Solubility and Densitv Isotherms for Sodium Sulfate-Ethylene Glycol-Water J
J
RAYMOND E. VENER' AND A. RALPH THOMPSON University of Pennsylcania, Philudelphiu, Pa. solubilities and saturated solution densities are reported a t intervals of 5" from 25" to 100' C. for s o d i u m sulfate in aqueous ethylene gl>col solutions. Only one liquid phase occurs regardless of glycol concentration. The lowering by the glycoi of the sodium sulfate nnhydroirsdecahydrate transition temperature in saturated aqueous solutions was determined from 32.4' to just below 20' C. Over a wide intermediate range of water-glycol compositions the temperature-solubility curve of the anhydrous salt is almost invariant with temperature.
0
WI?;G to the iiiverted solubility relationship of anhydrous
sodium sulfate in water, its commercial crystallization in most conventional evaporator-crystallizers is difficult. 011evaporating a coimritrated aqueous solution of sodium sulfate, a tenacious scale of the anhydrous salt tends to form on the heating surface. To evaluate the technical feasibility of a new method being investigated by the autliors to reduce or eliminate this difficulty, complete solubility data were needed for the system sodium sulfatt-etliylene glycol-ivater. I n essence the process involves inaintainiiig etliylene glycol in a crystallizer used either to dehydrate Glauber's salt crystals or to evaporate an aqueous solution of the salt. The presence of glycol lowers and renders the solubility almost invariant with temperature. Tile cryatallization process remains essentidly one of evaporation. T h e entire range of glycol concentratioii was investigated a t temperatures from 25' to 100' C. Deiisities of saturated solutions and salt solubilities were determined over this range. With only traces of impurities present in the unpurified salt and glycol, i t seemed possible that they would have a negligible effect on the solubility of sodium sulfate in aqueous glycol solutions. T o establish the purity of materials required for reliable and reproducible results foi this system, tests were run t o coinpare tlie readily available salt and glycol with purified grades of both.
SODICM SCLFATE.The solubility in water of Baker's C.P. aiittlyzetl anhydrous sodium sulfate was determined ovcr t h e temperature range of 25" C. t o the boiling point. Saturated solution densities of these solutions were obtained u p to 100' C. These values were compared with those obtained a t several of the identical temperatures, using salt that had been purified by the method of Phipps and Reedy ( 5 ) . This involved five recrystallizations of the Baker's C.P. salt from distilled water, operating between 5" and 30" C. t o obtain the decahydrate salt. Recrystiillizations at higher temperatures with the anhydrous salt as tlie crystalline form would not have been practical, owing t o the relatively small change in solubility with temperature. The solubility and clensity data for these two grades of salt showed agreemelit within the limits of experinieiital precision. Additional tests indicated t h a t possible impurities coiitained in the C.P. salt had no detectable effect on the solubilities in t h e aqueous organic solutions. As a result of these tests, Baker's C.P. anhydrous sodium sulfate was considered suitable for all other experiments in these studies. PREPAKATIOS O F SOLUTIONS. Water obtained from a laboratory Barnstead still w:ts used throughout this work. Conductivity measurements 011 periodic samples of the distilled water were all of the order of 10-6 reciprocal ohm per centimeter.
TABLEI. ANALYTICAL DATA FOR S O L V E N T S SOLUTIOXS (IX VACUO) Solvent No.
11'0,
G-2
G4i" C-8 G-10" G-12
G-144 G-16 G-25
G-32
G-3dQ G-40 c:-41=
SOLUBILITIES
AQUEOUS GLYCOLSOLUTIOSS. The solubility of Baker's C.P. anhydrous sodium sulfate in aqueous ethylene glycol solutions was determined a t severid teniperatures for identical concentrations (31.4 weight yoglycol in the solvent) of the technical and purified grades of etiiyleiie glycol. The salt, solubilities and saturated solution densities using these two grades of solvent were identical within the esperinieiital error of check determinations. Both grades of solveiit u.we adjusted t o the desired compositions, utilizing the density-composition data of Spangler and Davies ( 5 ) . The technical gmde of glycol, obtained from Carbide and Carbon Chemicals Corporation, was filtered before use for these determinations. Purified ethylene glycol was obtained by careful vacuuni diatillatiori of tlie technical grade under a pressure of 10 t o 20 mm. of mer c Tlie values of Sj)aiiglcr and Davies (8) a t 25' C. for density, 1.1101 grains per nil,, aiid for refractive index, 1.1300, for purified ethylene glycol a w i l l iqgeernent with the data obtaiiied in this work. 1
Present address. Drone1 Institute of Technology, P h i l a d s l p i i ~ ,P3.
G-43
c;-fjo G-70 G-80
G-00 G-99 a
Density of S o l w n t a t 2 3 O C., G./311.
Weight % Ethvlene Glycol in Solvent 0.0 2.1 5.8 8.0
9.8 11.9 14.0 15.7 24.4 31.4 33.6 30.9 44,9 4.7 , 5
60.6 68.8
78.8 90.3 99.2
AND
WPight % Sa?SOd in Satd. S o h . a t 35' C. 32.98
...
27:69 25:22 22:59 16.84 12.85 8.878 6:ki3 3.251 1,8!38 1.122 0 699
0.487
SATURATE]) Density of Soln. S a t d . with SazSOd at 3.5' C., G./Ml, 1.3278 1.3143 1.2901 1.2754 1 ,2049 1 ,2522 1.2390 ' 1 ,2286 I . 1800 1.14!)2
1.1411 1,1223 1.1115 1 , I1I)l 1 . O!IN 1 . 0947 1 ,01164 1 , 1083 1.1081
Supplementary puints for analytical curves (Figure 1).
Aqueous etliylcnc glycol solutions of approximately 8, 12, lti, 25, 32, 40, 45, GO, 70, 80, 90, aiid '39 weight yo glycol Lvere used as solveiits i i i tlie regioii where ariliytirous sodium sulfate was thc, stable solid phase. Tiiey were inixed to approsirnately the ~ L ~ O V valucs, \vith distilled \yater and tcdiiiical gl,ade glycol. The exact compositions w e ixeseiited in T a l ~ l eI aloiig kvith a few ntlditional poiilts, indic:tted by u , which were used iri the construction of the niialyt icnl cui~vesof Figure 1. The density and refractive iiidexconipooitioil (lata of ~ p ; t i i g l warid l>:ivies (8) a t 25.00' C. f o r aqueous etliylciie glyccil solutions ~ v e r echecked a t sevor:tl points by nic:tIis of tlie purified glycol dexribed above. Tiley were found to he iri excclleiit :igreeinciit. Accordingly, their smoothed 2242
C
INDUSTRIAL AND ENGINEERING CHEMISTRY
October 1949
2243
to prevent poosible rcnioral of n a t e r by the -olid phase from the coii~tant-compositionsol\elit\. T h e only stable hydiate found over tfir iange of temperatures and glycol coilcentrations co\ered was tlie decahydiate. In the rclativelj amall region \\heic this u as encountered, cornplete analyses had to be run on liquid :md solid phases at each evperinieiital point. Foi these determiiiations the salt n AS adclcd as described abobe. T h r temperature \vas then lowered -Ion ly with vigorous agitation through the tlecahydrate-anhydrous transition point t o the d e -11 ed temperature. This procedure enabled the excess salt t o pick up tile nnter of llydratiori Density of Saturated Solullon - g /ml. nithout caking. Seed ciyit:il\ uf tlie d c a h y Figure 1 Plot for Determination of Ethylene Glycol-Water Compodi ,ite \$ere added pellodlcallg as tlie tp1llprasitions in Presence of Sodium Sulfate tule mas lomered t o pievent tiir forniatioii of a 1 he points shown represent experimentall) determined salt solubility and saturated i,i,,tnbtable ,,hase. T h e heDrallvt[r:ttr, uIl" solution density Falues, all a t 35.00' C. *table in the presence of even small amounts of tlie decahydrate, was detected occasionally bevalues for denaity and refractive index were used t o deterniine the + Ineeii . 20" arid 25" C. These studies were restricted to st:tblr composition of all salt-free aqueous glycol solutions encountered in solid phases. this work. Densities Tvere deterinined with a capped 10-nil. speSALTCOXTEST. The weight per cent sodium sulfate iri the >:%tucific gravity bottle arid refractive indices by a n Abbe refracrated solutions was determined by evaporation to constant n-right tometer, both a t 25.00" * 0.01" C. Solvent compositions were in 125-ml. glass-stoppered Erlenmeyer flasks in a vacuum oven. determined t o better than 1 0 . 1 weight yo glycol. The limiting T o determine the precision of such measurements, test runs were factor here n-as the degree of prcciaioii of the available density and made in which various amounts and compositioris of aqueous glyrefractive index-coinposition data. col solutions \yere successively added to and evaporated from given weights of salt. T h e salt, content values are accurate to 10.01 EXPERIMENTAL PROCEDURE weight % salt for solutions containing more than 10% salt and soinen-hat better for smaller solubility values. The constant temperature bath and much of the auxiliary DEKSITY.T h e densities of the aqueous glycol solutions mtuequipment employed in this m-ork have alre:idy beeu described rated with sodium sulfate were determined by a previously de(9, I O ) . Although 2 to 3 hours was found t o be more th:rii suffiscribed technique (9) employing weighing pipets. Solutions incient for equilibration, a minimum of 5 hours was always allowed. ' glycol or higher mere volving solvents of about 80 weight % The equilibrium time \vas again established by approaching the sampled with a sintered glass filter connected t o the tip of the desired temperature from above and below. The methods used pipet. The filter was required for thejc solutions since tlie disfor this system required some modification because of the low volapersed salt did not settle to the bottom of the cell completely, even tility of the glycol, the occurrence of some hydration in the solid after much longer than the 15-minute settling time usually alphase, arid the somexhat higher temperatures involved. lowed. For solutions with lover glycol coiit ent the diepersed EQUILIBRATIOSS. Carefully dried anhydrous sodium sulfate was slowly added t o t h e solvent maintained above 35" C., at which solid settled sufficiently in 15 minutes to give a clear supernatant temperature only the anhydrous salt occurs as the solid phase solution. Identical results were obtained n-it11 these solutions regardless of solvent compoFition. This procedure was required whether the filter was used or not. The precision of these mea+
Wt. % Ethylene IO 20
0
Glycol in Solvent
30
40
32 30 28 26
24 22
20 I
0
Figure 2.
Vacuum Distillation Apparatus
I
4
I
8 12 16 20 24 28 32 W t . % NaeS04 i n Saturated Solutlan
I 36
Figure 3. Variation of NaZSOI-~S:l,SOr.ZOII?O Transition Temperature with Aqueous Glycol Solvent Composition and Salt Content
2244
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 41, No. 10
coininonly used alcohol and ethrr rinses of c r yst al s
.
tlicx
1vr.t
In the event that some hydration or solvatioii was iiidicated by this test, a more precise analysis was run on the solid phase using the wetr esidue method of Schwinriiiakers (6). AXALYSIS OF AQCEOGSGLYCOL SOLUTIOSS COKTAISIXG SALT. The solutions in equilibriuni with a hydrate LIS thrsolid phase required the determination of all three c o n poiierits in both phases a t each esperinientnl point. The sample for salt content T V ~ Btreated as usual. .\II iriverted U-shaped glass tube vas used to aiphoii out rapidly about -100 nil. of the supernatant saturated solution. This solution v a s then equilibrated with n n escc+ of c:irefully dried ariliydrous salt a t 35.00” C., at nliich tciiiperature the anhydrous salt \vas the stahlc colic1 phase regardless of glycol content. Salt content and s:ituratetl solution density values xvere obtained. From :I c;irc,.fully deterniined relationship of solvent composition to soluW t . “r. NaeSOc in Saturated Solution bilitv arid densitv at 3,5,00°C., the glvcol content TWO readily arid accuktely obtained. Thew data are lidcd 4. So,ubility of Sodium Sulfate in Aqueous Ethylene in Table I and plot,ted in Figure 1. Glycol Solutions K h e n the aniount of available solutioii w i t s too snixll for the preceding niethod of analysis, a vacuum distillation urrnieiits W:LS about *0.0003 grain per nil. Hoivevcr. at teninietliod n-as utilized. The distillation method was also used for peratures above 75’ C. considerable difficulty was encountered in the analyses of the v x t solid pliase from the Schreineniakers’ vetdenhity determinations with solutions requiring the filter, owing residue saniples. I t irivolved the quantitative separation of anhyto pronounced cooling of pipetted solutions during the prolonged drous salt and aqueous glycol solution. The sample was sealed in Panipling time. one leg of the unit slroTvrr in Figure 2. rlfter the contents were SOLIDPHASE ASALYSIS. Two methods \\.ere used to deteriiiiiir frozen by surrounding this tube with a dry icr-acetolie slurry, the tlie composition of tlie solid phase. The fii,st, de-ignnted the unit !!-:I.< r:ipitlly evacuated with a Hy-Vac pump. The stoil“quick blot” test, was used to distinguidi between the arihj-droui cock n:w quickly closed and the slurry was placed a h u t the (lissalt :ind possible hydrates or solvates. For each anmpling, sevtillate leg. The teniprrature of the leg containing the sample eral grams of the Ti-et excess salt n-ere removed, and tlie slurry w:ta wab incrcwed slo~rlyto room temperature. By carefully distillejected 011 a filter paper in a Gooch crucible. The crucible W:LJ ness, the . d t content \YRS readily obtained. Density disconnected from tlie suction, inverted over filter paper, and ve index inensurements on the dijtillate permitted the blotted, and the n-eight loss determined. The entire procedure deterniiriatioii of the water-glycol ratio. These distillation unit. froiii the sampling to t,he capping of the weighing bottle rrquired were connected to :I manifol(1, and several analysr.; 7vere c:tri~irtl less tlinn 10 seconds. Preliminary tests on anhydrous salt showed out simultaneously. a n-eight loss of less than lye, due t o some adhering solutioii inFor the \vide range of salt and glycol contents encouutured, t h o conipletely removed by the quick blot method. When applied above methods were found to be more accurate and coiivenierit t o tlie decahydrate, the actual loss was slightly less than theoreiithan standard distillntiori methods, the Karl Fischer voluinetric cal, indicating a small loss of hydr:ition mater. Severtheless, the determination of x a t e r content (i?), and organic oxidation techdiscrepancy between actual arid theoretical values for t1ie.c arid niques as applied to glj-col (3,4). othrr materials !vas considerably l e s than that rehiiltiiig fmni TR.%YSITIOS POIKTS.The demarcation line betn.een the ri.gioii,of decahydrntr and anhydrous sodiuiu sull’atr, iii equilibrium 11ith aqueouq glycol vlution. :I‘ r.tablislir~r1 fioni 32.4’ (nater ‘1s ~ o l v e r i to t ~ 20’ C (~ipprounicltel>4Oyc gl>col). “-ynthc~tlc” method T\ a< consdered Inole convenient alltl 1 ~ x 1 haps more accurate than “aiialytlc” technique* tor thew determinations. T h e make-up of -1ir cell s o l u t ~ o nKas the same as desciibed above i f t e r an excess of 100 to 200 grams of w l t had tiren added, the tempeiature of the outside bCtth \ \ A lon cred do~!Iy and regularly. Thiee c11te11n*ere obselvctl to iiidicate . L ~ I ~ V L I J ,it thc truiiiition point: (1) T h r solld pIix5r U‘I< \:mipled ani1 anal) xed b y the mrthod- tlescl ~hctl above. (2) Tile solution n a s analyzed fol salt content. (3) The rate of fall of the ccll tempeldturc n i t h decrea,e of that of the outbide bath n ‘ ~ .ohwrvetl K h r n the transition point X ~ lSe t c h c ~ l , i n 1ncie:iiing arnount of hydrate n atei T T ‘ L ~ fouiicl 111 t h e solid phase, and w l t content of the wlutioli I04 IO8 1.12 1.16 I20 1.24 1.28 1.32 decreased dialply. I n addition, the tempci ‘iture Density ol Saturated Solution - g I rnl 111 the ccll, nhile still falling veiy s l o n l j , I ~ O R lagged fa1 behind t h a t of the outslde bath. I T hell Figure 5 . Density of Aqueous Ethylene Gllcol So~utions Saturated :ibout half of the excess salt had hcrn con1 1’1 t w l t o with Sodium Sulfate _ ”
INDUSTRIAL AND ENGINEERING CHEMISTRY
October 1949
2245
TABLE 11.
.~QL-COCS ETHYLESE GLYCOLSCJLL-TIOSS IS I,:QUILIBRILX WITH A SOLID PHASE OF BOTH S a ? S 0 4ASD S a ? S 0 41OIf*O .
U-eight Ethylene Glycol in Solvent
Transition Temp., C.
Density of h t d . Soln.,
G.;lIl.
\\-eight '1 1\-a2SO1 in Satd. h l n
90.23 29.32 28.3i "5 . !J i 2 3 . €2 20. I h
I J ~niixtures of the :inliydrou~: ~ i i ( I tlw:ihydrate salt. The vari:ition of t h r ti tioii teniperuture \vit!1 presented in Figu1.c. 3 . wlvcrit coinposition and salt coiiterit 1lip points >lion-ri rvprehrnt experimeiital values. The iiit erpol:ited v:ilucs in T:~iileI1 n-ere obtained at solvent corupo,siti o r i eo1,responchgt d those of T:hle I i'lOii1 h r g e s c d e plots ~iiiii1:ii~ I(I Figure 3.
a solid phase corisistiiig
r .
Wt
Figure 6.
Yo Nd2S04 in Saturated
Solutlon
Composition Isotherms for Sodium 5111fate-Ethylene Glycol-Water
the hydrate, tlie outside bath as brouglit up to the temperature of the cell. hftcr equilibrating for 21 hours, both phases i w r e sampled and analyzed. \Yater or gl>-col ivas then added to the cell, but insufficient t o convert the bolid phase entirely t o either the anhydrous or decnhydrate form. .liter re-equilibrating a t the asme temperature, the two phases n-ere agtiin analyzed. T h e tempemture involved was considered the transition point for t h a t particular solvent only when tlie anal of this solution proved to be identical with the preceding One in all three components. When t h e t x o sets of analyses differed beyond the limits of esperimental error>t h e runs x e r e repeated. Solution densities and sodium sulfate solubilities are listed in Tahle I1 for R q u e o u s ethylene glycol solutions in equilibrium with
0 1.00 Density
Figure 7 .
1.10 of Saturated
1.20 Solution
-
1.30 g./ml.
Density Isotherms for Sodium SulfateEthylene Glycol-Tater
I SOTH ER3I S
Tlie tleiiaity and solubility data were plotted on n scale I:irgt3 enough t o pwniit values t o be read within d i e precision ot' t11(. esperiincnta1 determinations. Curves \yere dr:in.ii through t htw. points, :inti iriterpolated ralues were obtnined a t intervals of 3' from 25' to 100" C. Tliese smoothed values for rolul~ility: i i ; , l deiisity isotherms are presented in Table III. Esperimentnl points for sodium sulfate solubility ~ i t :iqucBous h glycol solvent composition as parameter are plotted against teniperature in Figure 4. Similar plots for the density of the s : t t u rated solutions are presentpd in Figure 5 . The exact solvent conipositions corresponding to the various curves may be deteriniiii~tl by reference t o Table I. -111 open circles in these two plot;. :LH' experimentally determined values involving n solid phase of the, :inhydrous w l t . The solid points do not represent esperinic,iit:ll values but were included becauee i t was considered of interwt 1 1 1 show the sliape of the constaut-solvent conipositiori curves ~ v l i e i ~ extended into the hydratrd solid-phase region. Tlie vducs U J I ' respontliiig to the aqueoui glycol solveiits used for the conat:iiitsolvent composition runs in the anhydrous s:tl t region were iiit wpolated from l u g e scale plots of the experimental solubility and density against solvent compositions. Tlie sharp breaks in mint' of the curves represent transition points with mixtures of ailhydrous and decahydrate salt as the solid phase. The point3 on these curves a t temperatures above the transition values inr-olvc, the anhydrous salt as the Etahie solid phase; at teiiiperatures l)elolv the bred: points, m l i u n i sulfcite decali~-clrnteis the solid 1)haee. Several i+otheriiis are pi.c-eiitetl oii rectangular coordiri;itc.,;: lvith solvent coinpositioii plottctl :ig:iinst salt soluhility in Figure, ci and against saturated solutioi! ilensity in Figure 7 . Thc 25" C. isotherin is indicatrd by a broken line for greater cln!,ity. TI!(, h a r p infiectiori in tliis C L I I ' V ~oil hot11 of these plots C O ~ ~ ~ ~ ~ J O l l to t!ie aiili~-drou~-tic~caliy~li~~ite tr:iiisitiou poilit. I>otliri,iii> IJP in-een 35' ant1 100" C. rvoulcl lie tietn.e peratures and v-oultl 1 i a v ~t phase in equilibrium nit11 t The data for salt solubility nrid satur:ite(l >olutioii tleiisiiy 101) the system sodium sulfate-nztw are iii gootl ngrwnieiil \ Y i t l i tliokc of various other iiivestigators, including Berki4vy ( 1 ) nntl others wlio>e data are reproduced or referred t o hy Seidvll ( X S o previous i\-oi,k h:ts been reported on the solubility of s u t l i u m -ulf:ite irl nqueous ethylene glycol solvents.
l i -
INDUSTRIAL AND ENGINEERING CHEMISTRY
2246
Vol. 41, No. 10
AND DESSITY ISOTHERMS TABLE 111. SXOOTHED VALUESFOR SOLUBILITY
Wt. yo, XalSO, in Satd. S o h .
Density of S a t d . Soln.,
G./AII.
DIBTD. W A T E R A 6 BGLVENT
21.74G 29.10" 32.98 32.50 3 2 , os
31.72 31.46 31.20 30,97 30.71 30.47 30.24
30.02 29,86 2 ' ) .7 3 29.65
1.2075 1,2834 1.3278 1.3106 1.3123 1 .30.59 1.2903 1.292u 1,2866
1.2501 1,2734 1.2R86 1 ,2603 1.2545 1,2495 1.2480
11.9W T .
70 ETHYLENL QLYCOL I N S O L V E N T
(Solid phase is anhydrous sodium sulfate unlese otherwise indicated) W t . yo DPnsity of FVt. Eatd. S o h , Na?SO, in D m s i t y of Satd. Soln., Temrr., XaiSO, in S a t d . Soln. G./.\Il. G,/M. c. Satd. S o h . 8 'CTT. 7 0 E T H Y L E S E GLYCOIi 78.8 W T . 70 E T H Y L E N E IS S O L V E N T
19.36a
25.22
24.76
1 ,0927
1.1113 1.1071 1.1033 I ,0994
1 ,0892 1,0856 1 ,0820 1.0785
1,0964 1.m16
1.0877 1 0889
1,0760
1.0804 1.07ii9 1 ,0733
1,0964
27.24 26,82 26,45
26.09 2.5 , 7 9 25.52
25.27 26.06
1.0718 1.0686
....
"4,88
.... ....
24.72 24.GO 24.52 24,45
15.7 W T . %
ETHYLESZ
IS 6 O L V E S T
9C3.3 1\ E I G H T
21.30
45,OO
m.no 53.00 60.00
20.3''
20.20 20.00
,...
'Cerny., O
C.
W t . C;. r)iw*ity o f ?ia?SOl in Satd. Soln. Satd. Soln. G . ,111.
7 0 E T H Y L E S E GLYCOL I N ROLVEI'L
1.1146 1.1113 1,1081 1,1052 1.1023 1.0995 1.0963 1.0'327
35.00 40.00
2 I . 06 20.84 20.64 ?I). 47
22.59
LVt, c; Drmsity of T < ~ : n ~ , , Sarq00i in Satd. S o h . , ' C. Satd. S o h . G./AIl.
25 , OIJ 8 0 . on
21.58
22.45
...
...
. .
21.8.7
24.40 24.08 23.79 23.53 23.30 2 R . 08 2 2 . 90 22.74
ETHYLENE Q L Y C O L I N SOLVENT
1.1n35 1 .0'390
27.69
17.46O 23.02 22.50 22.19
18.37" 27.69
Dmsiry of Satd. S o h , G./h21.
90.3WT. %
QLYCOL I N S O L V E S T
27 i o n
GLYCOL
'Cvf. %,
NamO. in Satd. Soln.
1, 08!10
65.00
70.no
1.0852
1.081'
75.00 80.00
85.00 90.00
95.00 ino.00
20.00 19.91
22.32 22.21 24.4
WT. 70 E T H Y L E S E GLYCOL I N S O L V E H T
13.05 12.85 12.67 12.51 12.37
Ici .3R
16.38
16.15 15.98 15.83
12.2.5
12.16 12.08
15.69
12.02
15.57 15.47 15.36 15.27 1.5, 19 15.11 15.03
11.96 11.9il 11.81
11.7R 11 73 11.67
39.9 W T . 70E T H Y L E N E QLYCOLISBOLVEST
1.is9 1,538 , 14!J2
Iernp.,
I ,
c.
,Ill5
TEMPERATURES
w t . 7%. Sa?SOI in Satd. Soh.
1333 , 1270
,1228 ,1181 ,1138 10:15 ,
1034
.IO12
0976
ETHYLE:NE QLYCOL I N SOLVE>-T
in3.oa 102.60 101.03 100,46
96.10 10.5
107,ia 106.65 104.50
29.688
10.5.60
29.663 20.721
98.85
W T . % GLYCOL AR SOLVEST
.,..
104,5n 101.20 103.50 iru.80 18.1 RYT.
8.047 8.878
R-t. (70 S a 8 0 4 in Patd. Soh.
22,913
22.915 22.922 22.932
c:
GI.TCOL
QLYCOI.
AS SOLVENT
29.631
2i:622
9Y.75
9.036
c.
W.4TER A0 S O L V E S T
,0942
45.5WT. s;
Temp.,
41.0WT. %
,1398 ,1310
ELEVATED
SOLCBILITY DETERXINATIOXs A T
GLYCOIi I N S O L V E S T
13.28
15 820 17.13 16.84
TABLFI\'.
'?1.4 m - ~ 7 .' E T H Y L E N E
103.50 100.00
7:iis 7.913
7.910 7.911 7.914
45.6WYT. 70QLYCOL AS SOLVEST
108.3a 108.00 106.60 105.05 100.35
6:k24
6.611 6.609 6.644
W T . % QLYCOL AS SOLVENT
48.6
AS CIOLI'EST
wt.
Temp.,
c.
GLYCOL AS SOLVENT
114.4a 113.85 119.50 103.80
1:j75 1.986 1.997
106.50
2.003 2 034
98.75 7 5 . 5 W'T.
llli.ia 11?.13 1 18.23
GLYCOI. h S SOLVEST
10:. 1" io-1.p.o 103.90 103.05 99.G5
8.3411
60.6 WT. 5%
ETAYLENI Q L Y C O L I N BOLVEST
69.8W T . %
ETHYLESE QLYCOLIN BOLVEST
3.2fi3
1.1021
1.922
1.1014
3.23ti
I . 0985 1 .00.51
1.910 1.808 I . 885
1 .m i
1.0!>22 1.088Y 1,0857 1.0823 1.0786
1,0748 1.0707
3 1.75
I , OR63 1.0621
3.113
1 ,Oi8@
R , l l i &
1.873 1.882
1.831 1 811 1.831 1.821 1.811
R.I.'J'I
1.0542
3.130
1 ,0504
1,79!1 1.788 1,770 1.758
1,0464
1.755
3,120
I 120 1.132 1 138 1.168
1,190
c/c
OLYCOI
I . 0'147
1.nn11 1,0879 1,0844 1 .o m 1.U77l 1 . 0731
I .n m 1.0033 l.O(il4 1 .0.?7:! 1 ,n:?o
1,
om
1.0444
36.2 WT. %
13.201
111.3& 110.03 110.13 108,'J.;
13.228
108.10
in:i89 l.i.102
ioo.no
0 792 0 7'31
107.20
0.840
90.30
3:iSs 3.187 3.183 3.184 3.201
O'i95
117.25
I?I..~O
60.1 WT. %
8.389
3.174
n'T.
3'1 123.45
8.399
3.205
1 108
.4S B O J l Y E I T
8.461 8.430
3.194 3.184
I , 103
1 1 5 , 80 ii2.in 1 ox.4n 103 40 101).00
114
8.4'34
3,"l'i
70
GLYCOI A S SOI.\-EST
80.0
8.330
3.251 3 "2 3.231
Ir,
67.5 W T .
8.820 8.762 8 707 8.056 8.610 8.569
9 '
Sad304 Fatd. Soh.
90.0 WT.
0.860 7 0 GLYCOL.
AS SOLVENT
GLYCOL
A S SOLVENT
106.P
106.73 104 40 103.00 101.75 0
,...
9.839 9.836 9.810 9.859
Approxiinate boiling point.
Figure 4 slion b that the temperitlure-solubilitS c u n e s become almost vertical over the whole range of 25 O t o 100' C. for solverite of a large intermediate range of water-glycol ratios. On in.
October 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
creasing the glycol content above about 50%, the decrease in wlubility with temperature increase tends to become a little larger w e n though the actual solubility value is decreasing. h large n u n h e r of aqueous glycol solvents was employed in order to establish definitely whether there is a reversal of the dupes of the inverted solubility curves. T h e decrense in solubility with increase in temperature over a wide middle portion - vertical for solut'ions with 40 weight % or higher glycol as solvent. The approximate boiling points included in Table I V are intended t o indicate the degree t o which these limiting temperatures were approached. LITERATURE CITED
(1) Berkeley, Trans. Rog. SOC.(London),203, 189-215 (1904). (2) Fisrlier, Karl, Anww. Chem., 48, 304-6 (1935). (3) Fleurs, P.. and Marque, J., J . p h a r m . ch,im., [ 8 ]10, 241 (1929). (4) kltiller, B.. Chem.-Ztg., 44, 513-16 (i920). ( 5 ) Phipus. H. E., and Reedy, J. H., J . Phz/a. C h r m . , 40, 89-100 (1986).
SchTeineinskers, F. A. K.. Z. phuisil. Chem., 43,671-88 (1903). Seidell, ;\,, "Sclubilitiec of Incrganic and Metal-Organic Conipounds," 3rd ed., Vol. I, pp. 1300-2, New York, D. Van Nostrand Co., 1940. (5) Spanglei. J., snd Davies, F., IXD.ENG.CHEM.,.IXAL. ED.,15, 96-9 (1943). - - , -
\
(9) Thompson, A. R., and Mclstsd, Id.C., ISD. E ~ GCHEN., . 37, 1244-5 ( 1 9 4 3 , (10) Thompson, A , R., and \-ener, R. E., Ihid., 40, 478-51 (1948). RECEI\-GD S?ptnnher 24, 1948. Based o n a dissertation presented by Rayinond E. Vener t o t h e Gredlintr School, University of Pennsylvania, in partial frilfillinent of t h e reqiiiremrnCP for t h r cirgrer of d o r t n r of philosophy.
Tack of Butyl and Natural Rubbers R . I l compounds.
I
N THE manufacture of Butyl inner tubes one of the major
problems is the making of a satisfactory b u t t splice. T h e Goodyear splicing machine shown in the adjacent photographs is in general use in the industry for h u t t splicing. The tube lengths which are cut sonicivhat longer than required are placed in position by the operator a3 shown in Figure A. T h e splicing is then done automatically as follon-s: (1) the clamp arms close down upon the tube cnds and flatten them int,o the clamp dies; (2) a pair of heated knives descend vertically onto a cutting anvil ttnd trim off both tube endi, leaving clean and tacky faces ready for splicing together; ( 3 ) the knives and anvil then move out of the way (Figure B ) ; (4)t h r clamps move linrinontally toward
each other, pressing forcibly together the two freshly cut tube ends and holding them so for a short interval of time; ( 5 ) after which the clamps open u p and return t o their ready position (Figure C), completing the cycle. T h e t i i n k g end pressures of any operation in the cycle can be varied brit the full cycle completes a splice in about 30 seconds. While i t has been clearly shown t h a t niechanical improvements in the splicing machine are effective in reducing rejects a t the b u t t splicer, there has been a general feeling t h a t Butyl h m a lower margin of safety for splicing than has natural rubber. Furthermore, i t has been reported t h a t Butyl shon-r, quite erratic results in the splicing operation. I n vien. of these difficulties, i t was felt t,hat a !aborntory Btudy of the factors influencing the tack ol" Butyl would be helpful in understanding the splicing problem. Since natural rubber is considered t o have good tack, Butyl and natural rubtler n-ere compared under t,hesame test conditions in so far as possilile. EXPERIMENTAL METHOD
The esperiniental technique which was used in this study i,. based on a method for quantitatively measuring tack in e l a s tomers which was used by Buise et (11. ( 1 ) . Certain mndifcntions were made in order to coiitribute as much information to the prohlrni of eplicing Butyl as possible. h diagrammatic sketch of the unit is presented in Figure 1 . It coiisists essentially of a platform scale for measuring pressure and tension and a moving arm for Contacting the rubber samples pnclosrd in an oven For temp
