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है”ह”ह

IS 9971 (1981): Lactic Acid, Food Grade [FAD 8: FoodAdditives]

Gr 3

IS: 9971 ·1981( R••m",,_ 1115 )

Indian StandardSPECIFICATION FOR

LACTIC ACID, FOOD GRADE

( First Reprint AUGUST 1998 )

UDC 664.022.3 : 661.733.2

© Copyright 1982

BUREAU OF INDIAN STANDARDSMANAK BHAVAN. 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

April 1982

IS : 9971 • 1981

Indian StandardSPECIFICATION FOR

LACTIC ACID, FOOD GRADE

Food Additives Sectional Committee, AFDC 19

ChairmanDR K. K. G. MENON

Me",~rs

DR M. 1. MULKY ( Alternate toDr K. K. G. Menon)

CHAIRMAN

SI!CRETARY ( Alternate)DrRECTORDIRECTOR OF LARORATORIES

RepresentingHindustan Lever Ltd, Bombay

Technical Standardization Committee (Food­stuffs ), Ministry of Agriculture & Irrigation,New Delhi

Central Food Laboratory, CalcuttaDirectorate of Marketing &. Inspection ( Ministry

of Agriculture &. Irrigation ), Faridabad

DR A. G. NAIK-KuRADE

SHRI P. MANSUICHANISHRI G. K. NAIR ( Alternate)

SHRI K. L. CHAITERJEE ( Alternate)DRUGS CONTROLLER ( INDIA) Ministry of Health &. Family Welfare

DEPUTY DRUGS CONTROLLIlR( INDIA) ( Alternate)

GOVERNMENT ANALYST King Institute, MadrasPUBLIC ANALYST, CoIMBATORE ( Alternate I

DR S. GUVINDARAJAN The Federation of Hotel &. Restaurants Associationof India, New Delhi

SHRI B. HANUMANTIiA RAu Bush Boake Allen ( India) Ltd, MadrasDR T. S. SANTHANAKRISHAN t Altrmate )

SHRI H. R. S. IYENGAR Indian Confectionery Manufacturers' Association,New Delhi

JOINT COMMISSIONER (DD ) Ministry of Agriculture & IrrigationDEPUTY COMMISSIONER ( DD ) ( Alternate)

SHRI 1. C. KATHRANI Asian Chemical Works, Bombay; and All IndiaSaccharin Manufacturers' Association, Bombay

.~II India Food Preservers' Association, NewDelhi

Glaxo Laboratories ( India) Ltd, Bombay

( Contin"ed on page 2 )

e Copyright 1982BUREAU OF INDIAN STANDARDS

This publication is protected under the Indian Copyright Act (XIV of 19S7) andreproduction in whole or in part by any means except with written permission of thepublisher shan be deemed to be an infriaement of copyright under the said Act.

IS : 9971 . 1981

( Continued from page I )

MemberJSHRI S. M. MEHTA

SHRI M. V. DESAI ( Altemat» )SHRf V. K. MENONSHRf N. S. MURTY

SHRI V. K. ATRH ( Alternate)DR K. M. NARAYANAN

DR M. K. JAIN ( Alternate)OPPICIHN-CHARGE ( CFP )SHRI S. R. PALEKAR

SHRI J. V. YARDI ( Alternate)SHRI S. RAMASWAY

SHRI S. N. PANDEY ( Alternate)DR L. V. L. SASTRY

DR A. G. MATHIlW ( Alternate)SIlCRHTARY

SHRI 1. A. SIDDIQIDR R. K. SINHA

DR T. V. SURRAfH

RepreJenlingAtul Products Ltd, Atul

Arnar Dye Chern, KalyanHickson &. Dadajee Ltd. Bombay

National Dairy Research Institute (ICAR),Karoal

Forest Research Institute &. Colleges, Dehra DUDCorn Products ( India) Pvt Ltd. Bombay

Directorate General of Technical I>eveloplllCDt,New Delhi

CenIraI Food Technological Research Institute( CSIR), Mysore

Central Committee for Food Standards ( Ministryof Health & Family Wdfare). New Delhi

Directorate of Sugar & Vanaspati. New DelhiAll India Institute of Hygiene &. Public Health.

CalcuttaIndian Chemical Manufacturers' Association.

CalcuttaDR R. K. MEHTA ( Alternate)

SHRI S. B. SULE Naarden ( India) Ltd, BombaySHRI M. a. TURAKHIA Idachem Industries Pvt Ltd, Bombay

SURI a. J. NAVLOOR ( Alternate )SHRJ T. PURNANANDAM. Director General, lSI ( Ex-officio Mmtber)

Director ( Agri & Food)

SecretarySHRI V. S. MATHUR

Deputy Director (Agri &. Food ), lSI

Preservatives, Anti-Oxidants, Emulsifying and Stabilizing AgentsSubcommittee, AFDC 19 : 3

ConvenerDR G. LAKSHMINARAYANA Regional Research

HyderabadLaboratory ( CSIR ).

MembersGOV~RNMENT ANALYST King Institute, MadrasSHRI R. HANLMANnlA RAU Bush Boake Allen ( India) Ltd, Madras

DR T. S. SANTHANAKRISIiNAN ( Alternate)SHIU RAMACHANDIIA VISVANATH Navasari Oil Products Ltd, Navasari. KARNll

SURI ARVIND HANUMANT VIDWANS ( Alternate)

( Continued on page 12)

2

AMENDMENT NO. 1 MARCH 1997TO

IS 9971 : 1981 SPECIFICATION FORLACTIC ACID, FOOD GRADE

(Page 9, clauses A·9 toA·9.2 ) - Substitute the following for the eXlslingmatter:

'A·' CYANIDE

A·J.l Metbod

Reagents

P·PhenylenedilJmine.Pyridlne Mixed Reagent - DIssolve 200 mg ofp-pbenylcnedulIlline hydrocblonde In 100 ml of water, warming 10 effectsolution Cool, allow tbe solids to settle, and use Ihe supernatant liquid 10 makethe mixed reagent DIssolve 128 ml of pyndme m 365 rul of water,add 10 ml ofhydrocblonc acid, and mill. To prepare the nuxed reagent, nux 30 ml of thep-phenylenedlilmlnesoluuon with all of the pyridmc soluuon, and allow to standfor 24 b before using The mixed reagent IS stable for about three weeks When'itored In an limber hottle.

Sample Solution - Transfer an accuratelv weighed quannty of the sample,equivalent to 20.0 g of 100 percent lacuc and into a loo-ml volumetric Ilask,dilute to volume With water, lind mix.

Cyanide Standard Solution - Dissolve 2.5 g of potassiumcyanide In 1000 mJof 0.1 N sodium hydroxide. Transfer a 10-m) aliquot into a lOO-ml volumetricflask, dilute to volume witb 0.1 N sodium hydroxide, and nux. Eacb ml of thissolution contains 10 ug of CN.

Procedure - Pipette a 10-ml aliquot of the sample solution intoa SO-m) beaker.Into I second 50-rnl beaker pipette 10m) of the Cyamde standard solution, andadd 10 ml of water. Place tbe beakers In an ice bath, and adjust the pH tobetween 9 and to with 20 percent sodium hydroxide, surnng slowly and addingthe reagent slowly to avoid overheating.

Allow tbe soluuons 10 stand for 3 min and then slowly add 10 percentphosphoric acid to a pH between 5 and 6 Transfer the solution into l00-mlseparators comarning 25 ml of cold water, and nnse tbe beakers and pH meierelectrodes wltb • few ml of cold water, collecting tbe washmgs m tbe respecuveseparator. Add 2 ml of bromine, stopper and DU". Add 2 mJ of 2 percentsodium

1

Amend No. I to IS 9971 : 1981

arsenite solution, stopper, and mix. To tbe clear solutions add 10 ml ofn-butanol, stopper, and mix. Finally, add 5 lUI of p-Pbenylenediamine-pyridinemixed reagent, mix, and allow to stand for 15 min. Remove and discard theaqueous phases, and filter the alcobol phases into 10-mm cells. The absorbanceof the sample, determined at 480 nm with a suitable spectrophotometer, is nogreater than that of tne standard.'

(FAD 8)

2Pnnted at SImco Pnntsng Pre... Deihl, India

IS : 9971 - 1981

Indian StandardSPECIFICATION FOR

LACTIC ACID, FOOD GRADE

O. FOREWOR D

0.1 This Indian Standard was adopted by the Indian Standards Institutionon 30 October 1981, after the draft finalized by the Food Additives SectionalCommittee had been approved by the Agricultural and Food ProductsDivision Council.

0.1 With the expansion of processed food industry, food additives, generallyin small quantities, are increasingly used to improve the appearance, flavour,texture or storage properties of the processed foods. As certain impuritiesin these substances have been found to be harmful. it is necessary to havestrict quality control of these food additives. This standard has been pre­pared to cover purity and identification of lactic acid. The standard wouldhelp in checki.ig purity at the stage of manufacture, for it is difficult todetectthe impurity once the additive has been added to the processed foods.Besides. the standard is intended to guide the indigenous manufacturers inmaking their product conform to the specification which is accepted byscientists, health authorities and international bodies.

0.3 Latic acid is used as acidulent in beverages like soft drinks, mineralwater, carbonated fruit juice, etc, to acid pickles, relishes, salad dressings andvariety of fruit products such as jams, jellies, gelatines, marmalades, frozenfruit desserts, etc. It is also used in the manufacture of beer and wine, anddairy products like processed cheese, unsalted butter and in processing ofmeat, egg whites and sauces for canned fish.

0.4 Chemical Name - Lactic acid is 2.hydroxy propionic acid or l-hydroxy­etbane-l-carboxylic acid. Its empirical formula is CaH.Oa. Its molecularmass is 90'08 and structural formula is:

HI

CHa-C-COOHI

OH

3

IS : 9971 - 1981

0.5 In the preparation of this standard considerable assistance has beenderived from :

Specification for identity and purity of some food additives. FAONutrition Meeting Report Series No. 57, FAO/WHO, Rome 1977;and

Food Chemical Codex. 1966. Ed 1. National Academy of Sciences andNational Research Council, Washington, D.C.

0.6 In the preparation of this standard, due consideration has been given tothe provisions of the Prevention of Food Adulteration Act, 1954 and Rulesframed thereunder. However, this standard is subject to the restrictionsimposed under these, wherever applicable.

0.7 For the purpose of deciding whether a particular requirement of thisstandard is complied with, the final value, observed or calculated, expressingthe result of a test or analysis, shan be rounded off in accordance withIS : 2-1960·. The number of significant places retained in the rounded offvalue should be tbe same as tbat of the specified value in this standard.

1. SCOPE

1.1 This standard prescribes the requirements and methods of sampling andtest for lactic acid. food grade.

2. REQUIREMENTS

2.1 DescrlptiOD - Lactic acid shall be yellowish to colourless syrupy liquidwith an acidic taste and no odour. It consists of a mixture of lactic acid( CaH.Oa ) and lactic acid lactate ( C.H100ll ) . It is obtained by lacticfermentation of sugars or is prepared synthetically. Purity of commonproducts of commerce is 50 to 90 percent.

NOTE - Lactic acid is hygroscopic and when concentrated by boiling. it condensesto form lactic acid lactate, which on dilution and heating hydrolyzes to lactic acid.

2.2 Identification

2.2.1 Solubility - Lactic acid shall be miscible with water and ethanol.

2.2.2 Test for Acid - One in ten solution of the sample shall be acidic tolitmus paper.

·Rules for rounding off numerical values ( revised).

4

IS: 9911-1981

%.3 Test for Lactate - The material shall give positive test for lactate.

%.4 The material sball also conform to the requirements given in Table I.

TABLE 1 REQUIREMENTS FOR LACIIC ACID

-"\

IS : 1699­1974·

MIlTHOD OF TEST. REP TO CL OF-A.-

Appendix A ofthis Standard

REQUllUl­MINI'

CHt.llACTIlR)STlCSLNo.

( I ) ( 2 ) ( 3 ) ( 4 ) (5 )

10

A-IIA-12

A-8

A-9

A-l0

A-1

A-6

A-S

A-2

A-3

A-4

A-I

3

dodo

0'7

0'1

02

1010

95'0 to105'0

Conform totest

Conform totestdo

i) Purity (CaH.O.), percentby QIUs of the tabled con­centration

ii) Sulphated ash. percent bymass, Max

iii) Chlorides, percent bymasa,Mev:

iv) Sulphates (as SO,), per­cent by mass. Max

v) Citric, oxalic, phosphoricand tartaric acids

vi) Sugars

vii) Readily carbonizable sub­stances

viii) Volatile fatty acidix) Cyanide

x) Methanol, percent by mass,Max

xi) Iron ( as Fe ), mg/kg, Maxxii) Heavy metals (as Pb ),

mgJkg, Maxxiii) Arsenic (as As), JDI/kg.

Max

·Method of sampling and test for food colours (first revision ).

3. PACKING, STORAGE AND MARKING

3.1 Packing - The material shall be filled in containers with as little airspace as possible. The containers shall be such as to preclude aircontamination of the contents with metals or other impurities.

5

IS : 9971 - 1981

3.2 Storage - The material shall be stored in a cool and dry place so as toavoid excessive exposure to heat.

3.3 Marking - Each container shall be marked legibly and indelibly to givethe following information:

a) Name of the material including the words 'Food Grade',

b) Name and address of the manufacturer,

c) Minimum net mass,

d) Batch or code number, and

e) Lactic acid content.

3.3.1 The product may abo be marked WIth Standard mark.

3.4 The use of the Standard Mark is governed by the provisions of Bureau ofIndian Standards Act, 1986 and the Rules and Regulations made thereunder.The details of condinons under which the Itcence for the use of Standard Markmay be granted to manCucaturers or producers may be obtained from the Bureauof Indian Standards.

4. SAMPLING

4.1 The representative samples of the material shall be drawn according tothe method prescribed in Appendix A of IS: 2557-1963*.

5. TESTS

5.1 Tests shall be carried out by the methods specified in col 4 and 5 ofTable 1.

5.2 Quality of Reagents - Unless specified otherwise pure chemicals anddistilled water ( see IS : l070-l977t ) shall be employed 10 tests.

NOTl! - 'Pure chemicals' shall mean chemicals that do not contain rmpunues whichaffect the results of analysis,

·Speclficatlon for annatto colour for food products.tSpeclficalion for water for general laboratory usc ( second revision ).

6

IS : 9971 - 1981

APPENDIX A

( Table 1 )

METHOD OF TEST FOR LACTIC ACID

A-I. PURITY

A-l.l Reagents

A-l.l.l Sodium Hydroxide - I N.

A-l.I.2 Phenolphthalein Indicator - Dissolve 0'2 g of phenolphthalein in60 ml of 90 percent ethanol and add water to make 100 ml.

A-l.l.3 Sulphuric Acid - I N.

A-1.2 Procedure - Weigh accurately a portion of the sample equivalent to5 g of lactic acid, transfer to a 250 ml flask, add 50 ml of sodium hydroxide,mix, and boil for 20 minutes. Add phenolphthalein, and titrate the excessalkali in the hot solution with 1 N sulphuric acid, and perform a blankdetermination. Each ml of 1 N sodium hydroxide is equivalent to 90'08 mgof lactic acid.

A-2. SULPHATED ASH

A-2.l Reagent

A-2.1.1 Sulphuric Acid - concentrated.

A-2.2 Procedure - Weigh accurately 5 g of the material in a tared crucible.Ignite, gently at first, until the material is thoroughly charred. Cool, moistenthe residue with I ml of sulphuric acid and ignite gently till. the carbon iscompletely consumed. Cool the crucible in a desiccator and weigh.

NOTE - Carry out the ignition in a place protected from air currents and use asIowa temperature as possible to effect complete combustion of carbon.

A-2.3 Calculation

Sulphated ash content by mass = M 1 X 100M.

where

M 1 = mass, in g, of the residue; and

M. = mass, in g, of the material taken for the test.

7

IS : 9971 - 1981

A-3. CHLORIDES

A-3.t Reagents

A-3.1.t Sodium Hydroxide Solution - 1 : 4.

A-3.t.2 Potassium Chromate Solution - 10 percent ( mill) in water.

A-3.t.3 Silver Nitrate - 0'1 N.

A-3.2 Procedure - Weigh accurately a portion of the sample equivalent toabout 5 g of lactic acid; dissolved in 50 ml of water, and neutralize to litmuswith sodium hydroxide solution ( I : 4). Add 2 ml of potassium chromateand titrate with 0·1 N silver nitrate to the first appearance of a red tinge.Each ml of 0'1 N silver nitrate is equivalent to 3'545 mg ofCl.

A-4. SULPHATE

A-4.1 Reageots

A-.U.l Sodium Hydroxide Solution - I : 2.

A4.t.2 Barium Chloride Solution - 12 percent ( mjv ) in water.

A-4.2 Procedure - Weigh accurately a portion of the sample equivalent to50 g of lactic acid, transfer into a 600 ml beaker, dissolve in 200 ml of water,and adjust the pH to between 4'5 and 6'5 by addition of sodium hydroxidesolution (I : 2), making the final adjustment with a more dilute alkalisolution. Filter, if necessary, and heat the filtrate or clear solution to justbelow the boiling point. Add 10 ml of barium chloride solution stirringvigorously, boil the mixture gently for 5 minutes, and allow to stand for atleast 2 hours, or preferably overnight. Collect the precipitate of bariumsulphate in a tared Gooch crucible, wash until free from chloride, dry, andignite at 600°C to constant mass. The mass of barium sulphate so obtained,multiplied by 0'412, represents the mass of S04 in the sample taken.

A-5. CITRIC, OXALIC, PHOSPHORIC AND TARTARIC ACIDS

A-S.t Procedure - Dilute I g of the sample to 10 ml with water. Add40 ml of calcium hydroxide solution [0'14 g of Ca( OH )2 in 100 ml ofwater] and boil for 2 minutes. No turbidity shall be produced.

A-6. SUGARS

A-6.1 Procedure - Add 5 drops of the sample to 10 ml of hot alkalinecupric tartrate solution ( Fehling's solution). No red precipitate shall beformed.

8

IS : 9971 - 1981

NOTB - Fehling's solution is a mixture of equal volumes of solution 1 and 2 pre­pared immediately before usc. Solution I consists of p4'64 g of copper sulphate In amixture of 0'5 ml of sulphuric acid and sufficient water to produce 500 ml andSolution 2 is 176 g of sodium potassium tartrate and 77 g of sodium hydroxide insufficient water to produce 500 mi.

A-7. READILY CARBONIZABLE SUBSTANCES

A-7.1 Procedure - Superimpose carefully S ml of the sample kept at I SoCon 5 ml of concentrated sulphuric acid kept at I SoC. No deep grey colourshall be produced within IS minutes at the contact zone of the twoliquids.

A-S. VOLATILE FATIY ACID

A-8.1 Heat 5 ml of the sample on a water bath. No strong fatty acid likeodour shall be evolved.

A-9. CYANJDE

A-9.l Reagents

A-9.l.1 Sodium Hydroxide - 20 percent.

A-9.1.2 Chloramine-T Solution - Dissolve I g of chloramine-T( C7H7NaOaSCl . 3H aO ) in water to make 100 ml, Prepare fresh beforeuse.

A-9.l.3 Pyridine-Pyrazolone Solution - Dissolve 0'5 g of l-phenyl-rnethyl­5-pyrazolone in 100 ml of hot water at 75°C and cool to room temperature.Mix it with 20 ml of pyridine containing 0'025 g of bis-( l-phenyl-J-methyJ­5-pyrazolene). Prepare fresh before use.

A-9.l.4 Phenolphthalein Solution

A-9.t.S Acetic Acid Solution - 30 percent in water ( m]v ).

A-9.1.6 Dilute Acetic Acid Solution - 6 percent in water ( miv ).

A-9.2 Procedure - To 0'1 g of the sample add 3 ml of 20 percent sodiumhydroxide solution and heat for 10 minutes on a water bath. After cooling,add I drop of phenolphthalein solution and add dropwise dilute aceticacid solution until the pink colour has disappeared. Add 3 drops of diluteacetic acid solution and water to make 40 ml. Add 0'6 ml of the chlora­mine- T solution and allow to stand for 3 minutes. Add 10 ml of thepyridine-pyrazolone solution and allow to stand for 25 minutes. No bluecolour shall be produced ( limit approx 1 mgJkg ).

9

IS : 9971 - 1981

A-tO. MEmANOL

A-IO.l Reageuts

A-IO.I.t Potassium PermDIIganate Solution - Dissolve 30 g of potassiumpermanganate and IS ml of phosphoric acid in 100 ml water. This solutionmay be retained for a month.

A-IO.l.2 Sodium Salt ofChromotrophic Acid Solution - 5 percent ( mlv ).

A-IO.I.3 Calcium Carbonate

A-tO.2 Preparatioo of Sample - To 5 ml of the sample add 8 ml of waterand 5 g of calcium carbonate and distil. Dilute 5 ml of the initial distillatewith water to 100 ml.

A-IO.3 Determination - Pipette 2 ml potassium permanganate solution intoa 50 rnl volumetric flask. Chill in the ice-bath. Add I ml of sample solu- ..tion ( see A-IO.2 ) and let it stand in ice-bath for 30 minutes. Decolourizewith a little dry sodium bisulphate and add 1 ml of chromotrophic acidsolution. Add 15 ml of sulphuric acid slowly with swirling and place in hot( 6O-75°C) water bath for 15 minutes. Cool, and change water to bring to50 ml mark, mix. and dilute to volume with water at room temperature.

A-IO.4 The colour of sample solution treated as in A-tO.3 shall not bedarker than that of control prepared by 1 ml of methyl alcohol diluted to10000 times and subjected to same treatment as given in A·IO.3.

NOTE - Temperature of standard and sample solution should be within 1°C.

A-H. IRON

A-ll.t Reagents

A-ll.l.1 Dilute Hydrochloric Acid - 1 : 2.

A-Il.I.2 Ammonium Persulphate - Crystals.

A-ll.1.3 Ammonium Thiocyanate Solution - 7'6 percent ( mlv) in water( approximately N ).

A-ll.I.4 Standard Iron Solution - Containing 20 ",g of Fe.

A-ll.2 Procedure - To the ash obtained in the test for sulphated ash ( seeA-2.2 ) and 2 ml of dilute hydrochloric acid and evaporate to dryness ona steam bath. Dissolve the residue in I ml of hydrochloric acid, dilute to40 ml with water, and add about 40 mg of ammonium persulphate crystalsand 10 ml of the ammonium thiocyanate solution. Any red or pink colourshall not exceed that produced by 2'5 ml of the Iron Standard Solution in anequal volume of solution containing the quantities of reagents used in thetest.

10

IS : 9971 - 1981

A-12. HEAVY METALS

A-12.1 ReagentsA-12.1.1 Ammonia Solution - Dilute 400 ml of ammonium hydroxide

(23 percent) to 1 000 ml with water.A-12.1.2 Hydrochloric Acid - 10 percent.A-12.1.3 Lead Nitrate Stock Solution - Dissolve 159'8 mg of lead nitrate

in ]00 ml of water containing] ml of nitric acid. Dilute with water to1 000 ml and mix. Prepare and store the solution in lead-free glasscontainers.

A-12.1.4 Standard Lead Solution - Dilute 10 ml of lead nitrate stocksolution. accurately measured, with water to ]00 ml. Each ml of thesolution so prepared contains the equivalent of 10 f'g of lead ion ( Pb ).Prepare the solution on the day of use.

A-ll.1.5 Nitric Acid - to percent.A-I2.1.6 Sulphuric Acid - 94'5 to 95'5 percent.A-12.1.7 Acetic Acid - 6 percent.A-12.1.S Hydrogen Sulphide - A saturated solution of hydrogen sulphide

made by passing HaS through cold water.

A-12.2 Procedure

A-12.2.1 Solution A - Take 2 ml of the standard lead solution in 50 mlNessler tube and add 25 ml of water. Adjust the pH to between 3'0 to 4'0by addition of acetic acid or ammonia solution. Dilute with water to 40 mland mix.

A-12.2.2 Solution B - Place 2 g of the sample, accurately weighed, in asuitable crucible, add sufficient nitric acid to wet the sample, and carefullyignite at a low temperature until thoroughly charred, covering the crucibleloosely with a suitable lid during the ignition. After the substance is thoro­ughly carbonized, add 2 ml of nitric acid and 5 drops of sulphuric acid, andcautiously heat until white fumes are evolved, then ignite preferably in amuffle furnace, at 500 to 600"C until the carbon is all burned off. Cool.add 4 ml of dilute hydrochloric acid, cover, and digest on a steam-bath for10 to 15 minutes. Uncover, and slowly evaporate on a steam-bath to dry­ness. Moisten the residue with one drop of hydrochloric acid, add to ml ofhot water, and digest for 2 minutes. Add dropwise ammonia solution untilthe solution is just alkaline to litmus paper, dilute with water to 25 mi. andadjust the pH to between 30 and 4'0 (pH indicator paper) by the additionof diluted acetic acid. Filter, if necessary, wash the crucible and the filterpaper with to m1 of water. Transfer to a 50 ml Nessler tube. Dilute thecombined filtrate and wash with water to 40 ml and mix.

A-12.2.3 - To each tube add 10 ml offreshly prepared hydrogen sulphide,mix and allow to stand for 5 minutes and view down over a white surface.The colour of Solution B shall not be darker than that of Solution A.

11

IS : 9971 - 1981

( Colltillued from page 2 )

Members

DR S. K. KASHYAPDR D. N. Roy ( Alternate)

DR I. M. PATEL

DR C. V. RAo (Alternate)DR R. V. RAOSHRJ B. B. SAVDESH PANDE

SHRJ S. R. PALI!KAR ( Alternate )DR L. V. L. SASTRY

SBCRETARY

SHRJ I. A. SroDlQI

RepresentingIndian Council of Medical Research, New Delhi

Kaira District Cooperative Milk: Producers UnionLtd, Anand

National Dairy Research Institute ( ICAR ), KarnalCorn Products Company (Ind,ia) Pvt Ltd,

Bombay

Central Food Technological Research Institute( CSIR ), Mysore

Central Committee for Food Standards ( Ministryof Health & Family Welfare ), New Delhi

Directorate of SUlar &. Vilnupati, New Delhi

12

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Patliputra Industnal Estate, PATNA 800013

lnsntuno«of Engineers (India) BUilding 1332 ShlVaJI Nagar, PUNE 411005

t c No 14/1421, University PO Palayam, THIRUVANANTHAPURAM 695034

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8394955

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8-288801

8-711996

541137

201083

372925

21 6876

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62117

'Sales Office IS at 5 Chownnghee Approach, PO Pnncep Street,CALCUITA 700072

tSales Office IS at Novelty Chambers, Grant Road, MUMBAI 400007

:j:Sales Office IS at 'F' Block, Unity BUilding, Narashtmaraja Square,BANGAlORE 560002

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Pllnted at SImco Printing Press, Deihl