THE HEATS OF COMBUSTION OF SOME AMIDES AND AMINES

Citation preview

THE HEATS OP COMBUSTION OP SOME AMIDES AND AMINES A Thesis Submitted to the Faculty of Purdue University

b

y

.

William C, Dsombak In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy August, 1950

PU R D U E UNIVERSITY

THIS IS TO CERTIFY THAT THE TH ESIS PREPARED UNDER MY SUPERVISION

William C • D&ombak

by

e n t it l e d

THE HEATS OF COMBUSTION OF SOME AMIDES AND AMINES

COMPLIES

w it h ; t h e

u n iv e r s it y

r e g u l a t io n s

on

g r a d u a t io n

theses

AND IS APPROVED BY ME AS FULFILLING THIS PART OF THE REQUIREMENTS

FOR THE DEGREE OF

__________ Doctor of Philosophy

________________ _

P

r o f e s s o r in

Charge

of

T h e s is

TO THE LIBRARIAN:—THIS THESIS IS NOT TO BE REGARDED AS CONFIDENTIAL.

PHOFESBOB

GRAD.

S C H O O L F O B M O—3 . 4 0 —1M

T K OHABGE

ACKNOWLEDGMENT

The author wishes to acknowledge the warmth and consideration he has received from Dr. Herschel Hunt, the director of this research, with whom it has been a pleas­ ure to work, and to express, to Dr. E. T. McBee, apprecia­ tion for the special assistance he rendered in securing, from the Purdue Research Foundation, the financial support which permitted the investigation to proceed without inter­ ruption.

TABLE OB1 CONTENTS Page A B S T R A C T .............................................

i

INTRODUCTION .........................................

1

EXPERIMENTAL.........................................

3

Method

. . . . . .

...

3

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

5

Preparation and Purification of Reagents........

10

P r o c e d u r e ..................................

16

Apparatus ........

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

Calculations

•

24

Units and S t a n d a r d s ............................

31

Results • • . . « . . • • • • • • • • • * . • • •

32

DISCUSSION OF RESULTS.................................

56

SUMMARY...............................................

54

BIBLIOGRAPHY

65

VITA

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

LIST OF TABLES

Page 1.

Data for the Heat Capacity of the

Calorimeter*....

33,34

2.

Data for the Heat Capacity of the

Calorimeter.....

35,36

3.

Data for the Heat of Combustion of Sallcylaldoxime.•••••

37,38

Data for the Heat of Combustion of p-Dimethylaminobenzaldehyde •. .

39,40

Data for the Heat of Combustion of 3-Hydroxy-2-naphthoic Acid......

41,42

4. 5. 6. 7.

Data for the Heat of Data for the Heat of

Combustion of 2,6-Diaminopyridine.••••••

43,44

Combustion of n-Propyl carbamate•••.•••

45,46

8.

Datafor the Heat of

Combustion of Pentanamide. . ..

47,48

9.

Data for the Heat of

Combustion of Hexanamide...••

49.50

10.

Data for the Heat of

Combustion of Octanamide .. . .•

51,52

11.

Datafor the Heat of Combustion of 3-N-Phenyl amino-2-naphthoic Acid......

53

12.

Datafor the Heat of Combustion of 4,7-DUceto-5,6-dlaza-decanedioic Acid....

54,55

HEATS OP COMBUSTION VI.1 THE HEATS OP COMBUSTION OP SOME AMIDES AND AMINES * 'A

By William C* Dzombak and Herschel Hunt (Department of Chemistry and Purdue Research. Foundation Purdue University. Lafayette. Indiana.) AN ABSTRACT The Heats of combustion have been evaluated for some organic compounds which contain nitrogen.

The apparatus and

the experimental procedure employed for these measurements have been described In previous communications (1,2,3) from this laboratory.

Using the ordinary, non-adiabatic method of

calorimetry, the heat of combustion has been determined for each of the following compounds:

pentanamide, hexanamide,

octanamide, sallcylaldoxime, n-propyl carbamate, 2,6-diamlnopyridlne, p-dimethylaminobenzaldehyde, 3-hydroxy-2-naphthoic acid, 3-N-phenylamino-2-naphthoic acid and 4,7-diketo-5,6diaza-dec&nedioic acid. The energy equivalent of the calorimeter was deter­ mined with benzoic acid, Standard Sample 39g, obtained from the National Bureau of Standards. of the compounds were formed.

Cylindrical pellets of all

In some cases, a wafer of

1 This article Is an abstract of a thesis submitted to the faculty of Purdue University by William C. Dzombak In partial fulfillment of the requirements for the degree of Doctor of Philosophy.

benzoic acid was placed above the pellet, In order to promote ignition, or below the pellet. In order to prevent the forma­ tion of the alight deposit of oarbon often found in the Igni­ tion cup before this measure waa taken.

The weights of the

pellets were adjusted so' that the amount of heat liberated was comparable to that liberated by the burning of the 1.075 +0.02 gram of benzoic acid employed for each calibration experiment. Stainless steel crucibles, pre-lgnlted to provide a clean and reproducible surface, were employed to contain the pellets. The Parr double—valve oxygen bomb used has a volume of liters.

0.358

The ignition cup and 1.1 ml. of water were placed In

the bomb, and the bomb was filled with oxygen to a pressure of 30 atmospheres, absolute, at 25°C. Temperature measurements were made with two ninejunction copper-constantan thermels and a White double poten­ tiometer

These observations were made, during the 60-minute

test period, at 1-minute intervals sounded by a timer (3) mod­ ified by Klbler (4) to operate from the beam of light reflect­ ed from a mirror mounted on the shaft of a synchronous elec­ tric motor. The energy liberated by the ignition of the fuse wire was evaluated in the manner previously described (2). Details concerning the treatment of the experimental data have been presented in other publications (1,2). weights of all of the samples were corrected to vacuum.

The

The values for the heats of combustion listed are to be referred to the process which occurs at constant vol­ ume and at 25°C to produce gaseous carbon dioxide, gaseous nitrogen and liquid water.

COMPOUND

HEAT OP COMBUSTION kg.-cal./mole

Pentanamlde

754.56 + 0.25

Hexanamlde

905.83 + 0 . 1 8

Octanamlde

1218.5

+ 0.2

Sal 1cylaldoxime

854.03 + 0 . 1 6

n-Propyl carbamate

551.41 + 0.10

4,7-DIketo-5,6-diaza-decanedioic acid

846.01 + 0.49

2,6 -DIaminopyr idlne

708.10 + 0.11

3-Hydroxy-2-naphthoic acid

1177.6

+0.2

3-N-phenylamino-2-naphthoic acid

1980.4

+ 0.5

p-Dlme thyl amlnob enzaldehyd e

1189.0

+0.2

The standard deviation of each value has been reported as recommended (5) by Rossini and Deming.

iv,

REFERENCES

1.

Miles, C, B. and Hunt, H.t J, Phys. Chem•, 45, 1546 (1941)

2.

Millar, A, J# and Hunt, H , : J , Rhys, Cham,, 49, 20 (1945)

5.

Sullivan, M, V, and Hunt, H.: J, Fhys, Colloid Cham,, 53, 497 (1949),

4.

Kiblar, G, M., Eb.D. Thesis, Purdue University, Lafayette, Indiana,

5*

Rossini, F, D, and Doming, W« E,, J, Wash, Acad, Sci,, 29, 416 (1939),

THE HEATS OP COMBUSTION OP SOME AMIDES AND AMINES INTRODUCTION The purpose of this investigation is to obtain val­ ues for the heats of combustion of some compounds for which data have not been available*

The use of this Information for

the calculation of bond energies, heats of reaction and other thermodynamic properties indicates the Importance that may be attached to these data (1)* It is possible to derive, from combustion data, the value of the standard heat of formation of a substance*

This

knowledge, combined with a knowledge of the value of the stan­ dard entropy of formation, suffices for the evaluation of the value of the standard free energy of formation of the substan­ ce.

The latter quantity may be employed, then, for the calcu­

lation of the equilibrium constant and the change of free en­ ergy for a process, provided that the requisite thermodynamic data are available for each of the components of the chemical reaction* The end for which these measurements are made, then, Is the compilation of the thermodynamic properties of all sub­ stances (1)*

It is essential that this Information be of the

highest quality, with respect to accuracy and precision. requirement applies, particularly, to combustion data*

This As

Rossini (1) observes, the uncertainty in the value for the

2.

atandard free energy of formation of a substance depends, largely, upon the uncertainty In the value for the heat of formation of that substance, which value, In turn, Is derived from combustion data.

An effort has been made In this labora­

tory, therefore, to supply data of the kind and quality that are desired for Inclusion In such a compilation. Organic compounds containing nitrogen have not re­ ceived the attention accorded to the compounds which contain only carbon, hydrogen and oxygen (2,3,4),

Conspicuous is the

lack of Information concerning the heats of combustion of the aliphatic amides, a deficiency which may, in part, be elimin­ ated by this study.

EXPERIMENTAL Method The heats of combustion, reported here, were evalu­ ated by the ordinary, or non-adiabatlc, method of calorimetry. The theoretical and practical development of this method of calorimetry is, to a great extent, the work of Dickinson (5), White (6), and Rossini (7), who have refined the method to comply with the current need for calorlmetrlc data of high quality.

These principles of calorimetry have been adopted

and brought to Increasing perfection through the cumulative efforts of previous workers in this laboratory (8,9,10,11,12, 13) and have been employed, In this investigation, without essential modification. In the present application of the ordinary method of calorimetry, the amount of heat liberated by the burning of the sample was deduced from the measured temperature change which that quantity of heat produced, In the calori­ meter assembly, under controlled conditions.

In order to

translate this temperature change Into thermal units, the observed temperature change was compared with the tempera­ ture change produced In the same calorimeter when, under similar and controlled conditions, a known quantity of heat was evolved by the burning of some substance of known heat of combustion.

4

.

In this work, a specimen of* benzoic acid, obtained from the National Bureau of Standards, was the calorlmetrlc standard to which all of the heats of combustion, here evalu­ ated, are referred.

This specimen of benzoic acid, Standard

Sample 39g, was employed In the manner suggested by that agency on the certificate which accompanied the sample (refer to the section designated, "Units and Standards"). In these experiments, thermal quantities were not measured directly; rather, temperature effects were compared. In order to Insure that equal quantities of heat would always produce the same temperature change in the calorimeter, an attempt was made to reproduce and to maintain identical en­ vironmental conditions for each experiment.

In pursuance of

this policy, the weights of the samples were adjusted so that approximately the same quantity of heat was released during a combustion experiment as was evolved during each of the refer­ ence experiments performed with benzoic a d d .

These measures

were taken in order to establish a uniform shape for the timetemperature curve for each of the experiments •

Since the rate

and duration of the temperature change was the same in all of the experiments, Inaccuracies which can be traced to the irregular flow of heat In the calorimeter were minimized.

The

observed temperature change was due to the evolution of heat in the bomb, to the generation of heat by the action of the stirrers, and to the exchange of heat which occurred between the calorimeter and its environment.

The method employed for

the evaluation of the amount of temperature change produced by the burning process is discussed, later, in the section designated, "Calculations11. Apparatus The design of the calorimeter and the calorimeter jacket is similar to that devised by Dickinson (5) and modi­ fied by Rossini (7).

These components of the apparatus em­

ployed In this investigation have been described In detail, elsewhere (8,10,12,13).

Only one mechanical modification has

been Introduced during the course of this work.

The stirrer

used to agitate the calorimeter water was repaired.

The

Bakelite shaft of this stirrer was badly worn by the set screws which fix the stirrer in the coupling on the drive shaft.

In order to eliminate the eccentric and Irregular

motion of this stirrer, which Impaired the validity of several experiments, the upper end of the stirrer shaft was fitted with a permanently attached brass sleeve• The set screws which hold the stirrer In a vertical line on the drive shaft now bear on this brass sleeve.

The life of the stirrer has

been prolonged and its action improved.

This modification

did not result in a change In the value for the heat capacity of the calorimeter. The air bath housing the calorimeter was maintained at 25.00 + 0.05°C, the mean temperature of each experiment. Although the choice of the temperature at which the air bath was operated was, within a reasonable limit, arbitrary, the

daily variations in this temperature were minimized.

This

operating temperature was chosen In order to achieve better control of the jacket temperature.

The temperature of the

jacket was always maintained at approximately 26°C, which was slightly above the final temperature attained by the calori­ meter.

Since the temperature of the air bath was reduced be­

low this value, to 25°C, the jacket was no longer "floating", but tended, spontaneously, to cool to the ambient temperature. The present construction of the jacket does not permit the Introduction of thermostatic accessories.

In order, therefore,

to provide for the dissipation of the heat transmitted to the jacket from the calorimeter and to provide for the mainten­ ance of a constant temperature of the jacket, a thermal head was established between the jacket and the air bath.

The

jacket was already equipped with an electrical heater.

The

power input to this heater was adjusted, with the aid of an auto—transformer, to equal the rate of Newtonian heat loss from the jacket.

This operation required little attention

during an experiment, and reduced the drift In the tempera­ ture of the jacket to 0*005 C° over the 1-hour test period. It was the practice of Sullivan (12) and Klbler (13) to thermostat the galvanometer by conducting air, from the calorimeter chamber, to the galvanometer housing.

In the

course of this work, It was found that parasitic electric currents In the potentiometer circuit could be eliminated if this air duct were disconnected from the galvanometer housing.

Apparently, static electricity was carried to the galvanometer by the moving air.

The temperature of the room was not allow­

ed to change abruptly during an experimental period, so that the slow drift of the galvanometer did not affect these obser­ vations adversely. The vacuum tube relay (13), used for the operation of the air bath, was rewired, with slight modification, to improve its stability of operation.

It is pertinent to note,

here, that the appearance of parasitic currents in the poten­ tiometer circuit was correlated, definitely, with the Inter­ mittent surges of current through the exposed wire mesh which serves as the air bath heater.

In humid weather, particular­

ly, it was necessary to control this heater manually.

In

order to eliminate these periodic disturbances, energization of the heater was permitted for only a brief Interval of time immediately following each observation. A White double potentiometer (Leeds and Northrop, number 226773) was used to measure the electromotive forces developed by the thermels employed to indicate the tempera­ tures of the jacket water and the calorimeter water.

The two

nine-junction eopper-constantan thermels were calibrated, over the temperature range 23°C to 27°C, with the aid of a mercury thermometer which had been calibrated at the National Bureau of Standards.

The temperatures indicated by this thermometer

were known with an accuracy of at least 0.01 C°, which was sufficient for the evaluation of the thermoelectric power and

8*

the absolute temperature of each thermel*

A new nine-junc­

tion, copper—constantan calorimeter thermel was constructed for this series of measurements* oped an open circuit*

The old thermel had devel­

The junctions of the new thermel were

soft-soldered, wrapped with silk thread, and immersed in wax contained in a glass sheath*

A new dummy, or “check**, resis­

tor was wound entirely of copper to match the resistances of the thermels•

The potentiometer resistance colls were check­

ed for uniformity by the method of internal comparison de­ scribed by the manufacturer of that Instrument*

The poten­

tiometer working cells and the standard cell were housed In the air bath.

The working cells were on continuous discharge

during periods of Inactivity, the potentiometer master switch was set to the check position so that these cells would con­ tinue to discharge, at a uniform rate, through the appropri­ ate dummy resistors contained In the Instrument.

This meas­

ure, coupled with continuous operation of the air bath, served to establish a steady working current*

The electromotive

force of the standard cell was found to have changed only 0*02^ in two years.

Periodic checks revealed that the desir­

ed constancy of this voltage was assured by adequate control of the temperature of the air bath* The deflections of a reflecting galvanometer were observed, through a telescope, with an estimated uncertainty of + 0 * 0 5 microvolts.

The galvanometer sensitivity was

approximately 0*75 microvolt per millimeter of deflection,

9.

at 2 meters.

The galvanometer should be provided with a

support designed to eliminate vibrations which often Inval­ idated an observation. The audible Interval timer described by Kibler (13) was employed.

The failure of the loud speaker of this Instru­

ment required the replacement of this speaker with a buzzer. The amount of energy dissipated by the Ignition of the fuse wire was evaluated by the method described by Kibler (13).

The electrical components of this ignition circuit

were rewired, without modification. An Ainsworth analytical balance, provided with an optical lever, was used for the weighing of the sample.

The

sensitivity of this balance was approximately 0.02 milligram per scale division, the balance load being about 8 grams• The accuracy of the sample weights Is estimated to be 0.05 milligram. The calorimeter water was weighed on a Henry Troemner beam balance, of 10 kilogram capacity.

The sensitivity

of this balance, under a three kilogram load, was 100 milli­ grams per scale division. Both sets of weights used with these balances were calibrated with the aid of a set of weights recently cali­ brated at the National Bureau of Standards•

Preparation and Purification Of Reagents The benzoic acid, Standard Sample 39g, used for the purpose of evaluating the heat capacity of the calorimeter, was obtained from the National Bureau of Standards and was employed as received from that source. Commercial (Linde) oxygen was assumed to be of a purity sufficient for this work, since the use of oxygen from different cylinders did not result in a change in the value obtained for the heat capacity of the calorimeter. A technical grade of octanamlde, which was colored lightly brown, was boiled with activated carbon in an ethanol solution, and the solution was filtered.

The filtrate was

treated with a fresh portion of adsorbant, and was filtered. The filtrate was crystallized.

The solid was dissolved in

ethanol and was precipitated by the addition of water to the solution.

The solid was crystallized from acetone, carbon

tetrachloride, and three times from a solvent mixture composed of benzene and petroleum ether • ligroln.

The solid was washed with

The crystals, so obtained, had the form of plates,

and melted over the temperature range of 105.0 - 1 0 5 .2°C. The values for the melting temperature of this substance that are reported In the literature (14,15,16,17,18,19,20) range from 98°C to 110°C. A specimen of hexanamide was found to have a melt­ ing temperature of 99.5 — 100»0°C.

This material was

crystallized from a saturated solution prepared by diluting

a hot benzene solution of hexanamide with petroleum ether. The melting range of the hexanamide plates, so obtained, was 101.3 - 101*5°C.

Values for the melting temperature of this

compound, to be found In the literature (14,20,21,22,23) range from lO0°C to 1 0 1 .5°C. The Eastman Kodak (White Label) grade of pentanamlde was found to melt over the temperature range 102.0 102.5°C.

This material was dissolved in ethanol, and the

solution was warmed with activated carbon.

The solution was

filtered and the filtrate was crystallized.

The solid was

crystallized, once, from water and three times from a solvent mixture composed of benzene and petroleum ether.

The white,

waxy plates were found to melt over the temperature range of 102.2 - 1 0 2 .5°C •

Values for the melting temperature of this

substance, reported in the literature (14,19,21,24,25) range from 101°C to 106°C •

The crystals of pentanamlde employed

for the combustion experiments did not possess the perfection of form displayed by the samples of hexanamide and octanamide employed for the manufacture of pellets.

Sustained attempts

to Improve the extent of crystal development were not success­ ful, although the specimen of pentanamlde was recrystallized from several solvents.

The moderately great solubility of

pentanamlde In most solvents, and the difficulty experienced in attempting to separate the crystallate from the solvent, are factors which rendered Ineffectual the effort made to increase the melting temperature of this specimen.

An impure specimen of 2,6-diamlnopyridine was dissolved In ethanol.

The solution was boiled with two sepa­

rate portions of activated carbon.

The solution was filtered,

repeatedly, through several thicknesses of retentive filter paper in order to remove particles of carbon from the solu­ tion.

The clear filtrate was crystallized.

The solid was

then crystallized, three times, from a solvent mixture com­ posed of benzene and petroleum ether.

The product obtained

was white in color and melted, sharply, at 121°C, which is the melting temperature already reported (26,27) for this substance. A quantity of n-propyl carbamate, an Eastman Kodak (White Label) product, was found to melt over the temperature range 59.8 - 60.0°C.

This material was crystallized once

from benzene solution and once from a petroleum ether solu­ tion.

The fine white needles so obtained melted over the

same temperature range, 59.8 - 60.0°C (28).

The material was

dried in vacuum. A specimen of 4,7-dlketo-5,6-diaza-decanedioic acid was used as received from Dr. H. FCuer, of Purdue University. The melting temperature of this specimen was 222.5°C (29). The material was prepared by E. White, whose dissertation may be consulted (30) for further information concerning the nature of the material employed in this investigation. A specimen of salioylaldoxime, an Eastman Kodak (White Label) product, was found to have a melting tempera­ ture of 56.7 - 5 7 .0°C•

This material was light brown in color.

13.

A benzene solution of the material was warmed with activated carbon, and was filtered*

The filtrate was crystallized.

The solid was then crystallized, three times, from a solvent mixture composed of benzene and petroleum ether.

The white,

needle-like crystals, so obtained, were washed, on the filter, with petroleum ether.

The material taken for use melted at

56.8 - 5 7 .0°C, a value which Is to be found In the literature (88).

This material was stored in the dark, as it appeared

to acquire a pink tint upon being exposed to light. A specimen of p-dimethylaminobenzaldehyde, an East­ man Kodak (White Label) product, was found to melt over the temperature range 72.3 - 72.5°C. yellow, faintly. acid solution.

The material was tinted

The solid was dissolved In 1*6 hydrochloric The solution was diluted with water and a

solid was precipitated by the addition of a 10)6 solution of sodium hydroxide to the acid solution.

Following recommenda­

tions (31), only the middle portion of the precipitate was retained.

The filter cake was washed with water.

The white

residue was then washed with water by forming a slurry of the solid In a beaker of warm water. ethanol. lized.

The solid was dissolved In

The solution was diluted with water and was crystal­ After two further crystallizations from a mixture of

ethanol and water, the white crystals still melted, sharply, at 72.7°C.

The melting temperature of this compound Is

reported to be 73°C (31,32) and 74°C (28).

The melting temperatures of the substances just mentioned were observed In an electrically heated Avery type apparatus (33) •

The thermometer was calibrated, for use

under conditions of partial Immersion, by observations made at the steam point and at the melting temperature of benzoic acid, Standard Sample 39g.

The emergent stem correction was

applied to all of the melting point observations made In this work.

The electrical heat supplied to the apparatus was

adjusted so that the rate of temperature rise did not exceed 0.1 C°

per minute. In order to purify a specimen of 3-E-phenylamino-

2-naphth.oic acid, the material was dissolved In a dilute solu­ tion of sodium hydroxide In water.

The solution was filtered.

The filtrate was acidified by the addition of dilute hydro­ chloric acid solution. obtained.

A bright yellow precipitate was thus

The solid was warmed with four separate portions

of water in order to remove Inorganic, water-soluble contam­ inants.

The slurry was filtered after each extraction.

The

final filtrate did not form a precipitate with silver nitrate solution.

The compound was crystallized, twice, from ethanol

solution.

The product appeared as fine yellow needles.

The

melting temperature of this material was found to be 235.5 — 236.0°C.

The melting temperature of this compound Is reported

to be 235-237°C (34).

The starting material used to prepare

the specimen employed for the burning experiments was supplied by Dr. G. B. Bachman, of Purdue University, and was prepared

15

by P. M, Cowan, whose dissertation (35) may be consulted for further Information concerning this specimen* A specimen of 3-hydroxy-2-naphthoic acid melted over the temperature range of 221-222°C.

This material was

dissolved in a dilute solution of sodium hydroxide and was precipitated by the addition of sulfuric acid to this solu­ tion*

The precipitate was crystallized from water solution.

An ethanol solution of the solid was boiled with activated carbon, and was filtered. the adsorbant* crystallized*

The solution was again boiled with

The filtrate was diluted with water and was This process was repeated twice*

After two

further crystallizations from ethanol solution, the material was found to melt over the temperature range 221 - 222°C. The only melting point values found in the literature are 216°C (28) and 222°C (36)* The melting temperatures of the two compounds, 3-N-phenylamIno-2-naphthoic acid and 3-hydroxy-2-naphthoic acid, were observed in an electrically heated and thermally insulated aluminum block*

The electric heating current was

adjusted, by the use of an auto-transformer, so that the tem­ perature of the thermometer Immersed In the block was either stationary or varied at a rate which did not exceed 0,1 C° per minute.

Capillary-slze test tubes containing the samples

were dropped into a well in the block when the temperature of the block was below, at and above the melting temperature of the compound*

The melting temperature of each compound was

16.

measured with two thermometers: one of these was a partial immersion thermometer and the other was of the total Immer­ sion type.

Both of these thezmometers were calibrated by

employing them for the observation of the melting temperature of a specimen of purified anthracene.

The known melting

temperature of this compound Is recommended for such refer­ ence.

The anthracene used was white In color.

After the

required thermometer corrections had been applied, both thermometers were found to have Indicated identical values for the melting temperatures of the two compounds • Procedure Since all of the compounds studied are solids, these materials were prepared for the burning experiment by forming them into cylindrical pellets, with the aid of a press •

The nature of the crystal form of the crystals employ­

ed for the manufacture of pellets and the densities of the pellets formed are two very Important factors which affect the rate and the completeness of combustion.

The proper

state of the pellet, to insure complete combustion, was determined by trial•

In order to prepare pellets firm enough

to withstand handling with forceps, It was necessary to mois­ ten the solid contained in the pellet press mold.

Prior to

the compression of the pellets, the samples of 2,6-diaminopyridine and salicylaldoxime were moistened with a few drops of petroleum ether; the samples of the naphthoic acid deriv—

17.

atlves were moistened with ethanol.

The semi—dry cakes* so

obtained, were dried in vacuum or in an oven.

The oven, held

at 80°C, was also used to prepare benzoic acid pellets.

It

was found that benzoic acid pellets with a smooth, firm sur­ face were obtained if the pellets were held at 80°C for a few hours.

Under these conditions, loose and tiny granules of

benzoic acid, which may have been dislodged from the pellet and so lost, were vaporized, thus eliminating an Inaccuracy due to Incomplete combustion. As has been stated, the weights of the samples were adjusted so that the temperature change observed in a burning experiment was commensurate with the temperature rise pro­ duced by the burning of the selected quantity of benzoic acid. The specimen to be burned was weighed into a stain­ less steel crucible.

Before being used, the crucible was

cleaned, either with steel wool or emery dust, was washed, and was heated to a dull red color for about ten minutes. The crucible was cooled and, after this ignition, was handled with metal forceps until the experiment had been completed. This treatment was expected to provide a reproducible oxide surface free of combustible matter. A.

measured length of fuse wire, of the kind suppl

by the Farr Instrument Company, was tied between the elec­ trodes attached to the head of the bomb. The ignition cup, containing the known weight of sample, was transferred from the balance to the loop support

which Is Integral with one of the Ignition electrodes .

With

the aid of forceps and a pointed steel probe, the fuse wire was

bent and Its position adjusted with respect to the sam­

ple.

The positioning of the fuse wire was a most crucial

operation.

Complete combustion was obtained only if the fuse

wire dipped just to, or below, the upper edge of the pellet. Apparently, If the burning of the pellet were initiated over a

small peripheral area, the resulting combustion conditions

were more propitious for the movement of oxygen Into the com­ bustion zone. may

In support of this opinion, the observation

be submitted that If the cup, containing the pellet, were

tilted in the loop support, incomplete combustion occurred almost Invariably.

In the case of compounds which have a low

melting temperature and a low density, the fuse wire was made to dip approximately 4 mm. below the upper fur face of the pellet.

It is believed that this arrangement permitted the

pellet to be lifted from the crucible by the movement of the hot gases in the vicinity of the cup.

For an unknown reason,

at any rate, the deposition of a slight amount of carbon, in the cup, was eliminated.

It is believed that the application

of these techniques concerning the orientation of the fuse wire greatly enhanced the possibilities for the occurrence of complete combustion. In certain cases, the Ignition contained both benzoic acid and a pellet of the compound under study.

19.

A wafer of benzoic acid was stacked above the pellet of the 3-N-phenylamino-2-naphthoic acid, in order to promote the ignition of this high-melting compound.

Wafers of benzoic

acid were placed above and below the pellet of 4,7-diketo5 ,6-dIaza—decanedloic acid.

One of these served to promote

Ignition, while the lower wafer of benzoic acid eliminated the deposition of carbon which tended to occur during the burning of this compound.

A disk of benzoic acid was also

placed under the pellets of pentanamlde, hexanamlde, octan— amide and n-propyl carbamate In order effectively to shield these low-melting materials from the cold surface of the crucible.

In the other cases, It was possible to eliminate

the deposition of traces of carbon by the proper arrangement of the fuse wire. After 1.1 milliliters of water had been added to the bomb, the bomb was assembled, care being taken not to jar the pellet as the bomb head was being seated.

The amount of

water added to the bomb, in order to saturate the gaseous atmosphere with water, was the quantity recozmiended by the National Bureau of Standards.

The bomb was filled, with

oxygen, to a pressure of 10 atmospheres, and then was bled to atmospheric pressure.

The bomb was rinsed three times, in

this manner, after which it was filled with oxygen to a press ure of approximately 27 atmospheres •

The bomb was then put

into the air bath, for approximately 20 minutes, in order that it might attain the temperature of 25°C.

Before the

20 .

bomb was placed In the calorimeter, it was removed from the air bath and filled* with oxygen, to a pressure of 30 atmos­ pheres, absolute. The amount of water added to the calorimeter was determined by weighing a capped flask before and after it had been emptied of Its water content (12,13). taining the weighed quantity of water,

The flask, con­

was brought to the tem­

perature of a water bath held at 23°C. No attempt was made to maintain the cold Junctions of the thermels at precisely the ice (triple) point.

One

hour before each experiment, these Junctions were Immersed In an ice slush contained In a tall Dewar vessel.

The finely

shaved ice was washed with water before it was used to pack the Dewar.

Approximately ten minutes before the temperature

measurements were begun, the excess water which had accumu­ lated in the Dewar was drained, and enough ice was added to cover the sheaths of the thermels completely.

During the

five minutes immediately proceeding the experimental period, the ice slush was stirred, vigorously, at one minute Inter­ vals .

If these operations were performed,

it was found, by

test, that it was not necessary to stir the ice bath during an experimental period in order to maintain the equilibrium temperature established for the cold Junctions. The calorimeter can, which had been standing In the air bath, was located In the well provided for It in the jacket of the calorimeter.

Prior to each determination, the

21.

outer surface of the calorimeter can and the surface of Its jacket well were polished with a soft cloth, since the condi­ tion of these surfaces affected the heat transfer processes which occurred between them*

The bomb, on its support, was

lowered into the calorimeter can, care again being taken not to move the pellets contained in the bomb. ignition wire was affixed to the bomb.

The water was emptied,

from the flask, into the calorimeter can. immediately recapped for later weighing.

The detachable

The flask was The calorimeter

stirrer and lid were placed into position, and the jacket cover was bolted to the jacket.

The calorimeter thermel was

lowered, through the jacket cover, into the calorimeter can. The calorimeter and jacket stirrers were attached to their drive shafts, the jacket lid was filled with water, and the heater for the jacket was inserted.

Electrical connection

of the ignition wires completed the process of assembly. Immediately, the jacket water was brought to a tem­ perature which was expected to be approximately 0.01 C° above the temperature attained by the calorimeter at the completion of the determination.

In order that all of the components of

the calorimeter might reach thermal equilibrium, stirring was allowed to proceed for 20 minutes before observations were begun.

With the bomb at an initial temperature of 25°C and

the calorimeter water at an initial temperature of 23 C, the pre-run period was of uniform duration.

In this manner, the

amount of water lost from the calorimeter, by evaporation,

was standardized* Temperature observations were made during a period of 62 minutes*

These observations were begun when the calor­

imeter water had reached a temperature such that the mean temperature of the experiment would be 25°C* The electromotive force of the calorimeter thermel was measured every other minute, on the even-numbered minutes, including zero time, except at the twentieth minute, when attention was focused upon the ignition of the sample.

Addi­

tional measurements were made, with this thermel, on the min­ ute proceeding zero time, and at the nineteenth, twenty-first, twenty-third, and sixty-first minutes. The electromotive force of the jacket thermel was measured every other minute, on the odd-numbered minutes, except at the nineteenth, twenty-first and twenty-third minutes, at which times the electromotive force of the calorimeter thermel was being measured. In making thdse measurements, the electromotive force of the thermel was balanced to the nearest microvolt, except at the twenty-first, and twenty-second minutes, at which times the electromotive force developed by the calor­ imeter thermel was changing very rapidly.

An effort was al­

ways made, however, to minimize the extent of potentiometric unbalance, as Indicated by the magnitude of the deflection of the galvanometer from its rest position.

In this manner, the

effect of an uncertainty In the value for the sensitivity of

the galvanometer was reduced.

Immediately after the galvanom

eter deflection had been noted, the rest point of the galvan­ ometer was determined by setting the potentiometer switch to the "check1* position and noting the associated galvanometer deflection.

The difference between these two deflection

readings, which rarely exceeded one of the millimeter scale divisions in magnitude, was deduced by mental calculation. By employing this method of observation, it was possible to evaluate the magnitude of the parasitic electromotive force almost simultaneously with the temperature observation.

In

order further to reduce the uncertainty in these observations the galvanometer scale was moved, as required, to maintain one of the scale divisions in coincidence with the vertical hair In the telescope when the potentiometer switch was set to the "check" position.

It was necessary, therefore, to

estimate the value of only one deflection located in the markless field between scale divisions.

The working cells

were referred to the standard cell every minute, on the half­ minute, although an adjustment of the working current was not always required. After the potentiometer measurements had been com­ pleted, the stirrers were stopped, the calorimeter assembly was dismantled, and the gases in the bomb were allowed to escape slowly In order to avoid the loss of nitric acid from the bomb.

The Internal components of the bomb were examined

for the presence of carbon.

If no evidence of Incomplete

24 .

combustion were found, tbs Interior of the bomb was rinsed with water.

These washings were diluted, with water, to a

volume of 50 milliliters and were titrated with 0.1 normal sodium hydroxide solution to a modified methyl orange end point in order to assay the nitric acid content of the bomb condensate •

As a further check for completeness of combus­

tion, the electrode posts and the Interior of the crucible were wiped with toilet tissue.

If carbon were discovered

in the bomb, the experiment was rendered void.

The unburned

fragnents of fuse wire were collected, straightened, and their lengths measured in order to determine the length of fuse wire consumed In the combustion process. Calculations The principles which underlie the Interpretation of the experimental data have been defined by White (6) and described, in detail, by Eckman (40) and Jessup (41), and in previous publications (8,9,10,12,15) from this laboratory. The 60-mlnute period of observations was resolved into three 20—minute periods of time•

The two periods extend­

ing from 0 to 20 minutes and from 40 to 60 minutes are re­ ferred to as rating periods, while the period 20 to 40 min­ utes may be called the experimental period.

The data obtain­

ed during the rating periods were employed for the evaluation of the

amount of heat transfer which occurred between the

calorimeter and Its environment during the experimental

period, and for the evaluation of the amount of heat gener­ ated, in the calorimeter, by the action of the calorimeter stirrer during the experimental period. All of the electromotive force values were plotted on large graph paper, and smooth curves were drawn through the points.

Following the recommendations of Rossini (37),

the calculations have been performed and the data reported in terms of potential measurements rather than in the conven­ tional temperature units.

The mean temperature of the calor­

imeter is, however, reported in degrees Centigrade.

The val­

ues of the electromotive force developed by the calorimeter thermel at zero time and at the twentieth, fortieth and six­ tieth minutes were read from the electromotive force-time plot.

The value of the electromotive force of this thermel

at the twentieth instant was obtained by the extrapolation of the curve for the first rating period.

The difference between

the values of the electromotive force of the calorimeter ther­ mel at zero and twenty minutes, twenty and forty minutes, and forty and sixty minutes yielded the value of the temperature rise which occurred in the calorimeter during each of those 20-minute periods of time. The temperature changes which occurred during the rating periods were related to the amount of heat generated by the action of the calorimeter stirrer, to the flow of heat along the stirrer shaft, thermel, and ignition lead wires, and to the heat exchange which occurred between the jacket

and the calorimeter.

It was assumed that during the experi­

mental period, the rate of production of heat by the calorim­

eter stirrer did not undergo change, and that the heat trans­ fer processes continued at a rate which was instantaneously proportional to the

magnitude of the thermalhead

isted between thejacket and the

calorimeter.

which ex­

In order,

therefore, to evaluate the amount of temperature rise, attri­ butable to these processes, which occurred during the experi­ mental period, two simultaneous equations were employed. These equations are 20 K f A x L

s 5^

20 K -h Ag L

: Eg

In these equations, each term has the significance stated below: K

is the rate of change of the calorimeter temperature, expressed as microvolts per minute, due to the pro­ duction of heat by the action of the calorimeter stirrer•

L

is the proportionality factor, expressed as recipro­ cal minutes, employed for the evaluation of the tem­ perature change which occurred, In the calorimeter, due to the exchange of heat between the calorimeter and its environment.

A

is the area, expressed as microvolt-minutes, between the calorimeter and jacket curves on the electromotive

force—time plot already mentioned•

Since three areas

were evaluated for each plot, a subscript is employed In order to indicate reference to one of these periods of time. E

is the temperature change, measured as microvolts, which occurred In the calorimeter during the time period Indi­ cated by the subscript. The ten&s, K and I», were evaluated by the simultan­

eous solution of these equations.

These equations are based

upon observations made during the two rating periods.

In­

spection of the equations reveals that the temperature rise observed during each rating period was equated to the sum of two terms.

The first term, 2OK, is the product of the length

of the rating period (20 minutes) and the value, K, for the constant rate of change of calorimeter temperature due to the action of the calorimeter stirrer.

The second term, AL, Is

the product of the value of the area (A microvolt-minutes) between the calorimeter and jacket curves for that period and the value of L, the thermal head factor.

The dimensions asso­

ciated with the thermal head factor, L, are microvolts per minute, per microvolt, or simply, reciprocal minutes. The quantity I», then, Is the differential coeffi­ cient which expressed the rate of change of calorimeter tem­ perature per unit difference between the temperatures of the calorimeter and jacket.

At any Instant, the product of the

quantity I» and the instantaneous value for the difference in

28 .

temperature between calorimeter and Jacket provided the value for the rate of* change of calorimeter temperature, due to the flow of heat between calorimeter and Jacket- under the Instan­ taneously prevailing thermal head.

If the instantaneous val­

ue for the rate of change of calorimeter temperature, due to heat flow processes, were multiplied by the increment of time during which the temperature continued to change at that rate, the amount of temperature change which occurred during that brief interval could have been evaluated.

It Is evident that

the value of the product of these quantities has the dimen­ sions of microvolts-minutes, and is Interpreted to be the area of a strip between the calorimeter and Jacket curves on the electromotive force-time plot.

The sum of the areas of

all such strips that could be drawn for a 20-minute period yielded the value of the total amount of temperature rise which occurred in the calorimeter, during that period, due to the flow of heat at a rate which was instantaneously pro­ portional to the magnitude of the thermal head between the calorimeter and the Jacket.

The value of this sum was

obtained by the method of graphical Integration. The corrected amount of temperature rise, Ec, which occurred in the calorimeter during the experimental period, was obtained by the evaluation of the equation B c* Eg- 20 K - A 2 I> The magnitude of the observed calorimeter tempera­ ture rise, associated with the evolution of a given amount of

heat, was inversely proportional to the weight of water con­ tained in the calorimeter can.

Approximately 2700 grams of

water was weighed into the calorimeter for each experiment. The water equivalent of the metallic components of the calor­ imeter was 400 grams.

The corrected temperature rise value,

E c , was converted to the value that would have been obtained

had the calorimeter contained exactly 2700 grams of water. In order to execute this conversion, Ec was multiplied by the factor actual mass of water in grams +- 400 grams • ---------- 5700’ grtos y i O a ’graas

---

The value so obtained, corrected to the constant weight of 3100 grams of water, was the value of the calorimeter temper­ ature rise due to the evolution of heat by the burning of the sample, to the dissipation of energy during the ignition of the pellet, and tothe production of heat associated with the formation of aqueous nitric acid. The correction for the amount of calorimeter tem­ perature rise produced by the dissipation of energy during the ignition of the pellet was calculated in the manner described by Sullivan (12) and Kibler (13).

The equation

employed for the evaluation of this quantity is 0.31 S + 1.10 T s Ignition correction, in microvolts. In this equation, S is the length of fuse wire consumed, expressed as centimeters, and T is the length of time, expressed as seconds, during

which the ignition current flowed. Finally, a correction was applied, to the value of the calorimeter temperature rise, for the amount of this tem­ perature rise produced by the evolution of the heat associa­ ted with the formation of aqueous nitric acid in the bomb.

The value of this correction was 59 kiloJoules per mole of aqueous nitric acid found in the bomb at the completion of an experiment.

In order to simplify the calculations, the

known value for the heat capacity of the calorimeter was employed to convert this quantity to the equivalent value of 1650 microvolts of calorimeter temperature rise per mole of aqueous nitric acid found In the bomb. If benzoic acid were burned with another substance, the amount of temperature rise affected by the burning of the benzoic acid was also deducted from the value of the calorimeter temperature rise• The corrected value of the temperature increase was divided by the weight of the sample In order to obtain the value, expressed as microvolts per gram, for the tempera­ ture rise per gram of sample burned.

For this calculation,

the weight of the sample in vacuum was employed.

The mean

value of this quantity was multiplied by the value for the heat capacity of the calorimeter, expressed as calories per microvolt, in order to obtain the value for the heat of com­ bustion of the substance, expressed as calories per gram. This result was multiplied by the value for the molecular

weight

of the substance In order to obtain the value of the

heat of combustion of the substance, expressed as calories per mol e . TJnit8 and Standards The provisional certification, from the National Bureau of Standards, which accompanied the Standard Sample 39g of benzoic acid, is here quoted: HThe quantity of heat evolved by the combustion of Standard 26.4338 abs. kj./g. mass (weight in vacuo) with an estimated uncertainty of 0*0026 kj./g., when the sample Is burned under the follow­ ing conditions: A. The combustion is referred to 25 C, B. The sample is burned In a bomb of constant volume In pure oxygen at an initial absolute pressure of 30 atm* at 25°C. C* The number of grams of sample burned is equal to three times the volume of the bomb in liters • D. The number of grams of water placed In the bomb before combustion is equal to three times the volume of the bomb In liters• If the heat of combustion of the sample in calories per gram is desired, the following conversion factor may be used: 1 calorie ■ 0*004184 abs. kj • The reduction of weight in air to weight In vacuo was made using the value 1*320 g./cm.3 for the density of benzoic acid at 25°C” • Sample 39g of benzoic acid has been found to be

In this work, the specifications and recommendations mentioned on this certificate have been employed. The atomic weights employed for the calculation of molecular weights are those of the 1949 revision: C s 12.010, H = 1*0080 and N = 14.008.

Osl6.QOOO,

Results The experimental data and the results of the calcu­ lations pertaining to the benzoic acid calibration experiments and the combustion experiments for the ten compounds studied are presented In the tables, numbered 1 through 12, which appear on the pages that follow. A note is required here, to explain the signifi­ cance of the two tables (1 and 2 ) which pertain to the cali­ bration experiments with benzoic acid.

Table 1 contains the

selected value for the heat capacity of the calorimeter em­ ployed for the evaluation of all of the heats of combustion reported In tables 3 through 12.

Table 2 contains additional

values for the heat capacity of the calorimeter which define the penumbra of uncertainty associated with the selected value of the heat capacity of the calorimeter found in Table 1.

The data In Table 2 are Included only in order to

indicate the degree of confidence that may be attached to the more closely circumscribed value for the heat capacity of the calorimeter which appears in Table 1.

33.

o* to 03

to to • Os

to • o rH I> 03

to to • 03

00 O • o

to to • 05

t-

• to oo rH

to o

24*80

to

o> to • to &

. t o IO CO

03

o to• to to co

f-H

O• to 03

C-

C**

rH

• 00 o £> 03

to• o

•«* e- 8. *? • IO

to CO

+1 o o• to to

24*12

8

rH

00 * o> o t03

03 to

o• O

to

o« to o co

o • co CO

O

rH

c • IO

00

IO

to• o>

00 to

H c-

to

ol co

I—1

Data

for

the Heat

Capacity

of the Calorimeter

CO

IO

CO • to 8

to

H• IO CO

c*—4 • o 1—1

cto * Eo tco

* c-• IO cC T > t> Co to

o

Ol

■«* to • CO

o o o

•

CO • o>

o CO

r-l

CO • to IO co

o

•stl

-H IO i— i o• CO to

Ol *

to

*t»l t-

00 CO•

to

IO

IO CO

o

o

rH

36.

IO IO

• Ol co

Ol

o e-• o

IO CD

0 01

00

H• Ol

CO

o o

H

IO

• 00 o

IO

co •

IO

H* 0• IO 01

s

Ol

to

00 oo• IO

H 00• H
O • c0 c01

00 rH

• CM

IO O

Ol OO

o

c-

♦

• o>

o 0 * • +1 o>• rH IO H* 00 IO 01 O 00 Ol H*

IO Ol

IO

to

to

• IO o CO

o

IO •

to CM•

00 0 3•

Ol

rH

H« O CCM

o

00

O • Ol

to

o• o

IO

HI • co 00

to IO 00

IO

O

o>

Ol

IO

to

00

CO

a*•

H«

Ol

© HI

© 4-3

©

®

CO to

•

OIQ EOl to o» • to o E> CO

CO E-

•

rH

CO to * rH

CO to • (O

to e

IO

E-•

to to

-

00 tri *

£> 00 S>

rH

so 0•

to

E-

o rH

e-

£

09

rH t-

Ol

E-

o

IO

to •

•

so rH • Oi

to • to O

rH

Oi E• iH

to

00

0

IO

•

-H

o o

CO

E-

Hi

IO

E-

• E02 E-

c oo o

05

•

to to

01

_

CO

1o

0

o o

o o•

co

a O

01 C»

«H

K O *CJ

IO

co

tO

Oi

°. rH

to

-1 O

“{“I "H E-

to

ECO 03 to

•

*

O

LQ 00

Hi CO

03

•

E-

co E-

CO

at co 'O

O *4 O

o

O Ft o

o > o u o

•H

O > O u o

Ft

©

as

§

Ft

ft

S3

«H 43

a

O ©

Ft Ft

O O to

e

© ©

43

O

a

*H

14 Ft «H 43 CO

?► *3

*4 14 O rH © O 1-1 O

O > O Ft O

a

©

43 iH

O > O Ft O

a

lb o a © ©

l©b

to

n © *H

o S

rH

c8 0 1• t>0 AS

S3

S3

§

08 o

© os «

•H

m

O *4 o

09 43 rH

©

43

u o

43 rH

*

a

© w © A 43

43 rH

n

§

•H 43

«H

O

«

O

43 O

Ft Ft

O

O

©

S4 14

O

tj

-H O

fl *< o

•rH 43

&a

© «H 14 43

»2i

43 © Ft

©

& «

Eh 03 ©

43

O © Ft Ft O O

S3

© rH

-rH 43

I Ia

CO

c © © 33

Ft

©

TO

s

43 «

1

Eh

O

S3

43

O V-4 O 43

«

w

Pt

a © ©

©

O

0

•H

© «

© ©

39*

c c• to

00 02 • t o 04

fcto

Ok

8

o>

of p-Dimethylaminobenzaldehyde

03

2

GO

2

9 w rH to

to

03

o> rH

H»

02

O

rH

O

•

in o»•

lO

t• h * 00 03

Oi

H* H»

co 3 E-

03

00 • H* 03

O m • Oi

03 IO

8 E03

§

to

0 w*

00

CO

03

to 00 • H» rH 00

2

rH

•

CO

00

OS

to

to

o>

•

+1 o g 8 *

H* co

lO

rH

•

00

03

e-

HI O

to to

E-

0

•

to

oo

•

to 01

+1 +1 O

[H

•

Oi

00

to

0> ,-j

»

*>

rH

o> 03•

Hi 03

Data

for the Heat of Combustion

04

to •

O o-

03

03

in oo

r-l

M

40 .

(O

o> e-• Oi

c-

oi

to

•

.

to

Oi

Oi

to oi• to o c

£>

CD

co

CM

a* * iH

h«

to a * •

01

0 to

0•

°a 0 r~

01 CO

I

i—{

01 Ol Oi « H*

CM

01

1 S•d

43 ©

s

•o

•H

I •H

p
O

+©3 rH O

.s

o

©

a ©

43

> o

to

Pi

1

4©3 rH O > O to O

4©3 rH O > o

14 ©

B

I jl U) 2 N. © a © 43 4©3 rH > rH O > a > «rt O O •

to ©

to

B

B

©

t o fctQ

o

N

© © ©

© •H

© •o

to

fH O

rH ©

O

© o

&

• rH © © 1 • e>0

o

u

o

IH

43 ad ® td ©

$ to

g Pi § 493 © © ©to © .O Q O

§ •H

43 O © 14 & O ttf C3 •H

43 ©

s& rH

3

8

02

§5 to

i

of Hexanamide

oo

IO to *H o-

■© X©

Ol

V> *% o

3 X©

o e-

O • 02

00 •

rH

in

in

X©

“i O)

^ co C-

■©

03

00

o o to

in

X©

02

rH

o

to •

H 00 00

O' to •

to

for the Heat of Combustion

in

in oo

02• x©

03

02 00

•

oo

in 00

•

o> to

03

rH

•

03

rH • rH

e-

x* m • Ctn 00

02

n

a

(0

0 4-> 1

4-3

4»

iH

H

O > O Ft O

O & Ft O

to

+a3 rH O > O Ft o xrl Q

Data

Ft

Ft © O 3 » d

o

•H 43

3

d *H

& Ft

©

43 ©

© >© a o •rH rH PCS K 0 Ft Ft O d 43

43

© Ft «

£

& S

as

0

&4

•a ©

> Ft

© a 40 o

O

« ©

w

rH d Q

© .d 64

0 4-3 S

rH

o>

to

o>

3

•

to

rH 02 • x© oo 02

£~ co

o e-

d o

•rH 43

O © Ft Ft O

O

o

O

O O •O H

0

o-

fi o

4»

Ft Ft •rH

*rl

43 CO

a o

xrl

O o 4

IH • ©

+1

+1

IO

§ •

to t“

GO

to O o>

02

o*

03

*

x©

03

02

iH 03

§

©

iH

tfc

O > o Ft O

+©3 rH O o

Ft

O

o

n © ©

Ft to ©

•n

ft 0 0 H Ft O rH 0 O

O

G © o

s

•

to JW

•H

c O

*H +3

to d •H

>

d o © ► a tH

02 O *+l CO • 00 B• I—I o> IO

00

to • «H

©

S «H

Ft

g ©

02

H•

o o• m

©

Ft

© 43

0 4«3 rH O > O Ft o

03

O

3 +» rH O & Ft o

O O* in

00 rH

to • o> rH o >

02

IO 00

02

•

to*

to

03 o

o-

»o •

o> tOo X© o c-

02 00 • 00

03

■©

«

o d o

4-3

O

© Ft Ft

«H

4>

&

Ft

43

K

0

O IH O

O > O u a •rl B

©

0

p

P

rH

rl

O > O Ft o

O > o u o

p © p

to

eS ? to

~ j! ^ o © >

P

•rl

to B

•

o o• to

O O•

o>

•

02

O

4-1 to • to Tjt to to

4-1 rH o • to -«*• co

IO

CQ

02

§ fib \ m

fib at

p

p

rH

rl

O >

O F«

o

O > O Ft O P S

o o)

& » ©

o J3

u

u o

a 0 1

©

©

to

©

©

bO

•P

P

rH

•

o

>4

S3

S3 0

m

1oo

Ft ©

0 •H P3

Vl

o p © ©

txj ©

■P +3 Fi

o

Vl

© -P © P

Ft © o 3 52S

S o3

•rl P ©

S3

•rl

£ ©

p

© «

©

Fi

3

p

©

O

rH Ft

© © F » © £ Pi S •©q ©

EH

•P © > Fi © 0 o O

© w rH

© a

Ft ©

.P

EH

0

P

55s

K

O P

©

P ©

P O

P P

O © Ft

Ft O O

U> P P Ft

h

P P

to

F# © P

© a P Fi O rH O© Vi O P

.bPO •rl © Ss

P O

p

o P P o © F« F« OO P O P P P

§1

IH

03 ©

*P P

U q o PP *0 © © Po © Ft Fi © H o r04 F i O P *3 O B P © © •a E h CQ CO p Vi Q •O Vi O © o P P p o o © p 1) F t •s F P

P P

P P

J25

Ft O

O

p

©

“S

©

5S

a 0

•H P

P

•rl P 0 2

&H

Vt o

Vl

p

p

•rl P

©

1o

©

p

3 © > S3

0

o