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ENVIRONMENTAL ENGINEERING LAB(BKC3771)

2011/2012 Semester I

Title of Experiment: Determination of Chemical Oxygen Demand (COD) In Water and Wastewater

Date of Experiment : 20 OCTOBER 2011

Instructors Name : SAID NURDIN

NORFADHILAH BINTI HAMZAH

Group of Member :Name ID

1. WAN MUHAMMAD SYAHMI BIN WAN MUHAMMAD KA08119

2. AHMAD FIRDAUS BIN MOHD KA08050

3. HAITHAM MOHAMMED ALI AL-ABEE KC09064

4. NOR RASHIDAH BINTI AHMED KA08129

5. RENU A/P SEKARAN KC09041

Group No. : 04

Group : K01

Marks :

Part A 55

Part B 45

TOTAL 100

Tear here

FACULTY OFCHEMICAL AND NATURAL RESOURCES ENGINEERING

UNIVERSITI MALAYSIA PAHANG

Please keep for student reference.

Received by;

( )

Submitted by;

( )

Subject Code :

Title of Experiment: Date Submitted :

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REPORT EVALUATION FOR PART A

Instruction:Please assess each item using the given scales. Fractional marks will be given for each category.

Item AssessedUnacceptable

(1)

Acceptable

(2)

Good

(3)

Very Good

(4)

Excellent

(5)Score

Organization and

Format

Not follow FKKSA

laboratory report

format. Not well

organized. Contents

show lack of

knowledge.

Partially follow

FKKSA laboratory

report format.

Contents show

enough of knowledge

but still a few concept

and ideas are loosely

connected.

Follow FKKSA

laboratory report

format of writing; all

needed sections

present. Well

organized. Contents

show enough

knowledge of

subject.

Follow FKKSA

laboratory format of

writing; all needed

sections present.

Well organized and

easily followed.

Contents show full

knowledge of

subject.

Follow FKKSA

laboratory report

format of writing; all

needed sections

present. Tables and

figures are correctly

drawn and numbered.

Excellent organized

and easily followed.

Contents show full

excellent knowledge

of subject.

Keywords: Front page, Content, Page No., Total page >8, Arrangement

Abstract Several major Abstract misses one Abstract contains Abstract contains all Abstract contains

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(1)

Acceptable

(2)

Good

(3)

Very Good

(4)

Excellent

(5)Score

aspects of

laboratory report

are missing.

Incomplete

description of

experiment.

Student displays a

lack of

understanding

about how to write

an abstract.

or more major aspects

of laboratory report.

most major aspects

of laboratory report.

Abstract may be too

technical and only

understood by

specialist in the

discipline.

major aspects of

laboratory report i.e.

main purpose of the

experiment, its

importance,

methodology/

approach, most

significant results or

findings, main

conclusions and/or

recommendation.

references to all major

aspects of laboratory

report i.e. main

purpose of the

experiment, its

importance,

methodology/

approach, most

significant results or

findings, main

conclusions and/or

recommendation.

General audience

easily understands

abstract.

Keywords: Introduction, Objective, Method, Result, Conclusion, Suggestion, 1 page

Introduction Very little

background

Some introductory

information, but still

Introduction is

nearly complete,

Introduction is

complete and well

Introduction is

complete and well

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(1)

Acceptable

(2)

Good

(3)

Very Good

(4)

Excellent

(5)Score

information or

information is

incorrect OR, does

not give any

information about

what to expect in

the laboratory

report

missing some major

points. OR, gives

little information

missing some minor

points.

written but theory

may not be backed

up to concise lead-in

to the laboratory

experiment.

written; provides all

necessary background

principles and theory

for the experiment.

Present a concise

lead-in to the

laboratory

experiment.

Keywords: Related Theory, Principles, Process Background

Literature

Review

Poor understanding

of topic

experiment,

inadequate

information or very

little information

Acceptable

understanding of

topic, adequate

information evident,

sources cited.

Insufficient literature

Good understanding

of topic, adequate


sources cited.

Sufficient literature

review.

Good understanding

of topic, adequate


sources cited.

Sufficient and

relevant literature

Complete

understanding of

topic, topic

extensively well-

informed and variety

of sources are cited.

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(1)

Acceptable

(2)

Good

(3)

Very Good

(4)

Excellent

(5)Score

regarding

experiment topic.

No external

literature review.

review or may contain

unrelated materials.

review. Literature review

contains information

relevant and directly

related to experiment

topic.

Keywords: Experiment Topic Information

Experiment

Objective

No objective or

objective missing

the important

points.

Objective is partially

defined.

Objective is relevant

but not elaborated.

Objective is clear,

relevant and

elaborated but

missing some point

on relevant

explanation.

Objective is precise,

clear, relevant and

well elaborated with

relevant explanation.

Keywords: Objective Elaboration

Methodology Missing several

important

Materials and

methodology nearly

Materials and

methodology are

Materials and

methodology are

Materials and

methodology are

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(1)

Acceptable

(2)

Good

(3)

Very Good

(4)

Excellent

(5)Score

explanations of

materials and/or

methodology. Not

sequential. Most

steps are missing or

are confusing.

Some procedural

components

generally described

but are not

replicable.

complete but still

missing some

important

experimental details.

Others may have

difficulties following

procedures; some

steps are

understandable; but

most are confusing

and lack detail. Can

replicate experiment

if reader makes some

inferences.

explained with

sufficient detail;

some lack detail or

are confusing.

Mostly easy to

follow. Description

of procedure makes

it likely that the

work can be reliably

replicated.

complete. Mostly

easy to follow.

Description of

procedure can be

replicated.

complete and

adequately detailed.

Logical and easily

followed. Description

of procedure is

complete, ensuring

that it can be

replicated.

Keywords: Experiment Procedure, List of Equipment

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(1)

Acceptable

(2)

Good

(3)

Very Good

(4)

Excellent

(5)Score

Conclusions and

recommendations

No conclusions or

conclusion missing

the important

points. No

recommendation

given to improve

the experiment.

Conclusions

regarding major

points are drawn, but

many are misstated,

indicating a lack of

understanding.

Conclusion is too

general. Several

recommendations

have been given but

they are too general

and not contributing

to the experiments

improvement.

All the important

conclusions are

drawn could be

better stated.

Conclusion is

related to general

interest. Several

recommendations

have been stated and

they are partially

contributed to the

experiments

improvement.

All the important

conclusions have

been made.

Conclusion is

precisely stated.

Conclusion and

recommendation

relates the study to

general interest and

other studies that

have been

conducted.

All the important

conclusions have been

clearly made.

Conclusion is

precisely stated and

relates the study to

general interest, other

studies that have been

conducted.

Recommendations

given are significantly

contribute to the

experiments

improvement.

Keywords: Experiment Summary, Recommendation

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(1)

Acceptable

(2)

Good

(3)

Very Good

(4)

Excellent

(5)Score

References Some citations in

text are not

available in list of

reference.

A few citations in text

are not available in

list of reference.

All citations in text

are available in list

of reference but list

of reference is less

than 3.


are available in list

of reference and list

of reference is more

than 3.


are available in list of

reference. List of

reference is more than

3 and variety source.

Keywords: Book Reference, Journal Reference, Website Reference

Appendices Appendices notavailable in

laboratory report.

Only a fewappendices available

in laboratory report.

Appendicesavailable in

laboratory report but

poorly constructed

Appendicesavailable in

laboratory report in

structured manners

Appendices availablein laboratory report in

structured manners,

clearly and precise

Keywords: List of Formulas, Tables, Figures, Calculation

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(1)

Acceptable

(2)

Good

(3)

Very Good

(4)

Excellent

(5)Score

Grammar and

Spelling

Numerous spelling

and/or grammar

errors. Transitions

confusing and

unclear.

Still many spelling

and/or grammar

errors. Few or weak

transitions, often

wanders and jumps

around.

Occasional

grammar/spelling

errors. May have a

few unclear

transitions.

Occasional

grammar/spelling

mistakes. Spell

checked and proofed

throughout. Good

sentence and

paragraph structure

and transitions.

Minimal to no

spelling mistakes.

Spell checked and

proofed throughout.

Good sentence and

paragraph structure

and transitions.

Keywords: Language

Timeliness Laboratory report

handed in more

than one week late

Up to one week late Up to three days

late

Handed in one day

late

Laboratory report

handed in on time

Keywords: Punctuality

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(1)

Acceptable

(2)

Good

(3)

Very Good

(4)

Excellent

(5)Score

Total Assessment Marks (55%)

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i

ABSTRACT

The wastewater is created when the water is spent or used with dissolved or suspended

solids as well as the water that discharged from communities, homes, industrial, homes,

commercial establishments, and farms. There are a lot of contaminants in the wastewater such

as heavy metal, dissolved solid as well as organic matter. The goal of this experiment is to

determine amount of chemical oxygen demand (COD) of organic pollutants in the water and

wastewater. There are 5 types of solution is used in this experiment which are river, distilled

water that act as a blank, industrial and diluted industrial, domestic and lastly diluted domestic

solution. The diluted solution is form when 2.5mL of domestic and industrial solution were

add with distilled water into 250mL volumetric flask respectively. 2mL of each solution is put

into a vial and hold it 45-degree angle. After that,it was rinsed with distilled water and wipe

with clean paper tower before put into COD reactor. All the samples were put into COD

reactor for 2 hours at temperature of 1500C. After 2 hours, samples were cooling down to

1200C and put out to cool in room temperature. Lastly, after all the samples were cooled, it

was put into spectrophotometer to detect the amount of COD of each samples. Based on the

result, the COD for river water, industrial wastewater and domestic wastewater were (20, 12,

and 35) mg/L. The domestic wastewater contained the most COD level while the industrial

wastewater contained the lowest. As a conclusion, the result that get from the experiment

were complied with the Environment Quality Act 1974 Standard A or B, Sewage & Industrial

Effluent as the result were below both of the standard (A & B).

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TABLE OF CONTENTS

CHAPTER TITLE PAGE

ABSTRACT i

1 INTRODUCTION 1

2 LITERATURE REVIEW

2.1 Literature review 2

2.2 Overview 2

2.3 Method to use 3

2.4 Errors 4

3 METHODOLOGY

3.1 Materials and methodology 6

3.2 The experiment procedure 7

4 RESULT & DISCUSSION

4.1 Result 8

4.2 Discussion 8

5 CONCLUSION & RECOMMENDATION

5.1 Conclusion 12

5.2 Recommendation 12

REFERENCES 13

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CHAPTER 1

INTRODUCTION

Chemical Oxygen Demand (COD) is defined as the quantity of a specified oxidant

that reacts with a sample under controlled conditions. It is used as a measure of oxygen

requirement of a sample that is susceptible to oxidation by strong chemical oxidant. The

quantity of oxidant consumed is expressed in terms of its oxygen equivalence. COD is

expressed in mg/L 02. The chemical oxygen demand test procedure is based on the

chemicaldecomposition oforganic andinorganic contaminants, dissolved or suspended in

water. Theresult of a chemical oxygen demandtest indicates the amount of water-dissolved

consumed by the contaminants. . The dichromate reflux method is preferred over procedures

using other oxidants (e.g. potassium permanganate) because of its superior oxidizing ability,

applicability to a wide variety of samples and ease of manipulation. Because COD measures

the oxygen demand of organic compounds in a sample of water, it is important that no outside

organic material be accidentally added to the sample to be measured. To control for this, a so-

called blank sample is required in the determination of COD.

The mg/L COD results are defined as the mg of O2 consumed per liter of sample

under conditions of this procedure. In this procedure, the sample is heated for two hours with

a strong oxidizing agent, potassium dichromate. Oxidizable organic compounds react,reducing the dichromate ion (Cr2O72-) to green chromic ion (Cr3+). When the 3-150 mg/L

colorimetric or titrimetric method is used, the amount of Cr6+ remaining is determined. When

the 20-1,500 mg/L or 200-15,000 mg/L colorimetric method is used, the amount of Cr3+

produced is determined. The COD reagent also contains silver and mercury ions. Silver is a

catalyst, and mercury is used to complex chloride interferences.
http://www.businessdictionary.com/definition/decomposition.htmlhttp://www.businessdictionary.com/definition/organic.htmlhttp://www.businessdictionary.com/definition/inorganic.htmlhttp://www.businessdictionary.com/definition/contaminant.htmlhttp://www.businessdictionary.com/definition/result.htmlhttp://www.businessdictionary.com/definition/test.htmlhttp://www.businessdictionary.com/definition/test.htmlhttp://www.businessdictionary.com/definition/result.htmlhttp://www.businessdictionary.com/definition/contaminant.htmlhttp://www.businessdictionary.com/definition/inorganic.htmlhttp://www.businessdictionary.com/definition/organic.htmlhttp://www.businessdictionary.com/definition/decomposition.html

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CHAPTER 2

LITERATURE REVIEW

2.1 Literature review

Chemical oxygen demand (COD) is used as a measure of oxygen requirement of a

sample that is susceptible to oxidation by strong chemical oxidant. The dichromate reflux

method is preferred over procedures using other oxidants (e.g. potassium permanganate)

because of its superior oxidizing ability, applicability to a wide variety of samples and ease of

manipulation. Oxidation of most organic compounds is 95-100% of the theoretical value.

2.1 Overview

For many years, the strong oxidizing agent potassium permanganate (KMnO4) was

used for measuring chemical oxygen demand. Measurements were called oxygen consumed

from permanganate, rather than the oxygen demand of organic substances. Potassiumpermanganate's effectiveness at oxidizing organic compounds varied widely, and in many

cases biochemical oxygen demand (BOD) measurements were often much greater than results

from COD measurements. This indicated that potassium permanganate was not able to

effectively oxidize all organic compounds in water, rendering it a relatively poor oxidizing

agent for determining COD.

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Since then, other oxidizing agents such as ceric sulphate, potassium iodate, and potassium

dichromate have been used to determine COD. Of these, potassium dichromate (K2Cr2O7)

has been shown to be the most effective: it is relatively cheap, easy to purify, and is able to

nearly completely oxidize almost all organic compounds. In these methods, a fixed volume

with a known excess amount of the oxidant is added to a sample of the solution being

analyzed. After a refluxing digestion step, the initial concentration of organic substances in

the sample is calculated from a titrimetric or spectrophotometric determination of the oxidant

still remaining in the sample.

2.2 Methods to use

According to J.Stone, Chemical Oxygen Demand (COD) is a quick, inexpensive

means to determine organics in water. COD samples are prepared with a closed-reflux

digestion followed by analysis. Determinations can be made titrimetrically by several

approved methods, or photo metrically (colorimetric ally) with EPA Method 410.4, Hach

Method 8000 and Standard Method 5520D. The COD chemistry reviewed here applies to

colorimetric methods. The first step is digestion. Concentrated sulfuric acid (H2SO4)

provides the primary digestion catalyst. The secondary catalyst, Silver Sulphate (AgSO4),

assists oxidization of straight-chain hydrocarbons such diesel fuel and motor oil. Heat from

the digestion block (150 C) also acts as a catalyst. During digestion the samples organic

carbon (C) material is oxidized with the hexavalent dichromate ion (Cr2O72-) found in

potassium dichromate (K2Cr2O7). The dichromate readily gives up oxygen (O2) to bond

with carbon atoms to create carbon dioxide (CO2). The oxygen transaction from Cr2O72-to

CO2 reduces the hexavalent Cr2O72- ion to the trivalent Cr3+ ion. In essence a COD test

determines the amount of carbon based materials by measuring the amount of oxygen the

sample will react with. This oxygen transaction is the source of the tests name, Chemical

Oxygen Demand.

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2.3 Errors

According to T.Lofuts, COD has two common error sources. First, the oxidation step

does not distinguish between organic and inorganic carbons. Where carbons are available,

oxidation will create Cr3+ ions. Its the organic carbon fraction of the sample thats sought

after, and its the organics that found the correlation basis for Biochemical Oxygen Demand

(BOD) and Total Organic Carbon (TOC). Unfortunately unknown oxidizable inorganic

introduce positive error, and skew any attempt to directly substitute COD results for BOD or

TOC. The more common interfering however is chloride (Cl).

The mass of any object is simply the volume that the object occupies times the density of the

object. For a fluid (a liquid or a gas) the density, volume, and shape of the object can all

change within the domain with time. And mass can move through the domain. On the figure,

we show a flow of gas through a constricted tube. There is no accumulation or destruction of

mass through the tube; the same amount of mass leaves the tube as enters the tube. At any

plane perpendicular to the center line of the tube, the same amount of mass passes through.

We call the amount of mass passing through a plane the mass flow rate.

Mass flow is the movement of a quantity of material through a conveyance per

quantity of time. SI units of measure for this parameter are kg/sec. Conversions of kg/sec to a

variety of other mass flow units are possible, such as g/s and mole/s. Other very common

mass flow units used in gas flow measurement are the volumetrically based type such as

sccm, slm, scfm, etc. Volumetrically based mass flow units should not be confused with

volume or actual flow units. Volumetrically based mass flow units define mass in terms of the

quantity of gas that occupies a volume understandard conditions of pressure and temperature.

When a gas flow system is in steady state, mass flow is the same at all locations in the

system and it is independent of the gas pressure and temperature conditions. Therefore, the

measurement of mass flow made by the molbloc/molbox system represents the mass flow at

all other points at the same time in a flow system that is in steady state. This characteristic

represents the strong value of mass flow measurement over volumetric flow measurement in a

gas flow system.

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Flow devices that are fundamentally based on the measurement of mass, or have the internal

capability to measure gas conditions and calculate mass flow from volume, can be directly

compared to the molbloc/molbox system in mass flow units.

In a gas flow system under steady state conditions, volume flow is likely to be

different throughout the system and it is highly dependent upon the gas pressure and

temperature at the point where it is measured. This means that the volume flow will not be the

same at all points within a system due to changes in pressure and temperature that naturally

occur as the gas moves through the restrictions caused by plumbing, valves, regulators, filters,

etc., even though the mass flow rate is the same.

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CHAPTER 3

METHODOLOGY

3.1 Materials and methodology

There are some material and equipment that been use in this experiment which is

a) COD Digestion Reactorb) Spectrophotometer, HACH DR/2400 @ DR/2800c) COD Digestion Reagent Vial LR @ HRd) COD racke) Volumetric pipette, 2 mLf) Paper towel/Tissue

3.2 The experiment procedure

The COD Reactor is turned on and preheated to 150C. The safety shield is placed in front of

the reactor.

The caps from two COD Digestion Reagent Vials are removed. The vial for the appropriaterange is chosen.

One vial is held at a 45-degree angle. A clean volumetric pipette is used to add 2.00 mL of

sample to the vial. This is the prepared sample.

A second vial is held at a 45-degree angle. A clean volumetric pipette is used to add 2.00 mL

de-ionized water to the vial. This is the blank.

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Figure 3.1.1: Flow work of methodology

The vials are held by the cap over a sink. They are inverted gently several times to mix them.

The vials are then placed in the preheated COD Reactor.

The vials are heated for two hours. The reactor is then turned off. About 20 minutes is let for

the vials to cool to 120C or less.

Each vial is inverted several times while still warm. The vials are then placed into a rack and

cooled to room temperature.

Touch Hach Programs. Program 430 COD LR(Low Range) is chosen. Touch Start.

The outside of the vials is cleaned with a damp towel followed by a dry one to remove

fingerprints or other marks. The 16-mm adapter is installed and the blank is placed into the

ada ter.

Touch Zero. The display will show: 0 mg/L COD. When the timer beeps, the sample vial is

placed into the adapter. Touch Read. Results will appear in mg/L COD.

The vials are capped tightly. They are rinsed with de-ionized water and wiped with a clean

paper towel.

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CHAPTER 4

RESULTS & DISCUSSION

4.1 Results

Types of Samples COD (mg/L)

River 20

Industrial 12

Domestic 35

Table 4.1: COD Data for Different Types of Sample Sources

4.2 Discussion

In order to reduce the concentration of the industrial and domestic samples, these

samples were diluted with the distilled water, where 2.5 mL of industrial and domestic

samples were diluted into 250 mL volumetric flask. Table 5.1 shows the chemical oxygen

demand (COD) for particular sample which are river, industrial wastewater, and domestic

wastewater. COD is a standard method for indirect measurement of the amount of pollution

that cannot be oxidized biologically in a sample of water. The COD test is used to determine

the oxygen needs by the sample effluences that go through oxidation to degrade the organic

pollutant. In other word, the higher the value of COD, the water is more polluted.

Based on the table, domestic wastewater contained the highest COD level with 35

mg/L while industrial wastewater contained the lowest COD level with only 12 mg/L. TheCOD level for domestic wastewater was the highest because there is no wastewater treatment

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facilities exist for domestic wastewater treatment compared to industrial wastewater

treatment. The difference of COD values found in the different sources of sample is because a

sample of waste water containing organic material is placed in contact with a very strong

inorganic oxidant, a mixture of dichromate and sulphuric acid with silver sulphate as a

catalyst. The temperature is increased to the point of ebullition of the mixture, resulting in an

increase of the oxidation rate. The different of oxygen requirement that is inclined to

oxidation by strong chemical oxidant.

The importance of COD test was to measured the pollution potential of organic matter

in particular wastewater. Besides, it can also be used to determine the decomposable organic

matter results in consumption of dissolved oxygen (DO) in the receiving streams. Based on

Environment Quality Act 1974 Standard A or B, Sewage & Industrial Effluent it state that for

COD standard A and standard B is 50mg/l and 100mg/l which mean that the solution cannot

exceed this limit. The result show that for industrial waste is 12mg/l, river waste is 20mg/l

and domestic 35mg/l. The value of COD for this wastewater is in a standard A which mean it

follow the standard that be state by Environment Quality Act 1974. The wastewater from

river, domestic and industrial do not need further treatment because the level of COD in the

solution is below the standard and the solution is not dangerous to human and environment.

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Table 4.2:Environment Quality Act 1974 Standard A or B, Sewage & Industrial Effluent.

The basis for the COD test is that nearly all organic compounds can be fully oxidized to

carbon dioxide with a strong oxidizing agent under acidic conditions. The amount of oxygen

required oxidizing an organic compound to carbon dioxide, ammonia, and water is given by:

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This expression does not include the oxygen demand caused by the oxidation of ammonia

into nitrate. The process of ammonia being converted into nitrate is referred to as nitrification.

The following is the correct equation for the oxidation of ammonia into nitrate.

It is applied after the oxidation due to nitrification if the oxygen demand from nitrification

must be known. Dichromate does not oxidize ammonia into nitrate, so this nitrification can be

safely ignored in the standard chemical oxygen demand test. Once a sample is taken, the

constituents of the sample should be maintained in the same condition as when collected.

When it is not possible to analyze collected samples immediately, samples should be

preserved properly. Biological activity such as microbial respiration, chemical activity such as

precipitation or pH change, and physical activity such as aeration or high temperature must be

kept to a minimum. There are two ways in which a sample can be preserved for a longer time

before being analyzed by doing COD test. Firstly, preservation of the sample can be

accomplished by adding sulphuric acid to depress the pH to 2 and the holding time with

preservation is 7 days. Secondly, preservation of the sample also can be achieved by cooling

the sample at around 4 C. However, freezing the sample is not usually recommended.

COD can be reduced by using chemical treatment. Two processes, known as flocculation

and coagulation, usually used to reduce the COD in the wastewater. In flocculation, small

particles with non-rigid surfaces are made to agglomerate by mixing the water (and thus

bringing the particles into contact with one another so that the surfaces can become stuck

together). When the agglomeration of the particles gets large enough, the aggregate can settle

in still water by sedimentation. Other suspended particles do not agglomerate well by

flocculation. To remove these particles from the water, coagulation must be used. Coagulation

is the process of gathering particles into a cluster or clot, often achieved by the addition of

special chemicals known as coagulants. The coagulant used is aluminium sulphate (alum,

Al2(SO4)3).

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CHAPTER 5

CONCLUSION & RECOMMENDATION

5.1 Conclusion

As a conclusion, the chemical oxygen demand in the particular river water, industrial

wastewater and domestic wastewater were (20, 12, and 35) mg/L. As the result were to

comply with the standard ruled on Environment Quality Act 1974, the result came back below

the standard ruled on Environment Quality Act 1974. Thus, it can be concluded that the water

and wastewater sample was safe for the environment and do not have to treat further.

5.2 Recommendation

In order to make this experiment more better, some recommendation can take into

action which is do not touch vial with hand because the hand contain a finger print and this

can effect UV light when analyze the sample. Another rrecommendation for this experiment,for every sample from domestic water and industrial water, it need to be dilute into 1:10000 to

make sure the data retrieve is in range. The data is recommended to take to authority to have

further investigation.

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REFERENCE

DOBBS, R.A. & R.T. WILLIAMS. 1963. Elimination of chloride interference in the chemical

oxygen demand test.Anal. Chem. 35:1064.

MOORE, W.A., F.J. LUDZACK & C.C. RUCHHOFT. 1951. Determination of oxygen-

consumed values of organic wastes.Anal. Chem. 23:1297.

MOORE, W.A., R.C. KRONER & C.C. RUCHHOFT. 1949. Dichromate reflux method for

determination of oxygen consumed.Anal. Chem. 21:953.

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