Pharmaceutical Technology >>> e-reports : EMULSION REPORT

EXPERIMENT 3 : ASSESSMENT OF THE EFFECT OF DIFFERENT INGREDIENTS ON EMULSION FORMULATION

OBJECTIVE
1) To determine the effect of HLB surfactant on emulsion stability

2) To investigate the physical effect and stability on emulsion formulation result from the use of different emulsifying agents

INTRODUCTION

Emulsion is a mixture of two or more insoluble liquids in which one of the liquid is present as droplets in microscopic size, and it is distributed throughout the other. Emulsions are formed from the component liquids either spontaneously or by mechanical means which is agitation, that provides the liquids that are mixed have no or a very limited mutual solubility. Emulsions need to be stabilized by some agents that form films on the surface of the droplets or that impart to them a mechanical stability (e.g colloidal carbon or bentonite). In other words, it is stabilized with addition of emulsifying agents. Without emulsifying agents, unstable emulsion will form and it will separate into two layers.

Emulsion is classified into two types, namely oil in water emulsion(o/w) or water in oil emulsion (w/o). There is a method, called HLB (Hydrophilic-Lipophilic Balance). HLB System is used to assign a number to the ingredient or combination of ingredients that is to be emulsified, and then to choose an emulsifier having the same number. In other words, it is used to determine quantity and surfactant types that is required to prepare a stable emulsion. Each surfactant is labelled one number in scale from 1 (lypophililic) to 20 (hydrophilic). An emulsifier that has low HLB will tend to be oil-soluble and the one that have high HLB will tend to be water-soluble.

HLB value for combination emulsifying agents can be determine using following formula.

HLB value = (surfactant quantity 1)(surfactant HLB 1)+(surfactantquantiy 2)(surfactant HLB 2)

Surfactant quantity 1 + surfactant quantity 2

MATERIAL AND APPARATUS

a) Apparatus

8 test tubes, 1 measuring cylinder 50ml, 2 set of pasture pipette and droppers, Vortex mixer tool, Weighing boat, 1 set of mortar and pestle, light microscope, microscope slides, 1 set of pipette 5ml and bulb, 1 beaker 50ml, 1 centrifuge tube 15ml, centrifuge device, Water bath (45⁰C) and refrigerator (4⁰C).

b) Material

Palm oil, Arachis oil, Olive oil, Mineral oil, Distilled water, Span 20, Tween 80, Sudan III (0.5%) solution, ISOTON III solution.

PROCEDURES

1) 8 test tubes were labeled and straight line were drawn 1 cm from the bottom of each of the test tubes.

2) Then, 4 ml of oil (Table 1) and 4 ml of distilled water were added into each of the test tubes.

Group	Oil
1, 5	Palm oil
2, 6	Arachis oil
3, 7	Olive oil
4, 8	Mineral oil

Table 1
3) Span 20 and Tween 80 (Table 2) were dropped into the mixture of oil and water in each of the test tubes. The test tubes were closed and the mixture was mixed using Vortex mixture tool for about 45 seconds. The time taken for the interface to achieve the 1 cm line were recorded. The HLB values for each sample were determined.

Tube No.	1	2	3	4	5	6	7	8
Span 20 (drops)	15	12	12	6	6	3	0	0
Tween 80 (drops)	3	6	9	9	15	18	15	0
HLB value
Phase separation time (min)
Stability

Table 2
4) 1g of the emulsion that is formed in each test tube was weighed in the weighing boat and Sudan III (0.5%) solution were drops to the emulsion. Dispersion of color in the samples was described and compared. A little sample for each of the test tubes was spread on a microscope slide and observed under a light microscope. The shape and size of globular that are formed were drawn and compared.

5) By using the wet gum method, a formulation of Mineral Oil Emulsion were prepared using the formula below :

Mineral oil

Acacia

Syrup

Vanillin

Alcohol

Distilled water, qs

(Refer to table 3)

6.25 g

5 ml

2 g

3 ml

50 ml

Wet Gum Method

a. Acacia is added to the mortar and triturated with water until smooth gum is formed.

b. The oil is added to the mixture while triturating continuously until a smooth emulsion is obtained.

Emulsion	Group	Mineral oil (ml)
I	1, 5	20
II	2, 6	25
III	3, 7	30
IV	4, 8	35

6) 40 g of emulsion that are formed was added into a 50ml beaker and homogenizing process was done for 2 minutes using a homogenizing device.

7) 2 g of emulsion that are formed was taken before and after the homogenizing process and put into the weighing boat and labeled. A few drops of Sudan III solution was added into the emulsion and it is spreaded. The texture, consistency, shape, degree of oil and dispersion color of samples were described and compared under light microscope.

8) Viscosity of the emulsion (15 g in 50 ml beaker) that are formed after the homogenizing was determined by using the viscometer equipment that has been calibrated at all times by using the "Spindle" type LV-4. The samples are then exposed to a temperature of 45 ⁰C (water bath) for 30 minutes and then at a temperature of 4 ⁰C (refrigerator) for 30 minutes. Viscosity of the emulsion after exposure to temperature cycles completed was determined and when emulsion reaches room temperature (10-15 minute).

Reading	Viscosity (cP)						Average + SD
Reading	1	2	3	4	5	6	Average + SD
Before the temperature cycle
After the temperature cycle
Difference (%)

9) 5 g of emulsion that had been homogenized was added into a centrifuge tube and it is centrifuged (4500 rpm, 10 minute, 25 ⁰C). The resulting high separation was measured and the ratio of the separation was determined.

	Height (mm)
Interface
Initial emulsion
Ratio of the separation

RESULT

Tube No.	1	2	3	4	5	6	7	8
Span 20 (drops)	15	12	12	6	6	3	0	0
Tween 80 (drops)	3	6	9	9	15	18	15	0
HLB value	9.667	10.733	11.343	12.44	13.171	14.086	15	0
Phase separation time (min)	>120	>120	>120	27	40	55	19	9
Stability	++++	++++	++++	++	+++	+++	++	+

Comparison of phase separation time between different groups( minutes )

OIL	Palm oil		Arachis oil		Olive oil		Mineral oil
	Group 1	Group 5	Group 2	Group 6	Group 3	Group 7	Group 4	Group 8
Tube 1	-	-	12 min	-	-	-	-	-
Tube 2	-	-	76 min	-	-	-	-	50 min
Tube 3	-	-	82 min	-	8.19 min	-	-	24 min
Tube 4	58 min	16 min	27 min	38 min	14.48 min	-	94 min	28 min
Tube 5	61 min	30 min	40 min	49 min	87.35 min	63 min	80 min	29 min
Tube 6	45 min	39 min	55 min	61 min	58.35 min	-	34 min	15 min
Tube 7	25 min	16 min	19 min	19 min	19.49 min	45 min	8 min	18 min
Tube 8	0.5 min	7 min	9 min	25 min	20 sec	2.5 min	0.5 min	0.5 min

Results for procedure 3:

Tubes	Color dispersion	Size droplets
1	More difficult to spread	Almost size is same, near to each other, evenly distributed
2	More difficult to spread	Almost size is same, near to each other, evenly distributed
3	Difficult to spread	Almost size is same, near to each other, evenly distributed
4	Difficult to spread	Mostly in same size, near to each other
5	Slight easy to spread	Mostly in same size, near to each other
6	Easy to spread	Mostly in same size, near to each other
7	More easier to spread	Most is bigger in size, far from each other, not uniformly distributed
8	More easier to spread	the size is irregular and the distance more far apart from each others

Emulsion before homogenization.

Emulsion after homogenization

Before homogenization	After homogenization
Texture: coarse	Texture: smooth
Consistency: less consistent	Consistency: more consistent
Dispersion: poor dispersion (Colour dispersion: Uneven colour distribution)	Dispersion: good dispersion (Colour dispersion: Easily and evenly distributed)
Oily degree: more greasy	Oily degree: less greasy
Globule size: large	Globule size: small

CALCULATIONS

Difference = (Average of after temperature cycle-Average of before temperature cycle ) / (Average of before temperature cycle) × 100%

SD =

where,

At 20 mL of Palm Oil :

Readings	Group		Viscosity (cP)			Average ± SD
			1	2	3
Before temperature cycle(˚C)		1	80	90	100	100±12.91
		5	100	110	120
After temperature cycle(˚C)		1	90	100	100	116.67±20.55
		5	130	140	140
Difference (%)		16.67%

At 25 mL of Arachis Oil :

Readings	Group		Viscosity (cP)			Average ± SD
			1	2	3
Before temperature cycle(˚C)		2	389.9	389.9	419.9	404.9±15
		6	419.9	419.9	389.9
After temperature cycle(˚C)		2	779.8	779.8	659.9	775.37±66.63
		6	857.9	842.9	731.9
Difference (%)		91.50%

At 30mL of Olive Oil :

Readings	Group		Viscosity (cP)			Average ± SD
			1	2	3
Before temperature cycle(˚C)		3	239.9	210.0	210.0	136.65±83.98
		7	50	60	50
After temperature cycle(˚C)		3	539.9	449.9	389.9	254.95±209.53
		7	50	50	50
Difference (%)		85.57%

At 35 mL of Mineral Oil :

Readings	Group		Viscosity (cP)			Average ± SD
			1	2	3
Before temperature cycle(˚C)		4	650	650	600	730±111.06
		8	740	820	920
After temperature cycle(˚C)		4	300	300	300	613.33±313.83
		8	900	920	960
Difference (%)		-15.98%

SEPARATION HEIGHT

Height ratio =(Separation phase) / (Emulsion phase)

20 mL Palm Oil:

Interphase	Height (mm)		Average
Interphase	Group 1	Group 5	Average
Separation phase	30	35
Original emulsion	49	48
Height ratio	0.612	0.729	0.671

25 mL Arachis Oil:

Interphase	Height (mm)		Average
Interphase	Group 2	Group 6	Average
Separation phase	36	20
Emulsion phase	46	39
Height ratio	0.783	0.513	0.648

30 mL Olive Oil:

Interphase	Height (mm)		Average
Interphase	Group 3	Group 7	Average
Separation phase	35	37
Emulsion phase	50	50
Height ratio	0.7	0.74	0.72

35mL Mineral Oil:

Interphase	Height (mm)		Average
Interphase	Group 4	Group 8	Average
Separation phase	29	30
Emulsion phase	50	45
Height ratio	0.58	0.667	0.624

DISCUSSION

1. What are the HLB values which produce stable emulsions? Discuss.

Emulsifiers with HLB values ranging from 3 to 6 will produce water-in-oil emulsions which are stable. On the other hand, in order to produce oil-in-water emulsions which are stable, emulsifiers with HLB values ranging from 8 to 18 should be used. For the HLB value between 7-9, emulsifying agents normally act as wetting agent, while between 13-15, they act as detergents, and value of 15-16, they are become solubilizing agent.

The HLB value for each tube increase from tube 1 to tube 7. The surfactants used in this experiment is Span 20 is basically the fatty acid esters of anhydro sorbitols which are good oil soluble emulsifying agents and also Tween 80, which a nonionic surfactant and emulsifier derived from polyethoxylated sorbitan and oleic acid, and is often used in foods. A high HLB value of the surfactant indicates strongly hydrophilic character while a low value is an indication of a strong hydrophobic nature. Span 20 has HLB value of 8.6 while tween 80 has HLB value of 15.

We can determine the stability of an emulsion more easily from the separation phase time. Emulsion which has the longest separation phase time is the most stable emulsion. A stable emulsion contains emulsifying agents added that able to mix and stabilize the two phases well for a very long time. From our experiment, a very short time (9 minutes) is required to separate the two phases in test tube 8 because there is no emulsifying agents added. In test tube 7 where there is only Tween 80, emulsion that is formed is not stable as it contains shorter separation phase time (19minutes). This shows that a combination of surfactants can give much better emulsifying effect than they are used alone.

The time taken for test tube 4 is 27 minutes, followed by test tube 5 (40min) and 6 (55min). However, for test tube 1, the time taken for the phase to separate is more than 120 minutes, same as tube 2 (>120min) and tube 3 (>120min). This shows that the emulsion in test tube 1,2 and 3 are much more stable due to the presence of more drops of emulsifying agent. The longer time for test tube 1 can also be explained by the hydrophobicity of span 20. Span 20 has a more hydrophobic character and a higher concentration of span 20 in test tube 1 makes it to have a longer separation time compared to the other test tube which has a lower amount of span 20.

In comparison with group 6 that use the same oil as our group, the time taken for test tube 1, 2 and 3 are the same, in which the time taken for interphase to reach 1 cm is more than 120 minutes. For test tube 4, the time taken is 38minutes compared to what our group obtained is 27minutes. In short, the time taken for interphase to reach 1 cm for group 2 is a little bit faster than group 6.

Some drops of Sudan III solution is dropped into 1g of the emulsion. The color in tube 1 spreads with “difficulty” (meaning spread slowly) than tube 2, 3, 4, 5, 6, 7 and 8. The spreading color in test tube 7 become more easier (meaning spread faster) and it does not need to be stirred before it can mixed with the emulsion. This showed that the viscosity in test tube 7 is not as viscous as in test tube 1. The viscosity of the emulsion more viscous in test tube 1, thus when the Sudan III solution is dropped into the emulsion, the solution cannot break through the particle in the emulsion. But, in test tube 7, the Sudan III easy to break through as the distant between particle is quite far and the size particle (droplet) also bigger. This is because test tube 1 with more drops of span 20 have more hydrophobic character and hence, this leads to an increase in viscosity and a greater difficulty for colour to spread.

Based on the microscope at 4x10 lens, in test tube 1, 2 and 3, the droplet size in the test tube is a binomial distribution. Most of the particles/droplets have the same size and the distance between particle also near to each other. For test tube 4, 5 and 6, the particles mostly have the same size and a little apart from each other. But for test tube 7, the droplets is far from each other and also bigger in size. While in test tube 8, the size is irregular and the distance more far apart from each other.

2. Compare the physical characteristics of the mineral oil emulsion formed and explain. What is Sudan Test III? Compare the colour dispersion in the emulsion formed and explain.

Characteristics	Before homogenization	After homogenization
Texture	coarse	smooth
Consistency	less consistent	more consistent
Dispersion	poor dispersion (Colour dispersion: Uneven colour distribution)	good dispersion (Colour dispersion: Easily and evenly distributed)
Greasiness	more greasy	less greasy
Globule size	large	small

The physical characteristics of mineral oil emulsion that will be discussed are the globule shape and size, texture, greasiness, consistency and dispersion before and after homogenization.

Before homogenization, the globules are not in uniform size and are coarse. There has a combination of small, intermediate and large size globules. However, the size of globules becomes uniform after homogenization and all globules are in smaller size. About the greasiness, the emulsion is greasy and less viscous before homogenization due to the reason of unemulsified oil. However, the emulsion becomes smoother and more viscous after homogenization. This is because the sample tube is spun in the high rate and breaks the globules into smaller sizes. Besides that, the emulsion is less consistent before homogenization. However, the consistency of the emulsion increased and the degree of greasiness decreased after homogenization because during homogenization, forces are applied to the emulsion and thus it causes a better emulsifying effect to take place. After adding Sudan test III solution, the colour of the emulsions becomes milky. It shows good colour dispersion in the emulsions.

Sudan test is a group of azo compound used as biological stains for fat. It is used to show the shape and physical characteristic of oily emulsion. It can differentiate which emulsion is oil-in-water emulsion or water-in-oil emulsion by determining the amount of globules in red colour and the colourless globules. Sudan solution is a red colour solution. It is dissolved in oily phase of the emulsion. So, it will cause the oily globules stain in red colour. The colour dispersion of the emulsions before homogenization is not consistent. However after the homogenization,the colour of dispersion is more consistent. Thus, the emulsion formed is considered as oil in water emulsion.

3. Plot and explain:

(1) Graph of sample viscosity before and after temperature cycle versus different amount of Mineral Oil.

(2) Graph of viscosity difference (%) versus different amount of oil.

(i) Graph of the sample’s viscosity before and after the temperature cycle against

different contents of mineral oil.

Amount of Mineral Oil (mL)	Average Viscosity (cP) (x ± SD)		Viscosity difference (%) (x ± SD)
Amount of Mineral Oil (mL)	Before temperature cycle	After temperature cycle	Viscosity difference (%) (x ± SD)
20	100±12.91	116.67±20.55	16.67%
25	404.9±15	775.37±66.63	91.50%
30	136.65±83.98	254.95±209.53	85.57%
35	730±111.06	613.33±313.83	-15.98%

In theory, an increase in the amount of mineral oil will produce a more viscous emulsion. From the graph above, the viscosity before temperature cycle increases as the amount of the mineral oil increases with the exception of the emulsion that contain 30mL of mineral oil that is emulsion III. For those emulsion after temperature cycle, the same theory is applied, whereby an increase in the amount of mineral oil will produce a more viscous emulsion. However, from the result that is interpreted above , the graph only shows an increase in viscosity from 20mL to 25mL mineral oil, and then it shows a significant decrease in viscosity when 30 mL of mineral oil is used. Although there is an increase of viscosity in emulsion that use 35 mL of mineral oil , the viscosity is still low if compared to emulsion that uses 25 mL mineral oil.

Besides, after the temperature cycle, all emulsion should have a higher viscosity compared to those before temperature cycle. This is because on heating the oil in water emulsion, there will be a conversion to the water in oil emulsion. Generally, emulsion of water in oil has a higher viscosity compared to the oil in water emulsion. This phase inversion is a phenomenon that shows instability. Therefore, it is true to say that the more unstable the emulsion, the higher the viscosity of emulsion. The purpose of treating the emulsion with exaggeration of the temperature fluctuations (temperature cycling) is to compare the physical instabilities of the emulsion. When the emulsion is heated and frozen, the continual formation of the small ice crystals disrupts the adsorbed layer of the emulsifying agent at the oil-water interface. As a result, the emulsion becomes unstable. Hence, its viscosity increases.

The theory above is proven by the 20mL, 25mL and 30mL mineral oil that are used to produce emulsion. However, for the 35mL mineral oil, the viscosity of emulsion produced after temperature cycle is less than the one before temperature cycle. The inaccurate results above may be due to the errors that occur during the experiment. Actually all the group members had done a mistake where we used different volumes of different types of oils to prepare the emulsions for procedures 5 to 9. In fact, we should use the same type of oil, which is the mineral oil, but in different volumes to investigate the effect of the amount of oil on the physical characteristics and the stability of the emulsion formed. However, this mistake was only discovered after the practical session and therefore we could not do any correction. This leads to the inaccurate result in this experiment.

Furthermore, for the measurement of the viscosity, the difference of the results from theory may also due to the different sizes of spindles that we used to measure the viscosity of the emulsions. We were not sure of the suitable spindle size to measure the viscosity of our emulsions. The viscosity measurements of the emulsion might not be accurate because we did not use the appropriate spindle size. This might cause the measurements to be inaccurate and cause the comparison between the viscosities of different emulsions to be inaccurate and differ from the theory. In addition, after the emulsion had been taken out from the refrigerator, it has to been left for some time until room temperature is reached. This is to ensure that the emulsion that is to measured for its viscosity melts completely and is not in its solid state(ice). However, we just wait for a while and the emulsion have not reach to its room temperature. There may be some residues of solids(ice) that makes the viscosity measurement to be inaccurate since the emulsion has not completely melt.

(ii) Graph of the difference of viscosity (%) against the different oil contents.

Average Viscosity (cP) (x ± SD)

The graph above shows the differences in viscosity versus amount of mineral oil. From the graph, it is shown that an increase in the amount of mineral oil will increase the difference in viscosity except for emulsion III (30mL mineral oil) and IV (35mL mineral oil). Emulsion made from 30mL mineral oil decreases slightly while emulsion made from 35mL mineral oil decreases dramatically. In theory, an increase in the amount of mineral oil will show an increase in viscosity difference. This is because mineral oil is the dispersed phase. If the dispersed phase increased, viscosity of the emulsion should be increased.

This might be due to some errors that occurred during experiment. For example, we use different volume for the different types of oil. Hence, it causes the existence of two manipulated variables in one experiment. This causes the result to be inaccurate and difficult to be compared. The correct way is that we should fix the type of oil, which is mineral oil while varying the volume of the mineral oil in order for experiment result to be valid. Moreover, the exact amount of ingredients used to prepare the emulsion might not be accurate due to the error while weighing the ingredients or may be due to the unsuitable spindle used in the viscometer. On top of that, inaccurate result might be obtained if the same spindle is used without washing every time the measurement of the viscosity of the emulsion is made.

4. Plot the graph of the separation phase ratio after centrifugation process against the different volumes of mineral oil. Give your comments.

Mineral Oil (mL)	Ratio of Phase Separation (x ± SD)
Emulsion I (20mL)	0.671±0.0585
Emulsion II (25mL)	0.648±0.1350
Emulsion III (30mL)	0.72±0.02
Emulsion IV(35mL)	0.624±0.0435

Theoretically, a stable emulsion is formed when the separation phase ratio is be kept as minimum as we can. When the volume of mineral oil used increases, the separation phase ratio is also increased. The tendency for the emulsion to be separated into oil and water is higher with larger volume of mineral oil. Separation will make the emulsion to become unstable. Thus, by increasing the volume of mineral oil used, the separation phase ratio will also increase and the emulsion will become more unstable.

Based on the plotted graph, the separation phase ratio decreases when the volumes of the mineral oil from 20 mL to 35 mL. However, the separation phase increase when the mineral oil is from 25mL to 30 mL and decrease again from 30mL to 35mL. The inaccuracy of the result may be due parallax error when measuring the length of the separation.

Errors may also happen during the preparation of emulsion using wet gum method. Inaccuracy of results may be caused by variable quality of acacia used in the experiment in different groups or the different methods used in preparation of emulsion. Our group had accidentally used the dry gum method to prepare the emulsion needed for the experiment instead of the wet gum method requested in the procedures. In both the dry and wet gum methods, the proportions of oil, water and emulsifier are the same, that are 4:2:1. However, the orders and techniques of mixing are different. In the dry gum method, the 1 part gum is mixed with the 4 parts oil until the powder is thoroughly wetted, then the 2 parts water are added all at once, and the mixture is vigorously and continually triturated until the primary emulsion formed is creamy white and produces a "crackling" sound. On the other hand, in the wet gum method, the 1 part gum is triturated with 2 parts water to form a mucilage, then the 4 parts oil is added slowly in portions while triturating. The mixture is triturated for several minutes after all of the oil is added to form the primary emulsion. As such, we quickly prepared a new emulsion using the wet gum method. This is to ensure that our group's results and the other groups' results are more comparable since the same method is used. If different methods are used, there may be a slight difference in the texture or homogeneity of emulsion produced. Low homogeneity of the emulsion will cause an increase in phase separation ratio.

5. What is the function of each ingredient used in the emulsion preparation? How can the different amount of ingredients influence the physical characteristics and the stability of the emulsion?

Ingredient	Function	Note
Different types of oil ( palm oil, arachis oil, olive oil, mineral oil )	The oily phase in the o/w emulsion.	Amount of the different types of oil (oily phase) and the distilled water (aqueous phase) used is important to determine the type of emulsion formed, whether o/w or w/o emulsion. The volume of the dispersed phase should not be more than the volume of the continuous phase. Or else, phase inversion will occur. Different types of oil will also affect physical appearance of an emulsion such as colour, texture, consistency, etc.
Acacia, Span 20, Tween 80	Emulsifying agent reduces the interfacial tension and maintain the separation of the droplets in the dispersed phase.	Acacia, Span 20, Tween 80 which act as the emulsifying agent should be used in appropriate amount according to the HLB value. If the amount used is less than which is required, the emulsion formed is not uniform due to the large interfacial tension between the dispersed phase and the continuous phase. Then the separation of phase will occur.
Syrup	Increase the viscosity of the emulsion and acts as sweetening agent to mask the unpleasant taste of the mineral oil so that the compliance of the patient is increase.	Syrup will affect the viscosity of the emulsion formed as it is a viscous liquid. Suitable amount of syrup should be used to give suitable viscosity to the emulsion formed. Viscosity of the emulsion will affect the physical stability and the rheological characteristic of the emulsion. This is to avoid the rheological problem in which the emulsion is maybe hard to pour out from the container and some of it may remain and form a layer surrounding the container wall. Syrup content should also be taken care for diabetes patients.
Vanillin	As flavoring agent.	Increases the taste of emulsion. As such, patient compliance can be increased.
Alcohol	As antimicrobial agent.	Alcohol which acts as the antimicrobial agent should not be used in large amount to reduce toxicity.
Distilled water	As the aqueous phase in the o/w emulsion.

CONCLUSION

HLB value should be 3-6 to form a stable water-in-oil emulsion while the HLB value should be 8-18 to form a stable oil-in-water emulsion. Besides the HLB value of the surfactants, we should consider type of surfactants. A combination of surfactants is more beneficial in stabilizing an emulsion. The composition of surfactant and volume of oily phase used are important factors in determining the physical characteristics and stability of the emulsions. The viscosity of emulsion before temperature cycle should be lower than the viscosity after temperature cycle. Furthermore, a stable emulsion should have minimum separation phase.

APPENDIX

Due to limitation of time, we are divided into 8 groups in this experiment. Every two groups will conduct the experiment using the same oil. Therefore, there are eight groups using four types of oil respectively to do emulsion.

Before the experiment start, Dr. Fern explained us how the steps should be taken to succeed the experiment.

After adding all chemicals into the mortar by using the wet gum method, the mixing is stirred vigorously by using pestle to produce the emulsion.

The formed emulsion is inserted into the electronic balance carefully to avoid spilling

The formed emulsion is weighed to get 40g for the homogenization process with the use of magnetic stirrer.

The weighed emulsion is filled into a test tube with closure. The closed test tube is to prevent spilling of emulsion when it is put on the magnetic stirrer.

The test tube is held tightly when the magnetic stirrer is operated. It is not stable to let the test tube stands on the magnetic stirrer without holder.

Product of emulsion looked more uniform in dispersion after using magnetic stirrer.

The products of emulsion formed into distinct layers after centrifugation.

Two glass slides containing emulsion (before and after centrifugation) are prepared to be observed under the microscope. The observation on the emulsion particles are illustrated in the form of drawings and compared based on their texture, consistency, dispersion, oil degree and globule sizes.

The lab assistant shows the right method to operate the viscometer. There are several steps to be conducted in order to take the actual reading of the viscosity of the emulsions. There is an error of reading if the steps were not followed.