September 1947
INDUSTRIAL AND ENGINEERING CHEMISTRY
OTHER TYPES OF CRACKING TESTS
\Tith the advent of fluid catalyst cracking other tests employing powdered citt:ilyst have been developed and are also being used. Thew niow recent trst methods have the advantage t h a t pilling is not i,c.rluircd and t h a t short catalyst holding times may be morr cla.;ily studied. On the other hand, some difficulty has been expcvic,iiccd i n tcsting powders of widely differing particle size. In sur11 cast's it is difficult to adjust for the effect of particle size on g:L,q-t o-solid contacting and hence on the conversion (activity i n t l ~ ~otitained. \-) In gcliicral it may be said that the fixed-bed test method descrihcd i n this paper doe9 not give results of high precision, but it has 1 1 ~ ~ c,st r i rc,niely usrful and has contributed a great deal to the devrlopnic~nt of ctatalytic cracking. The emphasis has been on rapidity i n ordrr t o survey a broad and extensive field. The need
1143
for improved precision for a inore intensive study of certain f:ic+tors has become a prime consideration in the continuing dcvelopnient of cracking test methodq. LITERATURE CITED
(1) Brunauei, S.,E m m e t t , P. H., a n d Teller, E., J . Am. Clhe7n. A M . . 60, 309 (193s). ( 2 ) C s r l s m i t h , L. E., arid Johnson. F, B . , 1x1).EXG.CHEM.,37, 461--5 (1945).
( 3 ) Murphree, E. I-.,Blown, C . L., F i d i e r , H G. M., Gohr., 1;. J., and Sweeney, X. J., I b i d . , 35, 76s-73 (19431. (1) Murphree, E. I-.,Gohr, E. J., and Brown, (1;. L., I 7 d . . 31, 11K1 (1939). ( 5 ) I-oorhie-. .Ueuis, Jr.,Ibid., 37, 31s-22 (1946). PREYESTEI) before t h e Division of PeLroleum Chemistry a t t h e 110th hlrc,t ing of the .LXERICAY C H E X I C SocrE-ri-, ~L Chicago. Ill.
Composition of Rosin Size Precipitate OCCURRENCE OF ALUMINA D. PRICE Hercules Powder Company, Wilrnington 99, Del.
A
nietlioc1 for deterniining alumina i r i wet rosin siae precipibte floc has been deieloped and applied. Its ube showed that a 5tandardized size precipitate contained no appreciable amount of alumina; this demonstrated that the aluminum ion, rather than alumina, was necessarj for the formation of an efYecti\e rocin size precipitate. It was also shown that an) ewe5s alkali introduced into the paperinahing sjstem reacted with alum to form alumina, which coprecipitated with the rosin &e.
M
A S Y cotiflict,ing opinions exist at, the present time bot,li i i i
the theory and in the practice of papermaking. One unanswered question of importance in this field concerns the roles oi' alumina [hydrated .41203or .ll(OH)a] and the aluminum ion in the fomiatioii and performance of an effective size precipitate. h n outline of the literature concerning alumina in t,he sizing system was pit:parcd and briefly discussed by Collins, Davis, and Ron-land (4)in 1941. To obtain a general view of the present status of opinion, recent conclusions mill be listed briefly. Collins et al. ( 4 ) , from thcir study of ranges of complete precipitation of alumina and/or rosin, favor the view that the rosin size precipitate is a coprecipitate of alumina and rosin rather than a precipitate of a compound such ~5 aluminum resinate; this seems also t o be the view of Booth (31.lIiller ( I f ) and Redd (Is),on the other hand, have concluded that the aluminum ion, rather than alumina, is necessary for the formation of an effectivc size precipitate. Miller and Booth both advocate the use of more, rather than less, alum than is current practice in papermaking; Price and Cameron (fa). in older t,o improve sizing, advise reducing the amount of alum is used in many cases. [Papermakers' alum, AL(SOa)3,18H?O, designated a? alum throughout the paper.] Thc piwent work shows that alumina, as .ll(OH)3, is not a part of a standardized size precipitate (defined in a later section), and that it is therefore the aluminum ion rather than alumina which is necessary for the formation of an effective rosin size precipi t a t e. This paper represents a portion of a broad program, now in progress, designed to study the physical and chemical phenomena involved in rosin sizing of paper.
ANALYSIS FOR ALUMINA
The first step toward determining the role of alumina in the sizing mechanism coiisists of developing a method of analyzing the size precipitate for aluniina. With such a n analytical tool it ib then possible to determine a-hether alumina, as such, is a necessary component of the size precipitat,e, whether it occurs during some sizing operations, and under what conditions it appears. .in analytical method for determining alumina in size precipitate flocs has been developed and i3: fully described in a later section. h standardized procedure of preparing the precipitate from rosin size and alum was used to obtain a standardized size prccipitate for analysis. Of greatest importance to the fundamental knowledge of rosin sizing is the fact that the alumina determination showed the absence of alumina in such a standardized size precipitate. Figure 1 shows typical potentiometric curves. While the standardized size precipitate (curve 11) required more acid to reach pH 3.5 than did the distillcd water adjusted to pII 4.5 with alum (curve I), the form of its curve is quite distinct from that obtained wit,h an alumina suspension (curve 111). I n contrast to the rapid fall of p H with the addition 'of acid found for the standardized sizc precipihte, the alumina suspensions maintained their pH above 4 until practically all the floc had reacted with the acid. The pII then dropped comparatively rapidly; the point of inflection was located a t about pH 3.5. Hence Figure 1 illustrates the absence of alumina, as such, in standardized size precipitate. Curve I1 of Figure 1 is typical in form not only of emulsions ot size .1(70% solids, 207, free rosin) but also of solutions of size B (a dry neutral size), and was found whenever the precipitate was prepared in distilled water. Xoreover, distilled w t e r , adjusted to pH 4.5 with alum, contained no floc and showed no alumina by electron microscope examination. Since satisfactory sizing can be obtained n-ith these sizes on a neutral pulp with distilled water used as the papermaking water (141, it follows bot'h from the analyses and the papermaking that alumina [rli(OH)a] is not a component of standardized size precipitate. D a t a t o be presented show that sodium carbonate, sodium bicarbonate, and sodium hydroxide added to the size reacted. apparently quantitatively, to form alumina when the sizc was
1144
INDUSTRIAL AND ENGINEERING CHEMISTRY
,
0
I
IO
5
VOLUME
Figure 1.
.. . ... .
1
0
0.0496 N
5
+
.xLUMIS.I I S SIZE PRECIPIT.4TES FROM f i I C . l R B O S . % T E .-n-ere chosen to parallel conditions of the paper sizing study dc,?cribed i n a previous paper (22 Former n-ork on sizing in bicarbonate nt l i l \ V c . d tliiit t l l r ~ best sizing I W ~ac!iieved at a pullj sluri,y cordingly, prrcipitarrs were macle in t a p ivater, ailju.!id t o pH 7.0 17-ith sulfuric acid, to x-hich 12.5 nil. of 6.03'; sodium caron16 cases, 4.95 nil. of lo", calcium vliloritle n L \ i c Throughout this discussion allialine liar11wat(>w ionate ion coricrntration equivalcut to G O p w t a per million of calcium carbonate. G;rnrmlly aii ecluiderit amount o i r\. to day n-as con;idere.d the most iniportant uncontrolletl v:ii,i;ible in t l i i q ~irocedure. That thi. was not genc,rally serious c a n l i t rcyroducihiiit:; (of results on tliffcrcnt preparation^ -in vrror: tlie!; have been niiiitted from tlw a rest of the data slioned xu :wid requirement of 11.8 .\-sulfuric acid; the inaxinnmi variation from this value i v a q S r ; . Hence, size ptrcipitatr mads under these condition. i ' o 21.0 * l.O'.> .4ilOHjz based on the size or 17.4 0.!)$ t)
TABLE I.
Vol. 39, No. 9
11.9 (13.5)n (13.8)" 11.7 (10.7)O 11 6 12.0 11.5 11.9
Ppts in
Order of l'repn,
0.0jlC -1-Ilr.0, Required by 100-111 Pp' Suspension, 111.
9
11.6 Il.ti 11.8 11 3
(,
10 10
11
10 11 11 11 13
il.,
1" 0 1'' 1
12.4
Average
\-aluea i n pa:entheses omitted from average.
11 8
C ~ S C L C ~ I O S(.)S . 1method of anal-+ for alumina in rosin 4zc precipitate floc has been developrd. ( b ) Use of this method ~Iiow-cdthat standardized size precipitates contain no alumina. (c) Alkali introduced into the paperriiakirig system by n a t e r or jiulp will react xitli alum t o iorm alumina \rhich \vi11 be coprec>ipitatccl with the alum-size precipitate. DETER3113AT103- OF .ALUMINA l ' i , i w , i i 4 L opiiiiiiti~ or' the coriipo~irionof r o s i n sizc. p ~ ~ i p i r a: irt iei l , liL,tn.iorc,, ( l i t lic roles or' aluniiria :ititl ( I F aluminum ion i n .iring :iri- c~ciiifuaecli i c c i u q e no bati>f:ictory aruilyticnl method-: have. lieen :ivaiiiililc f o rlic' ~ dcrcrinination oi alurniria, aluminum rcsiiiates,
T
iesin acids. ab such, in the prrcipiratc ivliirh is formed. i.\Icthotls wported in the literature lor tht. btucly of tht. coiiiposir i , J n of the prt'cipitatcl c,oiisi>tetloi detelininatim.- of toral ash and ot ~(11vciit csti~uc.tiotis( 1 6 ~ . Later \!.orli \\-illcoii4tlei t h v effect of i] I ( * pi~c~svii(x of c~c~llulo~~;t* on the, 5ize prec,ipitatc' conipo+ition. The v \ i F t ~anwuf WCII :in c4hIc.t has hwii emphasized in Uialko\r~Iiy's \viit,i< ( 2 , \vliich p r e c d e d inore r t w n t studit.': oi hasc exc,Ii:irige r:ip:icity of cel1ulo':ic material. ] Tiit1 first effort ninde i t t this \ m i ;1 to tlvtc-rniinit :ilumiiia, uc:li, i l l the prewnc~cbof duniinum t~c~i113t i'i: aiid of resin acids hy x-ray studies. Various size Im(4pitatw. piepared at hrater concciitratiun~of .*in, and of alum \\-,>i'evacuuiii ciritvl arid exaniiiieci. T$y n'cre all aniol~p!ious, :iltliougti soiiiv i.ihibirzd a halo :it j . 8 -1. .I .s.aniplc of aluniina \v:I> then prvpwcd by adding alum to a 0.0133c; soiliuni car1)oriate ~ ~ J h t i l JLO l l a pH ~i 4,s. (This solutiuu is eyuivaloiit in coticcntration to 3.Orc size 11 d on pulp ~ t 2.scb " cunaistency.) The pwcipitate was filteied off, \ra+heci free of sulfate [tiarium chloride teat) \\ it,h 0.01 .I1 amnionium liydroxide, and dried in a vacuum tlwiccator. Tllis aluriiina sample \\-as completel? aniorphous by x-ray c~saniiti:ition and showed only one fairit line by elrctron diffraction. It seems quite likely, thereiorcs, that any alumina preserit in size precipitate nil1 be amorphous arid not detectable by these physical means. Refractive indices t w r e equally ineffective for this analysis.
:itit1 r'i.cc\
DET-ELOIWXST O F TITRATIOX SIETHOD. The difficulties of quantitative titration of aluminum salts rvit,h alkalies are well know) 16). Bom- of the difficulties are introduced by the heterogeneity of the reaction mixture and by the characteristic surface
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
September 1947
pri>pc~rtiesIJ~' t l i t , aluniiiia iormeci. E'or ti titintioii i ) f aluniiiia r a lioniog~~riewith acid, lion.clvi,i, tli(1 c ~ n c lpoint \\-onld i i i ~ u ivith ous systc.rii. I t \\-astherefore decid(d to attcSni1)t a titration i i i dilute aluiiiiria suspeiisioiis n i t h dilute staiiclarti acid.. A f t c ~ r each addition of acid the misture was stirled uiitil tlw pH \vas constant: this meant 2 hours in some and days in others:. A rapid titration \\-as imposible and Id give nii~aningli~ss curves. since tliv reaciiori n-as not complete until an apprc'ciablc tirile after the acid had been added. :iluiiiiiia suspcn-ions n-ere prepared by adding alum t o a11 a i i i rnoiiia solutiou of pH 10 to obtain a pH of 4.5. H;andardizcd size precipitates \\-ere prtlpare(l by adding 25 nil. of 3r; size .I f7Orc total solid.;, 2 0 5 ii,ec rociiij t o a liter of distilled water and atldirig alum to p H 43. h 100-ml. sample of suspension was used for the titrations, and 0.05 S arid \vas added in 1-nil. portionz. The susperi>ion n-as stirred vigorously throughout the determiiiation, and the steady pH \vas recorded Tvhen it n-as attained after each acid additiciii. S o t 0111)- \vas the reaction slo~v,but attaiumcnt of ecjuililxiuiii of the glass electrodes of the Becknian iridustrialn i o d c ~ l pH meter with the suspension required an apprecial,lc length of time; occasionally the electrodes had t o he rleaiietl x i t h acid. Consequently, the curves of Figure 3 portray tleterniiiiation3 ivhich extended over a period of days. C'urves I11 and 11- of Figure 3 shon that the aluniiiia suspcnsions inaintairied their p H abo\-e 4 until practically all of the floc had rciictetl with the acid. The pH then dropped coniparativcly rapidly; pH 3.5 seemed to he the point or' iiiflectiori. TIit.~t> curve) are quite different from those reported bj- D a t t a (5')f o r alumina sols. His curves -honed nothing corresponding t o tilt, point of inflec>tionat pH 3 . 5 . -111 the titrations or' Figure 3 w r v carried out with 0.05 S sulfuric acid, except for curve IT-in ivliich hydrochloric acid was u?ed. .Ilthough curve 1- shon-s, for :i su-pension of the amorphous alumina prepared for x-ray esnniinat ion, a behavior very similar to suspensions in ivhich tlie alumina h a < not bcen dried, subsequent preparations of dried alumina. cxhibited iniolubilizecl portioii. of the material. Hericc~,t h e tit.terminations have been appliid unl>- r o \vet flocs and t o t h > e ot' less than two \reel;,.' agr. In C(Jlltr& to tlic curve.. oi aluniiiia, cu titratii)!i of distilled \vater a t l j u s e d with alum to pH 4.5. C'LUYY I1 ii for a staudard iize precipitate; n-liilc it required iiiorc acid t,) reach 11113 . 5 than did the control, the form of its c u r v e i- quirt. distiric,t froni tlint of t h e aluniiiir curve. Curve 1-1s l i o ~ st h r an ai,: ificinl mixture of S O r nluiiiiria suspension :mtl S o r i a i z t , prec~ipitntc~ su~peiiuionrequired slightly iiiorc than half tlit: :ici!l deiiiatlc!i4 by :til equal amount of alumina ,su..pciision. Tliiwoul(l \)e c s p c ~ c t c ~irolii l th(s acid requirement. -hon-lr by (turvc' 11
1145
1
0'
4.5
Figure 2 .
5.0 5.5 6.0 6.5 7.0 ADJUSTED p H OF BICARBONATE HARD 'WATER Ca(HCO,)z 450 PPM A S C O C c ' 3
iluiiiina Fornied in Size Alkaline IIarcI Water
~ c d u r edetectoci sinall amounts of aluniiria.
7.5
ao.
:
in
Precipitates
t'i
ti
precipitate mixture KET-IsEu 3IETHOD.
Becauze these deteriiiiii
niumiiia suspendion mi- uiecl.
-Inexcess of C1.05 -1-
acid which priduces :i solution of pH less t i a n 3..; 1 1 t .I' i,eaction is adccluate. In general, 311 excess to give pH 2 . 5 I The mixture vas allc,\vetl t o staiid overnigh>, a l t l rimci may tie u$ed iii most cases. ani1 then back-tit \\-ith 0.05 -\- sodiuiii llydroxidi>. The equii-dvr iiicttiods nitiy be illusirated by the folIo\\-ing 1J.pi. II ~l~-vriiiiir:~tiiins o n 10O-iiil. portion3 of the w i i e alunii!in .>\I (if
1.3: V u l . 0.0494 S H&Oa t o attain pH 3 5 , 1111. \-ul. contrul (100 mi.distilled water plus alum, pH 4 51, \-ol. acid required by alumina present, ml.
0.0316 Z HzSO4 r-ed
by 100-311.
Size Ppt Suspension, 1\11,
...
,3 0 4 i
1
t)
J
I 1
,2 0
6.0 6.5 i.O 7 3
Control (standardized size ppt.)
1 i
...
4.65 5.32
1.03 1,i?
7 ' i+
3.54
10 6 J
7 5 8 0
0.0316 .Y H?SO, Required b y .iluniinn i i i Size I ? ~ I . .?ItOH)t,' Suspension, 075 G 1\11, Size, G .
...
16.60 19 23 2 0 . 48
i.05 12 00 15.63 16.88
2i.03 3,60
Oh
0 0138
0.0227
0:04&5
0.09~8 0,158 0 206
0 222
'l'iiiie required b y determination, days .?lrOH\3 .il froill in Total .?I(OHII 111 Size P l i t . , Total Size c Ppt., < 0 0 1.81 0.63 2.94
...
1.02 1,192,
5.83 11.00 17.4 21 .5
2.03
3.80 6.02 7.44
22.8
7.88
lS'i3
.... 0.218
24.8
8.15h 8.88
0.0
....
0
...
0
This adjustment frees C O I w-hich is not immediately lost irom s y s t e i u ; hence adjusted w a t e r s are n o t a t equilibriuni when used. b Interpolated.
I!>,+ 1 0
19.: i d .
0 2 1'10
I!#
~
18.4
0.67
The tvio nic~tlioili,tliercfore. agreed within ai),liit 3.0' ;-!ancl m u c h of this difference could have been intrliduci:cl I ,;>-t,\;tr:lntwns factors such as laboratory fumes, rinsing of vlei:trolh,.>,\ , t r , ,n.hich \\-(~uldaffect the 19-ihy determination. Hencxt.. r itl: reviscd method !vas used for the rest of the work. [This I imilar to a procedure used by Graham ( 7 ) in hydrous alumina sols. It differs in the nature t i t the starting inaterial and in the end point of the back-titratioil However, tlic principle is the same in both cases.] .Is had been indicated in tiie preliminary work. tlie relative amount of alumina in prepared mixtures of aluniirix ,trid size precipitate suspencions could readily be found. For s~ l i ,letcrminations the control used \vas the standardized size p r e !pirste at pH 4.3 rathrr than distilled tvater alunied to pIf 4.5. .I> intlicatcd in Figure 3 , the size precipitate consumed, probably l~yiiydi~ul wnrc of t l i c , arid which was added.
1146
INDUSTRIAL AND ENGINEERING CHEMISTRY
m
I
10
P
0
I
10
VOL. 0.05
w z
P
n
SUSPENDED I N D I S T I L L E D WATER
E
fore, inconclusive as to the product of the reaction; the intermediate pattern might be that of a basic sulfate or of a hydrate other than the common one of -U2(8S0,13. 1Iany other hydrates liave been nrent ioned, but their x-ray patterns arc i i o t available. An indirect method of deterniiniug the reaction product is thi,oi~ghthe acid requirement of a drfirritc amount of alumina. Thus :
I
I
o
0
20
20
IO
ACID-ML.
T t 5 0 M L SIZE PRECIPITATE SUSPENSION 5 C M L . ALUMINA SUSPENSION
m T A P WATER ALUMED TO p H 4.5
Vol. 39, No. 9
pm S I Z E PREC PITATE PREPARED IN PRESENCE OF 0 5gr4.n NlI2CO3 L.
+ 3fI.W, --e=\l,(dOl)i + 611.0 2Al(OH)j + PII,SO, + 2AI(OH)SOa + 1II1O 2A1(OII)I f &SO, + .11,(OH),SO? + 211,iJ 2A1(OH),
/
3.5
(1)
(2) (3)
arc ~oriii:p o 4 l ) l c nciictionb if t 1 1 1 3 basic sulfates shown ai'e solublc. IIo\vc~vt~r, the acid requirements art' (li.5tinctly I 10 0 0 IO 20 different, and all samples t i t i . w i c > t l inV O L . 0.05 3 A C I D - M L . dicate that thc rcaction is awording F i g u r e 3. P o t e n t i o m e t r i c Curves for Various Suspensions to Equation 1 (Table 111). .Anothc,r indirect method of establishing the reaction product wits used. CHEMICAL FORM OF ALUMINA To tict eriiiiiie the trinount of alumina present iu dilute suspensions as accurately as possible, 1-liter samples of the s u 5 Xlthough the method just described offers a fairly corivenient pension \vert uscd instead of 100-nil. samples. The f i r s t suspenway of determining relative amounts of alumina present, t I I P sion was prepared by adding aluni to tap water to pII 4.5, A absolute quantity cannot be determined until the chemical foi,iii control was prepared by adjusting the pFI of tap ivatcsr to 4.5 of the alumina, and its reaction w.ith acids, is known. hIellor ( 1 0 : with sulfuric acid. The 1-liter samples ircre first run i n duplicate lists a multitude of basic aluminum salts which various iiivwtigaIiy the revised method. The data obtained were: tors have reported; both soluble and insoluble sulfates are illeluded. Miller (11) believes that, the alumina floc :it p I I 5.4 i> 0.0912 s lirSOr the basic salt 5A1,03.3S03.4H20,and that AliOH i. is fornicd only Sample Required, AI!./Liter a t pH 8.7. Weiser et al. (19) report a n iirsoluble product of the ;\iiiniina floc suspemion 1 33.28 33.26 approximate composition .41,03, SOa, 1.5Hn0 \vliich l o s c ~no SO, Average 3 3 . 2 5 a t 600" C. and decomposes a t 700" C. This material \vas obtained froin aluminum sulfate solutions a t pH the hacniatosylin method ( 1 7 ) . The determination gave': recogniac!d by the specifications given here for the preparation
and nge of the suspensions. If .ll(OH)s is t,he skeletal formula for the initial material, then i t rexctu x i t h sulfuric acid to form A12(SO& or sonic: soluble basic ,+ulfate a t pH 3.5. Mellor ( I O ) mentions several such sulfates, and Xilson (20) haspatented thepreparation of 11,O:. 2S03. DEIL). \]-hen the titration (preliminary method) of the alumina suspcnsion was stopped a t pll 3.5 and the solutcs n-ere recovered by evaporating this solution, the solid material \?its amorphous to s-ray examination. After standing for 10 days, the material gave a faint x-ray diffraction pattern; after heating to 370" oi-430' C., its x-ray pattern was definite but, did not correspond to any in Hanawalt's catalog(1). K h e n the material !vas heated to 550" C., the x-ray pattern was t h a t of anhydrous .U,(SO,j,. : I sample of 1811z0shon.cd the x-ray pattern reported Merclr's C.P. A12(SOa)a. by H a n a a a l t for this h y d r a k . Upon heating t o 200" C., the niaterial became amorphous. Further heating to 430" C. conrertcd it to anhydrous .A12(S0,,)s. The x-ray evidence is, there-
Sample
.
Total AI
( H a em at oxy ii 11 Ale t hod), hlg./I,iter
Aluniina floc suspension 1 dupernatant liquor Difference, A1 in floc
31, 31 20,20 11
By these analyses, the aluniiiiuln in t h o aluniina floc i~niounts to 11 ing. per liter. This is an escellcrit agreement with the 11.7 rng. pclr litcr found by acid titration, on the assuiiiption of the formation of .i12(S04'i:,, in vieiv of the limitations of the colorimetric analysis. SUM~MARYOF fixri-mL)
X-ray ivork has shown that the alumina from a floc at pI'L 4.5 is aluminum hydroxide rather than a basic sulfate. (The x-ray evidence of hoehniite and, therefore, of AI(OH), ils thc initial
INDUSTRIAL AND ENGINEERING CHEMISTRY
September 1947
TABLE111. ANALYSISFOR
.\LT?MIK.4
ON i T S R I O U S
FLOCS
Alkali l-sed to
Alkali/Liter H 6 O a Required Milliequivahlilliequivalent (Milliequivalent t o Dissolve lent Required Alumina. hlilliby EquaSiae Alumina Required by a t p H 4.5 Equation l a ) equiralentiLiter tion 2 a Present 30.0C 19.7 Yes YaSC03 29,N K O SaHCOs 9.5d 9.7d 6.3 SaOH 6.S 6.9d 4.5 Y O SaOH 3.2b 3.1d 2.1 I’es XaOH 6.9b 6.9d 4.6 Yes NaOH 12.lb 12.3* 8.0 Yes a Equations: (1) 2AI(OH)a ~ H ~ S O ~ + . ~ I Z ( S O6Hz0: ~ ) J (2) 2.41(0€1) 2HsSO4 + 2.41(OH)SO4 4Hs0. b By t i t r a t i o n of alkali with standard acid. C I i y titration of suspension with 0.03 S H2S04, original method. d R y titration of solution or suspension Kith 0.05 5 IISS04, revi.ed method. Prepare
+
+
+
+
ni:tterial does not rule out the possible presence of basic salts amorphous to x-ray examination, in n-hich Al(OH), is present as a unit in a larger structure. For exaniple, Kohlschutter (9) propose5 a basic salt of the composition -ilC13.2Aii(0H)3. - k i d ir-ould attack such a structure with the removal of the alumina, and the presence of the normal salt \r-ould have no effect o n the titration. However, the analytical determination of Al(OH), as a chemical unit is attained whether thc initial material is in the complex or the simple form.) TT7hen such a floc has reacted n-ith sulfuric acid and therefore obtained a p H of 3.5, the product in solution is the normal aluminum sulfate. On this basis the revised method of determining aluniina in dilute suspensions and in the presence of size precipitate gives the absolute amount of alumina in the sample. I t may he used on fresh (aged not more than 2 n-relis) n e t prccipitates ( p H 4.5), and consists of adding a known amount of 0.05 sulfuric actd (in excess of amount required by the aluniina present) t o the sample, allowing 16 hours for complete reaction, and back titrating t o pH 3.5 with 0.05 S sodium hydroxide standardized against the standard sulfuric acid. T h e presence of materials other than size and alumina does not interfere unless such materials form a complex with alumina or show buffering action between thc pH values 4.5 and 3.5. K i t h thr
1147
proper volume sample and the use of proper controls the amount of .41(OH)3 may be determined as equivalent to the acid usedt,hat is, formation of normal salt-to xithin 5% or better of the amount of size precipitate used in this investigation. ACKNOWLEDGMENT
e
The m i t e r Tishes t o thank J. D. H. Donnay for the x-ray determinations, and the other members of the Hercules Experiment Station who contributed t o this n-ork. LITERATURE CITED
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873-82 (1943). (9) K o h l s c h u t t e r H. W., Kolloid-Z , 96, 237-$4 (1941). (10) Mellor, J. ‘X , “ T r e a t i s e on I n o r g a n i c Chemistry," I o 1 V, Sen- York, L o n g m a n s . G r e e n 8: Co., I IC., 1942. (11) \filler, L. B., P a p & T r a d e J . , 108, No. 2, 34-40 (1939). (12) Price. D., a n d C a m e r o n , D . D., P u l p P a p e r M a g . Can., 40, No. 3, 142-8 (1046). (13) ILzd., 40, No. 3 , 143-8, F i g u i e 2 (1946). (14) Price, D., s n d C a m e i o n . D . D., u n p u b l i s h e d work. (15) R e d d , J. C . , P a p e r T r a d e J . , 119, KO.7, 42-7 (1944). (le) R o b i n s o n , J. J., Ibid.,103, No. 7, 104-12 (1936). (17) Strafford, N., a n d W y a t t , P. F., dnalyst 68, 319-24 (1943). (18) T h o m a s , A. TI-.,a n d W h i t e h e a d , T. H., J . Phys. Chem., 35, 2747 11931). (19) Weisei, H. B., hfilligan, W.o., and Pureell, W. R., IUD. ENQ CHEM.,33, 669-72 (1941). (20) Wilson, W.S.,U. S. P a t e n t 2,323,409 ( J d > G, 19*3). pREsEYTED before t h e Division of C e l ~ u ~ o chemistry se at the 110th lreeting the . \ X ~ E R I C A KC H E \ ~ I C A T . S O C I E T Y , Chicago. 111.
Molal Refractions of Mononuclear Aromatic Hydrocarbons KANCE- CORBIS, ALARY =ILEXODER, -4sn Gb ST-41TEGLOFF l‘nirersal Oil ProdiLcts Company, Chicago, I l l . T h e molal refractions of nioiionuclear aromatic hy drovarbons are additi\e in a homologous series, and may be eypressed by a n equation of t h e form R = k + a n , where K is molal refraction, calculated b y either the LoreiuLorentz formula or t h e Gladstone-Dale formula, and ri is the number of carbon atoms. Constants a arid k habe been eialuated by t h e method of least squares for fourteen homologous berieq of mononuclear aromatic h ? tlrocarbons.
R E C E S T collation arid critical evaluation of data on physical constants (3) has made readily available all recordcd values for density and refractire indes of mononuclear aromatic hydrocarbons. These d a t a have been used to evaluate the effect of structure on molal refraction, which is both an additive and a constitutional property. I t cannot be predicted, therefore, unless the effects of structure are known. Molal refraction depends on refractive index, density, and molecular weight. For com-
paratiw studies molal refraction is preferred to refractivc index liecause of the minimization of effects of temperature and density. Molal refractions of aliphatic hydrocarbons for the sodium D line are additive within a single homologous series. For many serici of aliphatic hydrocarbons the effect of adding a CII, group is constant ( I S ) . The effects of structxre, such as incrc,nirnis in nioial rcfraction caused by branching and by unsaturatioii, have been thoroughly investigated and evaluated for alip1i:it ic hydrocarbons ( 7 , 8.13). Physical constant data for aromatic: compounds ai’e uot nt>arly so complete as those for the aliphatics. Th1:y are, 1ion.evc.r. sufFicient to permit evaluation of the relation bet ween molal rt~i’raction and the number of carbon atoms for fourteen homologuu mononuclear aromatic hydrocaarbons. CALCU LATIOS S
Molal refractions have different numercial values, depending on how they are defined. The different systems are internally
