Chapter No.3 Experimental Setup

13

CHAPTER # 3

Experimental Setup

3.1) Raw Materials

The raw materials needed for the production of Ethyl Benzoate which is a base

component for production of Hydraulic Brake Fluid on laboratory scale are as follows,

1. Ethanol

2. Benzoic Acid

3. Sulfuric Acid (Concentrated)

4. Sodium Carbonate (Solution)

5. Ether (di-ethyl ether)

3.1.1) Ethanol

Ethanol, also known as ethyl alcohol, alcohol,

Methylcarbinol, grain alcohol, Ethyl hydroxide, Ethyl hydrate,

Algrain, Anhydrol, Tecsol, is a volatile, flammable, colorless

liquid with the structural formula CH3CH2OH, often abbreviated

as C2H5OH or C2H6O. Ethanol is a psychoactive drug and is one

of the oldest recreational drugs still used by humans. Ethanol

can cause alcohol intoxication when consumed. Best known as

the type of alcohol found in alcoholic beverages, it is also used

in thermometers, as a solvent, and as a fuel. In common usage, it

is often referred to simply as alcohol or spirits.

3.1.1.1) Production of Ethanol

Ethanol is produced both as a petrochemical, through the hydration of ethylene

and, via biological processes, by fermenting sugars with yeast. The economics of process

depends on prevailing prices of petroleum and grain feed stocks.

Ethanol for use as an industrial feedstock or solvent is made

from petrochemical feed stocks, primarily by the acid-catalyzed hydration of ethylene,

represented by the chemical equation

C2H4 + H2 3CH2OH

Fig 3.1 Ethanol

Chapter No.3 Experimental Setup

14

The catalyst is most commonly phosphoric acid, adsorbed onto a porous support

such as silica gel or diatomaceous earth. This catalyst was first used for large-scale

ethanol production by the Shell Oil Company in 1947. The reaction is carried out with

an excess of high pressure steam at 300 C (572 F).

Ethanol for use in alcoholic beverages, and the vast majority of ethanol for use as

fuel, is produced by fermentation. When certain species of yeast metabolize sugar in

reduced-oxygen conditions they produce ethanol and carbon dioxide. The chemical

equations below summarize the conversion:

C6H12O6 2 CH3CH2OH + 2 CO2

C12H22O11 + H2 3CH2OH + 4 CO2

Fermentation is the process of culturing yeast under favorable thermal conditions

to produce alcohol. This process is carried out at around 35 40 C (95 104 F).

Toxicity of ethanol to yeast limits the ethanol concentration obtainable by brewing;

higher concentrations, therefore, are usually obtained by fortification or distillation.

3.1.1.2) Physical and Chemical Properties of Ethanol

Sr. # Properties

1 Appearance Colorless

2 Density 0.789 g/cm3 (at 20oC)

3 Flash Point -5oF

4 Water Solubility Completely Soluble

5 Flammable Range (LEL UEL) 3.3% 19%

6 Flash Point 48 oF

7 Ignition Temperature 793oF

8 Melting Point −173 oF

9 Boiling Point 173oF

10 Vapor Density 1.49

11 Vapor Pressure 44 mmHg

Chapter No.3 Experimental Setup

15

3.1.2) Benzoic Acid

Benzoic Acid is also known as Dracylic acid, Benzene formic acid,

Carboxybenzene, benzene carboxylic acid, with formula C7H6O2 (or C6H5COOH), is a

colorless crystalline solid and a simple aromatic carboxylic acid. The name is derived

from gum benzoin, which was for a long time the only source for benzoic acid. Its salts

are used as food preservatives and benzoic acid is an important precursor for the

synthesis of many other organic substances. The salts and esters of benzoic acid are

known as benzoates.

3.1.2.1) Production of Benzoic Acid

Benzoic acid is produced commercially by partial

oxidation of toluene with oxygen. The process is catalyzed

by cobalt or manganese naphthenates. The process uses cheap raw materials, and

proceeds in high yield.

U.S. production capacity is estimated to be 126,000 tones per year (139,000

tons), much of which is consumed domestically to prepare other industrial chemicals.

Fig 3.2 Benzoic Acid

Chapter No.3 Experimental Setup

16

Benzoic acid is cheap and readily available, so the laboratory synthesis of benzoic

acid is mainly practiced for its pedagogical value. It is a common undergraduate

preparation. Benzoic acid can be purified by re-crystallization from water because of its

high solubility in hot water and poor solubility in cold water. The avoidance of organic

solvents for the re-crystallization makes this experiment particularly safe.

3.1.2.2) Physical and Chemical Properties of Ethanol

Sr. # Properties

1 Appearance

colorless crystalline solid

2 Odor Faint, pleasant odor

3 Density 1.2659 g/cm3

4 Water Solubility 2.9 g/L

5 Vapor pressure 0.001 hPa

6 Flash Point 250.7 oF

7 Auto ignition Temperature 1058 oF

8 Melting Point 252.34 oF

9 Boiling Point 480.6 oF

10 Refractive index 1.539

11 Viscosity 1.26 mPa

3.1.3) Sulfuric Acid

Sulfuric acid is a strong mineral acid with the molecular formula H2SO

4. It is

soluble in water at all concentrations. When it is mixed with water, a very exothermic

reaction occurs and the energy released can be enough to heat the mixture to boiling.

Therefore, concentrated sulfuric acid must be diluted by adding slowly to cold water

while the mixture is stirred to dissipate the heat. Sulfuric acid has many applications,

and is one of the top products of the chemical industry. Principal uses include lead-acid

batteries for cars and other vehicles, ore processing, fertilizer manufacturing, oil

refining, wastewater processing, and chemical synthesis. About 65% of sulfuric acid

produced annually is used in the production of agricultural fertilizers.

3.1.3.1) Production of Sulfuric Acid

Sulfuric acid is produced from sulfur, oxygen and water via the conventional

contact process.

Chapter No.3 Experimental Setup

17

Contact process:

In the first step, sulfur is burned to produce sulfur dioxide.

S (s) + O2 (g) SO2 (g)

This is then oxidized to sulfur trioxide using oxygen in the presence of a vanadium (V)

oxide catalyst. This reaction is reversible and the formation of the sulfur trioxide is

exothermic.

2 SO2 (g) + O2 (g) 2 SO3

The sulfur trioxide is absorbed into 97 98% H2SO4 to form oleum (H2S2O7), also

known as fuming sulfuric acid. The oleum is then diluted with water to form

concentrated sulfuric acid.

H2SO4 (l) + SO3 H2S2O7 (l)

H2S2O7 (l) + H2O H2SO4 (l)

Note that directly dissolving SO3 in water is not practical due to the

highly exothermic nature of the reaction between sulfur trioxide and water. The reaction

forms a corrosive aerosol that is very difficult to separate, instead of a liquid.

SO3 (g) + H2O H2SO4 (l)

3.1.3.2) Properties of Sulfuric Acid

Sr. # Properties

1 Molecular formula

H2SO

4

2 Molar mass 98.086 g/mol

3 Appearance Clear, colorless, odorless liquid

4 Density 1.84 g/cm3, liquid

5 Melting point 10 oC, 283 K, 50 oF

6 Boiling point 337 oC, 610 K, 639 oF

7 Solubility in water miscible

8 Acidity (pKa) -31.99

9 Viscosity 26.7 cP (20 oC)

10 Flash point Non-flammable

Chapter No.3 Experimental Setup

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3.1.4) Sodium Carbonate

Sodium carbonate (also known as washing soda, soda ash and soda crystals),

Na2CO3, is a sodium salt of carbonic acid (soluble in water). It most commonly occurs as

a crystalline hepta-hydrate, which readily effloresces to form a white powder, the

monohydrate. Pure sodium carbonate is a white, odorless powder that absorbs moisture

from the air, has an alkaline taste, and forms a strongly alkaline water solution. Sodium

carbonate is domestically well known for its everyday use as a water softener.

3.1.4.1) Production of Sodium Carbonate

a) Mining:

Trona, trisodium hydrogendicarbonate dihydrate (Na3HCO3CO3 2O), is mined

in several areas of the US and provides nearly all the domestic consumption of sodium

carbonate. Large natural deposits found in 1938, such as the one near Green River,

Wyoming, have made mining more economical than industrial production in North

America. There are important reserves of Trona in Turkey; two million tons of soda ash

has been extracted from the reserves near Ankara. It is also mined from some alkaline

lakes such as Lake Magadi in Kenya by dredging. Hot saline springs continuously

replenish salt in the lake so that, provided the rate of dredging is no greater than the

replenishment rate, the source is fully sustainable.

b) Leblanc process:

In 1791, the French chemist Nicolas Leblanc patented a process for producing

sodium carbonate from salt, sulfuric acid, limestone, and coal. First, sea salt (sodium

chloride) was boiled in sulfuric acid to yield sodium sulfate and hydrogen chloride gas,

according to the chemical equation

2 NaCl + H2SO4 Na2SO4 + 2 HCl

Next, the sodium sulfate was blended with crushed limestone (calcium carbonate) and

coal, and the mixture was burnt, producing calcium sulfide.

Na2SO4 + CaCO3 + 2 C Na2CO3 + 2 CO2 + CaS

The sodium carbonate was extracted from the ashes with water, and then collected by

allowing the water to evaporate.

The hydrochloric acid produced by the Leblanc process was a major source of air

pollution, and the calcium sulfide byproduct also presented waste disposal issues.

Solvay process:

Chapter No.3 Experimental Setup

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In 1861, the Belgian industrial chemist Ernest Solvay developed a method to

convert sodium chloride to sodium carbonate using ammonia. The Solvay

process centered around a large hollow tower. At the bottom, calcium carbonate

(limestone) was heated to release carbon dioxide:

CaCO3 CaO + CO2

At the top, a concentrated solution of sodium chloride and ammonia entered the tower.

As the carbon dioxide bubbled up through it, sodium bicarbonate precipitated:

NaCl + NH3 + CO2 + H2O NaHCO3 + NH4Cl

The sodium bicarbonate was then converted to sodium carbonate by heating it, releasing

water and carbon dioxide:

2 NaHCO3 Na2CO3 + H2O + CO2

Meanwhile, the ammonia was regenerated from the ammonium chloride byproduct by

treating it with the lime (calcium hydroxide) left over from carbon dioxide generation:

CaO + H2O Ca(OH)2

Ca(OH)2 + 2 NH4Cl CaCl2 + 2 NH3 + 2 H2O

Because the Solvay process recycles its ammonia, it consumes only brine and limestone,

and has calcium chloride as its only waste product. This made it substantially more

economical than the Leblanc process, and it soon came to dominate world sodium

carbonate production.

c) Hou's process:

Developed by Chinese chemist Hou Debang in 1930s. The earlier steam

reforming byproduct carbon dioxide was pumped through a saturated solution of sodium

chloride and ammonia to produce sodium bicarbonate via the following reactions:

NH3 + CO2 + H2O NH4HCO3

NH4HCO3 + NaCl NH4Cl + NaHCO3

The sodium bicarbonate was collected as a precipitate due to its low solubility and then

heated to yield pure sodium carbonate similar to last step of the Solvay.

Chapter No.3 Experimental Setup

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3.1.4.2) Properties of Sodium Carbonate

Sr. # Properties

1 Molecular formula Na2CO3

2 Molar mass

105.9885 g/mol (anhydrous)

124.00 g/mol (monohydrate)

286.14 g/mol (decahydrate)

3 Appearance White solid, hygroscopic

4 Density

2.54 g/cm3 (anhydrous)

2.25 g/cm3 (monohydrate)

1.51 g/cm3 (heptahydrate)

1.46 g/cm3 (decahydrate)

5 Melting point

6 Boiling point 1633 OC (anhydrous)

7 Solubility in water

8 Basicity (pKb) 3.67

9 Refractive index

1.485 (anhydrous)

1.420 (monohydrate)

1.405 (decahydrate)

3.1.5) Di-ethyl Ether

Diethyl ether, also known as ethyl ether, sulfuric ether, simply ether,

or ethoxyethane, is an organic compound in the ether class with the formula (C2H5)2O.

It is a colorless, highly volatile flammable liquid. It is commonly used as a solvent and

was once used as a general anesthetic. It has narcotic properties and has been known to

cause temporary psychological addiction, sometimes referred to as etheromania.

Chapter No.3 Experimental Setup

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3.1.5.1) Production of Di-ethyl Ether

Most diethyl ether is produced as a byproduct of the vapor-

phase hydration of ethylene to make ethanol. This process uses solid-

supported phosphoric acid catalysts and can be adjusted to make more ether if the need

arises. Vapor-phase dehydration of ethanol over some alumina catalysts can give diethyl

ether yields of up to 95%.

Diethyl ether can be prepared both in laboratories and on an industrial scale by

the acid ether synthesis.[23] Ethanol is mixed with a strong acid, typically sulfuric acid,

H2SO4. The acid dissociates in the aqueous environment producing hydronium ions, H3O+.

A hydrogen ion protonates the electronegative oxygen atom of the ethanol, giving the

ethanol molecule a positive charge:

CH3CH2OH + H3O+ 3CH2OH2+ + H2O

A nucleophilic oxygen atom of unprotonated ethanol displaces a water molecule

from the protonated (electrophilic) ethanol molecule, producing water, a hydrogen ion

and diethyl ether.

CH3CH2OH2+ + CH3CH2 2O + H+ + CH3CH2OCH2CH3

This reaction must be carried out at temperatures lower than 150 C in order to

ensure that an elimination product (ethylene) is not a product of the reaction. At higher

temperatures, ethanol will dehydrate to form ethylene. The reaction to make diethyl

ether is reversible, so eventually an equilibrium between reactants and products is

achieved. Getting a good yield of ether requires that ether be distilled out of the reaction

mixture before it reverts to ethanol, taking advantage of Le Chatelier's principle.

3.1.5.2) Properties of Di-ethyl Ether

Sr. # Properties

1 Molecular formula C4H10O

2 Molar mass 74.12 g mol−1

3 Appearance Colorless liquid

4 Density 0.7134 g/cm3, liquid

5 Melting point −116.3 oC, 156.9 K, −177.3 oF

Chapter No.3 Experimental Setup

22

6 Boiling point 34.6 oC, 307.8 K, 94.3 oF

7 Solubility in water 69 g/L (20 oC)

8 Viscosity 0.224 cP (25 oC)

9 Refractive index 1.353

10 Flash point −45 oC

11 Auto ignition temperature 160 oC

12 Explosive limits 1.9-48.0%

3.2) Experimental Work

3.2.1) Safety

Wear eye protection.

Protective gloves should be worn when handling acids and ether.

Proper ventilation should be provided in the laboratory.

Ether is highly flammable, keep away from ignition sources.

Concentrated sulfuric acid is very corrosive dense liquid, dehydrating agent, add

very slowly by continuously cooling the flask with water.

Do not empty the byproducts and unreacted chemicals into drains.

3.2.2) Preparation of Brake Fluid

3.2.2.1) Introduction

Brake fluids transmit the pressure on the brake pedal of a vehicle to the brake

shoes or pads, which rub on the wheels and slow them down. The fluids must withstand

high pressures without being compressed: air bubbles and vapors prevent this. They

need a high boiling point because heat is produced when the brakes are applied. The

fluid must also be chemically unreactive. It has been found that certain esters meet these

requirements best and industry uses esters from a glycol and boric acid. An ester is

formed when an alcohol and an acid react.

Chapter No.3 Experimental Setup

23

3.2.2.2) Preparation of an Ester

This experiment is to prepare an ester, ethyl benzoate, from ethanol and benzoic

acid, and then to purify it. The reaction involved is slow and needs heat to get it working

quickly. The reaction, which is reversible, i.e. it will go either way, is:

ACID + ALCOHOL ESTER + WATER

To stop it reforming the acid and the alcohol, the water is removed with

concentrated sulphuric acid. To enable the reaction to be heated for a long time and the

liquid not to be lost, a condenser is placed over the boiling liquid so that the vapors is

cooled and returned to the flask.

Measured 100 cm3 of ethanol into a flask.

Slowly and carefully added 12 cm3 of concentrated sulphuric acid, cooling the

flask as this is being done by placing it under a running tap.

Weighed 28 g of benzoic acid and added to the flask.

Arranged the apparatus as shown in Figure 1 and heated the flask over gauze so

that it boils gently.

Figure 3.3: Heating the mixture under reflux

Chapter No.3 Experimental Setup

24

Adjusted the flow of water in the condenser so that no vapors appear above half

way in the tube.

Heated the flask for an hour, and then left for five minutes with the water running

in the condenser to cool down the vapors.

Rearranged the equipment as shown in Figure 2, and then heated the water

gently.

condensed and then collected.

Kept heating the water until there was no boiling in the flask: then all the

unchanged ethanol has been removed.

Fig 3.4 Distilling to collect the low boiling liquid

Chapter No.3 Experimental Setup

25

To remove any unchanged benzoic acid, added a solution of sodium carbonate in

water containing 8 g in 100cm3 until the liquid has a pH of 8 (test with universal

indicator paper).

This changed the benzoic acid into sodium benzoate. The ethyl benzoate was

separated from this by using the fact that ethyl benzoate dissolves in ether and

sodium benzoate does not.

Poured the liquid into a separating funnel, added 40 cm3 of ether, stoppered the

funnel and shook for five minutes, removing the stopper occasionally.

Left to settle, and then separated the two layers by pouring off the bottom layer.

Collected the two layers, running the ether layer into a clean, dry flask. Added a

further 10 cm3 of ether to the other liquid and repeated the operation. Add this ether

layer to the original ether in the flask.

To obtain the ethyl benzoate from this solution, distilled off the ether using the

equipment shown in Figure 2.

The ether boils well below the boiling point of water and is condensed and collected

in the tube. This enables the ether to be recollected so that it can be used again. This

recovery of the solvent is very important in industry where solvents are used a lot

and much money can be saved by their recovery.

When all the ether had been boiled off, removed the beaker of water and placed a

tripod and gauze under the flask. Heated strongly with a Bunsen and collected the

liquid boiling at between 200

benzoate which can be used in the tests for suitability as a brake fluid described in

next section.

3.2.3) Tests on Brake Fluid

3.2.3.1) Introduction

To find if a liquid will work well as a brake fluid, its properties must be tested. A

brake fluid should:

a) have a high boiling point;

Chapter No.3 Experimental Setup

26

b) b) be tolerant to water mixing;

c) give suitable flow rates over a wide temperature change: the liquid must not be

syrupy (viscous) at low temperatures but must not get too thin at high

temperatures, otherwise it will not lubricate the brake shoes or act as a seal;

d) have no effect on rubber or plastic seals;

e) assist metals to resist corrosion;

f) be resistant to chemical change at high temperatures;

g) provide good lubrication for moving parts in the system;

h) mix with other brake fluids;

i) Not lose much volume by evaporation in working.

Industry needs to test all fluids used in braking systems to make sure that they are

up to standard in each of these respects. Below are some experiments which were carried

out in the laboratory to test whether the above properties are present.

3.2.3.2) Finding the Boiling Point

Apparatus and chemicals required

Round-bottomed flask

Liebig condenser

Thermometer

Bunsen burner

Stand and clamp

Anti-bumping granules

The boiling point of a liquid can be found in the laboratory by following way. The

method involves setting up the equipment as shown in Figure below.

The best way to heat the flask is to use a variac-controlled heating mantle that

fits the flask. However, a Bunsen burner can be used, and the flame was adjusted to give

a constant boiling rate to the liquid. The liquid was heated until it boil, with a condenser

liquid flowing at a rate to keep the vapors condensing and refluxing (the condensed

liquid falls back into the original liquid). Adjusted the heat so that the liquid boil gently

and refluxes at a rate of two to four drops per second. Left for five minutes to allow the

condition to settle, and then taken the temperature reading every 30 seconds for two

minutes and the average result was used.

Chapter No.3 Experimental Setup

27

Fig 3.5: Boiling Point Measurement

3.2.3.3) Tolerance to water mixing

In normal use, brake fluids absorb small amounts of water which percolate in

from the surroundings through the brake hoses. This can affect the ability of the fluid to

operate at low temperatures as ice may form in the pipes, blocking the system, and can

lower the boiling point of the fluid, causing vapors to form in the brakes. The effect of

water on the boiling point of a typical brake fluid is shown in the graph in figure.

Figure 4: Effect of moisture on boiling point of Brake Fluid

Chapter No.3 Experimental Setup

28

Apparatus and chemicals required

Measuring cylinder 250 cm3

Flask 250 cm3

Syringe 10cm3

Sample tube (2)

Beaker 250 cm3

Fluids to test

A sample of the test fluid can be contaminated with about 3 per cent water by

measuring 200 ml of the fluid in a measuring cylinder and pouring it into a flask, then

adding 6 ml of water from a syringe and shaking the flask for several minutes. This

mixture can then be used for the following tests. Filled a small sample tube with the

mixture, sealed it and left it in a freezer overnight.

Tested the fluid for transparency and clearness by placing the tube over a piece of

graph paper and observing the lines through it. Examined the liquid for traces of solid,

turning it over several times. Another sample tube was taken and filled with liquid and

to allow the liquid to reach

60 oC, then performed the same tests.

3.2.3.4) Viscosity

Apparatus and chemicals required

Glass tube (0.5m long, about 0.5 cm diameter)

Stopper to fit tube (2)

Water bath to fit tube

Fluids to test

A glass tube about 0.5 m long was taken, sealed at the bottom, and filled to within

10 cm of the top with the fluid under test. Stoppered the top, then turned the tube upside

down and found the time needed for the air bubble to travel the length of the tube. Left

the tube in a freezer for half an hour, then repeated the experiment. Placed the tube in

quicker the bubble travels through the tube, the lower the viscosity of the liquid. For a

successful brake fluid, the viscosity should remain constant over a large temperature

range.

Chapter No.3 Experimental Setup

29

Another experiment that can be used to measure the flow of a fluid is to take a glass

tube 2 m long and about 2 cm internal diameter, fill it with the liquid under test, then

drop a ball bearing down the tube. Find the time it takes for the ball bearing to reach the

bottom of the tube. This can be tried at different temperatures and using different liquids

to compare their viscosity.

3.2.3.5) Effect on Rubber and Plastic Caps

Apparatus and chemicals required

Rubber sheet

Polypropene sheet

Cork borer

Micrometer screw gauge

Magnifying glass

Brake fluid

Isopropanol

Using a cork borer, cut two pieces of rubber sheet about 2 cm in diameter. Two pieces

of Polypropene about the same size were taken. Measured the diameter of each of the

four pieces using a micrometer gauge. Placed one piece of rubber and one piece of

Polypropene in the fluid under test and left for a week at room temperature. After a

week, removed the rubber and Polypropene from the fluid. Held the pieces with tweezers

and cleaned by rinsing in isopropanol, then dried in warm air. Measured the diameter of

the pieces under test within fifteen minutes of removing them from the fluid. Using a

magnifying glass, examined the surfaces for blistering, pitting, or other signs of

disintegration. Compared these samples with the control samples which were not soaked

in fluid. The fluid should not cause corrosion of any sort or cause the material to expand

by more than 5 per cent.

3.2.3.6) Effect on Metals

Apparatus and chemicals required

Samples of:

Aluminum

Brass

Copper

Chapter No.3 Experimental Setup

30

Cast iron

Tinned iron

Steel

Tin cutters

Emery cloth

Isopropanol

Beaker 250 cm3

Tweezers

Brake fluid

Access to balance

A brake fluid must not corrode the metals with which it comes into contact. These

metals may include cast iron, steel, tinned iron (tin plate), aluminum, brass, and copper.

To test this, strips of each metal were suspended in the fluid. The strips were prepared

by cutting pieces about 7 cm long and 1.8 cm across and making a small hole near one

end. The strips can be cleaned with emery cloth and then were washed in isopropanol.

Each strip was then handled only with tweezers. Weighed each piece accurately and

noted the weight. Assembled the metal strips on a steel nail in the order tinned iron,

steel, aluminum, cast iron, brass, and copper, ensuring a gap at the top by bending the

strips slightly. Washed again in isopropanol to remove all dirt. Placed the metal strip

assembly in a beaker and poured sufficient liquid to cover by about 1 cm.

the strips to cool in the fluid at room temperature for an hour. Using tweezers removed

the strips from the fluid; examine the strips for sediment and shook them to remove any

sediment which might be present. Cleaned each strip by rubbing with a cloth soaked in

isopropanol. Inspected each strip with a magnifying glass for signs of pitting and

corrosion. Weighed each strip and found the differences in weight compared with the

original weight. Found the weight loss per unit surface area of the metal (remember

there are two sides to each plate). This is given by the formula:

Weight loss/unit surface area = Weight loss (mg)/Surface area (cm3)

Chapter No.3 Experimental Setup

31

3.2.3.7) Compatibility with other Brake Fluids

Apparatus and chemicals required Measuring cylinder 100 cm3

Beaker 250 cm3

Sample tube

Brake fluid

Ester

Used a standard commercial brake fluid supplied in the lab for the following test.

Mixed 50 ml of the fluid under test with 50 ml of the commercial fluid in a 100 ml

measuring cylinder. Mixed the fluid well in a beaker and examined for any solid

deposited and any layers forming. Poured into a sample tube, and then inspected a piece

of graph paper through it to test for deformation of the lines. Placed the sample tube in

the freezer for at least one hour, then repeated the test. Placed in boiling water for fifteen

minutes and carried out the test again. These activities test the compatibility of the fluids

at different temperatures.

3.2.3.8) Loss of Fluid by Evaporation

Apparatus and chemicals required Petri dish

Fluid

Access to balance

It is important that a brake fluid maintains its volume under working conditions or

an air lock may develop, reducing the efficiency of the system and making the brakes

'spongy'. The amount of evaporation in a closed system can be found by weighing an

empty glass Petri dish with its lid on, adding 25 ml of fluid from a measuring cylinder

and then weighing again. The weight of fluid in the dish can then be calculated. Placed

left to cool at room temperature and weighed the dish again. Found the loss of weight

of the fluid and expressed it as a percentage of the original. This can be repeated for

each fluid.

% loss of weight = loose of weight / original weight

Chapter No.3 Experimental Setup

32

3.2.3.9) Lubricant

The lubricant properties of a fluid are related to its viscosity. If the fluid is too

thin, it runs off too easily; if it is too viscous, it offers resistance to movement and also

lessens its ability not to corrode the metals involved in the movement.

3.2.3.9) pH Value

It is important that a brake fluid should not produce an acid reaction with the

materials with which it comes into contact. The acceptable range for the pH of a brake

fluid is between 7 and 11.5.

To find the pH of the fluids under test, mixed 25 ml with 25 ml of a mixture of

80 per cent ethanol and 20 per cent water, which had been neutralized to a pH of 7.

Determined the pH of the resulting solution by using universal indicator solution or a

pH meter with a calibrated electrode.