THE PHOTOLYSES OF NITRATES

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D oigan, P a u l, 1919- • ' The p h o t o l y s i s o f n i t r a t e s New Y o r k , 1 9 5 0 ° . . , I v s 73 t y p e w r i t t e n l e a v e s o ta h les diaerso 29cm0 T h e s i s ( P h . D . ) - New York U n i v e r ­ s i t y , G r a d u a t e S c h o o l . 1950° " L i s t o f r e f e r e n c e s ' : p70-73« C 50682

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TH IS D ISSERTA TIO N HAS BEEN MICROFILMED E XA CTLY AS RECEIVED.

TJBRARI OP HJW TORE URIVERSTTT UI5I7ERSITT HEIGHTS

THE PHOTOLYSIS OF NITRATES by Paul Doigan

A D issertation in the Department of C hem istry Submitted, i n P a r t i a l F u l f i l l m e n t of the Requirem ents fo r the Degree of D octor of P h ilo s o p h y a t New Y o r k U n i v e r s i t y

F e b r u a r y 1950

ACKNOWLEDGMENT

The author is very grateful to Professor Thomas W* Davis for his constant interest and assistance throughout the course of this in­ vestigation*

TABLE OF CONTENTS

Page ACKNOWLEDGMENT................

ii

LIST OF TABLES................

iii

LIST OF ILLUSTRATIONS....-

iv

Division I.

INTRODUCTION...

1

II.

CHEMICALS AND APPARATUS.....

8

III.

ANALYTICAL PROCEDURE..

17

IV.

EXPERIMENTAL PROCEDURE AND DATA....

23

V. SUMMARY

DISCUSSION.....

Ij.7

......................

LIST OF REFERENCES............

67 70

iii

LIST OF TABLES

Table

Page

1.

Spectral Distribution of Radiation for A-H6 Lamp...... llj.

2.

Effect of Temperature on the Decomposition of Barium Nitrate.......

27

Result of Placing Absorbing Medium in Light Path of Reaction Vessel...........

33

3*

[j.*

Comparison Studies-lst Series (Nitrate Decomposition as a Function of the Associated 35 Cation..................

£*

Comparison Studies-2nd Series (Nitrate Decomposition as a Function of the Associated 36 Cation...........

6.

Order of Decomposition (Compiled from Tables Ij. & 5>). 37

7.

Photolysis of Nitrates in Solution* ................

8*

1+2

Quantum Efficiencies for Nitrite Formation in Solid Nitrates*. ............ ••* 1|1|.

iv

LIST OP ILLUSTRATIONS

Figure 1* 2* 3*

Page Absorption Curve for Potassium Nitrate* ..... ••••••

5

Drawing of Apparatus*••*••••••••

12

Absorption Curve for Analysis Solution.............. *......

20

Ij.*

Calibration Curve for Nitrite Ion Determination*••••*•.. 21

5*

Nitrite Ion Formation vs. Time (Barium Nitrate Decomposition)*.

30

Nitrite Ion Formation vs* Time (Barium Nitrate Decomposition)••

31

Nitrite Ion Formation vs. Time (Cesium Nitrate Decomposition).*

32

Effect of Dehydration of Ca(N0,)2*l#20 on the Nitrite Formation. .....

IpL

9.

Decomposition of Lithium Nitrate and Cesium Nitrate Mixtures...*.

k$

10.

Infrared Absorption Curve of Nitrous Oxide*••.•••••••••.•.••*

6if.

6* 7* 8.

INTRODUCTION

2

INTRODUCTION

The p h o t o l y s i s

n itra te solutions 1-8 b y many i n v e s t i g a t o r s , b u t few

has been s t u d i e d

of in o rg a n ic

have s t u d i e d

the r e a c t i o n in the s o l i d phase, 9 Narayanswarni exposed f i n e l y powdered n i t r a t e

samples to a

source

th a t the degree creased

o f th e d i s s o c i a t i o n of the s a l t s

i n t h e o r d e r K,

Potassium n i t r a t e n itrate.

the

Sr,

Ba,

Cd, A l ,

w a s much more r e a c t i v e

NH4 .

th a n sodium The o v e r a l l

R a d i a t i o n o f 2 5 0 0 A a nd s h o r t e r w a s

in producing decom position.

was f i l t e r e d

Pb,

de­

photochem ical process is taken to be:

N0o + &CU. d d

effective

Na,

No e x p l a n a t i o n was a t t e m p t e d .

reaction for NO”

of u l t r a v i o l e t r a d i a t i o n and found

out,

t h e sample f o r t h e

region

no d e c o m p o s i t i o n w a s o b s e r v e d .

a given exposure p e r io d , t h e r a d i a t i o n was

When t h i s

For

r e a c t i o n s were r u n i n w hich

i n c i d e n t u p o n t h e same p o r t i o n o f e n t i r e p e r i o d and a l s o

in which

the r a d i a t i o n was i n c i d e n t . upon newly exposed s u r f a c e s fo r the d u r a t i o n of the exposure p e r io d . that

in the

latter

c a s e more d e c o m p o s i t i o n w a s o b s e r v e d .

Nar ayans warni a t t r i b u t e d t i v e n e s s of t h e

I t was f o u n d

the apparent

u ltrav io let

sm aller e f f e c ­

r a d i a t i o n in the

first

c a s e a s due t o t h e d e c o m p o s i t i o n o f layer

of the

and n i t r i t e

only a th in

sample and r e c o m b i n a t i o n o f t h e ion entraoped in the

in te r io r preventing

the d e c o m p o s i t i o n p r o c e s s from p e n e t r a t i n g into

the

oxygen

deeper

cry stal.

The b e h a v i o r o f one i n o r g a n i c

nitrate

in a

h i g h e n e r g y f i e l d was i n v e s t i g a t e d b y A l l e n a n d 10 Ghormley . They i r r a d i a t e d a t h i n l a y e r o f b a r iu m nitrate

c r y s t a l s w i t h a beam o f 1 . 2 Mev.

f r o m a Van de G r a a f f g e n e r a t o r . they d is so lv e d the r e s u lta n t

electrons

A fter exposure,

salt

in w ater,

a n e v o l u t i o n of g a s , wnich th e y assum ed to and fo u n d n i t r i t e n itrate

to

ion p re se n t.

n itrite

under standard steady s ta te

conditions,

The c o n v e r s i o n o f

su g g estin g a probable

a t a r o u n d 40% c o n v e r s i o n .

cry stal as

of th e

oxygen atoms o r oxygen m o l e c u l e s .

occurring a t a l l ,

the p e n e t r a t i n g

T h is work

o x y g e n was e n t r a p p e d

C o n t r a r y t o N a r a y a n s w a r n i *s c o n c l u s i o n s , if

be o x y g e n ,

was f o u n d t o d e c r e a s e w i t h t i m e ,

in d ic a te s t h a t alm ost a l l in the

observed

recom bination,

m u s t o c c u r v e r y sL o w l y .

p o w e r o f 1 . 2 Mev.

electrons

Since f o r atoms

o f low a t o m i c number i s a b o u t o n e - h a l f gram p e r square

centim eter,

1.6 m illim e te rs

p e n e t r a t i o n would ex ten d a b o u t

in to the c r y s t a l .

These c l e a r l y

k contradictory re su lts suggest another

l e d A l l e n and Ghormley to

explanation.

Since

e n e r g y a n d l ow e n e r g y e f f e c t s th e y suggested th a t

the

s h o u l d be c o m p a r a b l e ,

l ow d e c o m p o s i t i o n o b s e r v e d

b y N a r a y a n s w a r n i was d u e t o ultrav io let

the high

low p e n e t r a t i o n of t h e

ra d ia tio n ra th e r than

to any recom bina­

tio n process. 11 K r i s h n a n a n d Guha t wo a b s o r p t i o n

attrib u te

bands of n i t r a t e

the

ion,

o r i g i n of the Fig.

1,

to the

fo llo w in g photochem ical r e a c t i o n s :

We may to

NO”

— * NOg

■+

0 ( 3 P2 )

- 81 K c a l s .

(1)

NO”

— > NO"

+

0 ( 1D2 )

- 124 K c a l s .

(2)

take

be due t o

t h e a b s o r p t i o n b a n d b e g i n n i n g a t 3 5 u mu d isso ciatio n of n itr a te

into

n itrite

i o n and an oxygen atom i n t h e g ro u n d s t a t e , sented

in equation

g i n n i n g a t 2 3 0 mu, (2 ) occurs, n itrite

that

(1).

In t h e a b s o r p t i o n band b e ­

the r e a c t i o n

is,

repre­

own i n e q u a t i o n

the d i s s o c i a t i o n of n i t r a t e

into

io n and an e x c it e d oxygen atom .

The d i f f e r e n c e b e t w e e n e q u a t i o n s g iv es the

difference

in energy between th e

oxygen atom and an oxygen ato m i n th e 0 ( 1 DS )

-

(1 ) a n d (2)

0 ( 3P2 )

=

excited

ground s t a t e .

43 K c a l s .

(3)

$

0.3

o .k

EXTINCTION

0.3

0.2

0.1

0.0 WAVELENGTH (mu) ABSORPTION CURVE FOR POTASSIUM NITRATE Figure 1

This

is

in agreem ent w ith the sp e c tro g ra p h ic d ata 12 o f B a c h e r a n d G o u d s r n i t who l i s t t h e t e r m v a l u e s fo r the

and

^Dg l e v e l s

-1

cm -L r e s p e c t i v e l y ; or 45.1 K c a ls .

the

as lu9,837 and 93,969

d iffe re n c e being

The d i f f e r e n c e

1 5 , 8 6 8 cm

-1

b e t w e e n 3 5 0 mu a n d

230 rnu i s a b o u t 1 5 , 0 0 0 cm ^ w h i c h i s a p p r o x i m a t e l y the d i f f e r e n c e

listed

above f o r the

two o x y g e n

levels. From t h e r m o c h e m i c a l d a t a , NO" —> NOg + i O g

the r e a c t i o n ,

- 24 K c a l s .

i s o b t a i n e d f o r s :turddrers d-fl d i l u t e difference

between e q u a tio n s

(4)

solution.

(1) and

The

(4) g iv e

the

equation, £ 0g

0 ( 3 P 2 ) - 57 K c a l s .

o r 114 K c a l s . / g r . sociating

into

mol.

(5)

f o r an oxygen m o l e c u l e * d i s ­

two u n e x c i t e d oxygen a t o m s .

This

agrees w ith the

v a lu e of 114.6 K c a l s . / g r . m ol. 13 t a i n e d by H e n r i from s p e c tr o s c o p ic d a t a . The a g r e e m e n t a r r i v e d a t a b o v e

assum ptions re g ard in g trate

ion in to

oxygen atoms

n itrite

in the

ju stifies

ob-

the

the p h o to d is s o c ia tio n of n i­ io n ana normal and e x c i t e d

two a b s o r p t i o n b a n d s b e g i n n i n g

a t 350 mu a n d 2 3 0 mu, r e s p e c t i v e l y . 14 15 Schaeffer a n d Masl akowez: studied

th e ab-

7 so rp tio n of n itrate bands lute

both m o l te n and c r y s t a l l i n e

and found th e

in e s s e n t i a l l y the solutions.

trum in the

and s e c o n d a b s o r p t i o n

same p o s i t i o n s a s

for d i­

The s i m i l a r i t y o f a b s o r p t i o n s p e c ­

s o l i d and m olten s t a t e s

dilu te

solutions

of th e

absorption

to t h a t

is basis fo r a ttr ib u tin g in the s o lid s t a t e

s o c i a t i o n of n i t r a t e as

first

potassium

ion in to n i t r i t e

to

for

the o rig in

photodis­

io n and oxygen

described above. The c o n f l i c t i n g

conclusions a r r iv e d

at

by

N a r a y a n s w a r n i a n d A l l e n an d G h o r m l e y h a v e le d t o t h e undertaking

of t h i s

i n v e s t i g a t i o n which w i l l

th e problem f u r t h e r . com position of n i t r a t e tu re,

surface area

Th e e f f e c t

I t was p r o o o s e d t o

e xp ose d and q u a n t i t y o f

tem pera­

sam ple.

of s c r e e n in g the r e a c t i o n w ith v a r i o u s

d e c o m p o s i t i o n s t u d i e s on v a r i o u s a l k a l i

of

study de­

as a fu n c tio n of tim e ,

a b s o r b i n g mediums was a l s o a n t i c i p a t e d .

earth

examine

n i t r a t e s w^ere p r o p o s e d w i t h t h e

studying the

effect

In a d d i t i o n , and a l k a l i

thought

o f t h e c a t i o n on t h e

i n mind reaction.

chemicals

and a p p a r a t u s

9

CHEMICALS AND APPARATUS

A. C h e m i c a l s 1.

The s a l t s u s e d t h r o u g h o u t t h i s

in vestigatio n

were of th e h i g h e s t p u r i t y a v a i l a b l e . the

s a l t s were d r i e d a t

105 d e g r e e s , w e i g h e d

to c o n s ta n t w eight and s t o r e d over D r ie r ite u n t i l case

of s a l t s

in a d e sic c a to r

ready fo r use.

obtained as h y d ra te s,

t i o n was a c c o m p l i s h e d b y h e a t i n g o v e n a t 40 d e g r e e s f o r two t o to

A ll of

d r y i n g a t 105 d e g r e e s .

I n the dehydra­

i n a vacuum

four hours p rio r

Calcium n i t r a t e

is ■

e x t r e m e l y h y g r o s c o p i c and p i c k s up m o i s t u r e r e a d i l y w hile

samples a r e b e in g w eighed.

2 . The r e a g e n t s u s e d i n t h e c o l o r i m e t r i c a n a l y s i s of n i t r i t e

ion,

p a r a - a m in o b e n z e n e s u lf onainiue, ammonium s u l f a m a t e , N -(1-napthyl)-ethylenediam ine dihydrochloride, were a l l

E i m e r a n d Amenu s t a n d a r d r e a g e n t s .

The s u l f a n i l a m i d e

s o l u t i o n was k e p t u n d e r r e ­

f r i g e r a t i o n to prevent

o x i d a t i o n o f t h e amino

10 group. 3.

The m e r c u r y u s e d i n t h e a p p a r a t u s w a s aerated,

tre a te d w ith n i t r i c

w ith w ater,

an d d r i e d p r i o r

acid,

washed

t o vacuum d i s ­

tillatio n . 4.

A p ie z o n L g r e a s e was u s e d on a l l and j o i n t s

5.

stopcocks

in th e vacuum s y s te m .

Oxygen and n i t r o u s

oxide gases used

gas a n a ly s is t r i a l

ru n s were the

tainable

in the

b e s t ob­

f r o m t h e M a t h e s o n Company.

B. A p p a r a t u s All system . th is

r e a c t i o n s were c a r r i e d F i g u r e 2 shows t h e

out

i n a vacuum

essential

features

apparatus. The r e a c t i o n v e s s e l w a s a c y l i n d r i c a l

tube

of

six

inches long,

o ne i n c h

in diam eter,

f i t t e d w ith a sta n d a rd t a p e r e d ground g l a s s

quartz: and joint

th r o u g h a quartz: to p y re x g r a d e d s e a l . The s o u r c e pressure, arc

o f r a d i a t i o n w a s a 1 00 0 w a t t ,

w ater cooled,

high

ja c k e te d , mercury 16 ( G e n e r a l E l e c t r i c t y p e A-H6 ) . The l a m p i s

approxim ately 3i

quartz

inches o v e r a l l

and i s

construc­

t e d o f quartz; tu b in g w ith t u n g s t e n e l e c t r o d e s sealed

into

e a c h end a n d e x t e n d i n g

in to m ercury

KEY TO DRAWING- OF APPARATUS

A.

Furnace w ith r e a c t i o n v e s s e l and m ercury lam p.

B.

T o e p l e r pump.

C.

Me r c u r y ma no me t e r .

D.

ivicLeod g a u g e

E.

Rheostat f o r

control

of

com bustion tu b e.

F.

Combustion tube

w ith platinum

filam ent.

G.

Liquid n itro g e n freez:e-out t r a p .

H.

Liquid n itro g en t r a p .

I.

Expansion bulb.

J.

D o u b l e s t a g e m e r c u r y d i f f u s i o n pump.

K.

H eating

e l e m e n t f o r d i f f u s i o n p ump.

12

0 =3 Sa­ il.

+ "o X

pools

in the

lamp.

The l i g h t p r o d u c i n g p o r t i o n

of the

l amp i s a b o u t t w e n t y f i v e m i l l i m e t e r s

long.

The p r e s s u r e

is about f i f t y

in the

m illim eters,

a r g o n g as w ith which the

lamp b e f o r e

starting

the p re s s u re

of the

l amp i s f i l l e d .

The

heat from the a r c v a p o riz e s a p o rtio n of th e m e rc u ry and b u i l d s up t h e p r e s s u r e atm ospheres.

Full

brillian cy

to about

i s reached

110

i n one

t o t wo s e c o n d s a f t e r

power i s a p p l i e d .

starts

and 2 .6 am peres a n a o p e r ­

ates

on 1 2 u0 v o l t s

on 640 v o l t s and 1 . 4 a m p e re s t h r o u g h a

b allast

t r a n s f o r m e r connected to the l a b o r a t o r y

AC s e r v i c e

line.

The m e r c u r y a r c was p r o t e c t e d

by a f l o w i n t e r l o c k w h i c h a u t o m a t i c a l l y the rate

The l a m p

current

to th e

cut

off

l amp when t h e c o o l i n g w a t e r

d ro p ped below f o u r q u a r ts p e r m in u te ,

the

recommended r a t e . The e n e r g y d i s t r i b u t i o n f r o m t h e s e is high

in the

lamps

n e a r u l t r a v i o l e t and v i s i b l e

s p e c t r u m w i t h a l ow p r o p o r t i o n o f i n f r a r e d 17 rad iatio n . The s p e c t r a l d i s t r i b u t i o n over t h e r a n g e 2200 to 3000 A i s g i v e n in T able I . T h i s r a d i a t i o n b elo w 3000 A a c c o u n t s

for about

TABLE I

SPECTRAL DISTRIBUTION OP RADIATION PROM TYPE A-H6 WATER-COOLED MERCURY LAMP PITTED WITH A QUARTZ JACKET

Wavelength. Band (angstroms)

Microwatts/Cm^ at 1 Meter

2 2 1 6 -2 2 5 0

.023

2 2 5 0 -2 3 1 2

1.782

2 3 1 3 -2 3 I4.8

3.30

2 3 I4-8 -2I4IO

26.7

2iAl-2ij.59

29.6

2ij.59-2ij.96

ij.8.6

2i}.98-2550

33.1

25^0-2607

.833

2607-2671

2 6 .I4-6

2671-2705

2 8 .9

2705-27ijJ.

3ij-.6

27ijJ.-2820

90.2

2820-2861

ij-8.0

286l-290i{.

57.6

290ij.-29ij-9

U-8.3

29ij-9-2998

106.

is 9% o f t h e t o t a l

input r a d ia te d

by t h e

lamp i n

a q u a r tz w ater jack et. The r e a c t i o n v e s s e l was f i t t e d sp ecially polished

constructed

f u r n a c e w i t h two 4 x 4 i n c h

q u a r t z ; wi nd ow s t h r o u g h w h i c h t h e r a d i a ­

t i o n was a d m i t t e d . f o i l w ith a s l i t placed

into a

A mas k made f r o m a l u m i n u m

0 .9 x 7.7

c e n t i m e t e r s was

over the uppermost q u a r tz p l a t e

to

u n i f o r m r a d i a t i o n on t h e r e a c t i o n v e s s e l . m e r c u r y a r c was p e r m a n e n t l y i n s t a l l e d

insure The

at a d is­

tance of

e i g h t c e n t i m e t e r s from th e r e a c t i o n

vessel.

This e n t i r e

re actio n vessel, enclosed ag ain st

any s t r a y r a d i a t i o n e sc ap in g

the

periods; posure

f u r n a c e and m e r c u r y la m p — was

in an a s b e s to s housing as a s a f e g u a rd

lab o rato ry . posing

p o r t i o n of th e a p p a r a t u s —

is

"Sunburns" s k in to th e

c a n be o b t a i n e d lamp f o r

the

by e x ­

even s h o r t

more s e r i o u s b u r n s w i l l r e s u l t

if

ex­

f o r a m inute or more.

For th e solution,

into

decom position of the n i t r a t e s

in

t h e r e a c t i o n v e s s e l was im m ersed i n

a t a n k t h r o u g h w h i c h w a t e r w as c i r c u l a t e d m e a n s o f a c e n t r i f u g a l pump. was n e c e s s a r y t o k e e p t h e

by

The w a t e r b a t h

s o l u t i o n s from b o i l i n g .

16

A Be ck ma nn Model DU S p e c t r o p h o t o m e t e r was used

in the a n a ly s is

of th e

n itrite

ion p ro ­

duced in th e r e a c t i o n . A P e r k i n - E l m e r Model 12C I n f r a r e d m e t e r was u s e d i n a t t e m p t i n g of n itro g e n .

to

Spectro­

id e n tif y oxides

III.

ANALYTICAL PROCEDURE

18

ANALYTICAL PROCEDURE

A.

A n a l y s i s of N i t r i t e

Ion

The e x p o s e d s a l t w a s d i s s o l v e d and brought to th e m etric

flask.

resultant

desired

d ilu tio n

T hirty-five

m i l l i l i t e r volum etric f l a s k .

a fifty of

Then f i v e

o f 2/8 p a r a - a m i n o b e n z e n s u l f o n a r n i d e

s o l u t i o n was a d d e d ;

the

s o l u t i o n was s h a k e n

and a llo w e d to s ta n d f o r t h r e e w h i c h t i m e one m i l l i l i t e r

a g a i n s h a k e n and a l l o w e d two m i n u t e s .

ethylenediam ine

m inutes,

after

o f t h e ammonium s u l -

f a m a t e r e a g e n t was a d d e d .

the

to

of the

One m i l l i l i t e r

50% h y d r o c h l o r i c a c i d w a s a d d e d .

tional

in a volu­

m illiliters

s o l u t i o n was t r a n s f e r r e d

m illiliters

in w ater

The s o l u t i o n was to

stan d fo r an a d d i­

One m i l l i l i t e r

o f N- ( 1 - n a p h t h y l )