638
INDUSTRIAL A N D ENGINEERING CHEMISTRY
impossible to recrystallize this salt from boiling water without regenerating a considerable amount of alizarin. While this interesting property showed the pyridine salt to be probably too sensitive for dyeing operations, the alkali salts showed no tendency to decompose at temperatures requisite for dyeing or padding. Oxalic acid proved to be capable of hydrolyzing the alkali salts of the ester under conditions which would not damage the cotton fiber. Apparently the first reaction is the formation of the free ester acid which, being very unstable in the presence of water, decomposes a t once into alizarin and sulfuric acid at higher temperatures. In applying these observations the &st difficulty encountered in using the pyridine salt was its poor solubility in water. This could be offset by the use of an excess of pyridine, but even then, as was to be expected, the alizarin preparation decomposed in the boiling dye bath before it was fixed on the material, so that the color utilization was very poor. On the other hand, a padding process using material prepared in the usual way with calcium and aluminum salts was successful. The first experiments (A) with pyridine salt, without the addition of oxalic acid on material padded with calcium and aluminum salt, were not successful because the calcium and aluminum salts of the ester were formed in the agar before the ester had hydrolyzed. These salts, once produced, would not decompose at the temperature of aging without the action of an acid. Being a dull red, they impaired the brilliance of the shade obtained. Though they could be removed by a thorough washing of the material
Vol. 20, No. 6
after padding, this method was obviously not economical, since a certain percentage of the alizarin was lost as the calcium and aluminum salts of the ester removed. This difficulty was obviated by using a process (B) based on hydrolysis with oxalic acid which decomposes all the salts of the ester a t higher temperatures, thus allowing the use of the very readily soluble alkali salts of the ester. This process gives a brilliant red equal to the shades obtained by the old methods of dyeing Turkey red with alizarin, yet the whole procedure does not take more than fifteen minutes. PROCEDURES ROR PADDING PROCESS-(A) The material, previously treated in the usual manner with aluminum and calcium salts, was padded with l t o 4 per cent solution of the pyridine salt which contained 2.5 per cent pyridine for each per cent of dyestuff. The material was dried and a yelloworange color obtained. The alizarin red was developed by heating the material in a Mather Platt apparatus for 10 to 15 minutes at 2 atmospheres pressure. In order to obtain a brilliant and clear red, the material had to be washed very carefully with hot soapy water to remove the non-hydrolyzed and insufficiently fixed calcium and aluminum salts of the alizarin ester. (B) The material, impregnated with calcium and aluminum salts in the usual way, was padded with a cold solution containing 3 to 5 per cent sodium or potassium salt of the alizarinmonosulfonic acid ester and an equal amount of oxalic acid. After drying, the material was treated in the Mather Platt a t 110" C. for 10 to 15 minutes with fairly dry steam. Brilliant and clear shades of alizarin red were obtained.
Acknowledgment
The writers are indebted to E. Schwenk for assistance with some of these experiments.
Solid-Solution Formation in Mixtures of Paraffin Waxes' Latimer D. Myers with Gebhard Stegeman UNIVERSITYOF PITTSBURGH, PITTSBURGH, PA.
This investigation deals with the formation of solid solutions of parafin waxes and the infEuence of this poperty on the separation of oil and wax ARAFFIN wax is a mixture of hydrocarbons and does not have a sharp melting point. I n order to study the effect of one constituent of a wax mixture on the properties of another, it was necessary to obtain at least two fractions of reasonable purity. Fractional distillation appeared to be the only method available for making such a separation. Preliminary distillations using an apparatus similar to that used by Francis2 on waxes having melting points of 42", 50°, and 55" C. indicated that the proportionof high-andlowmelting constituents was approximately the same for the different waxes, and that no advantage could be gained by separating the low-melting fractions from one commercial wax and the high-melting fractions from another. They further suggested that the differences in the melting points of commercial waxes are due largely to the differences in oil content rather than to differences in the composition of the waxes.
P
Distillation of Paraffin Wax
The preliminary experiments indicated that sufficient quantities of fractions of high and low melting points could 1 Received February 8, 1928. Abstract of a thesis submitted t o the Graduate School of the University of Pittsburgh, February 1, 1927, by L. D. Myers, in partial fulfilment of the requirements for the degree of doctor of philosophy. 2 J . Chem. Soc. (London), 181, 496 (1922).
be obtained only by repeated fractionation of a large quantity of paraffi wax. Accordingly, the apparatus shown in Figure 1was devised. The distillations were conducted a t 0.1 111111. pressure. The pressure was measured by means of a McLeod gage and was maintained by means of a n oil pump. The fractions were introduced through the 250-cc. separatory funnel and were removed by means of the special receiver without in any way interfering with the continuous distillation. The distilling column was packed with broken antimony, which appears to be superior to the glass beads generally used. The distilling column was covered with an asbestos sheet and a resistance wire wound upon it kept the column a t a temperature somewhat below that indicated by thermometer No. 1. SoLidification of the paraffin distillate in the outlet tube was prevented by the use of a radiation heater. The distillations were carried out a t the rate of twelve drops of distillate per minute. At this rate approximately 150 hours were required for a complete distillation. If the rate of distillation were increased, the temperature a t which the distillate was evolved would rise from 5 to 10 degrees. It is probable that when the distillation rate is increased the material in the distilling flask is subjected to a slightly greater pressure due to the greater concentration of vapor present. This would cause the temperature of the distillation
t o rise nritl licnce nltcr the coniposition of the vnpor k i n g cvolvctl. Unlcss t,liis coiitlition wcrc corrcctctl in tlic distilling column, tlic vapor c~~olvccl froin tlic flask woriltl not Iinvc the vnii~ccompositioli ns tliirt protlriccd :tt tlic siiinllcr I ' I L ~ C . Coi1ipu:iIilc rcsrilts c*ouItl oiilj. IN obtniiietl i\.licii n riniform I X t c of tlis t i l l t i t ion W I S tiiriiri t iiiricd,
U
Siiic frnction:itioii:: w i ' c ' clirrirtl oiit on 2384 grtiriis o f rcinitiicrcinl pririiffin \vas li:i~.iiig :i iiicltirig point of %5' C. 'l':tl)l(~ I slio\vs: (1) tlic i\*ciglitsof tlic \xrioris frnctioiis 011t:iinctl during t11e nine frnctionnticms; ( 2 ) tlic pcrccntnp ol tlic pirnffin i v n s fount1 in cncli f r w t i o t i nftcr tlic ninth f r x tiomition. Jxisctl o i i tlic ivciglit of thc ririgiid w n s ; (3) n Cornprison of t h c x \~nlucsi v i t l i tlicisc o1)tniriccl by Frnnris :iftcr tlic tn.cnt,y-first, frnction:itioii. 'l'hc rcsults indicintc! tlint tlicrc is n colisiticrnblc siinihrity i n tlic ctinipoaition of pnrrifliri uxsw iron] cntircij. tliircrciit .sliri\v c\'cn gmitcr
son1c of t h ! rr:ictions wcrc redistillctl nntl the frnction boiling bct\vccn 165' nntl 1GO' C., n i i i o u n t i n g to 360 grnriis, wn,s coliectctl :mdtlcsifinntetl ns lvns A. ?‘lit frnction boiling bctwccn 155" nnti 1 8 5 " c. wns collcctctl n n cl tlcsignntccl ns ivns 13, Investigation of Wax hlixtures
Gurwitscli31ins csprcssctl t 11c o 11 inion t1i:it p a r n f f i n w n s pro1):ihIy csists :is a .wlitl solution of liytirncnri)niis, brit no c~.itlciiccnppc:irs to 1i:ii.c bcon prcscntc(l
tlint csist in Iiiisttircs of \vi~scsol' tliffcrc~itmelting points. Accorcli~igly,n wries of rriisttircs of tliffcrcrit Jm~)O~tiOiiS of w i s t i nntl W:LS 13 wns prcpircd. 'l'licsc iiiistiircs u'crc iiicltctl i n n l:irp! tcst tiilx? and iiIIo\vcd to cool slun.ly. l'hc tciiiper:~turcs:it wliicli crystals nppc:irctl in tlic iiiclts coiiltl 1 ) ~ rtvitlily nsccrtninctl. 'I'licsc tciiipcr~itiircs,hciiiji cli:irnctcristic of cncli riiistrirc, furnislictl tlic t1:it:i frmi \vIiit:li tlic iippcr ciiri'c i t i Figrirc 2 iviis constritctcrl. .Ari attciiipt wns in:itlc to tlctcriiiiiic tlic compositioii of tlic crj.stnls wliicli ivcrc tlic first to nppcni*. l'licy wcre i.c~iio\.ctlfrorn tlic ~vnllsof the t c s t tribc nntl tlicir composition w : i , q rlctcrmincrl IIJ, ii>c:imof n %ci,wimincrsion rcfrnctonictrr, which ux.: cqriippcrl with :in aiisilinry prism so that only n siii:iIl qii:ititit!* O f tlic crjrstnls \vas rcqiiirctl to ohtniii n rcding. Ilo\vc\.cr. tlic w t i i n l compositioii o f thc crj*st:ils could not lie ol~tniiictlby tl!is iiictiiotl, owing to tiicir cont:iininntion I)y tlic liqiiitl iroin \vliit!li tltcy Iind sepnr:ttc(l. 'Tlicsc cspcriIiicrits tiid slinw, Iio\vcvcr, that tlic composition o f tlic crystnls tvns \.Liridh :~tidtlcpciitled on the composition of tlic origiriiil niistur.~frnni ivliicli tlicy lint1 r;cpnr:itcd. Sricli 1,cli:i~~ior is cliornctcristic of solid ~oliitions. 111 ortlcr to tlct C 1'111 i 11 C tllc CfJlllpoqition of tlic crystnls tlic coolingc l i r \ ~ c I1lCtliOd \v:ts clliJ)1O\'Ct~. 'I'Cll griiiiis of n niistiirc of k i i o \ v i i coiiiposition ivcrc plr.rcccl in :in S-inch (20-cm.) test tulic, wliicli \vns iiiiiiicrscd in n liter i m k c r of liot Ivntcr. The wntcr bath was nllonccl to cool nt t h e r:itc of nbout 0.5" C. pcr tninute. Aftcr cryvtnls begnn to nppcnr the tcinpcrnturc rcm:iinctl fxirly constnnt, dcvrcnsing a t tlic rntc of a p p r o sirnn t e l y 0.1' C. pcr iiiinutc. Mtcr 20 to 30 iiiiiiritcs tlic mtc of ccioliiix nfinin iiicrcnsctl.
intiicntcti in Fipurcs 2 :ind 3 ,suggests tlint ~ n misturcs s form :I complctc scrics solid solutions, tlic frcczing points of lv!iich lie Ixtwccn :lie ircczing points of tlic components. This iiiny csplnin thc lnck of n tlefinitc niclti:ig point for pnrnffin n'ns csclusivc of tlic cffcct of oil cont:imin n t'ion. Investigntion of Oil-Wax Mixtures
K y n n t b hns reported tiic rcsults of somc scniicommcrcinl sncntinyc opcrntions n 1 i i c I i iiitlicnted tiint tlic grcntest loss in w s i n tiic sn.c:iting proccss occurred nt tlint tcmpcr:iturc nt n i i i c l i most) uC thc oil ~ v n s rcniovctl, nnd t,Iint tlic loss incrcncct! very rnpidly d t c r n ccrtnin temp c r n t u r c Iiiid bccn rcnclictl. l'lic f x t o r s g o v c r n i n g this loss wcrc not dcfinitcly dctcnnincd. although it was k n o w to be tlgc t o the soliihility of tlic w;ix i i i tile oil. 'Yhc in\;estiption of tiic o i l - n n s misturcs WLS cnrricd out to dctcrminc tlic intcrsoluLility of v n s nnd oil 2nd to tlctcrminc, if J 7 0 5 S i b 1 C , \vlicthcr oil nntl pnrnf!in wns arc cnp:ible of f o r m i n g solit! soliitions. Tlic fnlloning mist.iircs were prcpnrctl: (1) oil ant1 wns I3; ( 2 ) oil nritl i v n s con-
hnvc bcen arrnngcd to shorn the weights of different w n m soluble in 1 gram of oil a t different tempernturcs. It can bc sccn thnt thc solubilities of the WRXCS i n oil nrc rnthcr low up to nbout 10 tlcgrccs l~clow thcir melting points. This is the cnsc both for pure waxes nnd for niisthres. The increased solubility nt high tcmpcrnturcs accounts for the grcnt loss in wnx in thc lntcr stngcs of thc swcnting proccss. An nttcmpt wns mnde to dctcrrnine the compositions of thc solid phnscs scpnrnting from the fused was-oil misturcs by nnnlysis of the first crystals t o scpnrntc, using tlic rcfrnctomcter. Contnminntion of tiic crj-stnls by tlic liquid, lio~vcvcr, inncic this iinpossiblc. The cooling-curve mcthod could not bc 11sct1,ns tlic brcnks in tlic ciirvcs wcrc vcry indistinct. Somc irisigiit into tiic composition of tiic crjstnls \vas obtnincd by n scrics of pressing cspcriincnts. 1V:~s-oil misturcs of compositions DO, SO, ant1 i o pcr ccnt T3 plus oil nntl 90, SO, ant1 70 pcr ccnt A plus oil wcrc rcpcntetlly prcsscd bct~vccn filtcr pnpcrs untlcr prcssurc of 3000 pounds pcr squnrc incii ('211 kg. pcr sq. a n . ) , until no more oil \vas rcmovcd, ns s l i o ~ ~Ly n tlic nnnlysis of thc prcsscd mntcrinl by mcnns of the rcirnctornctcr. Encli s:uiiplc wis prcsscd froin tcn to trinity tiincs before tlic oil content of t,lio \v:is bccnme constant. The prcssing ivns tlonc a t - 5 " C., nt room tcmpcrnturc (21" C.), n n d n t 43" C. .kt -5' C. from 4 to 5 per ccnt of oil ~ v n srctnincd by tlic n n s ; a t 21' C. from 2 to 3 pcr ccnt of oil was rctnincd by tlic ~ n s nftcr ; precaing nt 4 3 " C. no oil coultl be dctcctctl in tlic rvns. I t \vas nlso found tlint R wns to ivhicli 2 pcr ccnt of oil h : ~ lbccn nddcct could bc prcsscd witliout producing any oil spots on the filtcr pnpcrs. A \CIS contniiiiiig 2.5 pcr ccnt of oil protlrlccd rt tlccidcd oil spot. Sincc this oil is hcld so tcnnciouFly tlint rcpc.ntctl prcssurc of 3000 jioiln(ls pcr srjiinrc inch (211 k g . pcr eq. ern.) fnils to rcrnovc it, nntl siiicc tlic ninoiint r c t n i n d is influrnrcd so :iinrkctlly by the teinpcrnturc, it is Iiiglily probnblc t.lint tlic oil is rct:iinctl i n tlic forin of n solid solution rntlicr t l i n i i incrcly by incclinnicnl ndmixturc. TIE fnct tli:it the oil can be rcniovctl only nt :! tcnilwraturc slightly Ixlon. tlic melting point of tlic wis riiny nccuunt for tlic ncccssity of cmploying R cniiip:~rntivclyI i i ~ I itciiipcrnturc in cnrrying out the sn.c:lt,inp opcriition. 'I'liis in t i i r n csplnias tlic loss i n wis in tlic proccss, :u tlic solubility of t.lic was in oil incrcnscs very rnpitlly with n n incrcwc i n tcinlmxturc. Conclusion I ~ i s t i l l n t i i ~ or ii
lnr:ifTin
i v : n sliows
that:
( a ) I'nrnfiti wnxcs from tliflcrccit sm~rccslinvc vcry similnr cotiil)osi tiotis.
Julie, 1928
I S D U S T R I A L ASD EAYGISEERISG C H E M I S T R Y
( b ) Differences in the melting points of commercial paraffin waxes are due t o differences in their oil content.
Investigation of the wax mixtures shows that: (a) Paraffin waxes form solid solutions. ( b ) The melting points of r i e solid solutions lie between the melting points of the compor ents. ( c ) Owing t o the existence of solid solutions, paraffin wax does not possess a sharp melting point.
The investigation of oil-wu mixtures leads to the following conclusions: (a) The solubility of paraffin wax in oil increases very markedly a t temperatures appr3ximately 10" C. below the melting point of the wax. (b) The IoMT-melting waxes are more soluble in oil than the high-melting waxes. nlixtures of high- and lcw-melting have solubilities intermediate between the solubilities of the components.
641
( d ) The increase in solubility of the mixtures in oil a t temperatures approximately 1C" C. below their melting points is as marked as in the case of pure waxes. ( e ) The marked increase in solubility explains the loss of wax in the later stages of the sweating process. oilcin f ) wax Paraffin wax apparently retains oil as a solid solution of (g) The wax retains approximately 2 per cent of oil a t room temperature, but the amount retained a t the temperature a t which the final sweating is carried out is too small to be detected. ( k ) The presence of this small amount of oil in solution offers an explanation for some of the difficulties encountered in the separation of oil from wax.
Acknowledgment -
The authors n-ish to acknowledge the aid of TIT. F.Faragher, who was associated with the lIellon Institute of Industrial Research a t the time of this investigation.
The Viscosity-Gravity Constant of Petroleum Lubricating Oils' J . B. Hill and H. B. Coats THE ATLAKTIC REFINING COMPASY, PHILADELPHIA, P A
ITH t h e present From data previously published on the physical ciple was used by Burton3 in properties of the viscous fractions from various types defining the s e r i e s of oils diversity of of crude petroleum, a mathematical relation has been which he obtained from prescrude p e t r o l e u m s and corresponding diversity worked out between Saybolt viscosity and specific sure-still tar, and for which he derived the expression gravity. The relation is a logarithmic one and exof lubricating oils made from presses the specific gravity in terms of the viscosity them, the simple classification o'51cc2+ '06" - 961x betrl-een paraffin-base alld and a constant which is different for each crude and is 2 9 ~ 2- 2 4 4 ~- 53296 = 0 n a p h t h e n e - b a s e oils is no characteristic of it. This "viscosity-gravity constant" is low for the paraffinic crudes and high for the naphThis equation is e x t r e m e l y longer a d e q u a t e . It frecumbersome and no attempt thenic crudes. Its value for any oil is a direct index quently becomes desirable to of the degree of the paraffinic or naphthenic character was made to correlate with it indicate the degree to tvhich a similar equations of oils from particular oil or group of oils which it possesss. other sources. is paraffinic or naphthenic -4 simple graphical inspection of the data on viscosities When one oil only is concerned, it has been custoqary to specify both the gravity and viscosity in order to define it, and gravities of fractions from any one crude indicated that since it has long been recognized that for oils of t.ie same they could be plotted as a straight line on semi-logarithmic viscosity a low specific gravity (high A.P.I. gravity) indicates coordinates, or that the curves conformed to the general a paraffinic oil, while a high specific gravity (low A.P.I. formula gravity) indicates a naphthenic oil. Where it is dekirable G =a blog ( V c) (1) to talk about a group of oils from the same type of crud? but where a, b, and c are constants, G is the specific gravity a t of different viscosities, the matter has not been so simple, 600 F. (15.60 c.1, the Saybolt viscosity at 1000 F, since it would be necessary to specify the particular gra Vity (37.80 c.1. A determination of the tilree for the for each viscosity. optimum plotting of the data for each of the crudes gave I n TOrk on the relation between the boiling points and values as shoTvnin Table I, It TT-illbe noted that the constant physical properties of viscous Oils,' the similarity between is identical for all the given crudes, that b (the slope of the the shapes of the various curves for fractions each series Of straight line) varies slightly, and that a shows a wide \.ariation. which was obtained from one sample of a different Crude, The jnsertion of these values in the gelleral expression gives appeared t o be rather striking. The same type of similarity 5 series of fi>y equations representing, respectively, the visis obtained when the specific gravity data from the above work cosity-gravity relationship betTveen the fractions from each are plotted against the corresponding viscosity data (Figure of five crudes. 1). Since these two properties are among the simplest to \LThile the equations thus obtained may Serve to define determine for viscous oils, an attempt has been made to work the fractions from any one of these givell crudes, they are Out a mathematical relation coordinating the viscosity and undesirable in that it is necessary to specify the values of tTvo gravity for the fractions of varying Tkosities for each crude, constantsin order to effectsuch definition. The calculations and to show the similarity and dissimilarity betn-een the Tvere ther?fore carried further in an attempt to derive an mathematical relations so obtained. The same general prinin Tvhich there appears only one constant which i S Characteristic Of the crude Source. It is h m e 1 Presented under the title "Relation between Viscosity and Gravity of Petroleum Products" before the Division of Petroleum Chemistry a t the diately apparent that the constant b bears, roughly, a straight74th llleeting of the American Chemical Society, Detroit, Mich., September line relationship to 51 and can therefore be expressed for most 5 to 10, 1927.
+
+
v
2
Hill and Ferris, IND. ENQ.CHEM.,17, 1260 (1925).
8
U. S. Patent 1,167,884CTanuary 11, 1916).
