PRELIMIMARY DRAFT CIRCULATION Our Ref : CHD 35/T- Doc (10810)P Date : 06 10 2016 Air Quality Sectional Committee, CHD 35 ADDRESSED TO: 1)All Members of Air Quality Sectional Committee, CHD 35 2) All others interested Dear Sir(s) Please find enclosed the following draft Indian Standard: i) DOC : CHD 35 (10810)P IS 5182 (P art 7):... METHODS FOR MEASUREMENT OF AIR POLLUTION Part 7 Hydrogen Sulphide (First Revision) These documents are also hosted on BIS website www.bis.org.in Last date for comment: 06 11 2016 Kindly examine draft Indian standard and forward your views stating any difficulties which you are likely to experience in your business or profession, if these are finally adopted as National Standard. Comments, if any, may please be made in the format as given overleaf and mailed to the undersigned at the above address. In case no comments are received, we would presume your approval of the documents. However, in case we receive any comments on the document, the same shall be put up to the Sectional Committee or necessary action. Thanking you, Yours faithfully Encl : As above (U K DAS) Scientist E&H(Chemical) chd@bis.org.in Fax: 011 23236428
र र मभक पररच लन स द हम र स दभ स एचड 35 (...) प दद क : 06 10 2016 तकन क सम तत : व य क ग णव त, स एचड 35 र प तकत 1 स एचड 35 क सभ सदस य 2 चच रख व ल अन य न क य मह दय,) य ( क पय न म ललखखत मस द र प त कर : i) स एचड 35 (10810)प IS 5182 (भ ग 7)... व य रद षण क म प क ललए तर क भ ग 7 ह इर ज स फ इड (आईएस 5182 (भ ग 7) क पहल प र ण) क पय इस मस द क अवल क कर और अप सम मनतय यह बत त ह ए भ ज कक यदद यह मस द र ष र य म क क प म रक ल त ह त इस पर अमल कर म आपक व यवस य अथव क र ब र म य कद इय आ सकत ह सम ततय भ जन क अ तत ततथ 06 11 2016 सम मनतय यदद क ई ह त क पय अध हस त रष त क उपरललखखत पत पर स लग फ म ट म भ ज यदद क ई सम मनत र प त ह ह त ह अथव सम मनत म क वल भ ष स ब ध र दट ह ई त उपर त रल ख क यथ वत अ नतम प द ददय ज एग यदद सम मनत तक क रक नत क ह ई त वव षय सलमनत क अध य क पर म स अथव उ क इच छ पर आग क क य व ह क ललए वव षय सलमनत क भ ज ज क ब द रल ख क अ नतम प द ददय ज एग धन य व द, स लग उपर तललखखत : भवद य, (य क द स) व ञ न क ई एव रम ख ) रस य (
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DOC: CHD 35 (10810)P भ रत य म नक मस द व य रद षण क म पन क तर क भ ग 7 ह इर जन स फ इड (आईएस 5182 (भ ग 7) क पहल प नर षण) Draft Indian Standard METHODS FOR MEASUREMENT OF AIR POLLUTION Part 7 Hydrogen Sulphide [First Revision of IS 5182 (Part 7)] ICS No. BIS 2015 B U R E A U OF I N D I A N S T A N D A R D S MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG NEW DELHI 110002 October 2016 Price Group
Air Quality Sectional Committee, CHD 35 FOREWORD Formal text will be added later on after finalization of the document by Air Quality Sectional Committee, CHD 35. Hydrogen sulfide gas causes a wide range of health effects. Workers are primarily exposed to hydrogen sulfide by breathing it. The effects depend on how much hydrogen sulfide you breathe and for how long. Exposure to very high concentrations can quickly lead to death. It is a colourless gas with the characteristic foul odour of rotten eggs. It is heavier than air, very poisonous, corrosive, flammable, and explosive. Hydrogen sulphide is a highly toxic gas. Repeated exposure to low concentration has an irritating effect on mucous membranes, eyes and respiratory tract. Hydrogen sulphide may be present in the ambient atmosphere at low concentrations. Concentrations in excess of 139 µg/m 3 are seldom encountered except as a result of an accident. Very high concentrations of H2S may be present in geo-thermal gases. For the workplace environment, the American Conference of Governmental Industrial Hygienists (ACGIH) suggested exposure limit for H2S is 14 mg/m 3. In the preparation of this standard, reference has been taken from Methods of Air sampling and Analysis (Third edition) by James P. Lodge. This standard was first published in 1973. In the first revision of the standard, the sampling collection efficiency of hydrogen sulphide has been increased by adding arabinogalactan to the absorbing solution. Some more possible interferences have been added to the existing standard. The analysis method has also been revised. The first revision aims to incorporate the latest international technology available. In reporting the result of a test or analysis made in accordance with this standard, if the final value, observed or calculated, is to be rounded off, it shall be done in accordance with IS : 2-1960 : Rules for rounding off numerical values (revised).
DOC: CHD 35(10810)P Draft Indian Standard METHODS FOR MEASUREMENT OF AIR POLLUTION PART 7 HYDROGEN SULPHIDE (First Revision of IS 5182 (Part 7)) 1 SCOPE 1.1 This standard prescribes a method for the measurement of hydrogen sulphide (as H2S) in ambient air. 1.2 This method is intended to provide a measure of hydrogen sulphide in ambient air in the range of 2.2 to 200 µg/m 3. When sampling air at the maximum recommended rate of 1.5 L/min. for 2 hrs, the minimum detectable sulphide concentration is 1.1 µg/m 3 at 760 mm. Hg and 25 o C. 2 REFERENCES The following standards contain provisions which through reference in this text constitute provisions of this standard. At the time of publications, the editions indicated were valid. All standards are subject to revision and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below: IS No. Title 1070 : 1992 Reagent-grade water (third revision) 4167 : 1980 Glossary of terms relating to air pollution (first revision) 3 TERMINOLOGY The definitions given in IS 4167 shall apply. 4 PRINCIPLE Hydrogen sulphide is collected by aspirating a measured volume of air through an alkaline suspension of cadmium hydroxide. The sulphide is precipitated as cadmium sulphide to prevent air oxidation of the sulphide which occurs rapidly in an aqueous alkaline solution. Arabinogalactan is added to the cadmium hydroxide slurry prior to sampling to minimize photo-decomposition of the precipitated cadmium sulphide. The collected sulphide is subsequently determined by spectrophotometric measurement of the methylene blue produced by the reaction of the sulphide with a strong acid solution of N,N-dimethyl-p-phenylenediamine and ferric chloride. 5 RANGE AND SENSITIVITY
This method is intended to provide a measure of hydrogen sulphide in ambient air in the range of 2.2 to 200 µg/m 3. For concentrations above 70 µg/m 3, the sampling period can be reduced or the liquid volume increased either before or after aspirating. When sampling air at the maximum recommended rate of 1.5 L/min for 2 hrs, the minimum detectable sulphide concentration is 1.1 µg/m 3 at 760 mm. Hg and 25 o C. Although a limit of detection limit of 0.2 µg H2S/m 3 may be computed for a 1 m 3 air sample based on the aqueous limit of detection of 8 ng/ml and a solution volume of 25 ml, losses averaging 46 % have been reported for 24 hr. sampling of ambient air containing 25 to 56 µg H2S/m 3. 6 INTERFERENCES 6.1 The methylene blue reaction is highly specific for sulphide at low concentrations usually encountered in ambient air. Reducing agents such as sulphite retard colour development if present in significant concentrations even in the case of solutions containing several µg S 2- /ml. Upto 40 µg/ml of sulphite interference can however be overcome by adding 0.1 0.3 ml ferric chloride instead of 0.05 ml for colour development and extending the reaction time to 50 min. 6.2 At levels of 0.5 µg/ml, nitrite produces a pale yellow colour with the reagents. No interference is encountered when 0.3 ppm NO2 is aspirated through a midget impinger containing a slurry of cadmium hydroxide-cadmium sulphide - arabinogalactan. 6.3 Atmospheric oxides of nitrogen cause interference. They may be avoided by adding sulphamic acid after the sampling is over. 6.4 Ozone at 57 ppb reduces the recovery of sulphide previously precipitated as CdS by 15%. Other possible atmospheric interferences like sulphur-dioxide and ammonia are not serious at their normal existing levels of concentrations. 6.5 Cadmium sulphide decomposes significantly when exposed to light. Addition of 1% arabinogalactan greatly reduces such loss but does not completely eliminate it. Consequently, the absorber vessel needs to be protected from light. 6.6 When sampling H2S concentration 7 mg/m 3, the sampling time must be limited to 5 min. Prolonged sampling of high concentration of H2S may result in deposition of sulphur in the frits of the absorber due to oxidation of sulphide. Such deposition causes a gradual decrease in sampling rate in the absence of a device to maintain the flow rate constant. 7 APPARATUS 7.1 Sampling apparatus The equipment to be used for sampling consists of a standard impinger of 35 ml capacity, a trap, a flow meter or critical orifice device and a suction pump. The arrangement of the sampling train is illustrated in Fig. 1.
7.1.1 Impinger All-glass impinger, 35 ml capacity, 220 mm in length and 26 mm wide. Impinging end of the tube shall be of 1 mm bore size or preferably with fritted disc with porosity of 50 microns or less (see Fig. 2A and 2B). Impingers shall be made from borosilicate glass. 7.1.2 Flow meter A rotameter calibrated accurately for the flow range from 0.2 L/min (for long-term sampling) to 1 L/min. (for short-term sampling). 7.1.3 Critical orifice device This device is used to give a flow of about 1 L/min. Normally hypodermic needles are used as critical orifice. The needles shall be protected by membrane filters. The arrangement is illustrated in Fig.3. 7.1.4 Trap This may be a membrane filter (see Fig. 3) or a glass wool trap (see Fig.1).
Fig. 3 Critical Orifice Flow device
7.1.5 Pump It shall be a suction device capable of drawing air into the sampling train at the rate of 10 to 20 L/min provided with a vacuum regulator and a moisture trap. It shall be of light mass, suitable for field work (portable) with continuous rating, self-lubricating and capable of operating at 230 V ac, 50 Hz. 7.2 Spectrophotometer capable of operating at 670 nm using 1 cm length cuvette. A long path length (2-5 cm) cuvette may be used to improve sensitivity. 8 REAGENTS 8.1 Amine-sulphuric acid stock solution Add 50 ml concentrated Sulphuric acid to 30 ml distilled water with continuous stirring and allow to cool. Dissolve 12 gm N,N-dimethyl-p-phenylene dihydrochloride in the Sulphuric acid solution. 8.2 Sulphuric acid, 50% Add 500 ml conc. Sulphuric acid slowly to 400 ml distilled water with continuous stirring and allow to cool. Quantitatively transfer to a 1 litre volumetric flask and make up to the mark. 8.3 Amine-sulphuric acid standard solution Dilute 25 ml of the stock solution in 8.1 to 1 Litre with 50% Sulphuric acid. 8.4 Ferric chloride solution, 3.7 M Dissolve 100 gm Ferric Chloride hexahydrate (FeCl3.6 H2O) in 30 ml water and add 9 ml of conc. Hydrochloric acid. Make up the volume of the solution to 100 ml. 8.5 Ammonium phosphate, 40% w/v Dissolve 400 gm of di-ammonium phosphate in water and make upto 1 litre in a volumetric flask. 8.6 Arabinogalactan. 8.7 Absorbing solution Dissolve 4.3 gm of Cadmium Sulphate octahydrate (CdSO4. 8H2O) and 1.8 gm Sodium Hydroxide in separate 250 ml portions of water. Add the two solutions to each other. Add 10 gm of arabinogalactan and dilute to 1 Litre. Shake the resultant suspension vigorously before removing an aliquot. Prepare fresh every 3 days. The ph of the absorbing solution recommended here is approximately 10 and yields superior results. 8.8 Sodium sulphide solution Dissolve 1.2 gm of Sodium Sulphide (Na2S.9 H2O) in 1 litre of pre-refrigerated distilled water and stopper it. Since the solution is very unstable, it should be prepared just before use. It should be stored in a refrigerator. The approximate concentration of the Sulphde solution will be 420 µg S 2- /ml. The exact concentration must be determined by iodometric titration using sodium thio-sulphate solution immediately prior to dilution (see 9.4.1).
8.9 Dilute standard sulphide solution Dilute 10 ml of the standardized stock sulphide solution to 1 litre with freshly boiled distilled water. Protect the boiled water under an oxygen-free nitrogen atmosphere while cooling. This sulphide solution is unstable. Therefore, prepare this solution immediately prior to use. This diluted solution will contain approximately 4 µg S 2- /ml. 8.10 Standard iodine solution (0.025 N) Dissolve 10 to 12.5 gm Potassium Iodide (KI) in a little distilled water and add 1.6 gm re-sublimed iodine. After iodine has dissolved, dilute to 500 ml with distilled water. 8.11 Standard sodium-thiosulphate solution (0.025 N) Dissolve 6.205 gm Sodium thiosulphate pentahydrate (Na2S2O3.5 H2O) in distilled water. Add 0.4 gm solid Sodium Hydroxide and dilute to 1 litre. 8.12 Standard potassium iodate solution (0.025 N) Dissolve 0.8925 gm Potassium iodate (KIO3) in 1litre distilled water. 9 PROCEDURE 9.1 Cleaning of equipment: All glass-wares should be thoroughly cleaned. The following procedure is recommended - Wash with a detergent and tap water solution followed by tap water and distilled water rinses. Soak in 1:1 concentrated nitric acid for 30 minutes and then follow with tap, distilled and reagent water rinses. 9.2 Sampling: Procedures are described for short-term (30 minutes or 1 hour) and for long-term sampling (8 hours or 24 hours). One can select different combinations of sampling rate and sampling time to meet special requirements. Sample volumes should be adjusted so that linearity is maintained between transmission and concentration over the dynamic range. 9.2.1 Short-term sampling (30 min. and 1 hr. sampling) Place 20 ml of the absorbing solution in an impinger. Collect the sample at the rate of 1 L/min. for 30 minutes or at 0.5 L/min. for 1 hour using either the rotameter or a critical orifice device to control the flow. Shield the absorbing reagent from direct sunlight during and after the sampling is over by covering the impinger with aluminium foil to prevent deterioration. Alternatively, use amber-coloured impingers for sampling. Determine the volume of air sampled by multiplying the flow rate by the time in minutes and record the atmospheric pressure and temperature. After sampling, transfer the sampling solution on vigorous shaking to dark-coloured polythene bottles and cap tightly. Transport the bottles to laboratory for analysis. Refrigerate samples if analysis cannot be done within a day.
9.2.2 Long-term sampling (8 or 24 hours) Place 20 ml of the absorbing solution in an impinger and collect the sample at the rate of 0.2 L/min. for 24 hours. The applicability of the method to long-term sampling (8 hrs. or 24 hrs.) is subject to calibration at the intended sampling rate and concentration range for the intended period of time. Make sure that no entrainment of solution results within the impinger. During sample collection and storage, protect the sample from direct sunlight. Determine the total air volume by multiplying the flow rate by the sampling time in minutes. Preferably use amber-coloured impingers for sampling. After sampling, transfer the sampling solution on vigorous shaking to dark-coloured polythene bottles and cap tightly. Transport the bottles to laboratory for analysis. Refrigerate samples if analysis cannot be done within a day. 9.3 Analysis Add 1.5 ml of the amine-sulphuric acid standard solution to the midget bubbler through the air inlet tube and mix. Add 1 drop of ferric chloride solution and mix. Transfer the solution to a 25 ml volumetric flask. Discharge the colour due to the ferric ion by adding 1 drop ammonium phosphate solution. If the yellow colour is not destroyed by 1 drop ammonium phosphate solution, continue drop-wise addition until solution is decolorized. Make up the volume with distilled water and allow to stand for 30 min. Prepare a reference solution in the same manner using a 10 ml of absorbing solution through which no air has been aspirated and adding the same reagents as added to sample. Measure the absorbance of the sample at 670 nm in a spectrophotometer against the reference solution. After colour development, the methylene blue colour is stable at least for 48 hours at room temperature and in the dark. If ethanol is added to inhibit foaming, accelerated decay of colour may occur. 9.4 Calibration 9.4.1 Standardization of Sodium thio-sulphate (Na2S2O3) solution (0.025 N) Take 25 ml of Potassium iodate solution (0.025 N) in a 250 ml glass-stoppered conical flask. Add 5 ml concentrated H2SO4 to it. Add 1 gm KI to it. Stopper it and keep in dark for few minutes. Then titrate against sodium thio-sulphate solution taken as titrant using starch indicator. Note the titre value. Determine the strength of Na2S2O3 solution from the normality equation. 9.4.2 Determination of concentration of stock sulphide solution Take 100 ml of distilled water in a 250 ml conical flask and add 20 ml of standard iodine solution (0.025 N). Add 25 ml of hydrochloric acid (0.1 N) and titrate with the thio-sulphate solution using starch solution as indicator. Note the titrant reading as A. Take 100 ml of distilled water in another 250 ml conical flask and add 20 ml of standard iodine solution (0.025 N). Add 25 ml of hydrochloric acid (0.1 N) and 20 ml of the stock sodium sulphide solution (as prepared in 8.8 above) and repeat the titration with the sodium thio-sulphate solution. Note the titrant reading as B. Calculate the concentration of the sodium sulphide solution in terms of H2S as follows : Conc. of sulphide solution = ( A B) N 17 1000 20 µg H2S/ml
where, N = strength of sodium-thiosulphate solution. 9.4.3 Preparation of calibration graph Pipet 10 ml of the absorbing solution in each of a series of 25 ml volumetric flasks and add 0.25, 0.5, 0.75, 1.0 and 2.0 ml of the diluted sulphide solution (see 8.9) to each of the volumetric flasks. Add 1.5 ml of the amine-sulphuric acid standard solution to each flask and mix. Add 1 drop of ferric chloride solution and mix. Discharge the colour due to the ferric ion by adding 1 drop ammonium phosphate solution. If the yellow colour is not destroyed by 1 drop ammonium phosphate solution, continue dropwise addition until solution is decolorized. Make up the volume with distilled water and allow to stand for 30 min. Prepare a reagent blank by adding all the reagents as above except the diluted sulphide solution. Measure the absorbance readings of the sulphide standards against the reagent blank as reference at 670 nm. Plot the absorbance readings against the calculated concentrations of the standard solutions to prepare a calibration graph. Determine the slope of the graph. 10 CALCULATION The Hydrogen sulphide concentration in the sample = µg H2S in the sample µg/m 3 where, V = D x cal. factor µg/m 3 V D = absorbance reading of sample against reagent blank as reference, cal. factor = 1/ slope of calibration curve and V = volume of sample in m 3 NOTE - 1 µg/l Hydrogen Sulphide = 0.72 ppm Hydrogen Sulphide at 25 o C and 760 mm Hg pressure.
FORMAT FOR SENDING COMMENTS ON BIS DOCUMENTS DOC NO. IS 5182-7 TITLE: METHODS FOR MEASUREMENT OF AIR POLLUTION PART 7 HYDROGEN SULFIDE DATE OF CIRCULATION: 06-10-2016 NAME OF THE COMMENTATOR/ ORGANIZATION: BUREAU OF INDIAN STANDARDS SL NO. CLAUSE/SUB- CLAUSE/PARA/TABLE FIG. NO. COMMENTED COMMENTATOR/ ORGANIZATION ABREVIATION COMMENTS (1) (2) (3) (4) (5) BIS 1. The lines in 6.1 state Clause 6.1 & 6.4 that sulphite interference is a major concern. However in 6.4, it is mentioned that interference due to SO 2 is not serious. Since SO 2 produces sulphite in presence of alkaline solution, shouldn t SO2 also cause interference? 2. Figure 3 -do- Should it be "to impinger" or "from impinger"? 3. Clause 9.2.1, 9.2.2 & -do- In 9.2.1 & 9.2.2, it is 9.3 mentioned that samples are transferred to polyethylene bottles. However, in 9.3, it is written that aminesulphuric acid is added to midget bubbler. If the sampling solution is in polyethylene bottles, then aminesulphuric acid should be added to the DECISIONS
polyethylene bottles.