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Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public.

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है”ह”ह

IS 2720-22 (1972): Methods of test for soils, Part 22:Determination of organic matter [CED 43: Soil andFoundation Engineering]

IS : 2720 (Part XXII ) - 1972(Reaffirmed 2010)

Indian StandardMETHODS OF TEST FOR SOILS

PART XXII DETERMINATION OF ORGANIC MATTER

( First Revision)

Third Rrprint APRIL 1990

UDC 624.131.371

Copyright 1972

BUREAU OF INDIAN ST ANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

Gr 3 July 1972

IS I 2720 (Part XXII ) -1972

Indian StandardMETHODS OF TEST FOR SOILS

PART XXII DETERMINATION OF ORGANIC MATTER

( First Revision)Soil Engineering Sectional Committee, BOC 23

CflairmGII RlprlJllI/illlPIlO. DIIIUH MOHAN Ccntral Building Research Institutc (CSIR),

Roorltce

Land Reclamation, Irrigation & Power ResearchInstitute, Amritsar

In personal capacity ( P.820. N,w AllPOrt,CtJlclltltJ 53)

Hindustan Construction Co Ltd, BombayBihar Institute of Hydraulic & Allied Research,

Khagaul, PatnaIndian Geotechnical Society, Ncw DelhiIndian Institute ofTcchnology, New Delhi

University ofjodhpur, jodhpurCementation Co Ltd, Bombay

SHRI A. G. DASTIDARSIIRI R. L. DEWAN

SHRI K. N. DADINA

Oil G. S. DHILLONPRO. R. N. DOORA

SHill S. K. GULATI ( .411""Il/')JOINT DIRI!CTOR RI!SEARCH (FE), Railway Board ( Ministry of Railways)

RDSODItPUTY DIRECTOR RUEARCH

( SOiL MI!CHANIClI). RDSO ( Alternate ]SURI S. S. JOSHI Engineer-in-Chief" Branch, Army Headquarters

SHRI S. VAIlADAIlAJA ( AII""a/e )SHill l. P. K ....PILA Central Board of Irrigation & Power, New DelhiSHRI G. KUECKELNANN Rodio Foundation Engineering Ltd; nnd Hazurat &

Co, BombaySHRI A. H. DIVAN.!I ( Altemat« )

SHill O. P. MALUOTRA Public Works Department, Government or PunjabSHRt M. A. MEliTA Concrete Associalion of India, llombay

SIIRI T. M. MENON ( AI/midi. )SURI R. S. MILKOTE Central Water & Power Commission, New Dc.:lh.i

DEPUTY DIRECTOR (CI!NTIlALSOIL MECHANICS R~SBARCU

STATION) (Alternate )SHRI T. K. NATAII....JAM Central Road- Research InstilulC" (CSIR). New DelhiSIIRI RAVINDER tAL National Buildings Organisation, New Odin

SHRI S. H. DALACIIANDANI ( Alte-nat« )

M,mb",SHRI D. R. NARAHARI ( A/llmall to

Prof Dincah Mohan)PROP ALA" SINOHDR A. B....NItPJU

SIIIlI S. GUPTA (AII,ma/I)SHRIB. B.L.BHATNAOA~

( COl'llimm/ on "a.l!c 2 )

BUREAU OF INDIAN STANDARDSMANAK. BHAVAN, 9 DAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

R1p,snllitttBuildinp &: Roadl ReI~arch Laboratory, Public

Workl Department, Government of PunjabEnl{ineering Research Laboratory, HyderabadUnlvenity of Roorkee, RoorkeeIrrigation Research Institute, RoorkeeRoads Wing ( Ministry of Shipping &: Transport)

Institution of Enginec... ( India), CalcuttaAll India Instruments Manufacturers & Dealen

Association, BombaySIIRI S. R. TALPADE ( Allernat,)

SHRI H. G. VERYA Public Works Department, Government of UttarPradesh

SIlII.I D. C. CHATURVEDI ( 0411"""/)SIlRI D. AJITH.~ SIMHA, Director General, lSI (Ex-officio M,mb" )

Director ( Civ Engg l

RIWlAIlCH OPFICaRDR SIIAYSHAK PRAl'ASHSHRI H. D. SHARMASIIRr S. N. SINHA

SHRI A. S. BISHNOr (A.lt,matl)SUPI?RINTaNDlNO ENOINUR (PLAN- Concrete & Soil Research Laboratory, Public Works

NINO AND DurON CIRCLE) Department, Government ofTamil NaduEXEClmVEENOINtn!R ( !NCHAROE,

SOIL MECHANICS & RU&ARCHDIVISION) ( Alu,nal' )

SURI C. G. SWAYINATHANSIIRI H. C. VUMA

IS I 2720 ( Part XXII ) • 19n( OJnti"",dj,ompag, 1 )

M",.b"sRllSaAllcH OrrlCAR

Institute (CSIR),Research

University of Jodhpur, Jodhpur

Central Road Research Institute ( CSIR l, New DelhiRoads Wing (Ministry of Shipping &: Transport l

Central 13uildingRoorkee

Public \Vork. Department, Government of UttarPradesh

Associated Instrument Manufacturers ( India) PvtLtd, Nnv Delhi

United Technical Consultants Pvt Ltd, New Delhi

S",,'a,.,SHRI G. RAMAN

Deputy Director ( Civ Engg ), lSI

Soil Testing Procedures and Equipment Subcommittee, BDC 23: 3Convent'

j'''OF AI.AM Srxcn

M,mbusI)", R. K. 13I1ANDAIU~\lIl\ T. N. DIIARGAV!\

S1T:H A. S. BISIINOI ( Alternate l,"III:! R. L. Dnv.\N Bihar Institute of Hydraulic & Al1ied Research,

Khagaul, PatnaSill!! H. K. GUll \ Geologists Syndicate Private Ltd, Calcutta

:'IIRI N.:'>I. BIIATT\CIl.\PYv.\ (Allernnl')~Il'l.l S. K. GUI.IIATt Indian Institute of Technology, New Delhi';11"1 ~. s. Jovnr Eng ineer-in-Chicf''s Branch, Army HeadquartersSlIIU O. P. M \l.IIOTF. \ Buildings & Roads Research Laboratory, Public

Works Depar trncnt, Government or Punjabp" I. S. {;PPAI. ( ..Wrll/c'r l

"m'l R. S.l\IELKOTE Central W..ter & Power Commission, Ncw DelhiJ )"l'tr!'V DIRECTOR (( 'E"'fR \1.

SOIL l\{t:CHI\NIC~ H f.'1? \Rell

ST.\TtON) (Aflrmn't iSI\!U D. R. NAR!\II,\IU

SIlRt H. C. Vv.;:", \

SIIlU M. X. BAI; \ ( Al/rrnqt,')

S'IRI G. S. J \IN ( Altcinate )DR V. V. S. R'\o

Smu K. K. GlJl'l',\ ( Alternate )]{C,l"{ F.CioEN'T:\TI vs

2

AMENDMENT NO. 1 AUGUST 1983TO

IS:2720(Part XXII)-1972 METHODS OF TEST FOR SOILSPART XXII DETERMINATION OF ORGANIC MATTER

(Firat Revision)

(Page 5. c~e J.l.J, Line 2) ~ Substitute'15:266-1911·' for '1S:266-1961·'.

(Page 5. cLause 5.1, Line Z) - Substitute'IS:2720(Part I}-1983t' for 'IS:2720(Part I}-1972;'.

(Pag6 ~. fOOt-not611 with I.' and 't' nurka) ­Substitute the following tar the existing toot-notes:

'·Specification for sulphuric acid (firllt r6villion).

I~ethods of test for soIls: Part I Preparation ofdry soIl specimen for various tests {s6cond revision}. I

(BDC 23)

Reprography Unit, 815, New Delhi, India

IS: 2720 ( Part XXII) • 197'2

Indian StandardMETHODS OF TEST FOR SOILS

PART XXII DETERMINATION Of ORGANIC MATTER

( First Revision)

O. FOR E W 0 R D

0.1 This Indian Standard (Part XXII) (First Revision) was adoptedby the Indian Standards Institution on 25 February 1972, after the draftfinalized by the Soil Engineering Sectional Committee had been approvedby the Civil Engineering Division Council.

0.2 With a view to establish uniform procedures for the determination ofdifferent characteristics of soils and also for facilitating comparative studiesof the results, the Indian Standards Institution is bringing out this' IndianStandard Methods of Test for Soils' ( IS : 2720 ) which is being publishedin parts. Thirtythree parts of this standard have been published so far.This part deals with the method of test for the determination of organicmatter content in the soil. Organic matter is an undesirable constituent ofthe soil from the engineering point of view since it causes swelling orshrinkage of the soil when the moisture content or the applied load changes.The estimation of organic matter, therefore, forms an important part ofsoil examination.

0.3 A wide variety of both dry and wet combustion methods are in me forthe determination of the organic matter of soils. Two methods which arewidely in use are given in this revision of the standard. These methodsgive reproducibJe results and the results are sufficiently accurate for commonengineering purposes. The first method is given as the standard methodand the other as an alternative method.

0." In the formulation of this standard due weightage has been given tointernational co-ordination among the standards and practices prevailingin different countries in addition to relating it to the practices in the fieldin this country.

0.5 In reporting the result of a test or analysis made in accordance withthis standard, if the final value, observed or calculated, is to be roundedoff, it shall be done in accordance with IS: 2·1960*.

eRulCi for roundiq otrnumerical valllCi (mi.u4).

3

IS: 2720 ( Part XXII) - 1972

SECTION f METHOD BASED ON ORGANIC CARBONCONTENT OF SOIL

1. SCOPE

1.1 Section I of this standard (Part XXII) lays down the method fordetermining the percentage by weight of the organic matter present in soilsbased 011 the determination of the organic carbon content of the soil.

2. APPARATUS

2.1 Oven - thermostatically controlled to maintain the temperaturebetween 105 and 110°C, with interior of non-corroding material.

2.2 Chemical Balance - sensitive to 0'001 g.

2.3 Volumetric Flask - two, of one-litre capacity.

2.4 Burettes - two, of 25 011, graduated in 0'1 ml,

2.5 Pipettes - IO-ml pipette and I-ml pipette fitted with a rubber teat.

2.6 Conical Flasks - two, of 500-011 capacity.

2.7 Graduated Mealuring Cylinders - 200-011 and 25-m!.

2.8 Desiccator -- with any desiccating agent other than sulphuric acid.

2.9 Gla.. Weighing Bottle - approximately 25 mm in diameter and of50 mm height fitted with a ground glass stopper.

2.10 Sieves - IO-mm IS Sieve and 425-micron IS Sieve and receivers.

2.11 Wash Bottle

3. REAGENTS

3.1 The reagents used shall be of analytical quality.

3.1.1 Potassium Dichromate Normal Solution - Dissolve 49'035 g of potas­sium dichromate in distilled water to make one litre of solution.

3.1.2 Ferrous Sulphate, Approximately 0'5 N Solution - Dissolve approxi­mately 140 g of ferrous sulphate in 0'5 N sulphuric acid to make one litreof solution ( add 14 ml of concentrated sulphuric acid to distilled water tomake one litre of solution for 0'5 N sulphuric acid).

NOTB - Thil solution il unstable in air and should be kept tightly stoppered. Itshould be standardized against the potaslium dichromate solution at least once in aweek.

, IS : 2720 ( Part xxn ). 19'72

3.1.3 Sulphuric Acid, Concmtrated - of specific gravity 1-836 (mIS: 266-1961*).

3.1.4 Orthophosphoric Acid, 85 Percent - of specific gravity 1-70 to 1'75.

3.1.5 Indicator Solution - 0-25 g of sodium diphenylamine-sulphonatedissolved in 100 ml of distilled water.

4. STANDARDIZATION OF FERROUS SULPHATE SOLUTION

4.1 Ten millilitres of the normal potassium dichromate solution shall berun from a burette into a SOO-ml concial flask. Twenty millilitres of con­centrated sulphuric acid shall then be added carefully and the mixtureswirled and allowed to cool for some minutes. Two hundred rnillilitres ofdistilled water shall then be added to the mixture followed by 10 ml ofphosphoric acid and 1 ml of the indicator, and the mixture shall be shakenthoroughly. Ferrous sulphate solution shall then be added from the secondburette in 0'5 ml increments, the contents of the flash being swirled, untilthe colour of the solution changes from blue to green. A further 0'5 ml ofpotassium dichromate shall then be added changing the colour back toblue. Ferrous sulphate solution shall then be added drop by drop withcontinued swirling until the colour of the solution changes from blue to greenafter the addition of a single drop. The total volume of ferrous sulphatesolution used (X) shall be noted to the nearest 0'05 ml (J ml ferroussulphate solution is equivalent to 10'SIX ml potassium dichromate ).

5. SOIL SAMPLE FOR TEST

5.1 The soil sample as received from the field shall be prepared in accord­ance with IS: 2720 (Part I) -1972t. The portion of the air driedsample selected for the purpose of this test shall be weighed, its moisturecontent determined using separate sample for the rurpose and the equi­valent oven-dried weight ( W ) recorded. It shal then be sieved on alO-mm IS Sieve and all particles other than stones crushed to pass throughthe sieve. The equivalent weight on oven-dry basis of the material passingIO-mm IS Sieve ( W. ) shall be calculated and recorded to the nearest 0·)percent of its total weight. A sample weighing approximately 100 g shallbe obtained from the material passing the IOvmm IS Sieve by quartering(su Notes 1 and 2). This sample shall then be pulverized so that it passesthe 42S-micron IS Sieve.

NOTE I - This -method gives high results of organic content in loill containingsulphides, The sulphides can be destroyed at thilllage by the addition of dilute (2 N I

·Specification for sulphuric acid.tMethoda of test for loils: Part I Preparation of dry lOiJ specimen for various teats (first

mWII ).

5

IS I 2720 ( Part UU ) • 1972

!lUlphuric acid. Acid shaH be added until no further evolution of hydrogen sulphideoccurs.

Non 2 - This method gives hiSb results of organic content in soils containingchlorides. The chlorides may be removed at this stage by washing the soil withdistilled water until no turbidity is obtained when a dror of the washing water is testedwith silver nitrate solution. Alternatively, the effect 0 chlorides on the determinationcan be partly eliminated by using concentrated sulphuric acid in which silver sulphatehu been diuolved in place of the concentrated SUlphUric acid specified in 3.1.3. Ifthe ratio of earbon to chloride does not exceed unity, 25 IIof silver sulphate per litre ofsulphuric acid will be sufficient to precipitate the chloride.

5.1.1 A 5-gram soil sample shall be taken from the thoroughly mixedportion of the material passing the 425·micron IS Sieve and used for thetest.

6. PROCEDURE

6.1 The sample shall be placed in a glass weighing bottle and weighetl to0·001 g. A small quantity, from 5 g to 0'2 g depending on the organiccontent ( se« Note) shall be transferred to a dry 500-ml conical flask, theweighing bottle reweighed and the equivalent weight on oven-dry basis ofsoil specimen removed ( Wa ) calculated by difference and allowing for themoisture content of the soil.

NOTE - The size of the specimen for chemical analysis will vary with the amount oforganic matter present in the soil. A. much as 5 g mAy be required for soil low in or­ganic matter and as little aJ 0'2 g with a very peaty soil. After a number of determina­tions have been made, experience will indicate the most suitable .ize of specimen to betaken. In unfamiliar types of soil it is sultSested that ft aeries of specimens of varyingsius should be weighed out and tested. The determination giving a total of 5 to 8 mldichromate aolution reduced Ihould be taken al the correct result.

6.2 Ten millilitres of N potassium dichromate solution shall be run intothe conical flask from a burette, and add 20 ml of concentrated sulphuricacid very carefully from a measuring cylinder. The mixture shall bethoroughly swirled for about one minute and allowed to stand on a heatinsulating surface, such as asbestos, or wood, for 30 min to allow oxidationof the organic matter to proceed. During this period the flask shall beprotected from draughts. Distilled water, 200 ml, shall then be addedalong with 10 ml of orthophosphoric acid and one ml of the indicator(see Note). The mixture shall be shaken vigorously. If the, indicator isabsorbed by the soil, a further 1 ml of the solution shall be added. Ferroussulphate solution shall then be added from the second burette in 0·5 mlincrements, the contents of the flask being swirled, until the colour of thesolution changes from blue to green. A further 0·5 ml of· potassiumdichromate shall then be added, changing the colour of the solution backto blue. Ferrous sulphate solution shall then be added drop by dropwith continued swirling until the colour of the solution changes from blue

6

IS a2720 ( Part XXII) • 1972

to green after the addition of a single drop. The total volume of theferrous sulphate solution used ( T) shall be noted to the nearest 0'05 ntl.

Non - If compIa ferric ionl which interfere with the end point are Prelel1t in thesoil, after the addition of 10 mI of orthophosphoric acid. 0'2 g of lodium fluoride maybe added before the addition of the indicator.

7. CALCULAnONS

7.1 The total volume ( V ml) of potassium dichromate used to oxidize theorganic matter in the soil is given by the following formula:

V= 10'5 (1 - r/X)

where

r == total volume of ferrous sulphate used in this test, and

X .... total volume of ferrous sulphate used in the standard­ization test ( StI 4.1 ).

7.2 The percentage of organic -matter (OM) present in the oven-driedsample shall be calculated from the following formula:

O'G7 W VOM, percent by weight = WI W, (see Note )

where

Wa = weight on oven-dry basis of the soil sample passinglfl-rnm IS Sieve,

V = total volume of potassium dichromate used to oxidizethe organic matter, (as in 7.1 ),

WI = weight on oven-dry basis of the total soil sampletaken for the test before sieving, and

Wa = weight on oven-dry basis of the soil specimen usedin the test.

NOTl' - The method is based on the determination of the organic carbon content ofthe soil and it assumes that soil organic matter contains an average of 50 percent ofcarbon by weight. With the technique employed approximately 77 percent of thecarbon in the organic material is oxidized. These factors are included in the formulagiven in 7.2.

8. REPORT

8.1 The test results should be recorded suitably. A recommended proforma for recording the results is given in Appendix A.

•r8.2 The organic matter content present shall be reported to the nearest0'1 percent of the original oven-dry soil.

7

IS I 2720 ( Part xxn )•1972

SECTJON 2 DETERMINATION O'F ORGANIC MATTER(ALTERNATIVE METHOD) BY THE CHROMIC

OXIDATION EQUIVALENT OF SOIL ORGANIC MA1"TER

9. SCOPE

'.1 Section 2 of this standard (Part XXII) lays down the method fordetermining the percentage by weight of the organic matter present insoils, by the chromic oxidation equivalent of soil organic matter.9.2 Determination of organic matter of soil by chromic acid method is themost rapid and popular type of analysis and has the advantage of mode­rately satisfactory discrimination of humus from highly condensed formsincluding graphite and charcoal.

10. APPARATUS

-10.1 Electric Hot Plate - with adjwtable temperature.10.2 Beaken - 250-ml and 400-ml.10.3 Heat Re.i.tant Glalll Te.t Tabe. - 30 X 200 mm.10.4 Heat Re.i.taat Glasa Beaker ( Bath) - of 2-litre capacity.10.5 Thermometer - one, 0 to 250°0 range.10.6 A Oae-Utre Shallow Heat Rut.taat G1as. Tray ( Bath )10.7 Torsion Balance -sensitive to 0'05 g.10.8 CapUlary Tube, Stirrer and Compre8led Air Supply10.9 Stirriag Rod. - with ends flattened.10.10 Volumetric Pipette.10.n Barette - 50-mI.

U. REAGENTS

11.1 Ortbopho.phoric Acid, 85 Perceat - of specific gravity1'70 to 1'75.11.2 Chromic Acid, 0·4 N Solution - Exactly 19'61 g of potassiumdichromate ( oven dry) is dissolved in about 50 ml of water and then thesolution is diluted to one litre with concentrated sulphuric acid,U.3 Ferrous Ammoniam Sulphate 0'2 N Solution - Exactly 78'44 gof ferrous ammonium sulphate is dissolved in 300 ml of water containing20 ml of concentrated sulphuric acid, and the solution is diluted to 1 litrewith water. This solution is made freshly, or titrated against the standardchromic acid each day.11.4 Orthopheaoathroliae ladicator 0'025 M Solutioa

12. SOIL SAMPLE FOR TEST

12.1 The soil sample shall be ground to pass a 212-micron IS Sieve and0'25 g of soil ( 0'05 g if peat, 1'00 g if soil has less than one percent organic

8

18.2720 ( Put XXQ) -1mmatter) shall be taken in a 250-ml beaker or 30 X 200 mm test tube( $" also 5.1 ).

13. PROCEDURE13.1 Osldadoa 01 Orpme Matter - From a pipette, 20 ml of 0'4 Nchromic acid solution shall be added to the soil sample in the 250-mlbeaker or test tube, and similar quantity shall be taken for the standardiza­tion blank. The vessel with mixture shall be placed in the orthophos­phoric acid bath and heated on the electric hot plate at such a rate that atemperature of 155°C is reached in 20 to 25 min. The-contents of tube orbeaker shall be mixed every 5 min during the heating period. Thetemperature is held at 155 to 160°C for an additional 5 mil}. Thethermometer shall be kept in the blank, which is simultaneoUlly heated,to follow the solution temperature.13.2 The vessels with samples and blank shall be then removed from thebath, allowed to drain in the air for 30 sec, and then placed in a ·waterbath at room. temperature for 2 min. The thermometer shall be removedwith care not to break it by thermal shock.13.3 Back Titration - The chromic acid solution, now cooled to roomtemperature, shall be diluted with water to 75 to 200 ml, either in the tubeor 250-ml beaker. Then 5 ml of 85 percent orthophosphoric acid and 4drops of orthophenonthroline indicator shall be added. The solution shallbe back titrated with the 0'2 N ferrous ammonium sulphate until solutioncolour turns from green to red at the end point. An air jet stirrer should beused with the tube. The colour at start is dark brownish, and then shiftssharply from blue to red at the end point. The blank shall be similarlytitrated. More chromic acid shall be added to fresh samples if the amountadded proves to be inadequate; not over one-halfof the chromic acid shouldbe consumed by oxidation of organic matter.

If. CALCULATION OF RESULTSIf.I The percentage of organic matter in a soil shall be estimatedas follows:

Organic matter, percent (in soil) ... 20 (1- ~) X 0":3 (see Note)

where •T = sample titration, ml of approximately 0·2 N ferrous

solution;S = standardization blank titration, ml of approximately

0'2 N ferrous solution; and" = weight of soil sample taken, in g.

Non - In deriving the constant 0"23, it il assumed a i valance change of carbonOCCUI'I, 58 percent carbon OCCUI'I in soil organic matter, only carbon il oxidized, andonly 90 percent of total soil organic matter is oxldized,

14.2 The organic matter content present shall be reported to the nearest0·1 percent of the original oven-dry soil.

9

U I 2720 (Part XXII ) .1972

APPENDIX A

( Clause 8.1 )

PRO FORMA FOR RECORDING TEST RESULTS

Determiaatioa of 0l'laDic Matter CODteDt of SoU

Project.................. Details of soil samples " .

Sample number

Total weight of original sample( Wd, in g

Weight of soil passing IO-mm ISSieve ( WI)' in g

Weighing bottle numberWeight of weighing bottle and

dry soil before taking specimenfor test, in g

Weight of weighing bottle and Idry soil after taking "uecimenfor test, in g

Weight of dry soil specimen used(W,),ing

__;__:: : : 1

Volume of ferrous sulphate Isolution added to standardizepotassium dichromate solution(X),inml

Volume of ferrous sulphate!solution used to oxidize excess Ipotassium dichromate solution(n, in ml •

Volume of potassium dichromate :solution used to oxidize or- Iganic matter in soil V .... 10'5 i

(l-r/X), in ml I IPercentage of organic matter in I ;

"I '6 W. V I ISOl =--- I

WI WI I

_-Remarks :--1---110

BUREAU OF INDIAN STANDARDS

53627331 77

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