shallow cylindrical metal frame. For coarse sieving a perforated plate screen with square or round holes may be used in place of wire mesh. Square hole perforated plate sieves range down to 4mm and round hole sieves down to 1mm aperture.

A sieve test is performed by first assembling a stack of interlocking sieves. In this stack, the sieve with the largest opening is at the top. Each lower sieve will have a smaller opening than the one on the above.

The materials which are tested in this experiment are lactose and microcrystalline cellulose (MCC). The lactose is first weighed and is poured into the sieve nest before being sieved by using mechanical shaker for a fixed amount of time. At the end of the experiment, the weight of lactose is recorded and the experiment is repeated by using microcrystalline celluluose. The overall results are then presented in histograms.

LIST OF MATERIALS

Microcrystalline cellulose (MCC), Lactose

LIST OF APPARATUS

Mechanical sieve, sieve nests, large weighing boats, spatula, electronic balance, newspaper

EXPERIMENTAL METHOD

1.      100 g of lactose is weighed.

2.      The sieve nest is prepared in descending order (largest diameter to the smallest, from top to bottom).

3.      The powders are placed at the uppermost sieve and allow the sieving process to proceed for 15 minutes.

4.      Upon completion, the powder collected is weighted at every sieve and the particle size distribution is plotted in the form of histogram.

5.      The above process is repeated using MCC.

RESULTS

Lactose
Diameter of sieve nest (μm)	50	150	200	425	500
Weight (g)	38.6768	0.1488	60.9122	0.0092	0.0218

MCC
Diameter of sieve nest (μm)	<53	53	150	200	300	500
Weight (g)	17.5855	76.8885	3.3547	1.8236	0.2216	0.1261

QUESTIONS

1. What are the average particle size for lactose and MCC?

 The average particle size of lactose is between 50 µm to 200 µm and the average particle size of MCC is between 50µm to 150µm.

2. What other methods can you use to determine the size of particle?

The other methods to determine the size of particles are surface area measurement, sedimentation, electron microscope analysis, Coulter counter, laser light scattering technique, dynamic light scattering technique and optical and electrical sensing zone method.

3. What are the importances of particle size in a pharmaceutical formulation?

For the pharmaceutical industry, particle size impacts products as an influence on drug performance. Particle size of the active pharmaceutical ingredient (API) and inert excipients are to be considered in pre-formulation, design of drug delivery system as it is influencing the proceessability, stability, bioavailability and efficacy of drug delivery system. Particle size is having a pronounced effect on the absorption of drugs with low aqueous solubility for the solid dosage form. Smaller particle size has higher absorption compared to bigger particle size for the conventional solid dosage forms such as tablets that are administered orally for local and systemic action. In the other hand, the particle size of disintegrants like starch influences the disintegration time of the tablets as starch grains with large particle size are more efficient disintegrants compared to the smaller one. Furthermore, the efficacy of lubricant is also influenced by the particle size and lubricants that having a particle size of 60-100 mesh are used most often.  For insoluble drugs, the particle size of the filler influenced the dissolution rate and affect on the solubility of the drug. Syringeability and injectability properties of a parenteral suspension are closely related to the particle characteristics of the parenteral suspension. The rate of reconstitution from a drug powder to form aqueous solution/suspension is influenced by the particle size. The particle size of the dispersed phase should be below 10um in order to minimize pain and tissue irritation.

DISCUSSION

Sieving is one of the oldest methods of classifying powders and granules by particle size distribution. The sieving will sort the particle by their intermediate size dimension when sieve using a woven sieve cloth. The particles larger than 75µm is sieved with mechanical sieving whereas for smaller particles, the light weight provides insufficient force during sieving and this will cause the particles to stick together and the particles expected to pass through the sieve will be retained. Sieving is a method of choice to classify coarser grades of single powders or granules in the pharmaceutical field.

                        In this experiment, the particle size distribution of lactose and are microcrystalline cellulose (MCC) are being observed. The method used to determine their particle size distribution was sieving method or sieve analysis. A sieve nest is used to determine the article size distribution. The sieve nest is arranged in descending order from top to bottom which is from largest diameter to smallest diameter. The sieve that have diameter of aperture of 500 µm will be placed at the top followed by 425 µm, 200 µm, 150 µm, and 50 µm. The coarsest sieve was loaded with the lactose powder and it is operated for mechanical vibration for 20 minutes. The procedures are the same for the microcrystalline cellulose (MCC).

                        In this experiment, the particle size of lactose is measured based on the principle that the particle cannot pass through the sieve due to larger size particle than the sieve. Based on the results obtained, the particle size of lactose is mostly in between 200 µm and 425 µm as 60.91g of lactose is collected in this sieve followed by particle size less than 50 µm as 38.68g of lactose is collected at the most bottom sieve. In microcrystalline cellulose (MCC), the powder is mostly collected in the 53 µm sieve with 76.89g and we can assume that microcrystalline cellulose (MCC) have particle size is in between  53 µm and 150 µm follow by less than 53 µm as 17.58g of microcrystalline cellulose (MCC) is collected. Comparing both lactose and microcrystalline cellulose (MCC), we can deduct that microcrystalline cellulose (MCC)  have smaller particle size and finer than lactose.

                        The initial total weight of lactose and microcrystalline cellulose (MCC) is both 100g but by the end of experiment, the weight of lactose is 94.9g whereas microcrystalline cellulose (MCC) remains 100g. This clearly indicates that some of the lactose powder is lost during the lab and error occurs. One is when transferring of lactose and microcrystalline cellulose (MCC) from the weighing boat into the sieve and after 20 minutes of mechanical vibration, the transferring of the powder back into the weighing boat for weighing. During the process of transferring, some of the powder is still preset either in the sieve or weighing boat. This explains why the final weight of the lactose powder is not exactly 100g. The second error that occurs during the lab is the sieve nest is not covered tightly due to the machine malfunction. . Some of the powder may spill out from the container as the machine is not closed tightly. In this condition, the vibration of the machine may be irregular and this will affect the separation of powder in the sieve nest. Thus, error occurs. The powders are light weight particles. Thus, when exposed to air, it may evaporate of carried by water vapour into the air causing loss of weight. The mass will not be accurate.  Before the experiment, the sieves are cleaned using a brush to remove any powder from the previous experiment. The machine needs to be sealed tightly to prevent error.

                                                                                          

CONCLUSION

Most particles size of lactose are in the range of 0 - 49µm followed by range of 151 – 200µm. While as for MCC, most particles size are in the range of 0 - 52µm followed by 53 µm. This shows that most particles in MCC is smaller than those of lactose.

REFERENCE

Martin, A. 2011. Physcial Pharmacy: Physical Chemistry Principles in Pharmaceutical Sciences. Edisi ke-6. Philadelphia: Lippincott Williams & Wilkins.

Chang, R. & Goldsby, K. A. 2014. Chemistry. Edisi ke-11. New York: McGraw- Hill Education.

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LAB 3 PART B MUTUAL SOLUBILITY CURVE FOR PHENOL AND WATER

TITLE

Part B: Mutual Solubility Curve for Phenol and Water

OBJECTIVES

The objective of this experiment are:

1.        To determine the phase diagram of phenol and water.

2.        To determine the solubility of two partially miscible liquids (phenol and water solution).

3.        To determine the critical solution temperature of phenol and water system.

DATE OF EXPERIMENT

1^st November 2015

INTRODUCTION

Miscibility refers to how completely two or more liquids can be dissolved in each other. It can be classified into three categories which are completely miscible, partially miscible, and completely immiscible.

Complete miscibility is a mix in all proportions, and can be described as “like dissolve-like”. Polar and semi-polar solvents such as alcohol-water, glycerin-alcohol, and alcohol-acetone are said to be complete miscible because they mix in all proportions. Non-polar solvents such as benzene and carbon tetrachloride are also completely miscible. Completely miscible liquid mixtures in general create no solubility problems for the pharmacist.

Partial miscibility is the formation of layers when certain amounts of liquids are mixed. Examples are ether-water and phenol-water.  Mutual solubilities of partially miscible mixture is influenced by temperature. In a system such as phenol and water (Here, phenol is not really liquid, but is considered to be so since the addition of the first part water reduces the solid’s melting point under room temperature to produce a liquid-liquid system), the mutual solubilities of the conjugate phases increase with temperature until the critical solution temperature (or upper consolute temperature) when the compositions become identical. Critical solution temperature is the maximum temperature at which the two-phases region exists. In general, both liquids become more soluble with rising temperature until the critical solution temperature or consulate level is attained, and above this liquids become completely miscible. In other words, at this temperature, a homogenous or single phase system is formed.

            There is a big possibility that any pair of liquids can form a closed system, whereby both upper and lower critical solution temperature exist, however, it is not easy to determine both the temperatures (before the substance freezes or evaporates) except the nicotine and water. At any temperature below a critical solution temperature, the composition for two layers of liquids in equilibrium condition is constant and does not depend on the relative amount of these two phases. The mutual solubility for a pair of partially miscible liquids in general is extremely influenced by the presence of third component.

LISTS OF CHEMICALS

Phenol, distilled water, parafilm, aluminium foils

LISTS OF APPARATUS

Boiling tube 20 mL, test tube rack, funnel, measuring cylinder 10 mL, dropper, thermometer, beaker 50 mL, water bath and ice

PROCEDURE

1. Phenol with concentrations of 8%, 25%, 50%, 75% and 80% were produced in tightly sealed boiling tubes containing amounts of phenol and water.

2. The tightly sealed boiling tubes were heated in water bath to increase their temperature.

3. The water bath was stirred and the tightly sealed boiling tubes were shaken as well if possible.

4. The temperature for each of the tightly sealed boiling tubes at which the turbid liquid became clear was observed and recorded.

5. The tightly sealed boiling tubes were removed from hot water bath and allowed for their temperature to reduce gradually.

6. The temperature at which the liquid in the tightly sealed boiling tubes became turbid and two layers were separated was again recorded.

7. The average temperature for each tubes at which two phases were no longer seen or at which two phases exist was determined.

8. Part of the tubes may be needed to be cooled besides being heated as instructed above.

9. The graph of phenol composition (horizontal axis) in the different mixtures against temperature at complete miscibility was plotted. The critical solution temperature was determined.

RESULTS

Records all the results:

Percentage of phenol (%)	Volume of phenol (ml)	Volume of water (ml)	Temperature at which the turbid liquid become  clear (°C)	Temperature at which the liquid become turbid (°C)	Average temperature (°C)
0.0	0.0	20.0	-	-	-
8.0	1.6	18.4	37.0	40	38.5
20.0	4.0	16.0	62.0	65.0	63.5
50.0	10.0	10.0	67.0	65.0	66.0
75.0	15.0	5.0	52.0	52.0	52.0
80.0	16.0	4.0	31.0	32.0	31.5

QUESTIONS

1. Plot the graphs of temperatures at complete miscibility against phenol composition in the different mixtures. Determine the critical solution temperature.

The critical solution temperature of phenol-water mixtures is 67 °C.

2. Discuss the diagrams with references to the phase rule.

Phase rule is a useful rule for relating the effect of the least number of independent variables for example temperature, pressure and concentration upon the various phases (solid, liquid, gaseous) that can exist in an equilibrium system containing a given number of components. The phase rule is expressed as : F = C – P + 2, in which F is the number of degrees of freedom in the system, C is the number of components and P is the number of phases present. As the number of components increases, the degrees of freedom also increases. Consequently as the system becomes more complex, it becomes necessary to fix more variables to define the system. Besides, the greater the number of phases in equilibrium, the fewer the degrees of freedoms.

Based on the diagrams, phenol and water system consists of phenol and water (two components) and it is a two phase system. When 8% of phenol was added to 92% of water, it gave a single phase which means the solution of phenol in water was completely miscible in water. The second phase appeared when the phenol composition increased. The tie line showed in the graph was drawn in temperature of 50 °C. The tie line in the graph showed in temperature of 50 °C, in 0% of phenol composition, the phenol composition in water will result in the formation of single liquid phase until the phenol composition reached 13%, at which the second phase starts to appear. The phenol-rich phase increases, the water-rich phase decreases as the phenol composition increases. Once the total concentration of phenol exceeds about 75.5%, a single phenol-rich liquid phase was formed. But, if the temperature is above 67 °C, the single phase will form at any phenol composition. This is the critical solution temperature of phenol-water system.

Applying the phase rule to the graph shows that with two component system having one liquid phase, the degree of freedom F = 2 – 1 + 2 = 3. Because of the fixed pressure, degrees of freedom is reduced from 3 to 2, both temperature and concentration (independent intensive variables) need to be fixed to define the system. When two liquid phases are present, the degree of freedom F = 2 – 2 + 2 = 2. When pressure is fixed, the degree of freedom is reduced to 1, thus, we know that there is only an independent intensive variable needed to be fixed to define the system. The variable is temperature.

3.Explain the effect of adding foreign substances and show the importance of this effect in pharmacy.

The addition of the foreign substances to binary system results in a tertiary system. Thus, the number of components in the system increased by 1. For example, a two components system becomes three components system. If the material added is soluble only in one component or if solubilities in both liquids are very different, mutual solubility will decrease. The upper consolute temperature will be raised while the lower consolute temperature will be lowered. If the foreign substances added are soluble in both liquids, mutual solubility of the liquid pair will be increased. The upper consolute temperature will be lowered while the lower consolute temperature will be raised. The increase in mutual solubility of two partially miscible solvents by another agent is ordinarily referred to as blending.

       The effect is very important in the preparation of drugs in pharmacy. If a contaminant reduces the miscibility of both liquids, the dispensed medicine may change its nature and may no longer be suitable for consumption. Besides that, the therapeutic effect of some drugs will be reduced and may be harmful to the body. This condition may arise due to contamination in extemporaneous preparation in unhygienic medicine preparation areas. However, the addition of third substance also brings benefit to pharmacy. The addition of micelle-forming surface-active agent increases the solubility of non-polar liquid in water (micellar solubilization). Besides, addition of third substance helps in selection of the best solvent for drug or drugs mixture, overcomes problem raised during preparation pf pharmaceutical solutions and enables the researchers or experimenters to obtain more information about the structure and intermolecular forces of the drug investigated. Last but not least, the addition of potassium chloride into phenol-water system will illustrates the salting-out effect under solutions of gases.

DISCUSSION

Phenol-water system is a liquid-liquid system by which usually we will omit the vapour phase, in principle by postulating that it is excluded from the system, in practice by working under the ambient fixed atmospheric pressure. Pairs of liquid often are classified into three categories which are completely immiscible (such as mercury and water), partially immiscible (such as phenol and water) and completely immiscible (ethanol and water).

Miscibility is the property of a substance to mix in all proportion. There are some factors that can affect miscibility, such as the nature of solute/solvent (polarity or molecular size), temperature (whether the experiment is exothermic or endothermic), pressure, concentration, etc. Since the experiment was carried out under an ambient fixed atmospheric pressure, the variables that still needed to be taken into account were temperature and the composition of the mixture (concentration). The graph above was drawn to present the schematic temperature-composition phase diagram for partially miscible pair of water and phenol. Any combination of temperature and composition giving point out of the phase boundary line (the curve) describes a homogenous system (single phase) which refers to complete miscibility while any combination of it that lies on or within the line exists in two different phases (partial miscibility). In this experiment, the graph obtained is an n-shaped graph which provided the phase boundary line that shows the critical solution temperature and concentration of phenol within which two liquid phases can be existed in equilibrium.

Theoretically, small concentrations of phenol will dissolve in water and vice versa, and as the temperature increases, the extent of mutual solubility increases. The tie line is located at 50 °C. Across the tie line, at 0% of phenol concentration, the phenol composition in water will result in the formation of single liquid phase which is water-rich phase until the phenol composition reached 11%. Starting from 11% of phenol composition (89% of water composition), the two liquid phases will be formed up to 63% of phenol composition. The two liquid phases are phenol-rich phase and water-rich phase. As the phenol composition increased from 11%, the phenol-rich phase will increase and at the same time, the water-rich phase will decrease. Beyond phenol composition of 63%, there will be only single phase exists which is phenol-rich phases disregarding any temperature as two liquids are completely miscible. On top of that, according to theoretical phenol-water system phase diagram, the critical temperature or upper consolute temperature is 66.8 °C for phenol-water system. Beyond this temperature, all the combination of two liquids are miscible and yield one-phase liquid systems.

Based on the experimental phenol-water system phase diagram, phenol and water system consists of phenol and water (two components) and it is a two phase system. When 8% of phenol was added to 92% of water, it gave a single phase which means the solution of phenol in water was completely miscible in water. The second phase appeared when the phenol composition increased. The tie line showed in the graph was drawn in temperature of 50⁰C. The tie line in the graph showed in temperature of 50 °C, in 0% of phenol composition, the phenol composition in water will result in the formation of single liquid phase until the phenol composition reached 13%, at which the second phase starts to appear. The phenol-rich phase increases, the water-rich phase decreases as the phenol composition increases. Once the total concentration of phenol exceeds about 75.5%, a single phenol-rich liquid phase was formed. But, if the temperature is above 67 °C, the single phase will form at any phenol composition. This is the critical solution temperature of phenol-water system.

Phase rule is a useful device for relating the effect of the least number of independent variables such as temperature, pressure and concentration upon the various phases (solid, liquid and gaseous) that can exist in n equilibrium system containing a given number of components. Phase rule is written as below:

F = C – P + 2, in which

F – number of degrees of freedom

C – number of components

P – number of phases present

In this experiment, the phenol-water system can exist in one of the three conditions which are single phenol-rich phase, single water-rich phase or both phases. Applying the phase rule to the graph shows that with two component system having one liquid phase (either single phenol-rich phase or single water-rich phase), the degree of freedom, F = 2 – 1 + 2 = 3. When two liquid phases are present, the degree of freedom F = 2 – 2 + 2 = 2.

There were some errors that may have occurred throughout this experiment which lead to the deviation of the results. Firstly, the boiling tube may be improperly sealed which may lead to the evaporation of the phenol and the escaping of heat from the tube, thus causing the deviation of the results obtained. Parallax error might also happened. It is possible for parallax error to occur when measuring the volume of phenol and water needed to mix by using measuring cylinder and when taking the reading of the temperature from the thermometer at which the solutions become homogenous (clear) in water bath and heterogenous (two layer) in the ice. This error can be avoided by ensuring the naked eyes are perpendicular to the meniscus of the solution measured and the mercury level in the thermometer. Last but not least, some errors occur due to the different time taken for reaction, different opinions and decision on the phases of the mixture formed.

CONCLUSION

The objectives of the experiment were achieved. Phenol-water system is a liquid-liquid system that shows partially miscibility. The phenol-water system can exist in two conditions which are complete miscibility and partially miscibility. In complete miscibility, the water-phenol system exists in either single phenol-rich phase or single water-rich phase depends on the temperature and the phenol composition in the water. Phenol-water system in partially miscibility exists as phenol-rich phase together with water-rich phase. The phenol-rich phase continually increases whereas the water-rich phase continually decreases as the quantities of phenol in the water increases. The critical solution temperature of the phenol-water system is about 67 °C, beyond this temperature, all combinations of phenol and water are completely miscible and yield one-phase liquid systems.

REFERENCES

Florence, A. T. & Attwood, D. 2006. Physicochemical Principles of Pharmacy. Edisi ke-5. London: Pharmaceutical Press.

Martin, A. 2011. Physcial Pharmacy: Physical Chemistry Principles in Pharmaceutical Sciences. Edisi ke-6. Philadelphia: Lippincott Williams & Wilkins.

Cairns, D. 2008. Essentials of Pharmaceutical Chemistry. Edisi ke-3. United States of America: Pharmaceutical Press.

Chang, R. & Goldsby, K. A. 2014. Chemistry. Edisi ke-11. New York: McGraw- Hill Education.