THE INSTITUTE OF PETROLEUM

A

of th e In s titu te w as held a t th e H ouse o f The R oyal Society o f A rts, Jo h n Adam S treet, London, W .C.2, on T h u rsd ay , 14th M arch, 1940, a t 5.30 p.m . Professor A. W . N ash, P resident, occupied th e Chair.

The following paper was presented b y Mr. A. H . N issan :—

“ The Dependence o f Viscosity of L iquids on C onstitution.” B v A. H . Nissan, B.Sc., A .M .Inst.P et., L. V. W . Clark, P h .D ., M .I.M ech.E., F .In st.P e t. and A. W . N ash, M.Sc., M .I.M ech.E., F .In s t.P e t. (see p. 155).

D IS C U S S IO N .

Dr. A. E . Du nsta n sa id it gavo h im th e g re a te s t p le a su re to p ro p o se a v o te o f th a n k s to th e a u th o rs fo r th e ir im p o r ta n t a n d in te re s tin g p a p e r. H o sp o k e w ith a c e rta in a m o u n t o f feeling, b e ca u se i t w as j u s t th ir ty - s ix y e a rs ago t h a t ho b eg an h is ow n stu d ie s o n th e s u b je c t o f v isco sity , a n d ho th o u g h t t h a t th o m em b e rs p re s e n t t h a t ev en in g h a d ta k e n v e ry m a n y ste p s fo rw a rd in th e ir a p p re c ia tio n o f w h a t w as, to h is m in d , a v ita lly im p o r ta n t p h e n o m en o n .

W hen ho began h is own work, w h ich perhaps Mr. N issan remembered, v isc o sity w as contem plated a s a high ly c o n stitu tiv e property, a property th a t w as particularly applicable in fathom ing m olecular structure, a particulate and specialized property, bu t a little later on it w as found th a t certain m athem atical derivatives o f tho v isc o sity constan t were n ot quite so particu late, b u t perhaps were oven general. O f those, thoro were tw o th a t em erged. Ono w as discovered b y E . C. B ingham in Am erica, who used tho reciprocal o f v isco sity , w h ich he called flu id ity, and th a t proved to bo specifically additivo, and n ot particularly con stitu tive. A bout tho sam o tim o his colleaguo T hole and ho investigated tho d erivative function log. v iscosity, and log.

v isco sity proved to bo definitely ad ditivo and by no m eans con stitu tive (D unstan and Thole, chem. Soc., 1913, 103, 127; 1 9 1 4 ,1 0 5 ,7 8 2 ; 1 9 1 5 ,1 0 7 ,6 6 7 ). H o w ou ld be interested to hear if Mr. N issan could say w h y it w as that v isc o sity itse lf w as pro­

foundly co nstitu tive, whereas tho reciprocal and tho log. wore definitely add itive.

H is colleague Thole and h im self had plotted log. v isco sity against molecular woight for a long range o f m any hom ologous series. Taking the fa tty acid s from C, up to CI8, a t a temperature o f 25° C., for oxam plo, log. viscosity against m olecular w eight worked out into a fairly linear relationship, i.e., log. t) = a + 6 X m .w t. Leaving ou t tho first two m embers, w hich were alw ays out o f tho picture, the relationship w as given b y a straight line which curved a t higher values o f m olecular w eight. I f ono took tho samo m aterials a t a higher temperature— for exam ple, 80°, 90° or 100° C.— then the relationship becam e m uch moro closely linear.

Thoy im agined a t the tim e that tho departure from lin earity a t the high-m olecular - weight end w as due to the fact th a t som e kind o f m olecular aggregation, or association or colloidal condition occurred— for exam ple, in th e case o f th e fa tty acids, tho sodium salts formed true soap w hich had qu ite different properties from thoso o f tho sodium salts o f tho acids farther dow n tho lino. Ho thou ght now th a t he and h is colleaguo m ight have been quite right in supposing th a t tho departure from lin earity w as due to tho form ation o f molecular aggregations. T hoy had taken th e norm al paraffins as far as th e y could get thom , and found th a t for these hydrocarbons log. CHa

x

x

x

x

x

0 091. T he avorago, as could bo soon, w as fairly good, and, b y taking tho log. C H2 from tho hydrocarbons, 0110 could obtain tho log visco sities for liydrogon.

A s a proof o f tho definitely additivo relationship o f log. v iscosity, thoy took tho tho normal paraffin line a s to ju stify a prediction o f but an indifferent fuel. cycioHexano is to tho right o f benzono, y o t it s octano num ber is n ot higher than benzono. blending numbor o f 132. M any other liquids could bo enum erated.

Tho caso o f the spark-ignition engino is com plicated b y the extraneous influence o f a spark w ith its therm al, and probably electrical and ca ta ly tic effects on tho courso o f the chom ical reaction o f oxidation. I t is thoreforo n ot surprising, although perhaps disconcerting, th at certaincom pounds should con stitu te a refu tation of these argum ents.

I n the caso o f diosol-fuel com bustion the reaction is spontaneous to a greater e x ten t than in tho former typ e, so th at, if th is rule should bo follow ed, it w ould have a greater chanco o f regularity in th is typo o f engino. Wo soe th a t th e alkyl benzenes support theso postu lates and tho paraffins thom solves offer a good proof. Other exam ples w ill bo found on detailed stu d y . Certain irregularities occur also, for the course o f the diesel fuel w as produced. The chain, howover, had to be o f a certain m inim um length.

F rom th e charts p u t forward b y Mr. N issan wo see th a t dibenzyl, although com posed m ainly o f tw o benzono rings, lies w ell to tho left o f benzono.

I t occurred to u s th a t it w ould be interesting to compare their spontaneous ignition tem peratures. Tho literature gives tho S .I.T . o f benzone, a s determ ined by Moore’s apparatus and usin g oxygen, as 639° C. From a te st carried ou t on dibenzyl under

214 N I S S A N , C L A B K , A N D N A S H : T H E D E P E N D E N C E O F

sim ilar conditions, w e found tho tem perature to be 435° C., or 204° C. lower than benzene. I t w ould appear, therefore, as i f dib en zyl sh ould prove a b etter starting poin t for alkylation for diesel fuel purposes, a s the probable effect o f a chain o f a certain length would be greater w ith dib en zyl than w ith benzene, a s w e are sta rtin g w ith an mid-carbon a tom s joining th o tw o benzene nuclei together.

P r o f . J . D . B e r n a l , F .R .S ., sa id th a t , a s o n e w ho h a d ta k e n a c e rta in in te re s t or dibenzyl it w as extrem ely difficult to m ake good fits betw een tho m olecules. Owing to their shapo in the liq uid sta to being oriented in different directions, th ey m ade rather bad fits, and th a t led to considerable increases in volum e, w hich tended to lower tho effective boiling p o in ts o f tho m olecules as com pared w ith the round m ole­

cules. T hat would need to be gono in to b y bringing in another variable—i.e., tho pressure and volum e relations. I f the experim ents were carried o u t a t com parative internal pressures, very interesting relationships m igh t bo obtained.

In producing the tables given in th e paper, tho authors had in a very ingenious

possibly be m ore ea sy to grasp than tho grouping o f linos w hich Mr. N issan had because the association num ber w as really tho averago num ber o f m olecules attached to an y given moloculo, and there w as no separate associated group in a continuous called normal neon-like liquids. Tho m om ent one introduced a derivative, a chlorine, brom ine, or iodino, ono produced a different kind o f field. Tho essential th in g w as th a t tho k in d o f p oten tial field w hich Mr. N issan had reproduced in ono o f h is figures w hich controlled th e distance o f closest approach in a liq uid would bo practically ex a ctly tho sam o for all neon-like substances, e x cep t whero th ey contained unbalanced electronic structures, and therefore local poles, as, for instan ce, in w ater. W hen therefore one could correlate w ith tho increase o f tem perature, bu t it w as a correlation w hich depended on tho form o f th e m olecular field.

216 N I S S A N , C L A R K , A N D N A S I I : T H E D E P E N D E N C E O F interested in tho connection betw eon v iscosity and constitution, and personally w ould bo very curious to see tho results of its app lication to a problem in w hich ho was servations had indicated th a t tho vapour pressure correspondingly decreased. A n accurate correlation of m o b ility and vapour pressure, expressed on th e basis of Air.

N issan’s w ork would, he expected, prove to be extrem ely interesting and open up a now field for research on a subject which had n ot received tho atten tion it deserved both from a purely scientific and a tech nical standp oin t.

Dr. E . B . E v a n s said ho w as sure th a t anyone interested in viscosity' wmuld bo stim u lated by Mr. N issan ’s very' interesting paper. Tho insistence on the fundam ental conceptions o f v isco sity w as very im portant, because particularly those who were organic chem ists w ere ap t to lose sight to som e ex ten t o f th a t asp ect. Tho discussion on tho relationship betw een vaporization phenom ena and v isco sity w as also o f p a rti­

cular im portance, and w as o f very' great interest, especially as developed in th is paper.

Tho m eth od o f plo ttin g used, involvin g T \ T B against log. rj, w as very ingenious, bu t

F in ally, ho w ould liko to know w hether th is m eth od o f p lo ttin g had boon tried out com prehensive equation relating v isc o sity and tem perature, and w ith the moro accurate data recen tly available on tho v isc o sity o f hydrocarbons it m ight be possiblo to develop a moro preciso form o f tho general equation q = Ac>TIT. Such an equation would,

Tho President had raised tho question o f applying tho valuable general relationship betw een con stitu tion and v isco sity show n in tho paper to other fields, such as cctane num ber in vestigation s; ho felt th at v isco sity w as influenced b y such factors as tho shape o f m olecules and p ossibly association in a w a y peculiar to th is physical property, and th a t there wore difficulties in applying tho results obtained in tho paper to physical properties dependent moro specifically in chem ical com position.

Dr. N . L . Antii.ogom' said he w ould like to congratulate th e authors on ono o f the reduced to Sutherland’s if tho oxponontial arising from B oltzm an n’s law were expanded in term s o f temperature and neglectin g all term s in 2’ after the first. I t m igh t be for liquids th at these neglected term s required consideration. Taking argon and hydrogen chloride, for exam ple, if ono considered those tw o gases from tho poin t o f view o f their

218 N I S S A N , C L A R K , A N D N A S H : T H E D E P E N D E N C E O F

another m odel type, w hich w as in th e case he exam ined, th e L ennard-Jones m odel, th e proton w as found to h ave quite an appreciable effect. T he Sutherland m o d el differed from th e L ennard-Jones sim p ly from fundam ental theoretical considerations, in that th e Sutherland m odel considered on ly a ttractive forces, w hereas th e L ennard- Jon es m odel brought into consideration attractive forces superim posed up on repulsive forces betw een the m olecules, and it was probable th at w hen th e fundam ental effects o f molecular force on viscous flow w ere established, b oth attractive and repulsive forces would be found to b e involved. Indeed, h e w as able to fit the experim ental results o f th e variation o f v isco sity w ith tem perature for these tw o gases over a very w ide range o f temperature quite accurately on to the theoretical curve evolved from fundam ental considerations b y L ennard-Jones. It w ou ld be remembered that H asse and Cook pointed o u t th at th is theoretical curve could be considered a s o f three portions— tw o linear portions corresponding to the extrem e cases where the v iscosity w as determ ined m ainly b y the attractive force and th e repulsive force respectively, and a curved portion where neither played a dom inatin g role. In a sense th e y felt th at th e three portions corre­ years ago) the variation o f viscosity' w ith tem perature w as no longer in conform ity w ith Sutherland's law. U r. X issan had now brought the subject back to the useful straight line again, and it m ight now prove possible to find som e theoretical fundam ental relations, so th at a satisfactory' fundam ental viscosity-tem p eratu re relationsliip for liquids could be evolved from first principles. H e felt th a t th e authors w ould appear present, conclusions relating v isco sity and molecular structure as such. In addition, there w as another poin t— namely', th e effect o f m eth yl groups on the alcohols. H e

M r . A. II. N i s s a n , replying on b ehalf o f tho authors, wroto as follow s : one assum os tho rovorso is taking place—i.e., dissociation.

In a note to Nature (N issan, Nature, 144, 383, 1939) th is law w as derived in a little

220 N I S S A N , C L A R K , A N D N A S H : T H E D E P E N D E N C E O F

«-paraffins than calculating its boiling point from valuos o f boiling p oin ts a t pressures o f 11 or 15 m m s. (cf. case o f ketones discussed in detail in paper).

I t appears from argum ents pu t forward in the te x t th at com paring viscosities a t equal tem peratures w ill n o t givo consistently regular results.

In tho case o f “ propyleno bromide ” the alm ost unforgivable sin o f usin g archaic in the bibliography. Thorpe and R odgers called CH3CH BrCH2Br “ propylene brom ­ id e,” and th is nom enclature has consequently crept into our paper. T he com pound has no double bond, and tho general rule th a t unsaturation brings the line to the left is not therefore broken by th is com pound. T hanks to the query raised b y Dr.

E vans, we pu t the formula n ex t to the nam e in the paper to avoid further am biguity.

Tho kinem atic v isco sity w as n ot tried, for the follow ing reason: Tliere appears chem ical significance o f such a property as visco sity .

Sim ilarly m ay be cited. The p h ysical and chem ical properties o f tho elem en ts are characterized to a greater e x ten t by the atom ic num ber than b y atom ic w eight. A tom ic num ber,

222 D E P E N D E N C E O P V I S C O S I T Y O F L I Q U I D S O I T C O N S T I T U T I O N .

T \ Tb = 0-500 0-550 0-600 0-650 0-700 0.-750 0-800 0-850 0-900 0-950 1-000 / T / T fl = 0-500 0-600 0-684 0-753 0-808 0-856 0-894 0-927 0-058 0-979 1-000

A ll th a t can be said is th a t it has been proved th at noithor the sim plo exponential formula nor

log. q = A / T + B log. T + C

expressed the relationship com pletely over a w ide rango. E v en i f an em pirical equation could be found, it w as considered o f no great value, a s thero were so m an y already. The equation, in so far as tho generality o f th e law is concerned, should n ot on ly givo tho variation o f v isco sity o f liquids w ith tem perature, b u t also th at o f gases.

P erhaps it is n o t ou t o f placo to p u t a warning here. E v e n w ith o u t an equation tho lis t o ff ( T ¡ T b) in term s o f T j T B given here would appear to be su itab le for c a lc u ­ latin g th e change o f v isco sity w ith tem perature. Thero is, how ever, a soureo o f error. Tho caso o f w ater w ill illustrate w h at w e moan.

log. q = A f( T I T s ) + B For water,

T . T b. T / T b. A T / Tb). 7- log. q.

293 373 0-786 0-884 1-0050 0-002166

353 373 0-947 0-977 0-3565 1-552060

To calculate A and B , w e have to obtain tho difference betw een tw o sim ultaneous equations, thu s :—

- 0-447940 = 0-977A + B 0 0 0 2 1 6 6 = 0-884/1 + B

- 0-450106 = 0-093/1 or A = - 4-8398

T h is is whero tho error is introduced. J ( T j T n) can bo interpolated to the third decim al place. H en ce it is o f a fair accuracy even assum ing it is accurate on ly to 2 in the third place. Thero is a possib ility o f an error o f 4 in 93, how ever, on su b ­ traction, lienee th e calculations can bo as m uch as 4-5 per cent, in error, purely duo to taking interpolated values. Added to th at are experim ental errors.

In so far as the shapo o f tho norm al paraffins is concerned, wo think th a t it is entirely a m atter o f opinion w hether tho m olecules are curled up or n o t. So long as one dim ension ¡r considerably greater than tho other a t right anglo to it, the m olecule satisfies the requirem ents o f being non-spheroidal.

Tho case o f the alcohols illustrates tho fact, so h eavily stressed in tho paper, th a t it does n ot m atter w h at is the skeleton or tho m aterial structure o f tho m olecule;

so long as tho external shapo, as defined, o f tw o m olecules look alike, th e y w ill behavo sim ilarly on these charts. In fact, th a t is an ossential part o f tho theory— m any exam ples are given in th e te x t o f sim ilar cases. I t is postulated th a t molecular shapo affects the position and the slope o f the v isco sity lin es because the ratios o f surface area to volum o o f m olecules differ. Spheroidal m olecules offer th e least area for other m olecules to use a s equilibrium p osition s, and henco m olecules m ake larger proportional holes in their fundam ental m otion in v isco u s flow. A nisotropic bodies offer greater areas per volum o than spheroidal ones. T hese larger ratios m ay bo obtained in different w ays, and henco our lino m ay roprosont tw o su bstances if b oth possess the sam o ratios o f surface area to m olecular

volume-OBITUARY

E U G E N E COSTE

E

C

w as born in Essex C ounty, O ntario, an d educated in Erancc, first a t Grenoble, th e n in P aris. Ho g ra d u a te d as a M ining E ngineer from th e Écolo N ationale Supérieure des Mines de P aris in 1883.

On his re tu rn to C anada in 1883 lie becam e a m em ber o f th e Geological