TitleThermal analysis of the catalytic action of colloids (I) :catalytic decomposition of hydrogen peroxide by colloidalplatinum

Author(s) 水渡, 英二

Citation 物理化學の進歩 (1939), 13(3): 74-86

Issue Date 1939-06-30

URL http://hdl.handle.net/2433/46184

Right

Type Departmental Bulletin Paper

Textversion publisher

Kyoto University

9fiT~lt~olit€~ Vol. 13n No. 3 (1939)

THERMAL Ai~ALYSIS OF THE CATALYTIC ACTION OF

COLLOIDS. (1)*

Catalytic .Decomposition. of Hydrogen Peroxide by

Colloidal Platinum.

sy EtJI SUITO.

]3redig and his collaborators'/ first made comprehensive researches on the

catalytic action by various colloidal solutions. They called the action of hydrosol of metal or metal oxide and hydroxide " Anorganische Ferments " because of

the similarity of the .action to that of enzyme. Since then, numerous investiga-

tions bout been made and most of them done concerning the catalytic decom-

position of hydrogen peroxide by colloidal platinum-> In aIl of these studies chemical analysis such as titration of t}te solution or the measurement of the evolved oxygen has been adopted for the deterntiitation of the reaction velocity.

The .present author investig.ded the said reaction by the thereto-analytical

method'/, which originated with Yrof. S. Horiba and was successfully applicable

for continued measurements of the reaction velocity, especially for the initial part

of the reaction, in order to elucidate the mecltartism of the decomposition and

colloidal catalysis.

Experimental. Materials.

The platinum aol was prepared by Bredi;;'s electric dispersion method, using a duect current {qo volts, 6 ampere) cooled in an ice-bath. After about t boar it became so dark

brown that no electric spark was seen. The concentration then determined by precipitating with a little electrolyte was 60~8o mg. of platinum per litre. After standing Cor scveml days to permit the lar,er platinum panicles to settle, the rol was carefully siphoned olf and diluted

*' This is the English rmnslarinn of the paper which apl.earcd in Rev, Phw. Chrm. Ja/.nn, 10, z5r (r936)•

a) G. iiredig and co-.corkers, Z. phytfk. Ckrnt., 31, z59 (r899); 37, +. 3a3 Gmr); 66, r6z (r9o9); 70. 34 (r9o9): 81, 385 (r9rz): Rer., 37, 798 (r8oq) rtr.

z) T. 5. Prim and A. D. Donning, 7,. fkyrik. Cfrm., 16, 89 (igo;); D. A. 1(c(nnes, J. Bm. Chem. Sot., 36, 878 (r9rq); J• Groh, 1, pkv>ik. Chem., 88, 4rq (r9r4); T. Iredale, J C/tem. Sac, 119,

ro9 (rgv ), I21,.r536 (t9zz); II. V. Tartar and N. K. Schallar, J. Bra. Ckem. Sx., 3Q, zboq QgzB): n1. A. Heath and J. P[. Waltnn, J. Pkyt. Ckrvt., 37, 979 (r933) rlt.

3) 5, Hnriha and T. Iehikawa, Rev. Pkyt. Cheer. tepee, 1, tq5 (t9z7); T. Ichiknwa, G fhyrik. Ckem., (Ti) 10, 2990930); S. (Ioriha, Rev. Phyt. C/tent. Jnpttt, I1, r89 (r937): T. KJsaki, i/iiJ.,

12, 21 0938); II. ]tatsuyama, ibid., 12, [68 (x938) ert.

9fiT~1t~~it€1 Vol. 13n No.

Yo. , CATALI'TIC ACTION OF COLLOIT)S 7i

4 times. 't'his stock solution was so. stable ~+•ithout any addilimt of -a protective colloid or

peptizer that coo precipitate was noticed after several months; and it never coagulated after the decomposition of hydrogen peroxide.

7/ic 7ydrogen yeraxide so&tlion was n diluted 1\lerk's `Perhydrol '.

All the water used was a conductivity water prepared thus: hvice distilled water was

reiistilled by means of a Pyres condenser and then the air without CQ was passed- for several

days. All the vessels used were made of `1'eles' glass'[ and were steamed out.

Apparatus and Procedure.

In the thermal analysis in the liquid system, the measurement of the temperature change.

of the reaction spstenr teas made by means of a glass calorimeter as shown in Fig. t. ]n the

e Bgurc, A is a glass Dewar vessel holding about too cc. ~~ r a n l o(a solution. B a glass vessel which holds about 6o c.c., C a normal Brd:mann's thermometer, D a glass stirzer

F ~ s rotating gootzo times per minute, and F, a heater with

B

r

a

1

A

Fig. x.

hydrogen peroxide solution

blowing from f. Lxstantly

a-tme moment, Reckmaixn's

initial concentration of hyd

standard potassium pcrman

Cal

The principle of the t

dT _ dT dt dt

Nheie ~~ is the tempemt due to the temperature d

thermostat, Q • ~~ is the

q) The 'Telex' lass m

U rotating gootzo times per minute, and F, a heater with

a platinum wire resistance movable up and down.

5oc.c. of plntinuro sot was. introduced into A and a solution of hydrogen peroxide in B to let just 5o c.c:

flow out of b". The lid which supports $ C, ll and E

was put on A ti~hlly and then P' was connected. The whole

apparatus was dipped in a thermostat at 3oto.ooz C. The

platimm~ sot in A .vas heated to almost the same tempe• r ratum tis 0tat of the thermosl.•t[ b}• E, and then E was

drawn on[ to avoid the catalytic rlecomposilion by il. After • thermal eyui]ibrium had been obtained abotic x hour later,

was siphoned o!f into platinum sot in A within 3-4 seconds, first

they ++•ere mired with each other and the reaction started. :\t the

thermometer which eras tapped automatically was read on. The

rogen peroxide e:vs determined in atxother Oask by titration +vit6

ganatc solution.

culation Method of Thermal Analysis.

hermal anal}'sis can be expmssed by the following equation

O dx t4' da

ore change in the reaction system, - dt is the cooling velocity iHerence between a reaction system and its surroundings, i.e. the

hu:u quantity produced by the reaction per snit time (Q and d~

ana(actured by Tot:}'o Electric l'a. Ltd. is similar to ' F ,rrer in quality.

3 (1939)

9fif~lt~mii~~ Vol. 13n No. 3 (1939)

78 F.. 3UIT0 Vol. Xlyl

are the reaction heat and the reaction velocity respectively), and If' the water equivalent of

the reaction s}•stem.-

Cooling Constant andWatcr Equivalent.

In the calculation of the reaction velocity anct reaction heat according to equation {r), it

is necessary to know - ~~ and W which are particular to the rrction system, ic. the apparatus. In this case the cooling follows Nex•ton's law, that is, it is proportional to the

temperature Difference, dT, between the reaction system and the thermostat. This was

empirically justified with some rnrrection, B or r, caused by stirring heat or others.et There-

fore,

d6 ... .

Thus, by the measurement of natural cooling velocity o/ the reaction system the cooling mn-

starrt K anti tbecorrection term B or r can be obtained.

Let r represent the resistance of the platinum wire of the heater and i the intensity

of the electric current transmitted through it, then the heat gaantity per minute q' liberated

by the current is r4 860 (cal.). Putting q' for Q• ~ in equation (r), we have

Accordingly, the water equivalent FV is obtained from the measurement of the rate of the

temperature rise. of the reaction system by electric heating.°~ 1'he resistance of the heater y

w•as measured preliminarily by a potentiometric method under the same condition as in the

calculation of Che water:equivalent and wag found to be o.M1g3 ohm. "Phe values of If and

fV obtained are given in Table I.

Table I.

No.r

(°C)B (rt) XIt (^) ~ (amP•) It'

(~•)N.H.

z

oo[gtz

oooozq it oot393 ~ 0.8I$ , 1390 ~ LO

n6.8q[t6.g5 }pnre walcr

3

456

Lg 30 tS95t397

I tqo;[38i

O.OI,39t[qoo[394

rgr

0.8no08o.g

t r6.57n6.38[[6q5u5.7o

solutian afterreactinn

7 t8 zo t3gz [397

Mean values: r=ooxS, 0=o.owz, A=o.ot39, iV=xxG.6

5) ~=A'; B u the rare of tempemturc rise by stirring; r is the temperature difference between the reaction system and the thermostat at thermal egoilibriam, being due to stirring heal.

G) The platinum wire of the heater is dipped in the solalien in this case and not in case of the reaction. Consequently, the water equivalent for the reaction must be eaactly IV-0.0x4, because

the weight of the patinum wire is oqG gm. and the specific heat _h o.o;[z. This cornctiox5 howeveq is negligible av compared with ~hevalue of ff!

7) As to the value of A; (n) was obtained from graphical method and (b) from calculation. Srq S. Iioriba and K. Sato, Rte. Ph~•r. Ckrm. Jajvtn, 6, z5 (x93z} ,

9fi(~1t~mi~~ Vol. 13n No. 3 (1939)

No. 3 CATALYTIC ACTION OF COLLOIDS i7

Reaction Velocity.

Substituting equation (z') in the fundamental formula (t), ~6e have

tit +If(dT-r)= Q ~i ....................................... (4) As dT is the inclination of the reaction curve (dT t curve), the value of ~ dx tit FV . tit can be easily obtained from equation (4)• In this case W is known and Q can he obtained as shoivn below; hencethe reaction velocity tit at a cer4lin time can be calculated. ;;ven if N~ and O are unknown; both are constants and so the plot of ~ • tit for a time t makes thereaction velocity curve.

If the reaction is of the Hrst order, dx =kr(a-x)=k,a x e ( ) ti

t -hr ......................................... j

where d•, is the velocity constant and a is the initial concentration. Putting (5) in equation

(4) and. taking logarithms, vve have dT Q ~lx _ Qk,a _ 1.•,t l~~ tit +K(dT-r)~=log ~' ~tC-IOg W 2.303....... (6)

Accordingly, plotting the value of l!!!og ~ tit (or a time t, a straight line will I>c obtained and the slope of this line will give k,.

Reactioa heat.

From equations (r) and (z), the following equation is obtained

dT +KdT -B= O dx ........................................... (4r) tit W tit

Integrating this equation from 1=o to t=t, a certain time after the rompletion of the reaction,

we have

Q= !a lJ dT+Kf dT•dt-Bt} .................................... (7)

Hence, if the value of S= f rdT• dl is calculated by the graphical integration of the dT t

v

curve, the reaction heat Q can be ob~lined. Irr the case of the first order reaction, the intersection of log Q dx-~-t line with the

Qk, a lV tit ordinate represents ]og iv as seen 6~om ey nation (6). Accordingly, From the initial con-

centration ¢, the velocity constant k„ and the water eyuivalent ITV, .the reaction heat. Q can >x calculated.

Experimental Results and their Consideration.

One of the results obtained is given in Table II. The curve obtained by

plotting dT(=T-T~) for t is shown as (a) in Figs, g, q., 6, ~ and 8.

(a) Series 7, EzPt• 4• ({kG 3, [935)

Pbsal

I{:Oo

3o°C

IOC.G

o.ozq g: mo1f1i1re

(mom temp.-IB--zz°C)

E. SUITO

4'aUle II.

9fiI~lt~mi~1 Vol. 13n No.

Vol. X1Ii

(b) Series IV„Expt. 3.,(Beb.S; 1936) Phsol 2oGC.

IisO; o.ozSg,-mol~litre

3o°C (room- temp. zo°C)

3 (1939)

T ~°C)

z~499

i

5co

Sz0

530

540

550 560

570

580 590 600

6[a Gzo

630 640

650

670

6So

690

Ton

7to

7z0

730 740

750

770

7fSo

790 So0

mm

T (°C)

f in)•(sec

z.8xo

3zo

830

Sqo

850

.857

861

867

87z

876

879

881

S83

887

S88

889

890

Sgo

Sgo

840

889

888

837

885

883

881

879

877

875

871

30

51

3 • 12

xz

z8

5'-

1xz

30

54

z ! tz

3x

53

1G

38

03

3z

I9

M

09

34

07

18

07

4z

x6

4•

5•

6•

7•

S•

9•

m

~ 1 • .37

5z •i5

13•~

5z

qo • o0

4~ •~

qz.• o0

4.i • .i0 45 m

T (e~

2.!368

S62

858

852

844

838

S;o

825

x.4

Sob

794

784

776

76fi

757

748

738

729

yzx

7x2

706

Ggo

679

668

660

650

(po

6zz

608

t min)•(secJ

qG . 30

q8 • ao

50 • ao

5z . ao

54.00

56•ao

58• m

60 . ao

63•ao

GG • o0

69 • o0

72.00

75 • ao

78 • o0

3x • ao

84 . o0

87.00

90 • o0

93 • o0

g6 • o0

99 • o0

xo2 • ao

xo5•m

xio • o0

tx5 . o0

xzo . o0

x25 • o0

x3o . o0

xqo . ao

x5o . m

T (°C)

z.5oo

T Sxo Szo 530 540 550 560 570 580 590 600 6xo 6zo b:;o Gqo 650 660

670 680 690

700 7xo 720 730 740 750 i7o 780 790 Sao 8xo Szo 830

T ~°L)

z.Rgo

Ssa

S6o

870

RRa

900

9ro

gzo

930

9qo

950

95R

9W

970

973

977

979

qRr

g8z

9R3

9R3

9R3

9R3

98r 'I7R

973

gLz

95~

93R

9zR

qtC

903 S93

L

(min){sec)

3.56 4' • ~

Ig

3x 44 56 5 I I :ice

49 6.08

31 7 . o0 io S•oo

30 9.00

30 ii fo . o0

30 II •00

;o 12.00

;o t3 - o0 i4 . 00 x5 . o0 ab • 00 18 . o0 zo. • o0 zz • ao 'zq • o0 a6 ~ rio z3 . o0 30 . o0

Using the values

ing to equation

dran•n as (h) in

nearly linear as

To=z.Soo

of Q d1 and log ~, d1 obtained from (q), as an example in Table III, the reaction Fi and 8. And the to dx ~• 3, 4, 7 g Q ~

(c) in Digs. 3, q, b,`j and 8, and from it+ slop

Ta=a5oo

this. curve accord-

velocity curve was

~-...t curve- is seen

k, was obtained.

9fiI~lt~mi~~ Vol. 13n No. 3 (1939)

No. CA'1'AL\'T1C ACTIONOF COLLOI US

'table TIi.

79

t (min.J

O

IA

.A

q.o

SA

4a

7.0

S.o

9.0

to.o

n.o

t zo

X3.0

iq.o

i5.o

iGo

i7.o

iS.o

~ g.o

zo:o

2Y.o

zzo

z3.a

z4•o

z5.o

dT (°~~)

-o.aol

}OA3405~ 083,

1 II2

I3T

h'(d T-r)

-0 .0003

~FO.oooi

~s

i6

~g

as

z5

as

31

33

35

37

39

4a

qa

4a

44

45

qG

47

4~

qs

49

Sa

+O

r (min.)

zh.0

2~.0

25.0

29.0

30.0

j2A

34.0

36A

38.0

4oA

42A

44'0

46A

48.0

5oA

55.0

60A

G5.0

BOA

75.0

SOA

55A

f0.0

300.0

tI0.0

I?OA

dT (°C)

to.38z

3~

388

389

390

390

389

387

383

379

37q

368

363

3i8

34i

3zi

3~

zgz

z76

z6a x3$',

~'9

203

r7gi

X60

(dT-r)

}o.msa

5~

5~'.

Ss

5~

5~

Sj

5~

5~

So

So

49

qS

4S

47

45

43

4~

3S

3~~

33

3a

zS

z;

zz

r9

dT

d!

+ooo

sa

~8

[3

-0.0001

:a

zi

z5

z7

z9

3~

33

35

33

3a

~a

z9

z7

z5

zz

p er Tv er

}ooo7G

73

6

SS

3

9

5

2

0

8

3

z

z

2

1

z6

12

og

r

5

4

7

l

O

Q Ar ~~{V dede

3• ~:;

~.

838

go7

780

744

703

6z6

5~9

qbz

398

34z

Sot

z55

zoq

079

(b)

k,=o.o5gx

e oT A'(JT _)i dT Q dsI

I ~ nT ~."(J T-r dT Q Js Q dsTv e'~ logty ei(min.) ( c~ m Tv dl

log Q ~ (nun.) (C) ~ Jl0.5

o.ooo -omo3

to.ogo; +0.0003

}0A~20

iogo

toAgi z • y6+il 6.5 to43S +o.ao58,xo;3, y • ox8i 7A 4.io~

}o.oz3o

i85

}OA2$

a45

z ' 459

~ 339Lo

i.5

II

i5o, x8

izoo

1000

uti oS3

xox>~ 003~7~5 4i& 6I8.0 46q~ 6z

t5a

l;a

2II

igz

3z-0

z83

z.o

25

tg6 zq

zgcj z&ogzo

sos

• 975

83 9zz

8-5 ~ 47a 639.0 ~ 474; 63

xo .5

oSa

i68

i43

zz5

x55

3.0 z8d 3fi 7zo 756 S79 9.5 477 6q Sa iiq 057

3.5 3i5~ 4i 6qc 6Si S 33 io.o 479 6q 4a ioq ox7

4.0 344 45 540 sxs 767 /LO 4gI 6q 034 3 • 9zq

4.5 370'' 49 460 So9 707 Izo 4g3 Gq a bq SoG

5.0 z 4~ 45z 655 i3•a q3z 6q -oml5 qr~ b9o

5.5

39xi 54 w 54 360 4I4 6r7 tq.o qSx Gq 30 34 53~

G.o 4z7. 56 z8o 33G 5z6 x5.o 478 Gq Ga oq

k~mo.zyz5

i

i

9fiI~1t~~itl~ Vol. 13n No. 3 (1939)

h0 - S . SUITO Vul . XRI

Five series of the experiments were carried out as follows (sf . Table IV) I and IL The concentration. of hydrogen peroxide was kept constant , add

that of platinum sol was varied. The activity of platinum of varied during the

stock as proved in Series . III. Series II were carried out on the sol , whose activity beca~i~e extremely high in half a ~ilonth's stock :after series I.

.III. The change of activity of the colloid caused with aging ryas examined . 1V and V. The concentration of hydrogen peroxide ryas changed . -The time

. Tahle 1V.

F.zpt. No.

x

3

4

5

z

3

4

2

i

a

~~

z~

s'

z

s

a

s

6

7

I

z

3

4

II

m

Iv

V

Date

Dec 5. 1935•

Nov. 30

Dec z'

•, 3

„ q

,~ -iy

., i8

„ t6

„ i9

~, iS } I5 days 8 »

~, z6 f 39 » FeL. 3

Deo. 4}'l .,

,~ t9.

,~ i7} 8 .~ Feb. 5~ i93G.

.. q 6

4

zo

i9 „ zx

Conc. of k3e0.

ratio

3.7

8 4

3.5

3

2.5

E

8 5

3 2

mo g: 1, litr /e

o.ozg

z9

zg

,y

z9

29

zg

z9

''-9

z~

z9

zg

zg

s9

,y

zy

6z

3I

z7

zq

zo

ib

03

G3

3g

zq

r6

io 5- 7

4

(min.)

t

t+

z

3

4

s

2

i

3

2

2

4

3

x

z

3

z

ki

(minri).

0.4677

zt9o i53z

o39z

02i0

X753

oy86

O$O7 O~(i7

os9z

0986 i ~b3

0686

0zta

oz67

oz6g

(z6zS)

335 z9zg~

3335

3346.

33zi 3316

(o75.i) 0675

o6ro

o91q

e

( CaL lg: moJ z3.94G

z4 474

24467

z3.88o

z4~r93

z3,6r3

zga63

(z3•>~J

(z3.6r;) z3 344

z'.78n

23:632

r.98q

23.653

z4•o45

z4.ogz

z3:5oz

z3,Gi5

z;.5zj

2;.683

23:568

z3.99o

mean z3•SS6

(Note) (i) The stock solution of P[-sot No. z. prepared on Nov. iz, r935 was used I,.II, III & V, and No.;-prepared oo I+eb.;, rg;6 (or Series IV.

(z) The concentrations of I~.O_ aad PI-sot indicate those al the reaction, after the miring of both solutioaA.

Cur

it,

Serjes

those

peroxide by metalic colloids is etther

of the fiat order or nearly of the first

order with some deviation. Lven in the

present experiments, if ki is calculated by

an ordinary method (k,= t In ~ > t a-x

neglecting the initial stage, it does not

become constant and the reaction does

not exactly appear to be of the first

order over the whole region. By the

ordinary titration method the initial

stage twill never be noticed, because this.

stage is too short for the time interval

of measurements. But it is interesting

to mention that by the thermo-analy-

tical method the initial stage was found,

which twill 6e discussed later.

(2} The Effect of Concen

From the experimental results of Set

the duration of time of the initial stag)

decreased as the concentration of the

constant k, is nearly proportional to th

as seen in Fig. 5 s~

$) The deviation of [hc plots of N~spls. I and z by taking into aceooot the increase in Uu

uu[ first and Exp[. I last in this seriee.

9fiI~lt~mitf 1 Vol. 13n No.

No. 3 CATALYTIC AC"PEON Ol+ COLLOIDS 81

of the reaction was shortened and both series were completed within a few days

to lessen the change of the activity. Series V were examined with the object of considering the initial part of the reaction.

(1} Reaction Type.

The reaction always proceeds as shown schematically in. Fig. ? : it proceeds

in the two stages-the initial stage (ab) and the later stage (cde). The later

stage, which is the. main part of the reaction, is exactly of the first order (for the

line c' d' e' is straight), and before this stage a special stage appears.

It has been admitted that the ta)

catalytic decomposition of hydrogen I ~~

a

i

/Be

E

F

3 (1939)

big

dl~ i

5~

~.I,a ..~

6

C

d

(81

2

-.1

Concentration

of Series I an

1 stage u (th

f the sol is it

to the square

. x and z from the :e in Ure nclivitf

_ --~/ ••~_ -•0303 fcl vb c

d'

e'

Fig. a.

of Platinum Sol.

d 11 as shown in Figs. 3 and 4,

e 7dt column in 'T'able IV) is !creased. The reaction velocity

of the concentration of the sol,

straight line n( Series I eau Le explained with aging and that Cpl. x w:u tacri<d

i

s~

a

O.j:

~~~1'~

'10.1

S`

-..+w

In/

9fi~~lt~mi~~ Vol.

J Q_

4

aYS

13n No. 3 (1939)

a ~?

did

i

/bl

Sa-. !{mina

Vol. XIII

r. m 0

,~.,.,

zs:« ,o_. ,~,. ,o.. s

.,

~~

o.~

21b

~I~ T

itl2

dy 0

3

javf(

too

Ibl

j0

m

a. o

-. [(mn.)

I L~ ~ )r.l, l

r 2.f u

l0.0

Y.T ^

5.0 ~~

f00

ICI

~~ riQ: ,-

o.q

mina

i

I

!iciica I. -'-' Serics Ii .

~ 0.3 i

i o;£o.iE

9/ t

:¢/

a

,~

f

5 ~o ~$ ~ =5 --(Conc. of Phv~l)-.

I•~g. S..

~~

Geuerall

catalysis, the

the amount

sol, and the f

So

Z'~` ~ icr

dl~

a

•'t '•+. 3

t'iGt 4.

y speakin„ in the

reaction ve]ocity is.

of catalyst, i.a. the-

ollowing relation ho

z

~ -~ ~~ ~* ' ~~' are [he veloci consta

-. t (min.Jtoo

case of cc111oi

not proi:ortional

concentration of

lds that is,

dal

to

the

where k and ty ~its'~ ftir c and-

c', the concentra[ions of the sol. For the valuesof ~i;

Bredig and his co-tdorken°' have obtained t.3-ri.6;

t.t~i.q gild ~ in the decompositioiis of hydrogeii

peroxide by Yt-soL Au-sol and Tr-sol respectively. In the prescnt experiment, iY tuffs as high as z,

y) Gx. til.

9fiT~1t~o1it1=1 Vol. 13n No.

Nd. g CATAi,YTTC ACTION GP COLLOiI1S 33

[3) The-.Change in the Activity'oE"the Colloid'. with-Time.

In the comparison between the experimental results Series I and II obtained with 5 c.c. and io c c. of the sol; it tuns formt3 that the reaction velocity ivas larger in Series II than in Series I. To make clear tliis change iu the activity. the clperimental results Ivitli some addition are shown in Fib- ~ as Series III.. It was found that the activity of colloid increased with aging, reached the

ors ca, maximum and. dten diminished. And it is to be noted that the.

o duration of the initial-stage' a tends e~'

, ~~ a ~~~~~ to become short with the time. 1t is interesting'tbat in colloidal

_o - I~ ~- catalysis the activity does not gra;

` Y ici dually diminish as in the common ~`•r e~p ny,. . p p_,p_,p ,,,,,,,,,, case of heterogeneous catalysts but

0-®~ ~ "' '" raffier increases to the maximum .~'~= -

T 3, ~ ~~• rs. s

has found in the dcwt

dispersity is high, r,e.

also .low. This rclatio

as a general rule to c

kith the sol which wa

contain many other su

as applicable to owe c

is due Yo the growth

that the phenomena is

colloid:

A liiore definite

periments: And fhe r activity is an interesti

activity falls off after

in the concentration o

lo) Gr Rnnmlano, Cn i x) S. Rusznyak„ Z, p ~

nposition o

the size

n behveen

olloidal cata

s prepared

bstances act

ase, we ma

of the col

radter du

interpretati

elation Betts

ng question

a long time

f the so] by

mom!. xm2., lZO, h ink, CF.rm... R.

This result G. Rocasoland01 has.

`~ attributed to die effect of oxygen contained in the_sol. $. Rusznyak"1

f hydrogen peroxide by Ag-sol that )vhen the of the. colloidal particle is small, ;the activity is

the particle size and activil}~ can. not be applied

ly;is; becaose his experiments were carried out cheliiically by reducing method and seemed to

ing as a poison ; but i( we regard 'his results

y thfnh that the increase in activiri• with aging loid particles. However; it is probably inferred

e to the change in the. surface nature of the

on of this phenomenon will require further ea-~een ttte size of the particle of a colloid and its

in the colloidal catalysis. The fact that the

as i~ Exl,t. ¢ may be ascribed to the decrease

precipit2tion•

3 (1939)

U

a

i

a (a

~~~

i

tJ:

a~a_

9fiT~1t~~i~1 Vol. 13n No. 3

84 E, SUITO Vol. X1II

(4) The Effect.. of -0oneelitration of Hydrogen Peroxide Solution.

'The experimental results (Series IV and V) obtained with . various concentra-

tionsof hydrogen peroxide areshownin I'IQS. y:and 3."'

0.8 IR1

tflf p

0.5 / ~ ® U F1

1 /~ o v

ff a oq fl ,- ® > m

1 ~

1 l 1

IO 20 O.D$ 2n Qn

o.I6 per`. ~~ Ibl

y ,, t,.a,so....l

ID 8 _

® 3.5 -

m,

~~ ~ 20 yp 4 , ~<, Y

is

P, °a„

3 1' ,-

r-;g. s.

It is that the initial reaction velocity

nearly p p of hydrogen peroxide, :and that

Iz) 7n all the experiments, except F.xpt. I in Series IV and V, the temperature difference (d7) of the reaction system is below o.5°C, and .within this temperature the effect of the velocity con-

xtnnt r3ue to tempen+nve rim may be negliGible. Expt. I in Series N and V was carried qut with lemp:ranire difference over I°C, only to examine the initial port of reactibri. Deviation of kt in Exyl. 3 in Series IV is probably ascribed to some error of the enncentratinn of the saL.

IO p

., ~~~'~ ~' -

a

- .~

.. Z,:,yw "o j 1 Fig. 7.

seen from the reaction velocity curve

ro ortiotia} to the initial concentration

(1939)

9fiI~lt~mi~~ Vol. 13n No. 3 (1939)

Na. 3' -' CATALYTIC ACTION•OF COLLOIDS Su

eac(t reaction. ends .almost at the same. lime. Nest, that the. linear part of tl:e

]oR Q `~"t ̂rt curve runs in parallel shows. that the reaction velocityconstant bV rit

d, agrees well with one another. The duration of the initial stage u is; about t

min. -in Series IV and z-3 min. in Series V.

{5) The Heat of Decomposition of H:Oe.

The reaction heat Q calculated according to equation. (y) is z3.9±o.g Cal.

per t g.-mol, being in considerably good agreement as shown in the last column of Table IV.

Let as mmparc this result witb those of .other 'un'cstigators. 14Tatheson and. Nlass'a%

obtained z3.4j Cal. as the decomposition of bydrogen peroxide solution with small, articles

of \~InO. by means of adiaMtic calorimeter.. Roth, Gran and Meichsner" I oh4•fined-. z3.gz

Cal. (a[ zo'C.) for a 9~.z7q solution and za.Cq C'al. for e.339o soluion. Frntn thermo-chemical

data's'. -zz~-zj Cal. ryas calculated as the heat of formation from water and oxygen gas.

In cmnpadsou .witk these values it is seen that the author's value is proper.

(6) The Initial Part of the Reaction.

As to the initial part of the ruction, the deviation of the curve from the

first order is very slight. But it is aso~ibed not to the errors of the apparatus,

such . as the time lag of Beckmann's thermometer, absorption of heat by the calori-

meter, etc., -but to the reaction itself as is clear from the following three points.

(t) The deviation can not be noticed in the case of electric heating.

(z) When the reaction heat was calculated from the intersection of the ex-

tension of the straight part in the log Q, !L ~..t curve with the ordinate under the assumption that the reaction proceeds according to the first order from the

beginning, the value obtained is generally larger than that obtained before, and there is no agreement in the value of each exlxriment.

(g) As to the duration of the initial stage rs, inspecting from the results of Series I and II, iE is found that the higher the concentration of the sol is, the

shorter the duration becomes. If the difference among the duration -is to be regarded as due. to the initial reaction velocity, that is, the rate of temperature rise; the error to be caused by the apparatus also should be taken into account. But; as seen. from the results of Series IV and. V, even though the initial reaction

velocity is different, when the concentration of the sol is definite, U is- nearly

a5) G. L. Matheson ~ O. Mass, J. Am. Clruie. Snc., 51, 674 (r929)• rq) W. A. Rotlt, R. C;ran u. A. Meichsner, 7.. a>rarg. Clunr., 193, t65 (rg3o).

r5) M. Relthelot, C'omjt. mrC., 90, 35t, 897 (r88o); P.. de Furcrand, iGid., I30, rz5o (rgoo); J. Thomsoq Tnernrochemirche U.ilernrcJrvul<n; ela.

9fiT~1t~~itt1 Vol. 13n No.

R(i E. SUITO Vnl. XUT

constant. itlorever; in comparison behveen the results of these two series it is

found that variation in the concentrations of the sol leads to the different value

of a even in the same initial velocity. Tlrerefore, it is inkrred that u is affected

not by the rate oLtemperature rise but by the reaction itself, and probably it is

related to the amount of the colloid.

The reaction velocity curve of the initial stage is indefinite iat each experi-ment, beinn not always linear. Therefore, the nature of the reaction of this

stage can not bz made clear. The appearance of this sage may depend upon the adsorption of hydrogen peroxide on the surface of colloid, namely, to reach

the adsorption equilibrium in liquid system may need a considerable time, which

will be tbe duration of initial stage rz. And in colloidal system the electric

double layer of its surface will play an important role for the adsorption (diffu-

sion). This preswnption is not certain and theoretical consideration on this

colloidal catalysis will he required.

Summary.

t) By the method of thermal analysis the catalytic decomposition of

hydrogen peroxide solution b}' platinum sol has been studied, especially the effect

of the concentration of platinum sol and that of hydrogen peroxide.

3) 1t has been found that the reaction proceeds in two stages: the initial

stage and the later stage. The duration of the initial stage is practically in-

dependent oP- the concentration of hydrogen peroxide. and is nearly ~n inverse

proportion to concentration of the sol. The later stage, which is tite main part of reaction, is of the first order with respect to hydrogen peroxide and the reaction velocity constant is proportional to the square of the concentration of

the sol, i.e., dx = k, (HOa), 6•, w(Pt-so!)=. d

t

g) The .activity of the colloidal catalyst increases at first with aging. q) The value of the decomposition heat of hydrogen peroxide .has been

found to be zg.q Cal. per g.•mol.

In conclusiat, the author has great pleasure in expressing his sincere thanks

to Yrof. S. Horiba for his valuable guidance during the course of this research.

Tlae LrsLoratary of Physical C)umiataq. I:yolo Lnperial Uaaiueraily,

(I.eceived.\faq t5, r939)

3 (1939)