Surface tension determination with the maximum differential pressure method Wang Zengbao 2012.11...

Surface tension determination with the maximum differential

pressure method

Wang Zengbao

2012.11

EXPERIMENT 1

1. Experimental purposes

(1)Master the principles and methods of maximum

differential pressure method for the determination of

surface tension.

(2)Measure the surface tension of n-butyl alcohol solution,

and understand the concept of surface tension and

influencing factors.

(3)Learn Gibbs equation and its applications.

2. Experimental principles

Polyacrylamide can be synthesized from acrylamide triggered by ammonium persulfate:

Polyacrylamide can hydrolyze in alkaline solution, which generates partially hydrolyzed polyacrylamide:

nCH2 CH

CONH2

(NH4)2S2O8 [CH2 CH]n

CONH2

[CH2 CH]n

CONH2

+ yH2O + zNaOH

[CH2 CH]x

CONH2

[CH2 CH]y

COOH

[CH2 CH]z

COONa

+ (y + z)NH3

R

P

P

R

P

2

1

2

1

11

2p

r

22

2p

r

22 1

1

p

p

（ 1 ）

RP

2

P

R

—The additional pressure which is formed when the water drops down in the wide mouth bottle

—The curvature radius of the bubble

—The surface tension （ N/m ）


11

2p

r

22

2p

r

22 1

1

p

p

Therefore, at the same temperature, once the ΔP1, ΔP2 are measured, and t

he IFT of the liquid(water) whose IFT is known is found out according to the

temperature table,then we can calculate the IFT of the unknown liquid from

the formula 。

（ 1 ）

RP

2


3.Apparatus and reagents

Apparatus One set of device to measure the IFT with the metho

d of maximum differential pressure,Bottle, rubber pipette bulb.

Reagents N-butyl alcohol (analytically pure), distilled water.

4.Experimental procedures

(1)Wash the external case and the capillary tube of the instrument used to measure surface tension with lotion. First add a little lotion into the external case,rotation it inclined so that the lotion can contact with the external case(be careful not to let the lotion outflow from the side of the tube).Then insert the capillary tube and maintain the inclined external case still.Rotate the capillary tube to make the lotion contact with the capillary tube.Adsorb some lotion with the rubber pipette bulb to the capillary tube to wash the inside of the capillary tube.Pull the spent lotion to its original bottle and wash the external case and the capillary tube with running water fully.Finally,wash the external case and the capillary tube with distilled water three times respectively.Then we can go on with the following experiences.


(2)Put some distilled water into the external case(regard as liquid of known IFT. See Appendix II to get its surface tension).Insert the capillary tube into the external case and plug the plug tightly and let the tip of the capillary tube touch the liquid surface exactly.Read out the zero level h0 of the tube beneath the inclined tube manometer(At this point both ends of the inclined tube manometer connect with the atmosphere).Install the device according to figure2-1,where the separatory funnel is filled with tap water..


(3)Open the piston of the separatory funnel to let the water in it drip slowly into the wild-mouth bottle.Then the pressure inside the bottle increase gradually and bubbles will pass through the end of the capillary tube.

Read out the highest level h1 from the inclined tube manometer when the first bubble pass through it.Repeat the same procedures three times and calculate the average value h2.


(4)Drain the distilled after the maximum differential pressure has been measured.Wash the external case and the capillary tube once with butanol with the concentration of 0.002mol/L.Then add the solution and measure its maximum differential pressure just like the distilled water.Measure the maximum differential pressure of the butanol solution with the concentration of 0.05,0.10,0.15,0.20,0.25,0.30,0.35mol/L .

(Note: every time the solution is changed, we should use the Pending liquid to wash the external case and the capillary tube)

(5) Record the experimental temperature.

(1)Isolate the surface tension of distilled water at experime

ntal temperature from the appendix.

(2)Calculate the surface tension of solution with different c

oncentration of normal butyl alcohol by (3)Using surface tension as vertical ordinate,concentration

as horizontal scale,draw the б-c figure of nomal butyl alcohol solution on the coordinate paper.

(4)Select some points from theб-c figure and draw the tangents of different concentration curve .Then calculate the surface adsorptive capacity according to the Gibbs equation ;and draw the isothermal adsorption curve of nomal butyl alcohol solution

5.Experimental results processing

21

22

p

p

6.Questions

(1)During experiment ,if the capillary insert the liquid su

rface by 1mm ,how much error will bring about?

(2)During experiment ,why do we slow the barbotage ?

(3)During experiment,why do we measure the surface ten

sion of different concentration solution from from low to

high.

Preparation and electrophoresis of

colloids

Wang Zengbao

2011.4

EXPERIMENT 3

1. Experiment purposes

（ 1 ） Learn the basic principles of preparation

of sol (colloid), and master the main methods of pre

paration sol;

（ 2 ） Mensurate the electrokinetic potential of

AgI (silver iodide) sol by measuring the movement

of interface.

2. Experiment principles

Colloidal sol is a highly dispersed system with solid of very small solubility dispersing in liquid. Its diameter changes in the range of 10-7 to 10-9 meter.

The formation of stable colloidal material involves two facets: the dimension of the dispersed phase within the colloidal range; the particles dispersed in liquid should not aggregate, so stabilizing agent usually added.Basically, the preparations of colloidal systems involve either degradation of bulk matter or aggregation of small molecules, ions or particles.

Electrophoresis of colloids Under an external electric field the colloidal particles movi

ng to the positive electrode or negative electrode, this phenomena is called electrophoresis.

Electrophoretic potential can be measured by electrophoresis through two methods: microscopic method and macroscopic method.



Apparatus Electrophoresis apparatus; Electrophoresis tube;

Stopwatch; Pt electrode, 2; 100mL Beaker, 3; Plastic head dropper ,2;25mL Graduated flask, 2 , and so on.

Reagents Silver nitrate solution (0.01mol/L); Potassium

iodide solution (0.01mol/L); Potassium chloride solution (0.005mol/L)

Preparation of AgI negative solution 20mL 0.01mol/L KI (Potassium iodide) solution is

added to a 100mL beaker, 18.7mL 0.01mol/L AgNO3 (Silver nitrate ) solution is dropwise added to th

e beaker under stirring, AgI negative colloid is prepared.

4.Experiment procedures

Determination of potential (1) The electrophoresis apparatus should be washed clean (2) Fixed the electrophoresis apparatus vertically on the iron sup

port stand (3)Close the piston, Add colloid through the funnel with plastic

head dropper (4) Assistant solution is added into the U-tube (5) Open the piston slowly, when colloid up to 0-tick ， close the

piston (6)Gently insert two electrodes, immerge assistant solution 1cm (7)Push the electrophoresis apparatus’s “start” button, and rec

ord the time that the interface rising 0.5, 1.0, 1.5 cm cost with a stopwatch.

(8)Turn off the power, measured the distance of two electrodes by a ruler. Wash the apparatus


（ 1 ） Summarize the method of preparation

of colloid;

（ 2 ） Calculate ξ potential of AgI negative col

loid.

5.Experiment results processing

6.Questions

（ 1 ） What are the similarities and differences among different preparation methods?

（ 2 ） Why must the conductivity of the assistant solution be equal to that of the colloid? What is the function of that for calculating the potential?

（ 3 ） What are the reasons that cause the color, definition and moving speed differences between the rising interface and declining interface?

（ 4 ） What are removed through dialysis of Fe (OH)3? Is there any way to detect degree of purification? Is it to remove all the ions dispersed in the solution during dialysis?

Coagulation of Inorganic Electrolyte and Flocculation of High Molecule Polymer

Geng Jie

2012.11

EXPERIMENT 4

1. Experiment purposes

(1) Master principle and method of sol

coagulation.

(2) Verify coagulation symbol and valence number

rule of electrolyte.

(3) Understand the flocculation of the water-

soluble polymer to the sol.

2. Experiment principles

(1) Coagulation of inorganic electrolyte

The entire process that the sol losses coagulation stability and then losses dynamic stability is called coagulation. The sol can be caused to coagulate by electrolyte. The reason is that the electrolyte can decrease ξ potential of sol, and the higher electrolyte concentration, the lowerξpotential is. When theξpotential drops to a certain value, the sol will lose coagulation stability, and then will occur coagulation.The higher ion valence number of opposite sign, the greater coagulation ability of electrolyte is. This is consistent with SchlZe--Hardy Rules. M+:M2+:M3+ ＝（ 25 ～ 150 ）∶（ 0.5 ～ 2 ）∶（ 0.01 ～0.1 ）

The mutual coagulation phenomenon is that mixing the

two sols with the opposite electric charge can also cause

coagulation. There are usually two mechanisms.

Electric nature neutralization about two kinds of sol

particles of opposite electric charge.

A sol with high counter-ion of opposite electric charge sol.


(2) Mutual coagulation phenomena

When the concentration of polymer is very low, main manifestation of polymer is flocculation for sol. Flocculation is created due to "bridging" of polymer to sol particles. "Bridging" theory: When the concentration of polymer is very low, polymer chains can be absorbed on several colloidal particles at the same time. Several particles join together through "bridging". Due to rotation and vibration of polymer chains, colloidal particles join together and subside.


(3) Flocculation of high polymer

3. Instruments and Chemicals

Instruments 722 spectrophotometer, 100mL conical flask, 10mL

micro-burette, 5mL pipette, 10mL pipette, 10mL test tube, 20mL test tube, 50mL plug graduated cylinder, 50mL beaker, 100mL beaker.

Chemicals 0.01mol/L KCl, 0.001mol/L K2SO4, 0.001mol/L K3(C

OO)3C3H4OH, Fe(OH)3 sol ， clay sol.

(1) Coagulation of electrolyte to sol

In the three clean, dry 100mL conical flasks, add

10mL Fe (OH)3 sol with pipette respectively. Then

instill electrolyte solution listed in Table 4-1 with

micro-burette respectively, and add each drop with

fully oscillation. Sol does not appear roily at least one

minute before adding the second. Record the volume

of electrolyte solution when just appear roily, and list

in Table 4-1.



Table4-1 coagulation record about different electrolytes to sol

Fe(OH)3 sol

electrolyte concentration of electrolyte solution(mol/L)

volume of all electrolyte solution(mL)

coagulation value

(mmol/L)

KCl

K2SO4

K3(COO)3

C3H4OH

(2) Mutual coagulation between clay sol and Fe(OH)3 sol

Take six dry test tubes, and add the amount of Fe (OH)3 sol

according to Table 4-2 in each test tube. Then add the clay

sol in all test tubes, so that the total volume of the sol is 6mL

in each test tube. Shake each test tube, rest 10 minutes, and

record the coagulation phenomena of each test tube.



Table4-2 the record sheet about mutual coagulation of sols

test tube number

1 2 3 4 5 6

Fe(OH)3 sol

0.1 0.5 1 3 5 5.5

clay sol 5.9 5.5 5 3 1 0.5

coagulation phenomena


Take three 50mL plug graduated cylinder with similar internal di

ameter, respectively add 30mL clay sol with pipette, respectively a

dd the 0.02% partially hydrolyzed polyacrylamide (HPAM) soluti

on of 2×106 molecular weight 2drops 10drops and 40drops and f﹑ro turn 10 times, rest 2 minutes, draw 5mL solution at 2cm depart

ment under the surface, with 722 spectrophotometer (the Appendi

x eight), at the wavelength of 420nm, measure optical density with

the distilled water as blank, and fill the data into Table 4-3.



Table4-3 the record sheet of flocculation about HPAM to clay sol

clay sol 30 mL 30 mL 30 mL 30 mL

HPAM 0.02 ％ 0 2d 10d 40d

C% system concentration of HPAM ( ％ )

T (T=I/I0)

D (D=-LogT)

Ar (Ar=D/D0)

*Ar is the ratio of sol optical density with HPAM and without HPAM. If Ar=1, that is not complete flocculation and if Ar = 0, that is complete flocculation. So Ar can show the degree of flocculation.


In this study, the volume of HPAM added is not fixed, only for

reference. Because the best flocculated concentration change with

the molecular weight of HPAM, degree of hydrolysis, the sol

concentration and preparative conditions. Therefore, the amount

of HPAM added can make appropriate changes based on the

actual situation.


(1) Particularly observe various phenomena in experiment, record these phenomena and data and fill in the form with the data.

(2) According to the results, determine the electric nature of Fe (OH)3 sol and clay sol.

(3) Compare the coagulation values of different electrolytes, and verify SchlZe–Hardy law.

(4) Draw up Ar-c curve with the quality percentage of HPAM as X-axis and flocculation efficiency Ar as Y-axis, and explain it..

5.Experiment results processing

6.Questions

(1) Why must the Fe (OH)3 sol go through dialysis

before flocculation test?

(2) Whether is the coagulation values of different e

lectrolysis to the same sol same? Why?

(3) When the concentration of polymer is higher in

the sol, what will arise, and why?

Preparation identification and breakdown of emulsion

Wang Zengbao

2012.12

EXPERIMENT 5


（ 1 ） Preparation of different types of emulsion;

（ 2 ） Understand some method of the emulsion

preparation;

（ 3 ） Familiar with some damage emulsion met

hod.


Emulsion is a liquid dispersed in another immiscible liquid in the form of dispersion. There are two types of emulsion, namely oil in water type (O/W) and oil-water type (W/O). Only two immiscible liquids can not form a stable emulsion. To form a stable emulsion, emulsifier must exist. In general emulsifiers are mostly surface active agent.

Surfactant could reduce the surface energy and form protective film of the droplet surface, or make the droplet surface charged to stabilize the droplet emulsion.


Emulsifiers could also be divided into oil in water emul

sifier and oil-water emulsifier. Generally monovalent metal

fatty acid soap (eg sodium oleate) is hydrophilic than hydro

phobic, so it’s oil in water emulsifier. Divalent or trivalent fa

tty acid soap (such as magnesium oleic acid) is lipophilic tha

n hydrophilic, so is the water-in-oil emulsifier.

The following three methods could identify the two types of emulsions:

（（ 11 ）） Dilution Dilution （（ 22 ）） Conductivity method Conductivity method （（ 33 ）） Staining Staining


Add one drop of emulsion in the water, if it spreads out

immediately, it means that the dispersion medium is water,

so it is oil in water emulsion; And it is water in oil emulsion

if it is not immediately disperse.

（ 1 ） Dilution


Water phase generally contains ions, so its conductivity is

much greater than the oil phase. When the water medium is

dispersion medium (continuous phase), the conductivity of

emulsion is large; the other hand, if oil is continuous phase and

water is the dispersed phase, water droplets are not

continuous, so the conductivity of emulsion is weak. Two

electrodes which are connected to DC power supply and

ammeter are inserted into the emulsion solution. If there is

significant deflection of ammeter, the emulsion is oil in water

solution; if the pointer does not move, the emulsion is water in

oil emulsion.

（ 2 ） Conductivity method


（ 3 ） Staining

The dye which is only soluble in oil but does not dissolve

in water or only water-soluble (such as Sudan which is Ⅲred dye and only soluble in oil but not water-soluble) is added

into the emulsion. If the dye dissolved in the dispersed phase,

the droplets stained one by one appears in the emulsion. If

the dye is soluble in the continuous phase, the emulsion

showed uniform dye colors inside. The type of emulsion could

be determined by the dispersion of dye.


Methods of destroy the emulsion

(1)(1) Adding the demulsifierAdding the demulsifier

(2)(2) Adding electrolyte Adding electrolyte

(3)(3) Heating Heating

(4)(4) Electrical methodElectrical method


（ 1 ） Adding the demulsifier

Demulsifier is often anti-emulsifier. For example, the wa

ter in oil emulsion made by adding magnesium oleic acid coul

d be broken by adding sodium oleate. The sodium oleate whic

h is hydrophilic could adsorb on the liquid surface and form t

he hydration shell that could reduce the emulsification of ma

gnesium oleic acid and break the emulsion. If adding excess s

odium oleic acid, the water in oil emulsion may change into oi

l in water emulsion.


（ 2 ） Adding electrolyte

Different electrolytes may have different effects. In

general, by adding electrolytes into oil-in-water emulsion,

it could change HLB of the emulsion and reduce the

stability of the emulsion. .


（ 3 ） Heating

Elevated temperature could reduce the emulsion agent

adsorption on the interface and thin the solvent layer and

low the medium viscosity and enhance the Brownian motion.

Therefore, reducing the stability of emulsion helps emulsion

damage.

（ 4 ） Electrical method

Under the action of the high voltage field, droplet could

deform and connect to each other, then decreased dispersion

results in the destruction of the emulsion .

3. Equipment and medicine

Equipment 100mL conical flask with a plug 2, Large test tube 5, 25m

L graduated cylinder 2, 100mL beaker 3, Small dropper 3, constant current source 1, milliammeter 1, one pair of electrodes

Medicine Benzene (chemical pure), Sodium oleate (chemical pure),

3mol/L HCl solution, 1%, 5% sodium oleate solution, 2% magnesium oleic acid benzene solution , 0.25mol/LMgCl2 aqueous solution, saturated NaCl solution, Sudan soluⅢtion.

（ 1 ） Preparation of emulsion Add 15mL 1% aqueous solution of sodium oleate into 100mL

conical flask with a plug. Then add 15mL of benzene (each of adding about 1mL) with severe shaking after each adding of benzene until there is no benzene layer phase. Type emulsioⅠn is obtained.

15mL 2% benzene solution of sodium oleate is added into another 100mL conical flask with a plug. Then 15mL of water is added (each of about plus 1mL) with severe shaking after each add of water until there is no water layer phase. Type emⅡulsion is obtained.


（ 3 ） Destruction and phase conversion of the emulsion

①Take two clean test tube, add 1 ~ 2mL type and type Ⅰ emulsion to each test tube, dropwise add 3mol/L HCl Ⅱ

solution, then observe the phenomenon.

②Take two clean test tube, add 1 ~ 2mL type and typⅠe emulsion to each test tube, heat the tubes in water bⅡath, then observe the phenomenon.



③Take two clean test tube, add 2~3mL type and type Ⅰ emulsion to each test tube, dropwise add 0.25mol/L MⅡ

gCl2 solution with severe shaking after each add of MgC

l2 solution, then observe the destruction and phase conve

rsion of the emulsion. (Identify the phase conversion usin

g dilution method, the same below)



④Take two clean test tube, add 2~ 3mL type and type Ⅰ emulsion to each test tube, dropwise add saturated NaⅡ

Cl solution with severe shaking after each add, then observe the destruction and phase conversion of the emulsion.

⑤Take two clean test tube, add 2~ 3mL type and type Ⅰ emulsion to each test tube, dropwise add 5% sodium oⅡ

leic acid solution with severe shaking after each add, then observe the destruction and phase conversion of the emulsion.



Record and collate the phenomena observed in Record and collate the phenomena observed in

experiments, and analyze causes. experiments, and analyze causes.

6.Questions

1. What is common point for the various emulsion identification methods?

2. It is said that if the water is more than oil it could form oil in water emulsion, whereas the water-oil. Is it right or wrong? Illustrate it by trial results.

3. Could the phase conversion method be used as demulsification? Could the demulsification method be used as phase conversion?

4. Could the two immiscible liquids form emulsion automatically by adding emulsifier?

Synthesis and hydrolysis of polyacrylamide

Wang Zengbao

2011.4

EXPERIMENT 6


1.Be familiar with addition polymerization by the synthesis of polyacrylamide from acrylamide.

2. Be familiar with the hydrolysis of polyacrylamide in alkaline solution.


Polyacrylamide can be synthesized from acrylamide triggered by ammonium persulfate:

Polyacrylamide can hydrolyze in alkaline solution, which generates partially hydrolyzed polyacrylamide:

nCH2 CH

CONH2

(NH4)2S2O8 [CH2 CH]n

CONH2

[CH2 CH]n

CONH2

+ yH2O + zNaOH

[CH2 CH]x

CONH2

[CH2 CH]y

COOH

[CH2 CH]z

COONa

+ (y + z)NH3


Apparatus Constant temperature water bath, beaker, gr

aduated cylinder, stirring rod, electronic balance.

Reagents acrylamide (chemical pure), ammonium pers

ulfate (analytical pure), sodium hydroxide (analytical pure)

1. The addition polymerization of acrylamide (1) Weigh the mass of beaker and stirring rod with a electronic b

alance (this mass would be used later). Then add 2g acrylamide and 18mL water in the beaker to match a 10% acrylamide solution.

(2) In the constant temperature water bath, heat the 10% acrylamide solution to 60 . Then add 15 drops of 10% ammonium pe℃rsulfate solution to trigger the addition polymerization of acrylamide.

(3) In the process of addition polymerization, keep stirring slowly and observe the changes of solution viscosity.

(4) Stop heating half an hour later, and the product is polyacrylamide.


2. Polyacrylamide hydrolysis (1) Weigh the obtained polyacrylamide, calculate the needed water to make 5

% polyacrylamide solution. (2) Add the required water in polyacrylamide solution, then stir it with a stirri

ng rod and observe the dissolution of the polymer. (3)Weigh 20g 5% polyacrylamide solution ( the rest is control group) , add 2m

L 10% sodium hydroxide, then place it in a boiling water bath and heat it to above 90 for hydrolyzation.℃

(4)In the hydrolysis process, stir it slowly and observe the viscosity changes, check the ammonia release (with wet pH paper of wide range).

(5)The beaker is removed from the boiling water bath half an hour later, and the product is partially hydrolyzed polyacrylamide.

(6) Weigh the product mass, add the loss of evaporated water, and 5% partially hydrolyzed polyacrylamide is made. Then compared the solution viscosity before and after hydrolyzation.

(7)Pour the prepared polyacrylamide into the recycling bottle.


Explain all kinds of observed phenomena in the experiment.


6.Questions

1. What is the impact of ammonium persulfate amount on the molecular weight of synthesized polyacrylamide?

2. Why the temperature is raised to 60 during ℃the synthesis of polyacrylamide?

3. Analyze the factors that affect the molecular weight of polyacrylamide.

Determination of Polymer Molecular W

eight by Viscometric Method

Wang Zengbao

2011.4

EXPERIMENT 7


Learn and understand one method to determine the polymer molecular weight .


The polymer molecular weight is an average value owing to the polydisperse molar mass distribution. The polymer molecular weight determined by viscometric method is called the Viscosity-average molecular weight ( ).

Viscometric method includes multi-point method and one-point method,we use one-point method.

vM

t A 0

0

0SP

0 r

Because

and

0

0

0

0SP t

tt

00

lnlnlnt

tr

)ln(2

1rSPc

vMk][

vM

Use these formulas to get Mv


In this experiment, for measurement of the viscosity of polymer solution at different concentration, the Ubbelohde-type viscometer illustrated in this Fig.

1, 2, 3—Branch pipe ；5, 8, 9 － Glass bulb ；4, 6 － Scale ；7 － Capillary

We need record the time between the scale 4 and 6



Apparatus The Ubbelohde-type viscometer, stopwatch, sucti

on bulb ， graduated flask ， Glass Constant temperature water bath

Reagents Polyacrylamide (PAM, industrial products), Sodi

um nitrate (NaNO3, AR), Distilled water.

(1) Place the viscometer vertically in a thermostat bath maintained at 30 , and let it stand for about 15min to attain the specified ℃temperature.

(2) Add 15mL 1 mol/L sodium nitrate solution through branch pipe 3 into the glass bulb 9 .

Close tube 1 with a finger and pull the sample solution up to scale 4 by gentle suction from the top of tube 2, and stop the suction.

Remove the finger from tube 1 and immediately close the end of tube 2.

Confirming that the meniscus of liquid column is cut off at the scale 4, open the end of tube 2 to make the sample solution flow down through the capillary tube 7.

Record the time required for the sample solution to fall from the upper scale (scale 4) to the lower scale (scale 6) by stopwatch. Repeat the above measurements at least 2 times and take the average value .


(3) Cleaning of the Ubbelohde viscometer three time

s with 0.01g/100mL polyacrylamide solution.

(4) Determine the polyacrylamide solution flow time

to fall from the scale 4 to the scale 6 using the meth

od mentioned above.



Calculation the vM

0

0

0

0SP t

tt

00

lnlnlnt

tr

)ln(2

1rSPc

vMk][ vM

6.Questions

1. Summarize the experimental methods for determini

ng molecular weight and their scope of application.

2. Why is NaNO3 added to determine of polymer mole

cular weight by viscometric method? Are other salts r

easonable?

3. How to choose the concentration of polymer solutio

n in the multi-point method?

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