media.iupac.orgmedia.iupac.org/publications/pac/1970/pdf/2101x0045.pdf · 2017. 7. 24. · ANALYTICAL CHEMISTRY DIVISION COMMISSION ON MICROCHEMICAL TECHNIQUESt A STUDY OF THE ACCURACY

INTERNATIONAL UNION OFPURE AND APPLIED CHEMISTRY

ANALYTICAL CHEMISTRY DIVISIONCOMMISSION ON MICROCHEMICAL TECHNIQUES

A STUDY OF THE ACCURACY ANDPRECISION OF METHODS FOR THEDETERMINATION OF CARBON AND

HYDROGEN IN ORGANIC COMPOUNDS

Prepared for publication by

M. VEEkA and J. HORSKA

Institute of Chemical Technology, Pardubice, Cechos1ovakia

LONDON

BUTTER WORTHSP.A.C. 21/I—D

ANALYTICAL CHEMISTRY DIVISION

COMMISSION ON MICROCHEMICAL TECHNIQUESt

A STUDY OF THE ACCURACY AND PRECISION OFMETHODS FOR THE DETERMINATION OF CARBON

AND HYDROGEN IN ORGANIC COMPOUNDS

1. INTRODUCTIONThe study was made within the terms of reference of the activities of the

Commission on Microchemical Techniques of the International Union ofPure and Applied Chemistry during the period 1962—1965. The objects ofthe study were as follows. (i) To test various methods for the microdeter-mination of carbon and hydrogen in organic compounds by analysingselected standard compounds of various compositions. (ii) To estimate theprecision of the various determinations in terms of standard deviation andto assess the confidence limits of individual analyses. (iii) To determinewhether or not some elements (particularly N, S, I, F, K, P) affect theaccuracy and precision of the determination of carbon and hydrogen.(iv) To obtain a survey of the procedures used in routine practice (weighingof samples, combustion method, reagents, methods of final determination,etc.). (v) To obtain a basis for further investigations and developments ofmethods of organic elemental analysis.

1.1 Standard compoundsEight substances were chosen from the standard compounds recommended

by the Commission on Microchemical Techniques. The compounds wereselected so that the following combinations of elements were obtained:(a) C, H; (b) C, H, 0; (c) C, H, N, 0 (nitro compound); (d) C, H, F;(e) C, H, I; (f) C, H, S; (g) C, H, P; (h) C, H, K. The actual compoundsare listed in Table 1.

Table 1. List of standard compounds analysed

CompoundEmpiricalformula

Molecularweight

C(%)

H(%)

I Anthracene C14H10 178234 9434 566II Cholesterol C27HuiO 386665 8387 1199IIIIV

2,4-Dinitrophenylhydrazineo-Iodobenzoic acid

C6H6N404C7H5102

198146248027

36373390

305203

V Suiphanilamide C6H8N2O2S 1722l2 4185 468VIVII

p-Fluorobenzoic acidTriphenyiphosphate

C7H,F02C18H15P04

140117326295

60006626

360463

VIII Potassium acid phthalate C8H5K04 204228 4705 247

t Titular Members: W. Schoniger, Chairman (Switzerland); R. Levy, Secretary (France);H. Flaschka (U.S.A.); N. E. Gel'man (U.S.S.R.); 0. D. Koch (Germany); W. Koch(Germany); A. Steycrmark (U.S.A.); M. VeeIa (Czechoslovakia). Associate Members:K. L. Cheng (U.S.A.) ;J. Korbl (Czechoslovakia); A. M. G. Macdonald (U.K.); H. Malissa(Austria).

47

M. VERA andJ. HORSKA1.2 Organization of the study

Compounds I—VIII (40—50 mg of each) were sent to the participants whohad previously agreed to cooperate. Four analyses of each compound wererequired, i.e. a total of 32 determinations. Each participant was asked togive basic information on the method of analysis used. Dr Al Steyermarkarranged for the dispatch of samples and the collection of results fromlaboratories in the U.S.A. Dr Ve&Ia was in charge of participants fromother countries.

1.3 Participants in the studyThe names and addresses of the participants are listed in Table 2.

1.4 Basic statistical methods usedThe standard deviations of the results obtained for each compound by

each laboratory were calculated according to the formula:

—

\ rn—iThe standard deviation of the results obtained in 1 laboratories (where the

particular compound was analysed in the same way) was calculated asfollows:

1 1a2 E(_)2— j=1 _____— I ' 1—1

The variances of the results were compared by means of the Snedecortest (Ftest).

The means and the deviations of the means from the true value for eachlaboratory in which m determinations were made, were calculated in theusual way, i.e.

- L=1m

Similarly, the deviation of the means from the true value for a method usedin 1 laboratories is given by the formula:

= _____X—/JThe statistical significance of the difference between the mean and truevalues was estimated by the Student test

t=— or t—s,v

whereIf m /1 1 m/I (x1 — )2 \ /1 (xjj — ) 2I '' d — f ( j=I1=1S/ \ m(m—1) / an SX—,\/ \ n(n—1)

48

a ia

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. jg VA

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Cam

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Lab

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., H

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Lab

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Lab

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403

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Gre

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R. A

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The

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Che

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.J.

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Res

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In

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Nat

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abor

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pton

, N.Y

C

olem

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nc., 4

2 M

adis

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Ill.

Sp

ecia

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ab.,

The

Dow

Che

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o., M

idla

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486

40

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ical

Lab

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121

5 So

uth

Jeff

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reet

, St

. L

ouis

4, M

o.

du P

ont E

xper

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ilmin

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, Del

. 198

98

E. I

. du

Pon

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Nem

ours

& C

o., W

ilmin

gton

98,

Del

. 198

98

S. J.

Tas

sina

ri

L.

Mal

ter

S. A

. Shr

ader

L. J

. Din

guid

V

. J. C

arri

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W. C

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F. &

M. S

cien

tific

Cor

p., A

vond

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Pa.

H

offm

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a Roc

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, N.J

. 071

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Mic

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Lab

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s, 3

830

Hig

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, P.

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heat

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Che

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epar

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.J.

The

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Lab

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& C

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Indi

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462

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Mer

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Co.

Inc.

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Min

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Man

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2301

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Nat

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of St

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Was

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ox 4

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Co.

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Lab

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7 R

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& H

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Inst

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144

Uni

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Dep

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Uni

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Dep

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Com

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8001

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Res

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B

urro

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-Wel

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Inc.

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.Y.

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. Huf

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. L.

Bau

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L

. M

. Bra

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. Bas

s, J.

C. D

ell, J.

Kitl

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R. K

aup,

J. P

ao, R

. Wet

ter

A.

C. B

row

n F.

Ant

es, L

. DeF

illip

o, J.

Mar

shik

, A

. Soh

a C

. Bea

rley

, J. G

ast,

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ever

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B.

Ost

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J. L

. Wai

ler

J. M

. Len

non

F. B

aiis

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. Boi

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. Jon

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C. W

. Koc

h J.

D. C

alla

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J. N

emet

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. Wea

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. Spi

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C. D

i Pi

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. Di P

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o

Uni

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Stat

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mer

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D.

F. L

eahy

, S. J

. Tas

sina

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H. K

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V. J

. Car

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, J. K

. Win

ter

M. A

. Sp

itzna

gle

01 0

0. N

. Hin

avar

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. St

eyer

mar

k

Stud

ents

G

. J. G

ips,

J. J

. Gin

frid

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. S.

Mod

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. A.

Pass

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W.

L. B

row

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. N. B

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. B

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P. B

. Ols

on

R. A

. Pa

ulso

n G

. M. G

ustin

H

. J. F

ranc

is

H.

W.

Wha

rton

C

. W. N

ash

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Flei

sche

r C

. W. K

och

J. N

erne

th

R. C

. And

erso

n

R. E

. K

olb

R.J

. Hai

l, R

. A.

Paul

son

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M. G

ustin

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. Min

nick

, R. S

mith

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. F. C

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. B

row

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Gio

rgio

DETERMINATION OF CARBON AND HYDROGEN

The statistical significance of the difference of two means was also estimatedby the Student test.

- = 1/ flAflB(flA + flB — 1)tD = (xA — XB) / I lA lflA lB mA I \ (flA + flB) [ E (XIJA — A)2 + (xj — XB)21\' \ j=1 i=1 j=lj=1

The values calculated for t and F were compared with tabulated valuesusing confidence level 005 (95 per cent). The symbols used above aredefined as follows:

u Standard deviation for each compound in each laboratorys Standard deviation for each compound using results from 1 labora-

toriesm Number of determinations done on a particular compound in one

laboratoryI Number of laboratories consideredn Total number of determinations on one compound in I laboratoriesxt Result of a single determination for a particular compound in one

laboratoryMean result obtained for a particular compound in one laboratoryMean result obtained for a particular compound in 1 laboratories

,a True valuesx, s Standard deviation of the mean.

2. RESULTS AND DISCUSSION

2.1 Results from individual laboratoriesThe data calculated from the results obtained for the determination of

carbon and hydrogen are given in Tables 3 and 4. These data include all thecompounds tested and all the collaborating laboratories. In the Tables aregiven the number of determinations, the deviations of the mean from thetrue value, the result of the t-test for this deviation, and the standarddeviation. The technique used for the final determination is also indicated.

Table 3. Determination of carbon—survey of the results found for individual compounds

I +014 2800 010II 4 +009 1636 011III 4 +005 2128 005IV 4 —011 2750 008 CONDV 4 +011 73330 000VI 4 +009 1241 015VII 4 -+-019 8444 006VIII 4 +002 0421 010

Table 3 continked; to be concluded on p. 59

51

4

Laboratory Compound Number of —Method of final

t s determinationdeterminations after combustion

M. VE5ERA and J. HORSKA

2 IIIIIIIVVVIVIIVIII

3 IIIIIIIVVVIVII


5 IIIIIIIvVVIVIIVIII


7 ITIIIIIVVVIVIIVIII

1

Table 3—continued

Laboratory Compound Number ofdeterminations

— t Method of finals determinationafter combustion

I 4 —0-14 0-940 0-30II 4 000 0000 027III 4 +019 3-166 0-12IV 4 —007 0848 017V 4 +015 1863 016VI 4 +002 0182 0-22VII 4 +008 0083 019VIII 4 +046 1-454 0-22

44444444

+002+002—005—003+014+012—004+019

02670-2130-4950-2611-656138204773512

0-150-190200230170170-170-11

6445556

+0-01—028+004—085+003—014+0-20

05025-8390518

1191303601-8673676

0•050-100150-16019017013

77757455

+014—055—0-10+007+012—004+041—012

1-3514-5050768033809830-26707610614

0270-320340460320-290-320-44

44444444

—006+0-02+0-01—003+002—006+012—0-06

1-7650234054008760-44210531-8091-770

0-070-170-040-07009011013007

44444444

+003—002—004+0-17+005—006—009+008

0-3950-306072965301-8870•75840300886

0•150130-110050050-160040-18

44444444

—001—0-10

0-00+0-07+013+006—008+014

0-1510-47400001037312513082-5258-860

0-130420-170-130080-090-060-03

52

CONDultramicro

method

GR

GR

GR

COND

GR

GR


Table 3—continued

8

Laboratory Compound Number of 2 —determinations

A'Iethod of finalt s determination

after combustion

I 4 —0-19 1-398 0-27III 4 +0-48 7-002 0-14IV 4 +004 0-487 0-16V 4 —053 4-152 0-26VI 4 —007 1-823 0-08VII 4 +003 0-447 0-13VIII 4 —002 0-359 0-11


44444444

0-00—0-33—0-13+0-03+0-08+0-08+0-07+0-07

0-0000-45849060-7891-3681-7391-8421-609

0-110-140-050-080-120-090-080-09

10 1IIIIIIVVVIVIIVIII

44443444

—0-09—0-11±0-01+0-06+0-19+0-17+0-31+0-40

1-9152-8950-2080-6860-2293-0369-2555-839

0-090-080-100-180-150-110-070-14

11 IIIIIIIVVVIIVIII

4444557

—0-29+1-14+0-23+ 0-63+0-45+0-61—1-64

3-14023-2656-319

48-83710-5743-4163-675

0-190-100-080-030-090-401-18

12 IIIIIIIVVVIII

444444

—0-04—0-044-0-02-—0-02+ 0-03—0-01

1-4291-4551-3790-4590-6000-488

0-060-060-030-090-100-04


44444444

4-0-02+0-09—0-02+0-10+ 0-06±0-014-0-21+ 0-03

0-2971-8460-4963-5902-4000-1162-0670-667

0-130-100-030060-050-170-200-09


44444444

±0-224-0-26±0-214-0-30±0-230-35±0-24-40-18

2-5432-7064-8806-6627-0996-4693-200

20-809

0-020-190-090-090-060-110-150-02

15 IIIV

44

±0-11±0-05

1-1390-949

0-190-11

53

GR

TITR

GR

GR

UR

GR

GR

GR

M. VEOERA andJ. HORSKA

Table 3—continued

16

Laboratory Compound Number of —determinations

Method of finalt s determination

after combustion

I 4 ±012 2-020 0-12II 4 —0-30 5-597 0-11III 4 ±0-29 2-192 0-26IV 4 ±094 9-558 0-20V 4 ±080 0-855 0-19VI 4 —033 2-436 0-27VII 4 ±027 2-423 022VIII 4 ±0-65 6-002 0-22


44444444

—0-15±0-45±0-42±029±0-40—0-33±0-47±020

1-5154-6156-8853-4737-3398-0498-785

12-903

0-200-200-120-170-110080-110-03


44444444

±0-09±0-26±0-30±0-03±0-12±028—0-13±0-24

0-0791-6595-1460-1941-9872-0381-4473-498

0-230-310-120-310-120-270-180-14


44444444

±0-13—0-36± 0-40±0-29—010±0-22±0-17±0-28

24309-3519-0905-0431-96128392-297

10-980

0-110-080-080-120-100-160-150-05

20 IIIIIIIVVVIVIIVilI

44444444

±0-11±0-08—0-05±0-13—0-13—0-03—0-14—0-15

2-5760-159208326533-0620-7396-4223-464

0-090-100-050-100-090080050-09


44444444

—0-03±0-34±0-06±0-20—0-01±008±007±033

0-2736-2330-9452-2490-1721-55309027285

0220-100-130-180-120-100-16009


45444454

±0-12±0-05±0-20±0-19±0-24±0-19±0-08±0-27

2-3080073

2666620214-8002-3907-4354-737

0-100-150-020-190-100-160-020-11

54

GR

GR

GR

GR

GR

COND

GR


Table 3—continued

Laboratory Compound Number of 2 —Method of final

t s determinationdeterminations after combustion

23 I 4 --004 1572 005II 4 000 0000 008III 4 +009 3232 006IV 4 +009 2182 008 GR* V 4 +016 4233 008VI 4 +002 0539 007VII 4 +005 0752 013VIII 4 ±012 16990 001

24 I 2 000 0000 006II 2 —013 2229 006III 2 000 0000 001IV 2 +042 14860 003 GRV 2 +003 0708 004VI 2 —006 4255 001VII 2 000 0000 010VIII 1 —007

25 I 4 ±003 0739 008II 4 —010 1658 012III 4 ±026 8553 006IV 4 —014 1608 017 GRV 4 ±008 1242 013VI 4 ±010 2107 009VII 4 ±002 0525 008VIII 4 —001 0177 011

26 I 6 -4-001 0064 039II 6 —061 3967 038III 6 —009 0692 032IV 6 000 0-000 040 GRV 6 ±001 0-095 023VI 6 ±015 1517 022VII 6 —015 2035 016VIII 6 —029 2258 029

27 I 4 —002 0228 018II 4 ±0-04 0361 022III 4 -j-010 1122 018IV 4 ± 005 2674 004 GRV 4 -4-005 05097 020VI 4 —003 0264 023VII 4 ±021 4918 009V1II 4 ±019 1916 018

28 I 4 —013 0850 031II 4 —0•27 2045 026III 4 —0•12 2162 011IV 4 -4-046 2667 012 GRV 4 ±027 7105 008VI 4 ±006 1111 011VII 4 —0•05 0450 022VIII 4 ±007 0993 014

29 Determinations were done by students and therefore not taken for thecalculations

55

M. VEERA andJ. HORSKA

Table 3—continued

30



after combustion

I 4 —0-15 4550 007II 4 +043 2630 0.10III 4 +006 0945 013IV 4 +006 1579 008 GRV 4 -+-01O 1563 0-13VI 4 +013 2063 013VII 4 +022 16296 003VIII 4 +020 7547 005

31 I 4 +039 3450 023II 4 —004 2-290 004III 4 +004 0635 013IV 4 +022 6-197 007 GRV 4 -+-019 3040 0•13VI 4 +009 1-956 009VII 4 +058 4-936 024VIII 4 +0-03 0288 021

32 I 4 —002 0323 012II 4 —018 2951 0-12III 4 +036 5806 0•13IV 4 +0-28 7677 007 GRV 4 +041 2075 041VI 4 +002 0•187 021VII 4 +001 0282 007VIII 4 +017 1-473 0•23

33 I 4 +005 0488 021II 4 +009 0340 053In 4 +03 9630 003IV 5 —029 1758 033 GRV 4 +017 1-675 020VI 4 +031 3054 020VII 4 —004 0246 0•33VIII 4 +021 7054 091

34 I 4 —0-15 4-411 007II 4 +007 1138 012III 4 +015 1•987 0-15IV 4 -1-006 0-622 019 GRV 4 014 5091 006VI 4 —005 0-680 0•15VII 4 —005 19200 003VIII 4 --013 1•898 014

35 I 4 +006 1000 0-12II 4 —012 1-008 0-24III 4 +009 2-466 007IV 4 +015 2679 011 GRV 4 +009 1315 044VI 4 +010 1-379 0-15VII 4 —032 5-664 011VIII 4 +014 1172 024

36 I 4 —006 0863 0-14II 4 —0-10 0-172 0-12III 4 ±0-13 2-000 0-13IV 4 +0-17 5-484 0•06 GRV 4 ±0-06 0-822 0-15VI 4 +0-16 4051 0-08VII 4 —018 2•687 013VIII 4 +0-05 1724 0-06

56


Table 3—continued

37



after combustion

I 4 +004 0851 010II 5 ±010 0-304 0-73III 4 +010 6-897 003IV 4 —0-03 1-818 003V 4 +015 7142 004VI 5 —0-59 16253 0-08VII 4 +012 1-875 0-13\TIII 6 ±0-24 9-375 006


44444444

±0-04—0-16—0-14—0-23±0-06+0-06—0-16—0-07

0-4761-633318231511-7653-5292-0512-741

0-170-200-090-150-070-030-160-05

39 IIIIIIV

4444

—0-05—0-27—0-04—0-49

1-8871-5430-7143-213

0-030-180-060-15


44444444

+012+0-11+0-10—0-11—0-03+0-10—0-55—0-02

1-3481-3751-0872-9330-3981-5877-0510-158

0-180-160-180-080-160-130-160-25


44444444

+0-04—0-02—0-01+0-04+0-10+0-04+0-03+0-11

2-2860-9010-1781-4821-6393-6360-5132-472

0-040-040-110-050-120-020-120-09

42 IIIIIIIVVVIIVIII

4444444

+0-02+0-02+ 0-09—0-05+0-09+0-09+0-04

0-4710-4214-3901-2662-8573-1031-290

0-090-100-040-080-060-060-06


43333333

—0-04—0-06+0-16—0-14+0-19—0-12+0-31+0-05

0-3700-6472-9201-2642-6750-8802-1230-525

0-220-170-100-190-120-240-250-17

57

GR

GR

GR

GR

GR

GR

GLC

M. VEOEIA amd J, HOB.SICA

Table 3—continued

Method offinalLaboratory Compound Number of t s determination

determinations after combustion

44 I 4 +0-02 0-315 0-13II 4 +0415 0-565 0-18III 4 +024 3-779 0-13IV 4 +030 4545 0-13 GRV 4 +047 2-267 0-14VI 4 +0-14 6087 0-05VII 4 +O-15 1-500 0-20VIII 4 +0-35 4-375 0-19

45 II 4 —006 1-065 0-11III 4 000 0-000 0-05 MVII 4 +003 0-952 0-06

46 I 4 —0-03 0-503 0-12II 4 +009 2-250 0-08III 4 +0-17 6-939 0-05IV 4 +0-10 5-540 0-04 GRV 4 +0-11 3-354 0-07VI 4 +0-01 0-371 0-05VII 4 +0-05 0-671 0-15VIII 4 +0-12 3-023 0-08

47 I 4 —0-30 2-399 0-25III 4 +002 3-340 0-12 GRV 4 —0-02 0-055 0-07VII 4 —0-01 1-419 0-14

48 I 4 —0-24 2-844 0-17II 4 —0-04 0-308 0-26III 4 +0-01 0-196 0-10V 4 —0-15 3-061 0-10 GRVI 4 +0-03 0-455 0-13VII 4 +0-26 3-059 0-17

49 I 4 —0-03 0-198 0-30III 4 —0-14 1-701 0-16IV 4 +0-03 0-503 0-12 GRV 4 +045 2-230 0-13VI 4 —0-01 0-066 0-30VII 4 0-00 0-000 0-10VIII 4 0-00 0-000 0-29

50 I 4 —0-09 1-579 0-11II 5 —0-30 4-630 0-15III 4 +0-14 11-765 0-02IV 4 +1-99 7-796 0-51 GRV 4 +0-19 8-085 0-05VI 4 —0-05 0-700 0-14VIII 4 +0-08 1-912 0-08

51 I 4 +0-01 0-166 0-12II 4 +0-02 0429 0-09III 4 +0-01 0-213 0-09IV 4 +0-03 3-000 0-02 GB.V 4 —0-06 2-027 0-06VI 4 +0-06 1-899 0-06VII 4 —0-02 0-816 0-05VIII 4 0-00 0-000 0-01

58


Table 3—continued

Laboratory Compound Number of I —determinations

Method of finalt s aetermination

after combustion

52 I 3 +005 1086 008II 3 —004 F242 006III 2 +011 7801 001IV 2 +010 7092 001 GRV 3 +009 4319 004VI 2 +007 08139 009VII 3 +004 1089 008VIII 2 +002 1418 001

53 I 4 +007 1311 011II 4 +006 1359 009III 3 —004 0703 0'lOIV 3 —081 31392 005 GRVI 4 +007 1132 004VI 2 —004 0800 005VII 4 +004 0186 010Viii 3 +004 0572 012

54 I 4 +019 6822 006II 4 —008 1163 014III 4 +011 2136 010IV 4 —012 2791 011 GRV 4 +126 33962 007VI 4 +012 2791 009VII 4 +007 4062 008VIII 4 —009 1033 017

55 1 4 —005 1856 005II 4 —009 7347 002III 4 000 0000 001 GB.V 3 +001 17300 001VIII 4 +003 1807 003

56 I 4 +022 2788 016II 4 —013 5963 004III 4 —012 1563 015IV 3 +020 1641 021 CRV 4 +016 1526 021VI 4 +005 3770 003VII 4 +020 1952 021VIII 4 +009 2541 007

57 I 4 000 0000 007II 4 —001 0343 006III 4 +006 1464 008IV 4 -fOil 1560 014 CRV 4 +010 4000 005VI 4 +008 5031 003VII 4 +005 1114 009VIII 4 +009 2195 0•08

GR gravimetric methods GLO methods with gas chromatography finish COND conductometrie methodsM manometric methods TITER titrimetric methods

59

M. VEERA and J. IfORSKA

Table 4. Determination of hydrogen—survey of the results found for individual compound

Laboratory Compound Number of —Method of finalt s determination of

determinations the combustionproduct

I 4 +002 0869 005II 4 —006 3243 004 CONDIII 4 —001 0556 004IV 4 +003 1•395 004V 4 +003 22143 003VI 4 +008 2860 001VII 4 +003 6000 001VIII 4 —0•01 0•769 003

1 4 —0•O1 0070 003II 4 —004 0762 010III 4 +002 108! 004IV 4 +002 1666 002 CONDV 4 +004 2580 003 ultramicroVI 4 +006 4800 003 methodVII 4 +002 l666 002VIII 4 —003 2727 002

2 I 4 —004 0435 018II 4 —016 1592 020III 4 +010 2976 007IV 4 —005 0840 012V 4 +006 1026 012 GRVI 4 —007 1354 010VII 4 +002 0•340 012VIII 4 +014 1622 017

3 I 6 +003 2190 004II 4 —020 5763 007III 4 +010 2•051 0.10IV 5 +004 2577 003 GRV 5 +014 5512 0•06VI 5 +043 2802 010VII 6 ±007 2243 008VIII 4 +022 3554 012

4 I 7 —003 0794 009II 7 +002 0356 015HI 7 +011 3380 0•09 GRIV 5 ±006 2300 002V 7 +011 2921 007VI 4 +019 5•200 0•07VII 5 +023 2•961 0.15VIII 4 +018 3298 0•11

6 I 4 0.00 0000 006H 4 ±001 0099 020HI 4 000 0000 017IV 4 ±012 2•419 010 GRV 4 +001 0•205 0.10VI 4 ±022 3640 012VII 4 +072 10•510 0•14VIII 4 +040 1•448 0•14

Table 4 continued; to be concluded on p. 67

60


Table 4—continued

7


Method of finalt s determination ofthe combustion

product

I 4 —002 0-854 0-05II 4 —008 2070 0-08III 4 +009 1-650 004IV 4 +000 0-000 004V 4 +045 5401 006VI 4 —0-06 2451 0-05VII 4 —003 0-839 007VIII 4 +002 1-332 0-03

8 IIIIIVVVIVIIVIII

4444444

+047+045+018+0-26+011+049+012

20398-18233585174296551210790

017011011010007007009


44444444

—0-12—0-40+0-04+0-01+01)1—0-01—0-02+0-01

1000068381429060604760-3641-8180-769

0-020120060-030-040060020-03


44443444

+01)6+0-05+0-23+01)8+0-20—0-05—0-05—0-06

3-7501-754

13-9392-0784-9501-0101-3333-158

0-030060-030-080-070-100-080-04

11 IIIIIIIVVVIIVIII

4444457

+0-39+0-05+0-05+0-21+F26+ 0-01+ 0-25

4-1341-41608618-75064380-1453679

0-190070-120-050440-150-18

12 IIIIIIIVVVIII

444444

+0-01+0-01+0-01—0-01+0-02

0-00

080004080-37704880-7840-000

0030-050-050040-050-04


44444444

+0-04+0-03+040—0-01+ 0-03+0-04—0-03+0-0861

4-6241-4156-3290-3652-4490-7020-8574-624

0-020-040-030-050-020-110-070-03

GR

GR

TITR

GR

GR

GR

GR

P.A.C. 21f1—E


Table 4—continued

4 —0164 —0044 +0074 +0284 +0464 +0424 +0074 +005

62

GR

14


Method of finals determination of

the combustionproduct

4 +0-li4 +0414 +0-254 +0-104 ±0-264 +0-244 +0094 +0-05

4-01527-1609-6156-6668-0257•154

138-462-77

0-050-010-050030-060-070-00004

GR

4 +004 0-560 0-144 ±0-19 4-000 009

IIIin:IVVVIVIIVIII

15 IIIV

16 IIIIIIIVVVIVIIviir

17 IIIIIIIVVVIVIIVI"



20 IIIIIIIVVVIVI'VIII

4 —0024 +0044 +0574 +0314 ±0-224 —0404 —0-014 +0-19

4 +0-394 ±0-274 +1-374 +0-434 +0-484 +0-204 +0334 +032

4 +0-114 —0-244 +0204 +0-174 +0-044 +0-144 —0-054 +0-23

4 +0-034 —0-054 +0-274 +0-114 +0-214 +0-064 +0-184 +0-03

0-5710-5379-3068-5160-4141-7530-1226-090

2-80657141085

1194414-11714-2866947

10-492

0-9311-9494-9632-2970-3322-4820-4462-669

0-5881-7866-5060-2163-6842-3532-8360-469

5-060-9931-5373-8993-6242-7710-7490-690

0-070-150-120-070-110-120-160-06

0-280-080-190-070-070-030-100-06

0-240-350-080-150-240-110-220-17

0-100-060-080-100-110-050-130-13

0-060-080-090-140-090-090-190-14

GR

GR

GR

GR

M


Table 4—continued

22

Laboratory Compound Number of g —determinations

Method of finalt s determination of


I 4 +003 0-400 0-08II 5 —0-01 0-018 0-56III 4 +011 2-588 0-09IV 4 +0-06 0-960 0-13V 4 —009 1-856 0-10VI 4 +014 5-833 0-05VII 5 +002 0-551 0-08VIII 4 +0-11 2-220 010


44444444

+003—009+0-07+006+0-01—001+003+0-07

1-4566-3603-1321-8520-6020-1620-5284-929

0-040-030-050-060-030-120-110-03


22222221

—0-02+0-01+0-05+0-08+0-02—0-01+0-13

0-00

0-3530-041-1790-9420-2021-003-601

0-060-040-040-080-100-010-04


44444444

—0-06—0-08+0-04—0-05+0-05+0-05+0-02+0-08

1-8993-2650-3491-0912-9940-8550-7072-049

0-060-050-230-090-040-120-060-07


66666666

—0-14—0-10+0-18+0-02+0-03+0-10+0-03+0-08

3-0322-2102-2700-2440-6132-0210-2960-077

0-110-110-190-200-120-120-250-26


44444444

—0-09—0-12—0-07—0-06

0-00—0-06+0-23+0-15

4-8102-7712-5552-2260-0001-9238-5344-471

0-040-090-050-050-040-060-050-07


44444434

+0-24+0-11+0-02+0-23+0-12—0-01+0-06—0-01

2-6851-8600-1855-0831-5630-0752-5560-178

0-180-120-220-090-150-270-050-11

63

GR

GR

GR

GR

GR

GR

GR


Table 4—continued

Laboratory Compound Number of —Method of final

I s determination ofdeterminations the combustion

product

29 Determinations were done by students and therefore nottaken for the calculations

30 I 4 +006 1073 011II 4 +005 I•091 009III 4 +005 0752 013IV 4 +013 3043 009 GRV 4 +041 1478 015VI 4 +014 4.179 0•07VII 4 +001 0495 0•10VIII 4 +018 5370 007

31 I 4 —009 1228 0•15II 4 —042 2225 0•11III 4 —017 2304 0•15IV 4 +022 2701 018 GRV 4 +047 2513 037VI 4 +018 1084 033VII 4 +015 1946 0•15VIII 4 +043 7544 0.11

32 I 4 —041 1692 013II 4 —044 2146 041III 4 +006 1200 010IV 4 +005 2083 005 GRV 4 +016 2406 013VI 4 +008 1270 013VII 4 +008 1975 008VIII 4 +042 1519 0•16

33 I 4 +022 3•492 013ir 4 +001 0•187 011III 4 +007 1207 012IV 5 +007 2029 007 GRV 4 +012 033 072VI 4 +049 0540 0•71VII 4 +008 1330 0•12VIII 4 +015 2•970 0.10

34 I 4 +009 1552 012II 4 +041 1•880 0•12III 4 +040 1370 015IV 4 +041 4681 0•15 GRV 4 +040 2273 009VI 4 +045 2804 011VII 4 +040 1•709 012VIII 4 +0.11 2651 008

35 I 4 +005 1299 O08II 4 —001 0187 0.11III 4 —006 2609 005IV 4 +005 0•082 0•12 GRV 4 0•00 0.000 0•05VI 4 +047 6939 005VII 4 +001 0•046 0.43VIII 4 +047 5000 007

64


Table 4—continued

Method of finalLaboratory Compound Number of t s determination of

determinations the combustionproduct

36 I 4 —0-22 6-027 0-07II 4 —0-21 6-364 007III 4 +0-08 2-539 0-06IV 4 —0-12 4-528 005 GRV 4 —0-04 1-194 0-07VI 4 —015 3-797 0-08VII 4 —003 0-833 0-07VIII 4 +0-03 2-222 0-03

37 1 4 +042 2-087 0-12II 5 +0-02 0-507 0-09III 4 +0-02 0-851 0-05IV 4 +0-11 3-385 0-07 GRV 4 0-00 0-000 0-07VI 5 +0-08 2-878 0-06VII 4 +0-06 2-308 0-05VIII 6 +0-06 5-469 0-03

38 I 4 +0-06 1-967 0-06II 4 +0-05 2-128 0-05III 4 +0-11 6-660 0-03IV 4 + 0-04 0-842 0-09 GRV 4 +0-05 6-470 0-08VI 4 +0-14 4-827 0-06VII 4 +0-09 11-250 0-02VIII 4 +0-07 4-000 0-04

39 I 4 —0-07 0-560 0-25II 4 +0-14 4-912 0-06III 4 +0-08 2-712 0-06 GRV 4 +0-04 0-976 0-08

40 1 4 +0-16 6-808 0-05II 4 —0-88 23-592 0-08III 4 +0-26 2-105 0-25IV 4 +0-02 0-339 0-12 GRV 4 —0-15 1-818 0-17VI 4 +0-09 1-029 0-18VII 4 —0-14 3-420 0-08VIII 4 +0-14 0-259 0-11

41 I 4 +0-06 2-105 0-06II 4 —0-14 1-806 0-16III 4 —0-03 0-612 0-bIV 4 +0-04 0-376 021 GRV 4 +0-14 5-185 0-OSVI 4 +0-22 11-892 0-04VII 4 —-0-02 0-360 0-11VIII 4 +0-21 35-000 001

42 I 4 —0-04 1-212 0-06II 4 —0-02 0-381 0-11III 4 +0-02 0-702 0-05IV 4 —0-01 0-333 0-05 GRV 4 +0-03 1-429 0-04VII 4 +0-02 0-727 0-06VIII 4 +0-03 3-000 0-02

65

M. VE1ERA and J. HORSKA

Table 4—continued

45 IIIIIVII

46 III'IIIVVVIVIIVIII

47 IIIIVVII

48 Iii:IIIVVIVII


4 +0024 —0484 +0024 +0484 +O34 +0484 —0404 +008

4 +0014 —0094 +009

4 —0024 —0104 +0034 +0074 +0444 +0454 —0084 —005

4 +0024 +0424 —0•044 +0044 —0084 —0064 —0074 0004 —0044 —O•07

4 +0014 —0474 +0124 +0024 +0054 +0014 +0114 +004

4 +0485 +0•104 +0414 —0064 +0404 0•004 +009

66

0400•100160•120•110•040051007

0•18002005

0•07005006008004012006003

0•150•110•12006

005010005005006008

0080•170030040100•150080•06

Laboratorj Compound Number of —determinations

Method offinalI s determination of


43 4 +0283 —0•013 —0463 —0063 —0•283 +0202 +0063 +022

IIIIIIIVVVIVIIVIII

44 IIIIIIIVVVIVIIviii:

0•150•170050010•030•03000001

3.73301026•1596897

19•4046•2890000

31•746

00383•87102433.1302•36497293•9222286

01097.3773346

0•5354•16709871•7777235084827443.533

0264202006321431

3•201641285700001.4361•724

02481•9938•16310001•0050.1372•8871351

42151•57380001 •14931650•0003•180

GLC

GR

M

GR

GR

GR

GR

GR

50 IIIIIIIVVVIVIII

0080150100•100060•13006


005:for 4 determinations 3182for 5 determinations 2776for 6 determinations 2-571for 7 determinations 2447

Table 4—continued

GRCONDGLCMTITR

51


Methods offinalt s determination of


I 4 —0-05 0-562 018II 4 —0-08 1-415 0-11III 4 —004 0912 009IV 4 +0-06 1-810 007 GRV 4 0-000 0-000 0-05VI 4 +0-02 0-166 0-24VII 4 +003 0287 021VIII 4 0-00 0-000 0-09

52 I 3 0-00 0000 008II 3 —0-36 12457 005III 2 +0-01 0353 003IV 2 +0-05 3546 001 GRV 3 +049 9-510 0-03VI 2 +0-05 0-393 0-13VII 3 —0-02 0-693 0-05VIII 2 —0-18 1-950 0-09

53 I 4 +0-08 1-347 012II 4 —0-04 0895 009III 3 —0-05 2747 0-03IV 3 —0-03 3-297 0-02 GRV 4 +0-10 4255 0-05VI 2 +0-12 3324 004VII 4 +043 1-704 0-15VIII 3 +0-03 0544 0-10

54 I 4 +043 1879 0-14II 4 —0-10 0684 029III 4 —0-28 2914 016IV 4 +0-23 4236 0-11V 4 +0-04 0537 0-15 GRVI 4 —0-02 0421 009VII 4 +049 15-510 002VIII 4 +012 1103 022

55 I 4 +0-02 1-786 002II 4 +0-04 1600 0-05III 4 + 0-03 3-000 002 GRV 4 +0-00 0-000 0-01VIII 4 +0-06 4-526 0-03

56 I 4 —0-08 0423 038II 4 +0-03 0427 0-14III 4 —0-01 0-205 0-10IV 3 +0-30 3-400 0-15V 4 +0-01 0195 0-10VI 4 +0-11 1350 0-16 GRVII 4 +0-20 1-641 0-24VIII 4 +0-12 10-710 0-02

57 I 4 —0-01 0-384 0-15II 4 —0-15 13-391 0-02III 4 —0-02 1-426 0-04IV 4 +0-04 2-213 0-04V 4 —0-04 1-597 0-05 GRVI 4 + 0-05 2-083 0-05VII 4 —0-05 2-771 0-04VIII 4 +0-07 1-761 0-08

gravimetric methodsconductometric methodsmethods with gas chromatography finishmasiometric methodstitrimetric methods

67

M. VEOERA and J. HORSKA

The distribution of the deviations of the means is shown in Figures 1 and 2for gravimetric techniques and for other techniques (e.g. electrical con-ductivity, thermal conductivity after gas-chromatography separation,manometry and titrimetry). For the gravimetric technique, the results forthe estimation of significant deviations are collected in Table 5. Systematicerrors in the determination of carbon in compounds III, IV, V, VII and

'I II III IV V VI VII VU!$ +1-99 +126 f+0-61 +3-21

÷1-14 +096 +050 +058 +0-65+063

+050- 0o o+0'40-o 0 0 0o 0 0I0 00

+0-30 00 00000 0 0 0 0000 0 000 00 00 0000 0 0 0 000+020 0 o• ooe oooo 0 OOS 00000 0 00 00 0 00 0000 00 00000 00 0 I Xooo 0 000 0 000 = 00 -coo- - -

oooo 0 0000 -0----- -oooo•-- 00 00 000+010 0 oooo• -00000-X- 0000 00000 00000 -I----- 000 oo 00 000 0000 0000 coo000 000 0000 0000 000000 00000 000 000000000 0 000 000000 0000 —00--- 00000 000000000004L 000 oooooo oo• oooo• 000 o•

14 —00- -00 0000—0 00 —0O-000 0000 00 000 00 0 00 0000000000 0000 000 00 0 0000 000000 .00---X 00 0 ooooo 0

-o-io - oo 8o 00 0 0 000 0 000 0 000 000 00 0 00000 0 0 00 0-0-20-o 0

0 0 0OOC-0-30 - 00 00 0O 0 0

-036 —081 —0-49 —033 1-0-66 -085 -053 —0-33 -055 1-1-64—055 3 —0-59 3-0-6 1

Figure 1. Carbon determination in substances 1—Vill. The distribution of the frequencies ofdifferences — s. The final determination of the combustion products [gravimetric 0;

conductometric heat conductivity 0; manometric 0; titrimetric }

VIII, and in the determination of hydrogen in compounds II, III, V, VIand VIII, were found in over 25 per cent of the laboratories involved. Thisstatistical treatment was only done when the number of gravimetric deter-minations made was sufficient.

2.2 Deviation of final means; standard deviationsThe systematic errors found in a relatively high proportion of the labora-

tories involved, made it necessary to estimate the significance of the devia-tions of the means for all laboratories. Tables 6 and 7 show the deviations ofthe means for compounds I—VIII and the corresponding values of I used toestimate the significance of these deviations. All the deviations given have a

68

DETERMINATtON OF CARBON AND HYDROGEN

I II III IV V VI VII VIII

+1'37 ¶+1.26+050 - +0•57 I+055co0 o 0

+040 - .0

J+0.720o 0- 0

o 0 0Co 00 0 0 CO 0 Co 0

0 CO Co COD+020- o Co CCO 0(0 0 CCI) 00 - - 0 0 CO —&x &o --c,mo- ------+0.10 -0 0 00 - ------ --s•---- —---- _____

cIDJO 0D CODCoS 0ooxoce o o1.1 —0 0———CIJOOO 0___ • OJS CXX) oo cxe os= o 0 xo 00 -CC- D 0 (0) CX)

Co 0) 0 CO—010-Co CX) 0 00$ co 0o 0 0o (0 0 0 0

(0 0000

o 0 0-0•40-01.4-088

Figure 2. Hydrogen determination in substances 1—Vill. The distribution of the frequencies— s. The final determination of the combustion products [gravimetric 0; conductometric

•; heat conductivity 0; manometric 0; titrimetric ]

Table 5. Frequency of systematic error

Number of Number of laboratoriesGompound laboratories with systematic error

DETERMINATION OF CARBONI 48 4 83II 46 10 217III 49 16 327IV 44 16 364V 49 14 286VI 42 8 190VII 44 13 295VIII 43 16 372

DETERMINATION OF FIYDROGENI 48 10 208II 46 12 260III 49 13 265IV 44 11 250V 49 15 30-6VI 42 13 310VII 44 11 250VIII 43 17 361

69

M. VEERA and J. HORSKAconfidence level of 0.05 (95 per cent) except for the determination of carbonin anthracene. This will be discussed further on p. 71. Tables 6 and 7 alsoshow the standard deviations calculated from the results for carbon andhydrogen in all compounds.

Table 6. Determination of carbon—survey of the results found for particular compounds bythe gravimetric method

Number ofNumber of determina-

Compound laboratories tions — je t s F

I 48 196 +0-003 — 0-0519 0-23 —II 46 193 —0-048 2-184 0-1075 0-33 2-071III 49 200 -1-0-093 6-445 0-0383 019 1-355rv 44 175 +0-116 6287 0-1978 044 3811V 49 198 ±0-118 7-812 00798 0-28 1-538VI 42 166 ±0-036 2153 00514 0-23 1009VII 44 184 —1--0-079 4-606 00677 026 1304VIII 43 178 +0-137 2630 04463 067 8-999

lio = 1980, F12012° =1-352 (005)

Table 7. Determination of hydrogen—survey of results found for particular compoundsby the gravimetric method

Number ofNumber of determina-

Compound laboratories lions — .e t s F—

I 48 196 +0038 3-363 Q•0316 0-18 —II 46 193 —0056 5-018 00461 0-21 1•459III 49 200 +0-109 6050 00667 026 2-110IV 44 175 +0083 8-200 0-0220 015 1-436V 49 198 +0-119 7069 00607 025 1-921VI 42 166 +0074 6-912 00230 015 1-374VII 44 184 +0-066 6-230 00351 0-19 1-111VIII 43 178 +0-106 l0•515 0-0195 0-14 1-621

1120 = 1-980, F12012° = 1-352 (0-05)

The corresponding scatter of the results (expressed as the square of thestandard deviation) was compared with the scatter obtained for anthracene.In the case of carbon, the scatters found were (except for compounds VI andVII) considerably greater than those found for anthracene. In the deter-mination of hydrogen, the scatters of the results for compounds II, III and Vwere significantly higher than those for anthracene, whereas the scatters forcompounds IV, VI and VIII were narrower. These results are discussed inmore detail on p. 71.

70


3. DISCUSSION OF METHODS, INDIVIDUAL ANALYTICALOPERATIONS AND THE RESULTS OF DETERMINATIONS

ON STANDARD SUBSTANCES3.1 Methods of combustion

All the methods used involved combustion with a catalytic substance.The fillings of the combustion tubes are listed in Table 8. Most collabora-tors (27) used the classical copper oxide filling; others used the Co304filling (12 collaborators) and the silver permanganate decompositionproduct filling (6 collaborators).

Table 8. Determination of carbon and hydrogen using tubes with catalytic fillings

Amount of gasLength of for one

Results Catalyst Temperature filling Gas flow determinationno. (°C) (cm) (mi/mm) (ml)

1 CuO 700 18 5 2003 CuO 775 - 7 150—2504 CuO 800 135 10 2256 CuO 850 12 7 1757 CuO 670—850 115 5—7 2508 Co304,AgMnO4 750 105;75 12 1509 AgMnO4 500—600 5 12 300

10 Co3O4 600 5 15 20011 Pt 750 27 6 20012 Pt 850 14 50-100 50013 Co3O4,Pt 760 3;13 5 17014 CuO 700 22 50 75015 Co304 800 9 10 15017 CuO 920 13 10—12 150—18018 CuO 550 20 14019 AgMnO4 525 35 3021 NiO 700—750 14 20—30 300—40022 Co304 750 5 80 10027 CuO + W03 820 19 25 20028 CuO,AgVO3 850—900 — 15 31329 Co203 700 8 10—12 15030 CuO 660 15 4 15032 CuO 800 30 10 30034 CosOi 700 8—10 220—23035 CuO 840—880 35 — 29436 Co304 800 18 12 18038 CuO 850 25 150 70039 Co3O 700 4 10—14 18042 CuO, Pb3O4 850 19 8 40043 AgMnO4 550 6 15—20 200—25044 AgMnOi 750 15 4 29045 CuO AgVO3 830—895 12 10—1 00 45048 CuO 680 14 10 21050 CuO 650 15 10 40051 CuO 880 19 15 45052 Co304 850 10 50 50053 Co304 700 -— — 30054 Co304,AgMnO4 800—500 20—225 12 18055 CuO 650 15 4 12056 CuO 850 125 6 27057 CuO, CeO2 800 18 8 200

71

M. VEERA and J. HORSKA

The analytical results for the standard samples indicate that all thecatalysts used ensure quantitative combustion of compounds I and Ill—Vill.The decisive factors in the successful use of a particular catalyst are (a) anappropriate length of layer, (b) the quality of the active surface of thematerial used, (c) the gas flow rate. The working conditions used in thedifferent laboratories (see Table 1) varied widely.

The average results of all the determinations of cholesterol were foundto be lower than the true value; oniy for this compound were low resultsfound to an extent which is statistically significant. The low results forcarbon in this compound may be due to various factors: (a) too low atemperature of combustion; (b) an insufficient volume of carrier gas(cholesterol has a slow combustion rate so that flushing the combustionproducts into the absorption vessels may take longer than usual); (c) choiceof catalyst; (d) impurity of the sample (this possibility was not considered).

25OmL

+040

0

+040 - t+o 45

+030 +030o

+020 - +O•20

o 0+010 - +0•10

0= 0--8-5- 8

-0•10- o.1o

!L—020 —020 -0 0

9 0 0-030 —030 0 0I -036I-044 0 0t -055

,-061

Figure 3. Carbon determination in Figure 4. Carbon determination incholesterol. The effect of the catalytic cholesterol. The effect of amount of gas

filling of the tube used

In a further study of the negative deviations of the average results fromthe theoretical values, the procedures involving a gravimetric determinationwere chosen. The data are shown in Table 9. Figures 3, 4 and 5 show themean results obtained in different laboratories in relation to factors (a), (b)

72

Tab

le 9

. Det

erm

inat

ion o

f car

bon

in c

hole

ster

ol

Num

ber o

f N

umbe

r of

labo

rato

ries

de

term

inat

ions

X

—jL

t

ttab

F Ft

ab

tD

tDta

b

EFF

EC

T O

F C

AT

AL

YT

IC F

ILL

ING

CuO

Co3

04

20

12

84

48

—0.

126

4007

20

00

0089

6

--00

43

1372

20

21

0059

2 15

l4

l637

35

32

198O

INFL

UE

NC

E O

F A

MO

UN

T

OF

GA

S U

SED

<25

0 m

l

>25

0 m

l

23

16

97

64

—00

85

2882

19

80

0094

2

—00

76

2630

20

00

0064

4 1•

463

1467

02

08

1980

EFF

EC

T O

F T

EM

PER

AT

UR

E O

F C

OM

BU

STIO

N

<75

0°C

>75

0°C

18

21

75

86

—00

91

0.10

21

—00

68

2611

1980

00661

1•545

1352

0•527

1980


and (c) listed above. It is obvious that the deviations of the means from thetrue value are significant when copper oxide or cobalt oxide was used ascatalyst. The influence of temperature or the total volume of sweeping gaswas not a governing factor; this conclusion was reached from the qualitativetrends in the results and was confirmed statistically. The precision of theresults was poorer when the temperature of the catalyst was less than 750°C;it therefore appears that the low results for carbon are caused by the catalystbeing insufficiently active to ensure quantitative combustion. Difficultlycombustible materials (e.g. cholesterol derivatives) are thought to splitoff methane (from angular methyl groups) on heating. It has been shownthat methane is the most difficult to decompose of all organic materials andthis may be the cause of the low results.

3.2 The removal of nitrogen oxidesThe various procedures used in the collaborating laboratories for the

removal of nitrogen oxides are shown in Table 10. Absorption on man-ganese dioxide was used by half the laboratories (25 per cent), 18 used leaddioxide and others used less common methods. As was mentioned in Section2.2 (see also Table 7) the range of individual results for hydrogen in 2,4-dinitrophenyihydrazine was wider (s ±026) than for other standards.

Table 10. Reagents for removal of nitrogen oxides

Reagent Laboratory

Pb02 1, 11, 15, 16, 18, 28, 30, 31, 32, 33, 37, 41, 48, 52, 54, 55,56, 57

PbCrO4 + CuO 29Mn02 2, 3, 4, 6, 7, 9, 10, 12, 13, 17, 19, 22, 24, 25, 26, 27, 34,

36, 38, 40, 42, 46, 49, 50Cu 20, 23, 45Diphenylamine —H2S04 8H2S04 cone. 21Hydroxylamine sulphate

on silica gel 14

The deviation of the average result is also higher than usual (+0l09). Boththese figures are statistically significant.

It is known that high results for hydrogen are usually obtained for nitrogen-containing compounds when manganese dioxide is used to remove nitrogenoxides (partial absorption of nitrogen oxides). Accordingly, the methodsusing manganese dioxide and lead dioxide were compared for the case of2,4-dinitrophenyihydrazine (see Table 11 and Figure 6).

When lead dioxide was used, the deviation of the mean for hydrogen was+O072, compared with +0111 for manganese dioxide; both deviationsare statistically significant but the mutual difference may not be significant.

t From the data submitted by the collaborating laboratories it was not possible to deter-mine whether a correction was applied for the amount of nitrogen oxide absorbed on themagnesium perchlorate.

74


-750°C '750°C Pb02 Mn02

0+040 - 040 -

3D - +030 - 0

0 0 80 0

20 - +020 - 00

001D - 010 - ..

-010 - 0000

00

-020 - -0200

0 o 00 o -030-

00

-0L0 - -055-061

Figure 5. Carbon determination in Figure 6. Hydrogen determination incholesterol. The effect of combustion 2,4-dinitrophenyihydrazine. The use of

temperature Pb02 or Mn02 for trapping nitrogenoxides

The results with manganese dioxide are more precise than those with leaddioxide (the ratio of the variances is significant). Both methods gave highresults for carbon (the deviation of the mean is significant); in contrast tothe case with hydrogen, the mutual difference is here statistically significant(Table 11, Figure 7). For carbon, the two methods are of virtually the sameprecision (ratio of variances is not significant). The conclusion can be madethat manganese dioxide should be preferred to lead dioxide in the analysis ofnitrogen-containing compounds: the results are more precise for hydrogenand more accurate for carbon.

3.3 Separation of halogens and sulphur oxidesThe methods used for the separation of halogens are summarized in

Table 12. It is known that iodine is difficult to absorb on silver and that silveriodide tends to dissociate at the working temperature (500—600°C), hence

75

M. VEERA and J. HORSKATabit 11. Determination of hydrogen and carbon in 2,4-dinitrophenyihydrazine. The use of

Pb02 or Mn02 for absorption of nitrogen oxides

Number Numberof of

labora— determina- — js t tt 2 F FBI ID ttIBbtories lions

PbO, 17 66DETERMINATION OF HYDROGEN

+0072 2•993 2000 004621949 1534 1437 1980

MoO3 22 91 +0111 7322 1980 00237DETERMINATION OF CARBON

Pb02 17 66 +0112 003121285 1467 2036 1980

MoO, 22 91 +0053 2629 1980 00401

Pb02+Ag Ag

++O•94I ÷O'63

+O4O

0

+0-30 -0

÷0-30

:+0-20 o ÷0-20 0

o __.;_ 0§

+0'lO - - 0

_i

-o.io -. 8 -O10 -o 0

00

-020 - -0-20 -0

-0•30 - -030 -

Figure 7. Carbon determination in Figure 8. Carbon determination in2,4-dinitrophenyihydrazine. The use of o-iodobenzoic acid. The effect of the usePb02 or Mn01 for trapping nitrogen of (Pb02 + Ag) and (Mn02 ± Ag)

oxides respectively

o-iodobenzoic acid was included in the study. The deviation of the meancarbon result was + 0116, which is, of course, statistically significant;obviously, iodine is not completely absorbed and passes to the carbondioxide absorber. In order to discover whether or not the high carbonresults were influenced by the use of lead dioxide or manganese dioxide in

76


Table 12. Reagents for removal of halogens and sulfur oxides

Laboratory Reagent Temperature Laboratory Reagent TemperatureNo. (°C) No. (°C)__-1 700 14 600

17 Electrolytic 530 15 50039 1 Ag 500 19 52540 750 22 750—5002 1 650 30 woo 6604 800 37 I 650—7007 600 50 650

10 600 55 J 130—55020 600 51 Ag on pumice 49027 570 5 Ag net 30029 520 21 400—50032 Ag 450 18 Ag20 15034 700 36 AgMnO4 55038 600—300 43 AgMnO4 + Ag 550—50042 850 44 AgMnO4 + Ag 55046 700 54 AgMnO4 + Ag 50048 680 45 AgMnO4, AgVO3, Ag 83052 550 28 AgVOI f Ag c. 70053 12 AgVO1 + Ag 85056 850 35 AgVO3 + Ag 840, 840—1 506 300—400 25 PbCrO4 3508 700 3 PbCrO4, Ag, Pb304 7759 500 49 CeO, perhydrite 300

13 500

the method, the results obtained when silver was used for iodine absorptionand one of the dioxides was used for absorption of nitrogen oxides, weretreated statistically (Table 13, Figure 8). It is obvious that the values of themeans (+0483 for lead dioxide and +0093 for manganese dioxide)differ significantly. This means that traces of iodine escaping from silver areabsorbed in manganese dioxide fillings. However, there is no difference inthe precisions of the determinations in the two cases (Spbo2 = ±036;SMflO2 = +0.24).

Table 13. Determination of carbon in iodobenzoic acid and in suiphanilamide. Effect of theuse of Pb02 + Ag or MnOl + Ag

.Wumber .Numberof

labora-of

determina- — I t, s F FIb ID tDI.btories lions

DETERMINATION OF CARBON IN IODOBENZOIC AcoPbOa+Ag 12 46 +0183 3•916 2021 01306 2180 1'594 1647 1980Mn02 + Ag 14 55 +0093 2995 2000 00599

DETERMINATION OF CARBON IN SULPIIANILAMIDEPb04 + Ag 11 46 +0235 — — 00599

2155 1594 3122 1980Mn02+Ag 15 57 +0114 4959 2000 00278

For the determination of carbon in suiphanilamide, methods in which acombination of lead dioxide and silver was used, gave results significantlydifferent from the true value. A combination of silver and manganese dioxidegave results which were more accurate and more precise (Table 13, Figure 9).

77PAC 21/1—F

M. VEEA and J. HORSKA

—0'20

-030

Figure 9. Carbon determination insuiphanilamide. The effect of the use of(Pb02 + Ag) and (MnOs + Ag)

respectively

Figure 10. Carbon determination inp-fiuorobenzoic acid. The effect of the

use of special fillings

For p-fiuorobenzoic acid, the deviation of the mean result for carbon(+0O36) is not significant. The results obtained with special fillings (Table14, Figure 10) were slightly more precise.

3.4 Analysis of compounds containing phosphorus and potassiumThe mean result for carbon in triphenyiphosphate is +0O79 per cent

higher than the true value. This statistically significant result may be dueto the passage of acidic vapours into the carbon dioxide absorber (as in thecase of nitrogen, sulphur and halogen compounds). This suggestion needsfurther evidence for substantiation. (In a sample of 5 mg of triphenyl-phosphate, the + 0081 per cent error observed corresponds to 4g P205).The results were found to be significantly higher (+0164 per cent) whenvanadium pentoxide or tungstic oxide was added to the sample in the boat(see Table 14, Figure 11).

For the determination of hydrogen, the precision (s = +0.19) andaccuracy (+0666) are within the normal range for the other standards.

In 17 cases (35 per cent), the sample was analysed without any additionto the sample boat; tungstic oxide was added in 21 cases (44 per cent);vanadium pentoxide was added in 5 cases and other additives were used in

78

PbO24Ag MnO2Ag

t÷0501+045

*030

Specat_fitLing NospecaL_fiuings

+O2O

0

001

00

+040

+O3O

+020

+010

—010

0

90cD0

0000

9

00

—0•10 0

0

0

0

0 0—059

Tab

le 1

4. D

eter

min

atio

n of

car

bon

in p

-flu

orob

enzo

ic ac

id, in

trip

heny

ipho

spha

te, a

nd in

pot

assi

um h

ydro

gen

phth

alat

e.

Eff

ect o

f the

com

bust

ion

addi

tives

Num

ber o

f N

umbe

r of

labo

rato

ries

de

term

inat

ions

2

—

t tto

S2

F

Ftab

ID

tD

tab

DE

TE

RM

INA

TIO

N O

F C

AR

BO

N

IN p

-FL

UO

RO

BE

NZ

O!C

Acm

Add

itive

s 16

66

+

0044

19

89

2000

00

411

1547

14

67

No

addi

tives

22

90

+

0035

13

41

2000

00

636

'-1

0 D

ET

ER

MIN

AT

ION

OF

CA

RB

ON

IN

TR

IPH

EN

YL

PHO

SPH

AT

E

V20

5, W

03

19

76

±0•

164

5674

2•

000

0068

2 10

01

1534

51

82

1980

N

o ad

ditiv

es

19

81

0.00

0 00

681

DE

TE

RM

INA

TIO

N O

F C

AR

BO

N IN

PO

TA

SSIU

M

HY

DR

OG

EN

PH

TH

AL

AT

E

V20

5 9

36

+01

09

3993

20

42

0-03

09

1285

1.

740

0-95

1 1.

980

W02

20

84

+

0077

41

32

2-00

0 00

397


5 cases. It is clear that the addition of auxiliary oxidants is not necessary forsamples of the triphenyiphosphate type. Impurities coming from the auxiliaryoxidant caused high results. However, this finding does not hold in generalfor phosphorus-containing compounds.

When potassium hydrogen phthalate was analysed, the normal precisionwas obtained for hydrogen, but the precision of the carbon results wasmuch less (for C, s +067; for H, s = +0.14). The poor precision forcarbon was caused by the use of acid additives for the liberation of carbondioxide from the metal carbonate. The additives also caused an increase(+O106) in the results for hydrogen (presumably because of inadequate

With Withoutadditives additives

t+061 t .+O4O

I° +040

+O3O +030000 0 0

+020 8 +020 000 0 o

00 +0•10 •p7 L

00 010

00 0

—010 —01008

—020 0 —020

-030 -0300

t_0.55

Figure 11. Carbon determination in Figure 12. Carbon determination intriphenyiphosphate. The effect of the potassium hydrogen phthalate. Theuse of additives in the combustion boat effect of the use of additives in the

combustion boat

drying of the reagent). The mean carbon result was +0137 per cent higherthan the true value, probably because of traces of organic impurities in thecompounds added to the sample (W03, V205). The average result forcarbon in 36 determinations with vanadium pentoxide was found to be+0109 per cent above the true value, whereas the average result of 84determinations in 20 laboratories with tungstic oxide was found to be+0O77 per cent high; the difference between these mean results is notsignificant (see Table 14 and Figure 12). It is therefore not possible to explain

80


the statistically significant high result for carbon in potassium hydrogenphthalate. Further experimental work is needed to decide if the high carbonresults obtained for compounds containing halogens, sulphur, nitrogen andphosphorus are caused by the presence of these elements.

Almost half the collaborating laboratories (46 per cent) used tungsticoxide as additive; vanadium pentoxide was used by 20 per cent of thelaboratories while others used different additives. In 7 cases, the analyseswere done without any additives. Clearly, tungstic oxide is the most com-monly used reagent for the liberation of carbon dioxide from componentscontaining alkali metals.

3.5 Treatment of weighing vessels in gravimetric determinationTwenty-five laboratories gave information on the method of weighing the

absorption tubes for the determination of carbon. In 9 cases, the absorptiontube was wiped; it was not wiped in 16 cases. The precision and accuracywere the same in both groups as shown for analyses of anthracene (Table 16,Figure 14).

The blank Carbon apparatus w&ghedSubtraction No subtraction After wiping Without wiping

+04O +040 -

+030 +030

0+02O - +020

8 o+010 - ° +010

X JL L-r °

—oio- 8 —010-0

-020- —020

-0'30- —030

Figure 13. Hydrogen determination in Figure 14. Carbon determination inanthracene. The effect of substraction anthracene. The effect of wiping the

of the blank absorption tube

3.6 Survey of other methods of final determinationAlthough gravimetric methods predominated, several other methods of

completing the determinations were used. Two collaborators used amanometric method on the ultramicro scale. One collaborator used atitrimetric process. In one case the carbon and hydrogen were determined bythermal conductivity after a gas-chromatographic separation, and in three

81

TaM

e 15

. Det

erm

inat

ion

of hy

drog

en in

ant

hrac

ene.

Eff

ect o

f cor

rect

ion f

or b

lank

exp

erim

ent

1652

1.

534

2755

19

80

0<

t!j

Tab

le 1

6. D

eter

min

atio

n of

carb

on in

ant

hrac

ene.

Eff

ect o

f wip

ing

the

carb

on d

ioxi

de ab

sorp

tion

vess

els

0 cI

Not

subt

ract

ed

20

Bla

nk

Num

ber o

f la

bora

tori

es

Num

ber o

f de

term

inat

ions

£

—

t tj

S2

F Ft

b ID

tf

ltab

Subt

ract

ed

19

81

—00

06

0016

l

81

+00

52

3172

20

00

0026

1

Wei

ghin

g of

ab

sorp

tion

vess

els

Num

ber o

f la

bora

tori

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cases, changes in electrical conductivity after absorption of carbon dioxideand water were measured.

The standard deviations of the carbon results were lower by the electricalconductivity methods than by the gravimetric method, while the standarddeviations obtained by the manometric, titrimetric and chromatographicmethods were close to that of the gravimetric method (see Figure 1).

4. CONCLUSIONSPrecise results for the determination of carbon and hydrogen are obtained

in most laboratories, indicating that adequate methods are in common use.Where precision is less satisfactory, the cause must be sought in somepeculiar working condition in a particular laboratory, because this studyhas shown that the precision of one particular method may vary from placeto place.

The study has indicated that there is no doubt about the theoretical basesof the methods used. It does appear, however, that it is impossible to usemanganese dioxide to remove nitrogen oxides when water is absorbed on tophosphorus pentoxide. The data collected on the various methods allow anassessment of the general suitability of individual conditions (e.g. types ofbalance, weighing temperature, combustion conditions, catalysts, etc.).

The large quantity of data allows conclusions to be drawn, which may beimportant for the further development of elemental analysis. For example,it has been shown that the accuracy and precision of the determinationsdepends to some extent on the elemental composition of the compoundbeing analysed. It has been definitely established that the overall mean ofthe carbon values is higher than the true value in compounds containingS, I, N, P and K, whereas the average carbon result for cholesterol is lowerthan the true value. The determinations of hydrogen show a positivedeviation (which is probably proportional to the hydrogen content of thesamples used) and this error is undoubtedly higher in nitrogen-containingcompounds. Methods in which lead dioxide is used for absorption of nitrogenoxides show a wider range of results for the determination of hydrogen thanmethods in which manganese dioxide is used.

The high results obtained in the analysis of compounds containingS, I, N and P call for further investigation. The low results obtained forcompounds of the cholesterol type should also be studied, though this erroris probably caused by inefficient combustion catalysts. The small deviationsand errors disclosed by the present statistical treatment could be studied bymeans of sensitive analytical techniques such as infrared spectroscopy, gaschromatography, etc. Experiments with appropriate standard compoundswould allow definite conclusions to be drawn about the concentrationdependence of errors. These would seem to be more profitable areas forfurther research than the development of further modifications of presentmethods.

The present study has also indicated that the simple deduction of a blankvalue is not valid. Proper corrections can be made only on the basis ofregression analysis of results, unless the general validity of a calculatedcorrection can be proved by long-term experiment.

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However, the use of corrections should be regarded as only a temporaryexpedient. It would be much more suitable to introduce new methods inorder to decrease systematic errors and errors caused by elemental com-position. As far as this study is concerned the majority of the participatinglaboratories still used the classical techniques. Less than one half employedrapid combustion on more effective catalysts in a fast oxygen stream.Further, the possibility of more efficient reagents for the absorption ofhalogens, sulphur oxides and nitrogen oxides should be studied and theoptimal conditions for quantitative chemical reaction established. Methodsof decreasing the pressure of water vapour over the drying agent (an-hydrone) are needed as well as stabilized conditions of weighing absorptionapparatus. Alternatively, precise non-gravimetric procedures could be used.

Further investigations of precision and accuracy of the new automaticmethods which have recently been introduced and of methods for thedetermination of other elements would be very useful.

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