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Research ArticleReceived: 16 September 2007 Revised: 2 November 2007 Accepted: 3 December 2007 Published online in Wiley Interscience: 29 January 2008

(www.interscience.com) DOI 10.1002/sia.2725

Survismeter 3-in-1 for interfacial tension (IFT),surface tension and viscosity measurementssimultaneouslyMan Singh∗

Interfacial tension (IFT) (γift, N m−1) of benzene-water; and surface tensions (γ , N m−1) and viscosities (η, N s m−2) of solventsmethanol, ethanol, glycerol, ethyl acetate, n-hexane, diethyl ether, chloroform, benzene, carbon tetrachloride [CCl4], formic acid,Acetonitril, and dimethylformamide [DMF] were measured with Survismeter-IFT. The ±1.1 × 10−5 N m−1, ±1.3 × 10−5 N m−1,and ±1.1 × 10−5 N s m−2 deviations in respective values were noted. It has 10 times better accuracy than those of individualmethods. The survismeter is inexpensive minimizing 2/3 each of consumables, human efforts, time, and infrastructure, cuttingdown 80% of the waste disposed the environment. Copyright c© 2008 John Wiley & Sons, Ltd.

Keywords: survismeter; surface tension; viscosity

Introduction

Interfacial tension (IFT), viscosities, and surface tension monitorqualities of antiwrinkle creams, facial creams, sunburn, oil andpetroleum, sol-gels, emulsions, lotions, biofluids, inks, syrups,coating materials etc. Frequent measurements of IFT, viscosities,and surface tension in industries, academics, and by researcherswith individual instrumental setups is not economized. IFT forimmiscible solvents offers crucial data for oil, blood, shampoo,and real-life fluids, which often do not obey fairly straightforwardBernoulli’s concept. Fluids flowing in a tube produce a frictionalforce, acting between parts of a fluid that travel at different speeds.Jean Louis Poiseuille or Poise, a French physician studied bloodpressure in small blood vessels forced water instead of blood dueto a lack of anticoagulants via capillaries. He discovered that a rateof flow in a tube is proportional to an overhead pressure and tothe 4th power of a tube diameter (r). The flow in a tube is restrictedto streamline, but blood flow in blood vessels is not exactly astreamline, but Poise’s rule is a reasonable first approximation.Blood viscosity is about 4 × 10−3 Pa s, and relatively a smallchange in r causes a significant change in flow. A decrease in rby 2 reduces a flow rate by a factor of 16. It enhances cholesterollevel that can clog the arteries – even a minor change in the size ofblood vessels can have a significant impact on the rate of pumpingof blood, and the amount of work done by the heart in circulatingblood. Viscosity is in N s m−2 (SI) = poise (P) and centipoise (cP);1P = 0.1 N s m−2; 1 cP = 0.001 N s m−2.

Laminar flow

Viscosity is an energy used in flow. 1P = (Force, N) (thickness,m) (time, s)/[(area of plate, m2) (distance, m)], 1P = N m s/m3 =N s/m2 is power per unit of area, unit of speed and speed gradient;1P (Poise) is an SI unit. CGS is dyne cm2 = Poise. Industries use cP(1/100 = 0.01 Poise); water has a viscosity of 1.002 cP at 293.15;1P = N s/m2 = Pa s = 10 Poise = 1000 cP unit. It infers hydrogenbonding force somewhat greater than several 1000 psi we mightapply; oils and others are not so self-compressed. Paraffinic oils,

in particular, are held together by much weaker induced dipolecharges.

MacMichael viscometer measured viscosity; 160 Machmichael isequal to 43 Brookfield. Kinematic viscosity is Stokes (St.), in cm2/sand 1/10 000 of a size. George Stokes established a science ofhydrodynamics with various flow relationships ranging from wavemechanics to viscous resistance. Poise is kg m s/m2s2 = kg/ms;density = kg/m3; so Poise/density = kg m3/kg m s = m2/s.Osborne Reynolds, Irish Brit gave Reynolds number (Re) = 2 rs/vk.Small Re infers dominant fluid’s viscosity, Re larger than 10 000infers negligible viscosity and kinetic or inertial effects rule,turbulence, cavitations favors chaos.

Surface Tension

Soap themselves form bubbles with minimal surface area, andwork to enhance surface area; hence surface tension is definedin terms of this work W, as surface tension = W/�A, where Ais area. If a thin film of fluid is tried to stretch, the film resists.Surface tension is a force F per unit length L tending to pull asurface back; surface tension = F/L. Water is used for cleaning,but surface tension makes it hard for water to penetrate into thesmall crevices or openings of clothes. The most familiar liquidstates at room temperature are water, alcohol, benzene, carbontetrachloride, corn oil, castor oil, and gasoline. Surface tension isan energy for stretching a unit change of a surface area, and isN m m−2 = N/m, without any direct correlation between viscosityand surface tension. Unbalanced forces at surface contribute tosurface tension. The substances with low surface tension tend to

∗ Correspondence to: Man Singh, Chemistry Research Laboratory, DeshbandhuCollege, University of Delhi, New Delhi-110019, India.E-mail: mansingh50@hotmail.com

Chemistry Research Laboratory, Deshbandhu College, University of Delhi, NewDelhi-110019, India

Surf. Interface Anal. 2008; 40: 76–80 Copyright c© 2008 John Wiley & Sons, Ltd.

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Survismeter 3-in-1 for IFT, surface tension and viscosity

form films; blowing soap water with a straw forms bubbles, due toa low surface tension. It affects everyday phenomena like food wedrink and eat. Cohesion is an intermolecular attraction betweenlike molecules, and adhesion between unlike molecules. Liquidswith high surface tension show stronger cohesive forces and poorwetting due to low adhesive forces. A wetting agent increases thewetting action of water with a nonpolar material to remove dirt;if adhesive force between tube material and the liquid is strongerthan the cohesive force, the level of wetting is higher; otherwise,the level is lower. It is a capillary action and transports liquid andnutrients in plants, and sometimes in animals, it is defined as amovement of water within the spaces of a porous material due tothe forces of adhesion, cohesion, and surface tension. Attractionbetween water molecules creates a strong film that permits waterto hold up substances heavier and denser than it; the water striderrelies on surface tension to walk on. A capillary action occursbecause water is sticky, due to the forces of cohesion keeping themolecules closely together and adhesion, as in a drop, which sticksto glass, cloth, organic tissues, and soil. Plants put down roots

into the soil to carry water from the soil up into the plants due tocapillary action.

Critical start-up

Survismeter produces data with 95.5% confidence level and isbetter than others with better temperature control, as liquidevaporates due to frequent disruption of setup and there is ahigh risk of instrumental damage. The survismeter deletes suchdamages due to self loading and evacuation of sample from bulbnumber 10 via tube number 11 of 2 mm inner diameter fusedwith bottom of bulb number 10. It siphons out solution from bulbnumber 10 after experiment is done using a manually run suctionpump number 14. It saves 80% time of a user when compared toindividual methods.

Merit

Usual instruments cannot accurately measure surface tension ofvolatile liquids, but bulb number 9 (Fig. 1), where drop formation

Figure 1. Numbers 1, 2, 3, 4, 5, and 19 marked on the upper ends of the survismeter work as limbs, and the 5, 6, 7, 8, 9, and 10 marked in the bulbs depictthe operational bulbs. The numbers depicted along with the vertical lines illustrate the dimensions of the instrument, and the darkened vertical tubesbetween the bulbs 6 and 9, and 8 and 9, the capillaries to allow the viscous and drop-wise flows respectively. Bulb number 10 works as a liquid reservoir,limb number 11 helps sucking out the liquid from bulb number 10, and number 12 controls the pressure of bulb number 9.

Surf. Interface Anal. 2008; 40: 76–80 Copyright c© 2008 John Wiley & Sons, Ltd. www.interscience.wiley.com/journal/sia

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and detachment occur, is closed and hence is easily thermostated.It is suitable for all concentrations with homogeneous solutions[1,2]

and minimum operational steps,[3 – 7] and is an asset for expensivebiofluids, which are either reduced or oxidized with time. It is anasset for formulations of chemical fertilizers, pesticides, dyeing,dry cleaning, sol-gel, emulsions, lotions, syrups etc. and bothfor Newtonian and non-Newtonian solutions.[8] It works withoutelectricity, light, and heat etc.

Material

Methanol, ethanol, glycerol, ethyl acetate, and n-hexane, diethylether, chloroform, benzene, carbon tetrachloride, DMF, andacetronitrile (AR, Merck, India) were distilled. Deionized water wastriply distilled with KMnO4 and KOH (AR, Merck, India), boiled offfor removal of CO2 and other dissolved gases. Its conductivity wasmaintained at 1 × 10−6 �−1 cm−1. The survismeter was cleanedas per standard methods and dried at 120 ◦C in an oven for 24 h. Abicapillary pyknometer (20 × 10−3 dm3) was used[9] and weighedwith 0.01 mg analytical balance model 100 DS, Dhona InstrumentsPvt., Ltd., Calcutta, India, for densities.

Description of survismeter

It consists six bulbs and five limbs. The upper openings of limbnumbers 2, 3, 4, and 5A are made with standard glass joints $B7and that of 1 with $B10 (Fig. 1). Another end of limb number 1 isfused with bulb number 10; and 2, 3, and 4 via bulb numbers 5, 6,and 7; 8 to bulb number 9; while number 5 is attached with bulbnumber 10 to hold liquid for measurements. Bulb number 9 iscommon for both viscosity and surface tension units for pressurecontrol via limb number 3 attached to bulb number 9 via tubenumber 12.

Measurements

It measures IFT, surface tension, and viscosity by liquid flow methodin capillaries.

Viscosity

The instrument was calibrated with water and kinetic energycorrection B/t was ±5 × 10−5, at ±0.05 ◦C control, read withBeckman thermometer (calibrated at NPL, New Delhi, India). It wasmounted on a stainless steel stand with nuts and bolts fitted clipsat a vertical position, checked with spirit level.

Unit 4, 5, 6, 9, 10 measures viscosity; unit 2, 7, 8, 9, 10, surfacetension; and unit 15, 16, 18, 19, B1, 13, B2, 1, 10, the IFT. The liquidis filled in bulb number 10, for viscosity and surface tension whenunit 13 is not fitted in limb number 1. For viscosity, the joints 3,2, and 5A are stoppered and the liquid is sucked up from bulbnumbers 10 to 5 via bulb numbers 9 and 6. The units 14, 17, and 18are used for sucking up a solution; for measurements, the stopperfrom joint number 3 is withdrawn for liquid from bulb number 9to 10. Then the stopper from joint number 4 is withdrawn for backflow of liquid to bulb number 10 along the glass wall. Viscous flowtimes for a liquid of bulb number 6 within its upper and lowermarks are noted with an electronic timer of 1 × 10−2 sec.

Surface Tension

A syringe was connected to a silicon tube of 1.5-mm inner diameterand the plunger of the syringe is pushed back for the liquid toflow from bulb numbers 10 to 7 via bulb numbers 9 and 8. Limbnumber 12 allows air pressure to push the liquid down from bulbnumber 9 to 10 on removing its stopper from joint 3. Then thesyringe stopper is withdrawn from joint number 2, for the liquidto flow downward. Since a capillary of bulb number 8 is extendedto bulb 9 and remains hanging by 3–4 mm, for an unhindereddrop formation and detachment, which are counted for liquid ofbulb number 8 within its upper and lower marks, joint number 1remains open. A nut-bolt fitted clip controls air pressure overheadlimb number 2 as and when it is required. Such a situation doesnot arise normally.

Interfacial Surface Tension

Water, a denser liquid is filled in bulb numbers B1 and B2 of unitnumber 13 with suction pump number 14, 17, and 18. Then jointnumber 18 is fitted in joint number 19. A silicone tube of 0.5-mminner diameter is attached to a suction pump number 14 whoseanother end is attached with a U tube of ground glass standardjoint number 18 of size $5, which is fitted in standard joint number19 of unit number 13. Then the plunger of pump number 14 ispushed back that sucks up the liquid in both the B1 and B2 bulbsvia its capillary of 0.5 mm id. Its capillary is dipped in a wantedliquid. When B2 is filled, the suction device is withdrawn and a jointof unit number 19 is airtightly stoppered. Then unit number 13 isproperly fitted in joint number 1, keeping the joint numbers 2, 3,4, and 5A open. The stopper from its joint is replaced by pressurepassage unit number 15, 16, 17, and 18. Pressure is permitted tounit 13 via a silicon tube 16 to push down liquid in its capillary intobulb 10. The standard joint of unit 13 between bulb number B1and its capillary has grooves made on its outer surface to pass airpressure out of bulb number 10 during drop formation at the tipof the capillary of unit 13 and the detachment in bulb number 10.

Drops are counted for a liquid of bulb B1 and the pressure isregulated through a separated pressure passage with knob fittedclip number 15 to allow 4–7 drop/min in bulb number 10 Thestopper number 18 is fitted in joint number 19. Knob number15 compresses the silicon tube number 16. Firstly, the dropsare counted in an air medium in bulb number 10 with 99.99%reproducibility. When water drops are counted with unit 13 in airin bulb 10, then unit number 13 is taken out from joint number1, and B1 and B2 bulbs are filled with water and fitted again injoint number 1. This time, bulb number 10 contains benzene anda lower tip of capillary of unit number 13 is dipped in benzene.The drops of water of bulb number B2 within its upper and lowermarks are counted similar to the previous.

Critical Overview

Since inception,[9 – 12] individual instruments are in use for viscosity,surface tension, and IFT study, but Singh has derived anequation[12] for friccohesity a new parameter. Attempts were madeby Newton[4,5] for internal friction from (dv/dx) velocity gradient.Stokes and Mills[7] applied the hydrodynamic law on a viscous flow.Gibson and Jacob developed the falling sphere method followedby Ostwald viscometer. Einstein[11] and Huggin[8] calculatedspecific viscosity of polymers. Wilhelmy and duNouy based their

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Survismeter 3-in-1 for IFT, surface tension and viscosity

work on capillary pull and Jaeger, Sugden, and Ferguson on dropmethod, and Poisson–Raleigh gave their correction to capillary.Falkenhagen[13] emphasized the drop size with surface force.[12]

These have been the individualistic approaches, but survismeteris a combined and simultaneous technique for three parameters.

Chemistry Education

Molecules due to partial charge result in an electrostaticstructure with higher viscosity and surface tension, which couldinfer valuable information on structures and electronic states.Solvents are extensively used to manufacture drugs, dyes,electronic doping, coating, fragrant, thinner, paper pulp, ink,soaps, detergents, cosmetics, syrups extraction, nail polishes,enamel, paints pigments, etching, and supercritical solvents.The survismeter is an asset for accurate physicochemical dataof these[12] for use in biophysics, electrophoresis, turbidity,conductance etc. where media viscosity and surface tensions areuseful. Further, viscosity and surface tension of hydrodynamicvolume of cellulose, proteins, soybean, gram, pepsin, casein,ospinine, BSA, and PSA, etc. infer a better understanding of proteinand carbohydrate chemistry. Hence survismeter is industriallyuseful for producing three kinds of data.

Features

Bulb number 10 holds about 15 × 10−3 dm3, but about 10 ×10−3 dm3 liquid is preferred with 5 × 10−3 dm3 empty volume ofpressure equilibrium. Bulb number 9 holds about 4 × 10−3 dm3

solution, and adjoins lower ends of limb numbers 2, 3, and 4respectively, for an upward flow being sucked to the bulb numbers6 and 5, and 7 and 8 of limb 4 and 2, respectively. Bulb number6 of 5 × 10−3 dm3 allows flow of its liquid within the upper andlower marks made on capillaries below and above it. Bulb number5 stabilizes a flow by equilibrating a pressure and thermal stability.Bulb numbers 8 and 7 are of 5 × 10−3 dm3 and 4 × 10−3 dm3.

The survismeter is calibrated with standard liquids like glycerol,dimethylformamide, and diethyl ether. Its calibration constantwith water is 0.1 m2/s2.

Results

Flow time (t, s) and drop counts (n) are fitted in the usual formula[3]

for viscosity and surface tension with ±1.7 × 10−5 N s m−2 and±2 × 10−6 N m−1 accuracies, respectively. The data for solventsare given in Table 1, and IFT in Table 2. The t and n data[3] forfriccohesity (σ/s m−1)[7,12] values are fitted into the Man Singh[12]

equation. The γ values are related to w = mg = 2π rγ ; for thisthe buoyancy correction is used; the B/t and kinetic correction(k) were obtained from η = ρ(k − B/t) with known values of η andρ. The B/t and k values are −0.182 × 10−5 and 1.898 × 10−5 at298.15 K, respectively. Energy constant B with water is calculatedfrom η/ρ = Bt − V/8π rLt, where V denotes the volume of waterthat flows, r, the radius and L is the length of the capillary.

Discussion

Surface tension and viscosity (Table 1) are close to those of theliterature with ±1.6 × 10−6 N m−1 and ±1.6 × 10−5 N m−1 s−2

deviations respectively. The surface tension of solvents are asdiethyl ether > glycerol > formic acid > benzene > chloroform> CCl4 > ethyl ether > ethanol > n-hexane, their viscosities asn-hexane > glycerol > formic acid > ethanol > CCl4 > benzene> chloroform > methanol > ethyl ether > diethyl ether.

These orders of the values infer a state of adhesive and frictionalforces where diethyl ether develops stronger adhesive forces andn-hexane, weaker forces. Similarly, n-hexane develops strongerfrictional forces, but diethyl ether, weaker frictional forces.[15,16] Ingeneral, a reverse trend of the adhesive and frictional forcesis noted among the chosen solvent. The IFT data (Table 2)predict binding forces during drop formation applied on thecircumference on the lowermost tip of the capillary, and onthe liquid layer being formed during viscous flow. The literature

Table 1. Surface tensions (γ /10−3 N m−1) and viscosities (η±4.4×10−5 N s m−2) with literature, � = exp . – lit. The exp. and lit. are for experimentaland literature, respectively

Measurements with survismeter

Surface tension ViscosityExp. – lit Exp. – lit

Systems T. K Lit. Exp. � Lit. Exp. �

Methanol 298.15 22.28 22.31 0.03 0.547 0.549 0.002

293.15 22.55 22.48 0.07

Ethanol 293.15 22.40 22.46 0.06 1.060 1.061 0.001

Glycerol 298.15 64.00 64.03 0.03 1.490 1.489 −0.001

Glycerol 293.15 63.40 – – 1.490 – –

Ethyl acetate 298.15 23.15 23.17 0.02 0.441 0.443 0.002

n-hexane 298.15 17.90 17.86 −0.04 1.790 1.794 0.004

Diethyl ether 293.15 72.8 72.768 −0.032 0.233 0.2332 0.002

Chloroform 293.15 27.1 27.101 0.001 0.58 0.5810 0.001

Benzene 293.15 28.9 28.889 −0.011 0.652 0.6518 −0.0002

CCl4 293.15 27.0 27.002 0.002 0.969 0.9691 0.0001

Formic acid 293.15 31.40 31.44 0.040 1.465 1.4649 −0.0001

DMF 293.15 39.0673 39.0653 0.020 1.5656 1.5651 0.0005

Acetonitril 293.15 29.8579 29.8590 0.011 0.4379 0.4378 0.0001

The literature values are extracted from Refs [2–6].

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Table 2. Number of drops of water in air (na) and benzene (nb)at 305.65 K for interfacial surface tension (IFT) between water andbenzene. 0.8725 and 0.99 455 × 103 kg m−3 densities of benzene andwater respectively were used, 71.10 × 10−3 N m−1 surface tension ofwater at 31.5 ◦C

na, of waterin air

nb, of waterin benzene IFT, 1 × 10−3 N m−1

46 13 30.81

46 13 30.81

46 13 30.81

46 13 30.81

46 13 30.81

46 13 30.81

46 13 30.81

46 13 30.81

46 13 30.81

46 13 30.81

46 13 30.81

data[14] closely match our experimental data of IFT obtained in 11different experimental measurements. They were reproduced to95.95% confidence level. The 71.10 × 10−3 N m−1 surface tensionof water at 31.5 ◦C measured in an air medium was reduced toabout 30.81 × 10−3 N m−1 when measured in a benzene medium.Hence benzene applies buoyant force on drop-wise flow.

Value-added instrument

It minimizes infrastructure and is an asset for biofluids in prevent-ing their interconversion and evaporated oxidation/reductions.Manufacturing, storing, and maintenance of 3 separate instru-ments cost 3 times, along with glass material and for blowingfuel gases for manufacturing. It is eco- and environmental friendlyas it minimizes by more than 80% uses each of glass materials,gasses acetylene, oxygen etc. washing reagents chromic acid, andspace in laboratories for storage and working. It saves at least 80%tap water, distilled water, and acetone used in washing individualinstruments and saves 80% time of user as compared to a separateoperation.

Similarly, it saves 80% electricity used for temperature control,cooling, and heating the systems. For example, a single viscositymeasurement requires at least 1 h; hence for n samples, n h arerequired. Similarly, n h are required for surface tension and nh for IFT along with an additional time required for filling andevacuation of solutions in individual instruments. Hence totally, 3(n h) times each of time, material, and electricity are wasted.

Acknowledgements

Survismeter-IFT is dedicated to the scientific community foraccurate, inexpensive, and fascinating technique. The authorthanks Dr A. P. Raste, Principal, Deshbandhu College, DU, forsupport.

References

[1] Man Singh J. Instrum. Exp. Tech. 2005; 48(2): 270.[2] Ira NL. Physical Chemistry (4th edn). Tata McGraw-Hill: New Delhi,

1995; 458.[3] Singh M, Chand H, Gupt KC. Chem. Biodivers. Helv. Chim. Acta 2005;

2(6): 809.[4] James AM, Prichard FE. Practical Physical Chemistry (3rd edn).

Longman, Burnt Mill: Harlow, 1967; 302.[5] Levitt BP, Kitchener JA. Findlay’s Practical Physical Chemistry (9th

edn). Longman: London, New York, 1972; 420.[6] David P, Shoemaker DP, Carl WG. Experiments in Physical Chemistry,

International Student edition. McGraw-Hill Kogakusha: USA, 1967;249.

[7] Stokes RH, Mills R. Viscosity of Electrolytes. Pergmaon Press: Oxford,1964; 31.

[8] Huggin ML. In Principles of Polymer Chemistry, Flory PJ (ed). CornelUniversity Press: Ithaca, 1953; 308.

[9] Singh M, Kumar S. J. Appl. Polym. Sci. 2003; 87: 1001.[10] Beece D, Einstein L, Frauenfelder H, Good D, Marden MC, Reinisch L,

Reynolds AH, Sorenson LB, Yue KT. Biochemistry 1980; 19: 5147.[11] Einstein A. Ann. Phys. (Leipzig) 1980; 190(19): 29.[12] Singh M J. Biochem. Biophys. Methods 2006; 67(2–3): 151.[13] Falkenhagen H, Vernon EL. Philos. Mag. 1932; 14: 537.[14] Paul CH, Rajagopalan R. Principles of Colloid and Surface Chemistry

(3rd edn). Marcel’s Dekker: New York, 1964; 294.[15] Singh M J. Chem. Thermodyn. 2006; 39: 240.[16] Singh M J. Chem. Sci., Indian Acad. Sci. 2006; 118: 1.

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