At ;KNCY F( IF4 I N'I'EHNA'I' I ( INAI, I )KV K1.OlbW.N1' 1JNITEl') STA'I'ES 1~f.:fBAH1'?WN7' (.)I.' S'fADI'E

A l l ) / ~ . q t f - 15HH ' ' t " t t 1 A r ~ r l f 3 t i l C > t * t * r~

Food G r a i n Dryin&!, , S t i ~ r i i ~ t * . it;trlclling nt;J ' T r ; ~ n ~ p o r t u t Lon

;.fit t h t *

E'(KJI, AND FEE11 I:RA I N I. NST 1 'I'IITE K i i n m s St i i t c l.lnivcr.rwity FCtrlhnt t a n , k'isnwrrn 66506

Ilr, WilIlom . I . fic?c>vc*r, Ijirector D r . i,t*onard W . Sc.t~rubr*n. Aneoc iate Director

TABLR OF CONTENTS

. . . . . . . . . . . . . . . . . . . . . . . . . . PREFACE

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

MATERIALS AMMETHODS . . . . . . . . . . . . . . . . . . RESULTSANDDISCUSSION . . . . . . . . . . . . . . . . .

Rate a f Desorpt I o n . . . . . . . . . . . . . . . . . . . . . . . The Change i n the So lu t ion Cczncentration

. . . . . . . . . . . . . . . Experimental Isotherm . . . . . . Application of Chung and Pfo~t Equation Heats of Adeorptfon annd Desorption for var ious beans

. . . . . . . . . . . . . . . . . . . . . . . CONCLUSIONS

REFERENCES . . . . . . . . . . . . . . . . . . . . . . .

PREFACE

The follaving report i n a copy of n thesir prcparad by Melquirder

Cuevsra Cuio ss part of h i s ~ t u d l e ~ for n Mn~ter of S c i ~ n c c Dtffrcc. I t daolr

with a ~ e r i o u ~ problem of bean w t o r r l g i r I n t rr)pitlrrl (Irlah ~rumltll t y ) rrrcrm

vhirh prcviordtaly h ~ v e had very l l t t l c Inverot l~nt lon . Inothrrm d r t t n of variaun

bean., that i s , the cqu i l i b r im rclationnhlp between t lw muinture rontcttt of

besnr nnd re la t ive humidity of a i r n t a apecifird ttmpcrat,urr, were dstarmincsd.

Thc hyatercais t8ffec.t wan found to clxtrt wi th htrna nr i t daen with varioua

otbcr grain crops.

Mr. Cuevarn wna spnnsorcd by tht* Bunk for Intcrnst tonal Dcv@Zapment md

wan given lplavr from I U F M , S . A . of (:olomhirr for h l ~ ~ t u d l e r . Hir rerearch

was supervised by Dr. Harry P f a ~ t , Profpe~or, Dcpnrtnvnt of Craln Sclcncc and

Indust,ry aasigned to the A 1 I)/cvrd- 1588 Tt~vt~nic+rr 1 Arru 1st irnc-c Cont rc~r t I n Posd

Grain Drying, Storage and Trnnrportat ion.

The resu l t s of the reerarch ahould hc ulaefr~l to Rtoregc engineers in

designing storage structures and those indtviduialsl involved tn atorafie

management of bean crop8 in both troplsal and temperate regions.

The reaul t s obtained from the invelrt i ~ a t i o n Indicate! that :

1. The equlllhrium motature (.ontent for heana investigated dcrreases w i t h an lnrrcasc i n temperature.

2. Thc Type 11 i ~ o t h e r a or slgmoid isotherm for beans i r consistent w i t h thore far other grainr found by e a r l i e r inveet igatots .

3 . The equilibrium moisture content for beans increarer with m increase i n r e la t ive humidity.

5 . T b r r t e of derorption f o r h ~ a n a t e r function of the relativa humidity rand tmpcrrturp.

6 . The rrtsr of dsmjrption for bcanm v c r e higher i n the f i rr t two drpr of r taragn period.

7 . The irafhr~ror equrmt Ion devcmlr~ped by Cf~ut l~ , and Pfost wi l l predict tk clrqui.llbrium r~r;r4rtutc o f brwnra, f o r a wide range o f relative humidity r t n p l v c r ~ tcmperartiTc,

8. Inant+ric hccrtw of J v n i r t r p ~ J r l r t a r r r f ntitolorpr lttn cont inusllv decrease with incrsnrrlnfi m ~ ~ i r t u r s c r t t l t cnt , n t ~ d t h e vtrlurrrp of Hst for denorpt irrn a r r Rrenrcr tiifirk t host* 4 1 1 ;odfic~rl*rt t o n . A

9. The heat of drortrptlorr f r j r ~ Y C ~ M I I N WJYO iot lnd t o be Rrcatcr than that of rhr l a t e n t ~ ( F F I ~ 01 v ~ l j l i l r 1 zdt f ~ l n o f Irtlre water.

Mr. Gwvata attended K,nnnas S t nr cN I inl vr*r& i t v f r crm A u g u ~ t 1971 through

1. Experimental iaotherm data a t 70. 00. 90, and l ~ ' ? . . . . . . . . . . . . . . . . . . . for varioun beans

2 . The f r e e energy change of d t ~ o r p t i o n nnd ndeorption for v a r i o u ~ brans . . . . . . . . . . . . . . . . . . .

3 . Tabulntlon of eclnntantrs A, 8, and corrrrlatl.on . . . . . . . . . . . . . c o e f f i c i e n t for varlour beana

4 . Conaparisrm of calcul~tcd w j i a t u r e c o n t c n t r and experlmrrtntrl awlr ture contents far irothertaa o f bean8 .

5. Valiles of hcatn of delaorpt Ion and ndaorpt inn f c ~ r varioupl beans . . . . . . . . . . . . . . . . . . . . ..., .

1 7 . Th. churl@ in f ree anar y of derorption for tad hru I! 6 t 766F, 8OOF and 100 P . . . . . . . . . . . . . . . . . 37

18. Heat# o f adrorption and dcrorption for red bccnr . . . . . 50

tarlatics of hygmscopic subntancms such ra grain8 and 1*guaoa I@ ot r

mnditionfn$, Cnina or ls~uaea ppln or lam rslstum, depending on

thr vapor prasaun, of roiatullrs In them and i n air surrounding War,

The procars of loalw moisturn f ma the sutmtncr i r r called derorptlan,

Cons ld~r~blr affort ha3 h a n do to obta in th, rorption

h o t h e m of gnrinsl that I a , the curve8 dsscribing the equilibrium

relationship batman the miaturn content of dublance and mlative

Found for gmifi.,. I t h.38 r l 3 o been found Ugrt Y i1y1tom8Ia affect i 8

exhibited In LX?)~..I *In l Y o t A ~ r n s o f &;rainti; t ~ a t &c, the equillbriu&

wis l turs content fc,r a givan mlative humidity i a highar during decorptlon

thnn rdsarptlon.

Numarnun attempt8 have been WII in the p t douebr to

derive th9 iclo tlxm cq w tim dcecri b i r ' sorption phenomenr af gm1 no

rrld a180 10 rctuity t30 hyateraslis affect on grains. Howavar, only

in the l i t"c'r"~tu?~' , :.:&;A ;~:r~tic-?ily no sork on the hyaturosir effect

tr18 &on Rcne for kt:lrrrs, 'I"hsr??rrrc, rcr f nitiatcd this invasti&ation

and expla in sorption ;1S'lrnonana of hygroacoplc natarhla.

types. These typca a m &own in F'l&un, 1. The Typo I curve 1s the

Lani.a?ulr ac:sorpti~n isothsxn aon3lr:gar. Type IX $u called the S-al.v.,.rpa

or slmold curre. Thla ma;.@ dcocrlbea tho adsorytlon of mkrr vapor

hlphly poroun o b n o r b n t s , .Ilks -tor vwpor onto carbon.

whrJthar tna neir,.licrinc p6aitloas on the ::uflarc wcup4.ed bv othar

roleculca O i not. ;?a also sssur.cd t!mt every no'iocule crmlng froa

"the f(La phse *lch 1, . tr lk31 :. n a l ~ r r l l s alm,-.,cty ubasbrad on the ct~ri'ocs

The iboti.c?,rlr, equstlon o l t : ~ ~ e a by fAI~etai~Lr 161

FICUHE 1. TYPES W ACSO.!4DTION ISOTWE.!KS ACCORDING lo THE CLASSlEICATlOII CW R ! U N A U M (1w3).

Poluyrl (1916) rrpn thc f isrt to eanridar rultiuolacnulrrr

for adsorption extends up thraupb the finst layer to bind another,

boause clach layer i a corngnsaod by all'thrr lryora rdaorbwl an top

of' it, The t o p layer would hrvo Eka Jenalty of tha w, The forces

attractlnc the noloculss to the surfacr decrcase w i t h distmae, Poluryl

mpresentcd hia potanthl theory by the follow in^ equation8

h e m d l The density of the rdaorbad aubstrnce

dx - The dens i ty of thc ma phase

V Tho adearbtn! V O ~ U ? ~

that the u?p+nost Layer of tho adsorbent inducus dipoles i n the

f lrst l e y ~ r of adzor'bcd nalacula3, wtrich in turn induce dlpolor in

the next layer and so 03 -ti1 COVC)~~LI 1ay8fi: a m built up. The pol&-

$&ation theory by b30er a d Zwicktr ura tha firat t o rucaunt for

the sigmold i8otnsr.a. LtB#r and Z w l c b r daveloped the r'ollowtng

equation t

vhela P .i L?c ~ q u i l i t r i ~ a p:'~.r;sure of Wrs n'th layer

.ol.culuc adrorption thaoxy. They dsrivcd m tscrrherr qurtia for

maltimolerEular 3ayez-a thnt i o a in l la r to X.mqmtir*s dsrirrtlon for

thr LrFh ~ r f o ~ a lb mum1 to ma t r t e of evaporation fron th+ flrrt

Uyar, ud th;t the evrpozatlan condcnartion propartles of the .

rolecu2es, in Cc. cacond arw hi&har layens ax* the mano as %!ujt~ of

tho purr l i q c l d s u k . T'hs derived equation i s r

C r pw.skr varying w i t h the gas and tszlp9rst;ure

V - V o l u r rdsbrwd

Vm m Voluae or &a.w~-rt cxS wr, adsorbs& wnen the er,tim rcisorbsnt

murfacs is covoma w i t h a acsor~olsculzr layer

Th. :;id squt ion Iti rntr U,OJL uic~ely used in odsorptian studies

krcrrusr of its ri(;oroua thacraticol a~proach and beaus. suzfaes rmaa

and approxixttc kb.rsts of ;larcr$.lon cc.n t?? c~ lcu la t& from the equation.

The conshat C can bs dc,Clr.ed arproxir..tely as

when El - The hat ci aasom-do2 cr' e m adsorbats in the flrtt & o m

T - ';'he hbeoluta tlrifwrraklm

Slith (1947) csnaiderad tha rpeot f le cur af m t d ~ mpoz

rolrptlon. Ha carjaidersd the .orbad uwr to ba of two prlhia1p.l

cIl.wam r

u a u p u, ( 5 )

&era Yb it the amount af -tar bound on the inner or outer aur foa

uf the ab~urtrllnt by foroam Cpwtcr UI.n tnoae ruaponribla for con-

dmnaatlw of water t o th. l i q u i d a t a h . Yo I 8 the a.ount of w a u r

n o l u l l y cordansad u l th ln the adaorbnt. Smith defln.d U,

Yo - - U' 3 s (1 - p/p*) ( 6 )

whenr U* is the amount of n o r w l l y condensed vmor rsquimd to utumb

thr flrst i ~ y o r of the Wc fmctlon thua,

Y - ~b + wc r ~b - Vln (I - P / P ~ ) (7)

Hodriguea-Arhs (1956) and Becker (1956) founri that the rpproxlnrk

r e ~ i o n cf cp;+lf cab3 l i t g of tho 5 ~ 1 t h tqrvltion was batwan 50 and 90

prcsnt mlative humidity for corn and whoat.

Hoover and nellon ( 13501) found that the sorption of uakr

at high r e l a t i v e humidity &I)penda on the prior sorption on ra t iva

sorptivcl ~;zvup3 such a6 the floe anino and paptide group. They rhomd

that isotherarrr tretwesn 30 to 90 percent rclllrtivo humidlty our

be d e ~ c r i ~ d by the simple mlation~lhipr

i o g a i[ i./., b (8)

*hem il in thc a r w n t atnorhed, F/P, l a roXatlre vapor pmutur, and

K, b are c.crr!rlcsl corfitantg.

An icott-era equation was boveAopdl hy t!mdarson (19%)

8 a q u l l i h r i u a a o i ~ t u r r content, pbmant dzy bi.8

Chrrry mb Pfott (1967) developad r n e w imthenr quat ion

t)ut the ld.orption potmnti.1 functlm cm b xwplmmd by the ft~.

mergy function or uacf ul work function. By us* themm4y~ILIc

and then they asauaed that the Y n a m a w functior., or useful

.qui.ti#e~ equation 10 w i t h squatiosrll they firully dewloped tin

a - m1sttu.w content

Stroh*;in md Yssmpr (1W) dovdlopsd m quatian fro.

Othrarer lib+EZ12ty in uonpar&aon to thr! fnn energy rppr#oh ua8d bgr

Chum Ukd Pf-t (1967)

them r , b, c, and d a n conllrttrntsl depnding con t t ro snln wed and 4

8 18 tho lbqullibriua rol8tum crc~rtent,

Chen (19n) devrlopd tha follow^ equation undnr araurptlan

that tho dUfu=llon 18 thr rate corrtroll lrq mchniaol in tho b;ox-ption

heoretically, r&orptlon-dcsorption curve6 ahould csoincib.,

homvcr, in practice, tney do not, rad the rr8ultl.nq ghenoaanon is

effect has been vmposad, hrt inveatigatom grbnerslly aaamirtad

l ,y~t i - i231z mbw.i ; , . i , i l l ~ 3 ~ * c~:; .Jxs?.~.~oYI*

I t I;;;% l.-.rn found t tw t the ert;;ilibriwl ~oollorture cantsnt

of cere.rlc en? tbc?;lr pruducta for dcaorptlon 18 hlmr th&n that for

2, tb ink-battle theory, md

mborptim l n c o r p l e k wsttlnq fckcss place Irr the c l p l l l a r i s s of tho

rkrorbnt korrut~a o f impurltiers, mostly perrurcnt gases rbsorbad on

th. mllr of aapll larica, TAls causes the adeomtlon aoistura oontent

to be Irsmr than C).,c denorptlon hoisturn contcr t ,

Xneabsr and J lchln (1935) sufi~eaksd that cavitia6 w i t h

conatrioted ntcks are mspansible for hysteresis.

R t r i n ~ adsorption the vapor p m s ~ ~ r ~ b I n thoam bottle mvltiea

i a dcttrsllned bj canacnaation in the portloz with a re la t ive ly Urga

dhneta?, diiri?!: dcaaorptlon, bgl condensation ln the narrower n e e .

Cohfn painted out that the ~1 ratmcturo may consist m o m -

Snurtly af pama which widen towued their baas and bahve rs though open.

Urnart 1 1 9 3 ) attributed the hys tera~ i s i a the sorption

of mtsr by cellulose to m i m v c d n i l l e wrcoupltng of hydroxyl &-ups

wl.Chin the cellulose rrrtaucturs, tho awufilng occurring duriaQI rdsorp..

t i o n and ms=ouplinlr; occurring at n mlatlvcly delayed strge in ths

dscorptlm pl'0cc3s.

Hart (15L4) fourid t h t am tempraturn incmwurea, hysteresis

sf;Tuqfad~(cr:.nscs. i:t f0w.J C:3t C;C hitit21 r ~ t e &t which hi@^ ~ l b e il %?"? * h

*t lt' ,~s h31: $ t ~ i t i r , r,- -3ter t?.m t i m rjta a t which low mooism I kh*

&mat m@Lht aatstum,

Sai th (1947) o w a r t w t that hystsrcnla Za dm Clr, awlllw

which incmassu t h o sullt'&cr, m a atPd duo ta tha p c a n c a 04 rigid

rtnrctus;sl elennntn of mch gmatsr dlmnniarw thRLn tho60 d tba

80rtPlt3 ~ ~ Q C U ~ Q S .

f o q and Kclson (1967) a%t@5 t hyarWmnla l a arub$aot

b n mttln,t cnvlmtrncnt, Slnca a bloloclcal ratat la1 is a combination

of nzny blulo@cal c:*lla, thrct ~ l r e h l n i ~ n n a m h,vl(otherrizdd by whloh

vster Ir: h e l d by tho uitsrr"ln1. a) Them can bo a wrinalecuhr bybr

of mtcr rzolscqllan bund to the curface of %ha ccslla, b) Thqrr ccn

be rultinoleculur Jayera of molcc.~leta staokod on top of tho firat

layer, c j l'hcm c ~ r : bo mai?itum vithln Ulo cc l ln , The aStrface ~ o l s o u l r r

of the cel l exert Z;lz?lng forc?..s an the water wleculea whlah prsvant

the= f mn :,3v ir - f ::":L rvt ... 8.1; t.": ,~xtunt of' t ~ a ? t r btrlkda up, the

dlf f u s l o r - 1 force?, n x c e d U..? b i n d in4 f crrcaa and allow so%a mcrl~oulrr

to mve into the c e l l , Thartj I s no force to p u l l the moiaturs out

of' the cells *until ~ i l the moisture has b s n raaovdl f r o m the murfrcs

during deswpbion,

Chuw and H o s t (1967) i n tho invsst lg .at lon of the caws

of hystc:rc.;is e f t e z %, i r r . J t ~ L t t.*.c! ; , ! r ~ ' h? ; 3 t . t l ~ ~ j lh8t ftorptlon

to urrtr:r v a p r du;.: nc the daoorpf I o n praccsa than durlrr& the rdaorptiqn,

pmcezn. '?h?y ,+.I.s* "n'!nl t h l ~ h v ~ ~ t h e n i o lq nhowinc: the dlffarencsa '4Y

botrrccn t:.i h a t 3 of da~lorptton a~.d haat* af adtwqtfon. They alno

@ thr -oL: l a m t i - 4- to ~ t k - . fAcl .obcl.-b that the

dlffem063 La *&a r r r l l a b l l i t y d ~ o r p t i v r sftee or p b x ritas oa

fbr, 8urfaor af the ndsorbsnt to mter vapor -1;d U1. hyste~w~~t. ,

They a1b0 fcund that In the thinl g c l e af drsorpti.cm urd adsorpticm

Ob h t , tb. hyr~t~m8ib 1-p pZ'8ct imy dkS&pps#mbm

Object ivsr,

Thr obj~ctlves af this i n v u t i ~ t i o n u e n r

1. To find adaorptlon and desorptlcn laoa..\cnrs of red hours, baby lira h a n a , and pinto iceana at 7Cu F, 80° P, 903 F, and 103' F, over a mnge of mlatL.de huridlty f rerm 10 to 90 percent.

3. To t@&t the fitr.ezs cIE the results in Ghur~~f uid PTott q u a t i o n .

4, To dctcrrplna t!!c hrats of dcrrorption ar,d adsorptiolli of water by various types of bsrra,

'I'm dLffemnt kids of d r y bsuYtir caai l mi f h l d kUU

(phrssalus v a l ~ r i a ) , bnby I l u b r n ~ (phoacalea ~wranrs), and pin*

field b . n r (phaseolun vul-ria) obtained f&r r p c a y atam wrr

u s d to obtain dasorptlon snd adnorptloa itlothcm at 70° Y. 80* kQ,

. p . 0 w0 7, and , du F tempmtume. anplem for obtainln& the dauorptlei%

inotherma wan! e t t c d t~ r h u t 25 prcent moiatun content , Wp1am

tor obtai:.inj UH ad~orptlon iqolherm warn oven drlsd a t 1 ZOO I'

krnpcraturr? to 51.0 prmnt of l n l t i r l nolrtur, contant, dry hsiar,

S u p l e aimxs fmx 4.0 t o 6.0 gram tam phcmd I n brrokoto u d s f r o m

f ins w i r s acmen. The relrtlvs humidity, ddyandiw on the taaspcatatm,

was controlled oy solutions of sulfuric raid, lChe aonccsntrrtion

mpc! fron; 10 t:! 6 ) ?ercc,?t of t p u i r ~ i c acfd. Perry's Chanical

Engineer Xandmok (1950) was urad to detsmlna mlrtiv8 hwpidltirr

a t dlffcmnt a o i u t i v n conc*~utratiuna, The f a n p of relative huzsidity

af 10 to 90 por~ent w3s ua.6. Thc, contairrer ucod for ralative hunidity

control was a -530 ~1 flask, W~IIC!I :MO r'illed w i t h 200 ml of sulfuric

acld solution, Tho baoket aontaining a srmple r e surpsndsd &bow

t!!e sclutian in the contai;:@r, then the fhrsk -8 sealad w i t h &

n b k r stopper, The f l a s k aontainlns the eacnpls #s placed in tho

Ccprahn: u o ~ t r a l chamber for three weeks. Tbn tho squilibrlum

a o i o ~ , t z mntrritrs of ~ ~ c p l r s WVXY det&nakrnod by an oven ruthaid (72

1 ~ ~ 2 % 2: 10-y c ) .

7s -.4i",!??;rr, ?he- mtcs c,f dc:arctiosr f o r m d bran wnar 8xwdn-d

at 23, and t 3 ;;re-tnt n l a t i v ; t s i d l t b s v i th 700 P and ~OO' F

tnprrrtumo, m s * ourplrr. ma% Csk.n oout af the --tun, ooortsol

ohubnr wow b8 houri ud #l&md u n t i l me w-ta af amplor rrcl,

mfnor) coactmat. Also during: thi8 taut r porutbla dmage in fh+

moltation ~os~orntrrtion wu, rtubi.6. Demitie6 of c#uro+mtat lan, ab

ru l fuslc raid for 20, 9, 80 parorat of relativr, hurldi4dlra -r+ - rrrlculrtad md chaakad psriodlcally every 4e bum.

RIEllrltLTS A;JD DISCUSSION

In P l g u m 2 we olra oborvr th. n r k a &p;rxwahiryg ta t h m

m&sturr qullibrlw at dlffsmnt mlaUvr huridtt5aa for rcPudl b u m ,

As wr our arm In F i a r e 2 the mtr of deaerption ir a fwctioa tho

nlrtlve humidity utzi bapazatura, For an axample a t 20 p~nrsent of

ml.t lvo hunidlty the xate af daaarption dsamssed r lv rp ly while &t

80 percent of ralatlvs humldlty the mto of da:rorptloa pxlur l ly

dacmaacrd. AS tha equilibrius was a p p w c b d tho =tar of denorption

decxwabed conaidem&ly. T b n t a a o f dosorption did appsar sLgnU1-

w t l y h i o f r In the f i r s t t w o Qya o f atarnfl;e! pmriod. Ua also obsanrcd

that a t hl~hsr tenrpmturss for a given relat ive humidity t h o rntrr

of dcsorptior u2rc Castor. A t 100' F for & ~ i v c . ? r.?:atlvc k d d l t y

the rate of chmrc? in ,aoiatum m s fimr tsr than a t 70' F but tho

actual squlllbriua wlaturr content a 3 less . A t hle$ur tetppbnturea

the period of t i n t to roach aquilibrilrm ma r l u o lson.

7% Charulrt in ttro Solutjon Concentration ---- In this lnven L I .--rtion denaitlea of 1.460 gr/cc and 1.193 p / c c

ef conccnt=tion of zLt*uic acid for 20 and 80 percent of relatire

hutidity ?-c:;pcctivsly, wen chockccl poriedica lly every 48 hours. The

val~*ns of r!crzi t l ~ z rt8r~ii:lcld carnt ? n t . The rn:;lrlta o h a ~ t l no chmm

Iln ths sulfut- lc acid cuncontrPltLzn 4:~rb.g a t e s t period.

P_xyurlncntal I 5.3 t!. . ~ r t s - - - Thr? equli. t.L:Jriit? F . ~ I J E ~ tur& contonta for decarptioa and cLdoorp44ws

V W W l t 2, Wbse a:: dc)orurp~lon for mi Zruuu at 700 P ud lo@' Pa

Days

p ~ c ~ c a r u l af b u m rzr 14;Im 5E1 Table 1. IwUmxm 0um1 OI b#UU for

6.llrorptjo;a ud Icl~wptlm a t mriwa Mni;#untutas; n+ rhaun: la F-

f Urnugh 14. I t cm b m n in th.n arms Ulrt for both .d.orpUm

rad dororption the equilibrium mlrtwcr coatant iaamamrs with &cr

iaousaaa 5n r a h t i v a huridity, A t equllibrtwr th0 vapor pmuaura

cob th. wtar in the grain l o the ma@ a8 %he preaaum of wrtcrr !.a

i t .nvironr.mt. As the onvlsoanntnl pnswaurc, Incr0~1.o~ ox nhtirr

b a i d i t y incrcaso;l, tha p e n u r n of tho wrrtrrr la th4 -in aurt

incraas. to reach eQuillbrlun,

F'5&umn 3 t l ~ q t r 14 s.bw that tb qui l ibr i sa wriotura

aar;tcnt dclrcpwes w i t h m Fncmaae la tempnoturn, Tnlm QUI b

@xplrlr.ed by tho principle of a L ~ ~ t a t l l s P , 1Che pflaaAp1a 0;tatu8

fhat if rtmrrn is applied ta a syrtclm rrt equilibrlur, ttw aystm

will r.l?adjast to decnase thR ttmas. Tki? atxm8~1 in thia cam 19 r

tamperat.-, AS the tsap@rrtum incrrauraer tha klnetio @norm bcfurr~,

aualng art increasr in atrasa. To rsduee Chis rtmsm .om of tba

rolsculbs eacapa t o tho anrlrQrtasnt, thus dramaring thr, m i s t u n

oaatmt. A Cllapmtic mp~cscntation of the in2luanm ad frmpontun,

for red bans is snown ln 7ltp;un 15.

Decoqtlon a r . aa%tr;rtf3n mn*cu for kana inve8tA@tod &re

rlgwiJ in shap, lika o = h e ~ cereal grairra md balorq~ to #a Type If

i ~ ~ t h t m ~ sccorclhq fa the ~ b s s i f i c s t i o n of anmurar (19%). EIdl

b.oW.crm ~ t 3 s 1 3 t s of thmu mf;ion3s thO low pnsaurr trgiozi ooxunn

to the ralative h u d d i t y &*&a, ths i n t o n e ~ d b t a l i i n a r portian and fhl,

hlch pr?r.xure I"JTL(~E~ CORY.~X t o rlr:.? mlattve iriuralaity axis.

b e 1 Y 3 c p e r S n a m t a l iaoth.zn eta at 70, 8% (rK1, M d l O O O Y for varlou. bslrara*

,...-* - * we,- Y r r - S Y '" __nsro. *A cz;tcmttr T r t r r h t ~ v u ~ m q t lor1 ~ ~ t ; k p i;Ond

htdrirl (C013:. ).2h-) Kuaidi t y ( A ) E, N.C. *"( d, b) P,t'r,C. ?S [ d b l

Tabla 1 (continued)

Taopamurrrs ; ~ o i a t i v a Mcoxmticm A e U a ~ pkrisl i Joc. iT'3k.r) Hunidit%* . . 5.M.C. $2 (bob)

Rclotive Humidity ,%

2 0 4 0 6.0 80

Relative Humidity ,%

Reloiive Humidity, %

20 40 60 80

Relotive Humidity, Y,

20 40 60 80

Relotive Humidity , O/.

2 0 40 60 80

Rolotivo Humidity, %

Relative Humidity, O/,

Relative Humidity , $

Rclut ivc Humidity ,%

20 40 60 80

Relative Humidity, %

Ralotive Humidify, %

A mll dlfferonc~ :a the vrlw of quUIbr%m~ ) I J L S ~ F L ~

emtat uong rarioud b a n s axadnod at a rpeaifisd o a v l r ~ w r r ~ ~ ~ & arrr-

ditkror rr. 0 ~ r V . d .

I r a ' rrrJI kind of bsur ma plrraartm, ocruroaly rabennd to

u hy8tomL.. lu prrstmt u shown la F-8 3 tbrptlah 14. Th6 result.

rhorrvd f&t hyskmcli. &azmssr; wlth .n lacruwco la tapatam. Yo:

tb. -9 of l l u a t r r t i c r i.rotboru avmr for ld baa a t 700 F

.Id 100' ? f.mp.mtulr rnm p1ott.d in FWXW 16. -nt, io tb.

hyrt8mrin ef fect for t h m U f e m n t kind8 air b 8 ~ 6 4t 4 give$ c?omUtion

ob nutire huslldlty ud tampntuzw #u obenad, Clolwular JllrUgr

d;uribg&rs8orption Ja belllevad t o nducc, 014 avll2aWllty af k)rptl(rl~

ritsr on norbont mrfaczr, ~ h u r y (1966) postulated that the Wfamoca

iR t& avrilrbillty of rarptiwr alto8 or polar n i b 8 on ths -ace

of W rrdclorbnt t o m t e r CSUB~ the hysteresis phbnaaelt~xz~

Attention hu been crllod ruputadly to th. dlffemUma in Wa

mlntarr oolrtonta of various orrrsrl gncLnr at diffelcbnt mhfSva

bidlWa8, 1r.4 tho rrlatfonshlp of these vrlusa to rllowabla aolskro

oonk#bt Ln rtorrge, I t i8 quite g;e?lenlly mad ttmt tha & t i c a l

roirttrn level fo r say olrzmal in the p.rcmtylr kolstun a t vbiah fb.

mod Sr Zn quLli\;=.iun w i t h a hwPidity of a b u t 70 prcont. 2"~.

t)n ~#~lrtulla contcrrrta a t 70 perccnt relative hwidlW of I r r l e y , orb

ud what ua, rkwt 1l.5, 13.9, 14.6 ptGent rsmpoctiv+ly, w k r c r c l

f h x matl and other o i l eseeda, a m lower In equilfkxlwr uoishm con-

twit, a t 75 yemoat mlativa M d i t y . Vo found that beM8 - higbsr

dttt ; valrio aiiuut ~ 7 . g iaoioturu. Ttrus, tho rptoxa45~ of beam at hm

l m l a oS miahm t'm~ 16 ta 171;;~ dry b s i a elm be eo~kderml amfa+

0 2 0 4 0 60 8 0

Relatks Humidity %

Ttn Chw~ and SYo'at equation rr crpkfsred ib the mview aFt

llkmf;wrrr, ur terM to find ifa rppllc~cMUty to fbr, maulta af

exporimatal b t r for aonshnt vuluer of r, Thaw valuer rr, Qrkrlrkd

in able 2, For the prrpcuse of Ellutration, morrl1ogurth.i~ japr

Wurr af -AF w l m t .ohtun for ad buar a t cUf'famnt tuglnturu

uorr p ~ t t . d . he plotting of th a u e a of -AF . g ~ t moirtura

~&Ofd+d 4 ~rbi@ht ul 1)59~1 h Fi&m 17 whi& 8upp02'b t)Cb *

ururrptbn expmssed by C h m g utd Pfoet in thrir aqurtion, maly,

-01 -AF - Am (11). men %e equation =a t m d o r n d into a - rr

fern In (4~) - I ~ A - M (19 , md UII oorutmtr A and B m a o n l u t e d

by the 3au5t aqmm mthod, The vrlurr of A , B Lnd th, values @f tba

oonrlrtlwi aoeffioient us t.buP.ted in 14rble 3.

Far the C h w a d Pfort equation the llnrr portion fotmd

.ad .horn ia F- 17 h s cornlatAo8i e d f i d m t of +0,97 or btk.

%b mtih an&@ of data b linsu for thir qurtion. For brb Uls

ban8 .ad pint? k v n s ci2i,ilar m s u l t s wen found a t a l l t r a p e a t m e

Table 2, The fr*w enemy ~ ~ r a m ~ a or demra,rptier. and rdsolt*frtlon t o r warioris sknainrc,

Pinto bsonr 100 5 7 9 11 13 15 17 39

Plnto burns deaorp dasarp deaorp d..orp adaorp r&orp rdaorp -0-

Thr ~orrt i c trr l besorption and adsorption iaathrcrar 06 kParr

wrre obtained by aubt i tu t ln f i l the eormspondin& tmnaburtr A rad I

frrm Table 3 into equstlan 15. h e Iaotberr data of vrarious b u m

calculs.t;cd by the theomtical Cfiun~1; ahd Pfoat equstfor, a m &lvan La

Tablo 4, In thio + a b l e we can eaea r close r(trwsr~ant between expcsalrr#~ct.l

ud thcromticu!. 1 co t l~e ra aAta for the entirrs range of relative hmld l ty .

As 8 conclu?ion, tbe i ~ o t h e n equation developad by C h w ,

and Pfcrat in vary ur.e!ul t o determine the ~ o r p t i o n of bcas;~ for r

wide mnge of re la t ive hurldZty at r given ternparatun.

f3382SSS a * . .

eJs;zmm+

tilast6 of adnarptfon E c r w ~ t inr, for vatdous bcnna --- -- ~ - -

Thrr haat o l adsorption or dcsort;tislsr Ir b : * a i ~ t t i ~ . d OFI.

lntamoleowlar farce bcrtwaan ttss nalc(cu1co of uater vapor and thr

mlwcolc~a of mtrr vapor and the C U C J ~ C C of abBor!xnt, If mter vapor IL

1s adnorksd on a nurfacs, s quant i ty of h a t has to bd rsleasect which

ir, known rs tho hoot of adaox-ption, In the aue nay if -tar \*upor

EB daaorbsd, a quantl ty of heat i s taken up, rhich i ~ , called tho itorat

Tho method of dstarnining tho haab of cieoorptlon I& b a d

an t h e ~ y ~ m l c princlalca, The lsosteric heat of c;or~.trsn is @xpssed

W the following oquation

tda@h.rr P1 and P2 a m c ~ u i l l b r ~ u m vapor pm~sums a t L?e ablolute tonperaturns

TI a"d T2# n n p a c t l v s l y . In the evslrutlon of isosterlc heats of

ad~orptim and dcrorption of beans, relative huhidlties ~ ~ 1 % and ~ 2 / % -re obtalnsd f mn k'ipma 3 #much 17 at constant values of a. The

sclatlve humidities wen! convcrtcd to the cquilibrLuoc v a p r yresftlm

PI and P2. The valucs of A Hst f l.aally ware calculated by equation 16

w i t h subst i tut ion oT f , and P n t ccrrcs;~ndinc c o n s k ! ~ t m, i 1

For oach kine of beans the isosteric heat of adsorption arJd

d e s o r p t i ~ was calculated. The values of iscrtsteric heats of adsorption

m/lb as slrom in ':'atlo 5. Frcn these tables h* ;en see that tho

V&~UL*S oi irc*::~:: o.' (1 :: ;o rp i ion ;:c r,Ki:e\tcr G:-, a thosi:. of' h.:,tt of iid30rpWon.

T'htls that the enercty involved In the dosorption psoaQas of baocns

rime J. h r ~ ~ t r uf ~ ~ W T P ~ ~ ~ S Q R wWerpat%an far w a r i o u a tmuma

R e d b@aau 5 1889 , X 8 ? X6?6,03 9 1186,85 ,

T , - ~ F 11 11X3.m $5 Wd 13 ltos9.94

T, - 100° F 15 1077.W 17 1 0 7 ~ m 35 19 1072.00

Bmby 1%- 5 kt& 7

9 TI - 8 0 O F 11

and 13 T2 - am0 F 15

17 19

5 (con t imad j

U dn#t8r t b n that in t)#, U a r p U c l a n proe-.slr;, Por th. punpaw cd

UUurtrrtlm in P i e r r , 18 ~r, au otwrrr, that thr, h n C r oJ uhaxpClm

and dellorptiaa deararm oaatlmnrlXy with Wkrrr ##iton%

uad a2ro tlyt hdlita uf derolcptgon and aborptlan o& kuu urrr

bi(gnr thrn haat af vlporircrtioa a@ pur -tor.

Mois ture , O/,

2. Th9 Type 11 irotherr or sigmoid i s o t h m tor k cwnrrlttont w i t h thssa for o a r gnrina found 'Cry aa.rUrs lnwutigton,.

3. The qul l lbr ium rotaturr mantent for bwrul in- wfth ur inarslaaa in ralutlvw hurpldity.

4, l!y#terrsla, for bema, decrurru with ua incrrwrme in tamperatw.

5. The zak of dasorption for bnm6 18 funotlon ob #a m b t i v a h u d i t y urd taapmturr,

6, The atem of dosorption for bun, wrm hi(Zh.r Aa fh. f i n s t t w o ~ L J I of mtdirIlr6. P-.

3. Th* isothcnr equation b@velopmct by Chwg urd moat vill predict thQ equilibrium moistur?s oC beam fa= a wine -a af mlat ivo humidity at a ~ i v o a kpaprrku+*

8. 1sos;teric hwts of dersnorptian and rdaorptloa oclntinurlly decnaue with Incrmasf#3 no in tun , content, and th.

- valusa of /\list f a r ciasorption arr -tar trhLn tha.0 of adwrptian,

9. Thz, heat, d datsorption for k#nr, wp. farnd to k grsrtur than t&nt of the lrtrnt h4.t of mpo~?if.tlOll of pure watar.

Bmumuor, 8.. P, H, EWmtt, and Re Taller: 19%. Admrpt larr af g n s in nulitirmkceubr hyarrr, J, A 8 0 ~ c r . (1309309-3119.

Bnrdley, R, S. 1936, R6l;ymalecuZor rdrorbd E i l ~ l l r XI. 'lb mmml thaorj, csf the c~llndsnmtlan ai vnpm on fhru b i w i d d co%lb80 3. Char. Soc, 1799,

Chun, C, S, . lW1 ~u l l ibr luar molntun curnu8 for WologiorJ, rtrrhb. Trrxlle, XYAL 14( 5) ~924-926,

C W , D. S, and He 5 . Pfwt, l i ~67e Adoorption m d d8aorption of uater wrpr by c m a l [:mlnr snd a a l r pFoducts, a r t I, IT, and 111, Trsns, t.L;AIr: 10(4)1~-JSi.

Co)ran. 1941, 3cp0r-t Mom the dfviaion of colloid crhcrnlatsy rt fhs 1026 w ~ t i n g of tllra American C b m i c j r l 80~i6ty , Saptarbas, 1951,

Coak, M. A , 1-918. Theory cd i ~ d r o r p t i o n of &%ses on . ~ l i d a . J. h. Cham, 9oe, ?Or 2925-29 30,

0. L. arxl C. L, fielson, 1965, Ikilorptlon l.oth+nu far wtwrt, Trans, ASAS dt29s%~td>.

0.Bosr. H. H. and C, Z w i c k n & 1929. Pobrlmtion -rye 2. -8. Cham, 3BsW7.

Ikll, C. Y, and J. ti. )t0ckd,g~4~+drhs. 19% E q u i U b i ~ cwt -nt a2 nh~l l c td crbrrl. .4c, !??I#, 3s-0.

H-w, S. tt. an? g. F, 1 1 S ~ l l o t r o 19413. A ~ l f ~ ~ i t l * of the p-~ l t i~~ thGOry to :-orptlisn of water vapor & hi@ po lyran . 3, A& C b n Sac, 721 tflc32-2566,

Wrt, J , H. 19641. Hy!$ter'cc',a pffccta Ln isolntYre af wYIwt taken f rolll the same wimpla but hnvisig d i i fermnt moisture emtent. C a t . Chaa. dcl # 3 4 U - 3 f ; O n

0

Ynremar, 1933. A traatits on phys icr l cheriatry, Vol. 2 , p. 1661, D Yon Noatnrnd Campmy,

Un@#uir, I , 1918, The sdaorption of msoa on plane surface c i f a u mica and phtlnum, J . Am. Chaa, Soc. 4011361,

H o E a i n , J, ri. and A . M. &kern 1935. A new s o q t i o n bolencs. S, Am, Cham. SOC. f j 7 t C . j . 3 . 4R1690-1926,

Parry, J, H. 1950, Chcnlc-11 enrtlncar'r hendbouk thf,d ediction, New Yorkr R c G ~ u - ! ~ ~ l l .

Snlth, 5, &re 1949. The sorption of water mpor by high polymns. J. An, Chea. Soc. 691646-651. .

Strot*, R. D. lzna H. R. Yoarqer. 1967. A new ca,?uIliSriu.m loistame co:itlont q t m t i o n . Trans ASAE l a ( 5 j I b?J;-b??,

Young, J, H. and. G. 1.. Y~l"lcon. 105'). Theory of h v . j t r a ~ s l s catweor, scrrt*tlon aZ4 d c s s q t i o n isoiire~z=s i n biologioxl ib.s*=eriaSs, T ~ B A S E 10(2):260.

Urgufurr*C, A . i t . 1929. The mechnnisa of the ~dsorpt.iorr of takr by cottorr, J. T x c t i l a Ir;st, 201T125-12,

*

ZaigRolDdy, H. 1913, Structure of *latiouts s i l l c i c acid theory of de.hyf3mtion. 2 Anorg. Chcm, 71t3!&rr).