Results of a round robin experiment on the crlibration of differential Scanning calorimeters

199

Thermochimica Acta, 94 (1985) 199-204 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands

RESULTS

OF R ROUND ROBIN EXPERIMENT

DIFFERENTIRL

SCRNNING

‘Sektion

fur

D-7900

Ulm

and

Kalorimetrie

K.-H.

der

BREUER;’

Universitst,

Postfach

4066

(FRGI

‘Mineralogisch-Petrographisches D-6900

OF

CRLORIMETERS”

HflHNE?, , W. EYSEL2

G.W.H.

ON THE CRLIBRRTION

Institut

Heidelberg

der

Universitat,

Postfach,

(FRG)

FlBSTRRCT Three substances (indium, rubidiumnitrate and Lithiumsulfate) with five samptes each were run on four scanninq calorimeters of different type to measure the heat of five well-defined transitions in the temoerature ranoe 150 - 580 -C. In order to avoid errors due to differences in composition and weighing, identical samples were The results of the two power measured on the different apparatus. compensated scanning calorimeters fit very wetl, but the heats measured on calorimeters of heat-flux type are systematically to smalt in cases of higher transition temperatures and large specific transition enthalpies. Explanation is possible by the theory of heat-flux calorimeters predicting such effects.

INTRODUCTION calibration

of

quires

The

standard

reference

(resp.

heat-flux)

and

orimeter.

parameters

sition

heat,

known.

Moreover,

nufacturers periments of

‘interest, In

the

this

four

not

testing

(RbNO, different

the and of

0040-6031/85/$03.30

results

of

LizSO,

at

the

6th

on tran-

shoutd

be of

trustworthy.

Thus and

substances

at1

the

are

welt the

maex-

suitabi-

of

high

experiments. testing by

two

inorganic

a miniature

are

not

cal-

factor specific

calorimeters

heat

respective

statements

reported.

calibration-factor is

the

etc.

the

very of

robin

of

re-

and

calibration

sample

reference

round

it

the

(USC)

temperature

temperature,

as

calibration standard

the

the

experience

taken

calorimeters

Certainly, presented

be

the as

of

of to

for

knowledge

transition

conductivity

materials paper

size,

calorimeters

both

dependence

according

should

determination

orimeter. *Poster

as

including

substances on

the

heat

scanning

substances a sufficient

Especially

sample

Lity

differential

possible

robin

Indium

was

of to

draw

Utm Calorimetry

0 1985 Elsevier Science Publishers B.V.

nonmetattic

round the

experiment added

respective

definitive

Conference,

for cal-

concluMarch

1985

200

sions

since

theless

the

the

cular

as

population

results

a base

of

of for

this

the

test

first

enlarged

was

attempt

test

rather are

limited.

Never-

valuable,

in

parti-

series.

EXPERIMENTDL Preceeding got

from

experiments metal-samples

with

literature)

tion

heat

was

of

fluctuate c,‘C were

Five cision for

salts

(at

choosen

for

the about

balance

into

sample

in

to

To normalize

the

samples

Indium fifteen

comparable samples

high were

were

to

be

institute.

The

in

the

ELMER DSC-2

Hohne,

ELMER DSC-2C

Wruck

C

DUPONT TFI 1090/910

D

HERFIEUS TF1 500

E

same

F1,B:

power

compensated

there

are

the the

age

samples

carried

out

these

return run

whether the

to

samples were

of

Indium of heat

the of

institutes calorimetry.

5 Klmin. of

1711

The the

calorime-

respective

used: of

Ulm and

Hannove

and

Braunschweig

Cammenga

holder

assembly

C,D,E:

heat

of

up

scientists other

scanning

flux

calorimeter)

calorimeters apploying

to

r

Heidelberg

Eysel

types or

with

contact

us

in

them. in

use,

May

order

to

experiments. of

once

within

one

pre-

suitable

melting

Salje

Type

hunt

a high

University

sample

more

encourages in

were

other

much

succeed

paper

participate Flfter

of

method

and

Reichelt with

we didn’t

they

scanning

were

Breuer

C but

at

the

Investigators

as

solidone

calibration

scientific

rate

calorimeters

PERKIN

this

in

individual

PERKIN

be

on

samples

the

we defined

precise

B

but

with

J/mot.

R

Indeed

defined

Rl-pans)

Five

a heating

with

well Li;,SO,

weighed

Pont

compare

measured

applying

transi-

apparatus

experiment. were (Du

results

Type

(Type

robin

and

3280

following

three

results (compared

the

different

<‘C) and

investigation.

control

were

calibrated

with

285

containers

experience

run

and

the

calorimeters

with

RbNO,

of

whereas

IO mg mass

the

samples

scanning

round

under

order

coincidence

(Ref.1,2,3),

225

of

equipment.

ters

Thus,

166,

calorimeters

the

determined

each

added

The

good

samples

all

were

different

more.

transitions

580

by rather

inorganic

sligthly

solid

showed,that

the

more

samples on

the

remained kept half

from

unchanged. in

a year,

the

calorimeter dry

During

atmosphere. the

round Fl in

control

robin order

experiment to

transport Rll run

test and

measurements after

one

storwere

year.

201

TRBLE 1 Results

of

the

round

robin

experiment

on

transition

heat

determination Calorimeter

Heat

of

transition

and

standard

deviation

(kJlmo1)

of

III

Li ,SO,

1.301+.015

24.8t

Type

Indium

RbNO,

I

II

R (l.runI

3.2802.003

3.83t

.Ol

3.16

B

3.28Of.006

3.850:.004

3.192t.008

1.31

f.02

24.82

C

3.28

+.0’S

3.86+

.04

3.19

t.04

1.29

t.O1

23.9

*, .3

II

3.28

5.06

3.82

+ . 13

3.09

f.10

1.21

t.04

22.8i

.5

E

3.28

2.03

3.72t

.03

3.02

2.03

1.235-+.006

22.121.3

R (2.rut-t)

3.28Ot.004

3.‘10

+-.04

1.28

24.52

3.81t.02

+-.02

t.01

.2 .3

.4

RESULTS The

experimenters

onset

and

of

expected well The

in

with results

this

whereas

the

results

in

obtained

temperature

transitions the

in

transition

of

the

question.

peaks

calibration,

from

factor

I%

fit

rather

however,

is

the

indium

(defining

samples

the

true

was

not

used

melting

of

the

respective

calorimeter

were

to

get

comparable

data.

1 includes

factor

the

round of

two

robin

the

power

case

specific

heats

of

observed

heats

from

heat

higher

transition. the

samples

compensated of

of

experiment,

five

i.e. as

the

well.

flux

type

transition

fit

rather

of

yielded

2 includes the

two

and

be

more

temperature

power

seepI

the the

well,

diverging

and

the

as

mul-

average

Fls can

calorimeters

Table average

Table

to

heat

this

calorimeters the

five of

the

!A11 results of

the

and

paper.

uncertainty of

the

heat

Temperature

heat

JlmoL).

results

of

temperatures

a normaLization

tiplied

random

the

calorimeters.

transition

caLcuLate

the

maximum

onset

all

considered

3280

the

the

on

reported

Larger

deviation compensated

of

the

calo-

rimeters.

TFlBLE 2 Difference the

average

between measured

the

heats on

power

measured compensated

on

heat

flux

calorimeters.

calorimeters

and

202

DISCUSSION F)s can lity’

be

of

seen

the

systematic

from

four

the

errors

in

the

factor

of

of

sample

holder

factor

versus

temperature

rather

unknown

the

Rnother (at

calorimeters

for

‘BC)

Here

was

the

a clear

than

that

of

curves

(Ref.51

the

Ref.4,5).

lead

to

straight-line

area

for

of

results

heat

third

the

peak

of

step

power

the

‘qua-

seem

to

calibration

calibration

unity,

a fact

transition calorimeters in

compensated

up

to

of

deviation

of

RbNO,

of

heat

baseline

(Fig.11

(for

calorimeters determining

three

applied

This

the

the

percent.

in

this is

The

case

peak

area

method

of

yields

an

considerably

lar-

calorimeters.

557

Plots of RbNOJ transition at 285 UC measured a) by a heat flux calorimeter (Du-Pont TFI 1090/910) b) by a power compensated calorimeter (Perkin-Elmer the same sample. The left curve shows a larger baseline

T/ K

Fig.1:

of

than ____

the right straight-line

one

be

replacement the

from

change

methods

small.

the the

altered

differ

the

correction

too flux

to

for

varying

baseline

the

of

E

has

1

calorimeter.

Larger

Different

systematically

ger

found

curves

showed

see

of

of

calorimeter

obviously

type

Table there

dependence

For

function

this

type

theory

E.

in

Moreover,

temperature

assembly

flux

deviations

differs.

D and

phenomenon

285

standard

calorimeters

caused baseline

by

the

heat flux method. . . . . . ‘true’ baseline

DSC-2)

shift

203 Furthermore

the

type

involves

the

calibration

C,D to

of

factor

method

errors

heat

of

transition

transition

heat

of

l_i,SO,

and E and be

caused

about

that by

eight

measured

this

times

calorimeters

parameters

to

heat

flux

a dependence

the

of

as mass,

heat

etc.

The very

deviation

measured

by means

of

The than

of

leading

by power

fact.

larger

of

(Ref.41

on sample

specific

vity, the

measuring

sources

compensated

transition that

of

calorimeters

calorimeters

heat the

the

conductibetween

of

other

this

seems

material

is

transitions.

SUMMFlRY The

round

cautions

robin

experiment

because

its

has

limited

ments

and

drawn

which

are

also

- 5)

and

other

literature

indicate

a slight

(Ref .I RI1 wer

materials.

results

compensated

need its

test

of

full

task

for

international of

of

permanent results

flux the

comparable the

differential the

the

the

calibration

factor

of

the

in

pretensions

ing

to

thermal

a less For

heat

analysis so

is

it

system

of

available.

time

calibraand cle-

care

and

and maintain

DSC.

On the

(oxidation)

the

heat

and

experimental

conducting

to

and

of

obtain

compensated by aging

transition

one

of

the

material,

a certain

extent

and

recorwnended

in

on

indi-

results

heat

DSC

can

and

accuracy

are

relation

to

close

electronic

reason

scanning far.

flux

its

yet

quality

to

depends of

covering

by great

possible

po-

the

on tempera-

question.

repeatability sensitive

that

quantity

in

advantage

compensated system

the

transition

Nevertheless

price.

and

(Ref.41

the

The major

probe

the

Only

the

instruments

development

on expense

a power

theoretical

combination

of

of

is

not

their

moment

may alter

hand

that

ture

it

those

be

authors

of

flux

are be

depends

factor

the

calibration

standards

experimenter.

temperature

other

cate,

to

of

heat

heat

should

Fit the

control

calibration

can

reproducibility the

for

Such

calorimeters

calibration

pre-

instru-

conclusions

experiences

better

future

respective

great

data.

standards

near

with

participants,

some

Moreover,

range.

the

evaluated of

on previous

recommendation.

heat

verness

hand

of

temperature

!A major tion

based

set

be

Nevertheless

instruments.

an excellent

to

number

be

measurement

is

easy

to

with

very

low

calorimeter

is

include costs,

available

case

slightly the

reduced.

DTA method

equipment a DSC module whereas only

the

the as

lead-

at in

a lower a

power

a complete

204

FICKNOWLEDGEMENT The B.

authors

Wruck

Hannover

of and

Physikalische Braunschweig The

investigations

wish the

to

Institut

H.

K.

und for

express fur

Caronenga

their

and

Theoretische careful were

gratitude

to

Kristallographie J.

Reichelt

Chemie

measurements supported

by

E.

der of

the

der

Technischen

and

very

the

Deutsche

Salje

and

Universitat Institut

fur

Universitat

helpful

cooperation.

Forschungs-

gemeinschaft.

REFERENCES The Calorimetric Calibration of K.-H. Breuer and W. Eysel, Differential Scanning Calorimetry Cells, Thermochimica Rcta 57 (1982) 317-329. W. Eysel and K.-H. Breuer, Differential Scanning Calorimetry: Simultaneus Temoerature and Calorimetric Calibration, in J. F. Johnson and P. S. Gill (Ed.): Analytical Calorimetry; Plenum Publishing Corporation, 1984, pp. 67-80. G. W. H. Hohne, K.-H. Breuer and W. Eysel, Differential Scanning Calorimetry: Comparison of Power Compensated and Heat Flux Instruments, Thermochimica Flcta 69 (1983) 145-151. G. W. H. Hohne, Problems with the Calibration of Differential Temoerature Scannino Calorimeters, Thermochimica Flcta 69 (1983) 175-197. W. Hemminger and G. Htihne: Calorimetry, Fundamentals and Practice, UCH Verlags-Gesellschaft Weinheim, Deerfield Beach (Florida), Easel, 1984.