The Chemistry of Wood IV. Water-Soluble Polysaccharide of Eastern Larch LOUISE. WISE, PHILIPL. HAMER,AND FLOYDC. PETERSON New York State College of Forestry, Syracuse University, Syracuse, N. Y.
0
N FURTHER investigation' of €-galactan of western larch (first reported by Schorger and Smith, 6), Wise and Peterson (7) established the presence of a pentose-arabinose-among the hydrolytic products of the galactan, and a number of quantitative determinations of arabinose and galactose indicated the presence of 11.95 per cent anhydroarabinose and 84.6 per cent anhydrogalactose. From the fact that these data account for over 96 per cent of the products of hydrolysis, and since no xylose, methyl pentoses, or uronic acids could be detected in the hydrolyBates, Wise and Peterson suggested, tentatively, that the polysaccharide might be a true arabogalactan, represented by the condensed formula [ (C5He04)(C~IIOO,)~],.Such a compound, on complete hydrolysis, should yield 11.9 per cent arabinose and 88.1 per cent galactose. This hypothesis is supported by the agreement in analytical data obtained from €-galactan isolated from two totally different samples of western larch. The investigation of the water-soluble polysaccharide of eastern larch [Larix Zam'cina (DuRoi) Koch] is in part a repetition of the work already carried out on e-galactan from western larch. This carbohydrate also proved to be an arabogalactan. I n physical properties the galactan from eastern larch wood appears to be identical with that from the western species. It is a white, amorphous, hygroscopic powder, easily soluble in water, and it is not precipitated from aqueous solution by lead acetate. Cuprous oxide, obtained by Allihn's method, indicated an average reducing value of 33.8 mg. of cuprous oxide from 0.500 gram of galactan. A 10 per cent aqueous solution of the galactan had a specific rotation [a]': = +13.02'. During the course of this investigation a greatly simplified procedure for galactan isolation and purification was devised. The limitations of the analytical procedures for arabinose and galactose have also been determined more fully. Determinations of arabinose and galactose indicated the presence of 12.0 per cent anhydroarabinose and 82.1 per cent anhydrogalactose in the polysaccharide. The study lends weight to the hypothesis that the polysaccharide is a chemical entity, rather than a mixture of an araban with a galactan, and that its distribution is not coniked to one species (2). The tentative formulation remains unchanged. Work on the constitution of the polysaccharide is in progress.
Several portions of the sawdust, weighing from 400 to 500 grams each (air-dry), were placed in 5-liter round-bottom flasks which were then filled with distilled water. Sufficient toluene was added to form a layer about 0.25 inch (0.64 cm.) deep over the top of the water. This prevented the entrance of bacteria from the air during the period of extraction. The flasks were allowed t o stand at room temperature for 10 or 12 days with frequent stirring or shaking. Subsequently the contents were filtered through several thicknesses of cheesecloth, and the residue washed with a small amount of distilled water. In several instances the extract was again filtered through coarse filter paper. Although the yield of polysaccharide from the cold-water extractions was presumably lower than when hot water was used, the lighter color of the extract and the simplicity of the procedure and apparatus required favored the adoption of this method in all subsequent extractions The extract was always concentrated under reduced pressure to avoid darkening The consistency to which the sirup was evaporated was largely a matter of personal judgment, based in later work on the effect of consistency on the subsequent purification processes. It was found, for example, that too high a concentration nearly always caused slow filtrations and was likely to result in the formation of gummy, poorly dehydrated masses of galactan even when the sirup was poured slowly into the alcohol. On the other hand, a thin sirup required much more handling as well as increased quantities of alcohol for precipitating and washing the galactan. Three methods of decolorizing the extract were tried: (1) by the use of tannic acid and lead acetate (6), (2) by infusorial earth, and (3) through partial precipitation by means of ethyl alcohol. The third method, which proved by far the most satisfactory since it gave a product with a lower ash content, was carried out as follows:
One liter of concentrated extract, which had been filtered through coarse filter paper and which represented the soluble portion of 1540 grams of air-dry wood, was slowly poured into 95 per cent alcohol in the ratio of 1 cc. of solution to 10 cc. of alcohol. The brownish colored precipitate which resulted was washed twice by decantation with alcohol. This crude galactan was then collected on a Biichner funnel, and dissolved in approximately 700 cc. of water, following which 300 cc. of 87 per cent alcohol were added with the production of slight turbidity. The solution was allowed to stand for several days in a refrigerator at a temperature slightly above 0 ' . During this time a small amount of galactan had settled out, carrying with it the coloring matter. The clear, almost colorless liquid was carefully drawn EXTRACTION AND ISOLATION OB POLYSACCHARID~ off, and the galactan precipitated as before. A perfectly white The aqueous extraction of the polysaccharide was accom- product, which settled out readily, was obtained. This was plished (1) by the use of hot water, and (2) by the use of cold washed several times with alcohol, and then with anhydrous ether, and was dried i n uucuo over sulfuric acid at 30' C. The water-i. e., a t room temperature. final drying was made at 105" C . The procedure and apparatus used in the hot-water extractions were identical with those described by Wise and The ash content of galactan pursed by this method varied Peterson (7). The extraction was stopped a t the end of 48 from 0.70 to 0.79 per cent. The average of five determinahours, and the various portions were combined and preserved tions indicated a reducing value of 32.7 mg. of cuprous from bacterial action by a layer of toluene. This method oxide from 0.500 gram of galactan, as compared with 39.2 always produced dark colored extracts. mg, for the same weight of galactan (containing 1.53 per I n the cold-water extractions, the following procedure cent ash) purified by the tannic acid-lead acetate method. was used: No effort was made t o determine accurately the yields of galactan from eastern larch wood, but in no case were they 1 Part I of this series wai published in IND. ENQ.CHEM., 20, 720 (1928) i as high as those reported for western larch. The maximum Part 11,I b i d . , 22, 362 (1930): and Part 111, Ibid., Anal. Ed.,3, 253 (1931). ~
184
INDUSTRIAL AND ENGINEERING CHEMISTRY
February, 1933
was slightly over 4 per cent, based on the air-dry weight of the wood. DETERhlISATION OF
FURFURAL
The general procedure outlined by Tollens was followed in the determination of furfural, with the exception that the phloroglucinol reagent was replaced by thiobarbituric acid as described by \Frise and Peterson ( 7 ) . All determinations (both on the original galactan and the hydrolyzed product) were made on material purified by alcohol. The results are given in Table I.
TABLEI. ANHYDROARABINOSE CONTENT OF GALACTAN CALCULATED FROM FURFURAL CORRESPONDING
Gram
Gram
Gram
Gram
%
0.0624 0.0644 0.0661 0.0894
12.4 12.8 13.3 13.4 12.2
0.0624 0,0629 0.0877
12.5 12.5 13.0 11.0
UNHYDROLYZED
0.5029
0.5019 0.4966
0.5172 0.5047
0.0770 0,0795 0,0817 0.0859
0.0761
0.0333 0,0344 0.0353 0.0371
0.0329
0.0617
HYDROLYZED
0.4972 0.5032
0.6746 0.5308
0.0772 0.0778 0.1083
0.0724
0,0334 0,0336 0.0468 0.0313
0.0588
HYDROLYSIS OF GALACTAN Four portions of the galactan from eastern larch and (for comparative purposes) one from western larch galactan were hydrolyzed with 2 per cent sulfuric acid for 7 hours d t 105" to 110' C. Three of these determinations on the eastern larch galactan were on material which had been purified and decolorized by means of alcohol, whereas in the fourth a product decolorized by the tannic acid-lead acetate method was substituted. Approximately 10 grams of galactan were used in each hydrolysis, and the required amount of 2 per cent sulfuric acid was added by means of a pipet. This made it unnecessary after hydrolysis to titrate the barium hydroxide solution used for neutralization, as the calculated amount of crystalline material required nearly t o neutralize the hydrolyzate could be weighed out and dissolved in the minimum volume of hot water. This solution was slowly added to the hydrolyzate with rapid stirring to avoid local overheating. The neutralization was finally completed with barium carbonate. After the neutral solution had been diluted to a standard volume (usually one liter) and the barium sulfate filtered off, the volume of the filtrate was carefully measured, and the whole or an aliquot portion was concentrated under reduced pressure. The concentrate was made up to a definite volume equivalent to approximately 0.0300 gram per cc. of the original polysaccharide for use in the galactose determinations, and slightly over 0.1000 gram per cc. for the arabinose determinations. The reducing value of a typical hydrolyzate was obtained by Allihn's method. Ten cubic centimeters of the solution, corresponding to 0.1000 gram of the original oven-dry ashfree polysaccharide, gave 0.2186 gram of cuprous oxide. Another 10-cc. sample gave 0.2161 gram of cuprous oxide. Assuming 12 per cent anhydroarabinose and 88 per cent anhydrogalactose from the hypothetical formula [(C6Ha04)(CsHioO&],, the theoretical reducing value of the hydrolyzed galactan was calculated. The values found by experiment indicated the degree of hydrolysis to be 98.1 and 96.5 per cent of the theoretical for the respective samples.
IDENTIFIC.4TION
OF
185
ARABINOSE
The presence of arabinose in the hydrolysis products of the galactan was shown by the formation of its insoluble diphenylhydrazone, with a constant melting point (after repeated crystallizations) of 198" to 198.5' C. (uncorrected). Arabinose diphenylhydrazone prepared from pure arabinose melted a t 198.5' C., and the mixture melted a t 197" to 197.5" C.
GALACTOSE AKD ARABISOSE I N KsOwN SUG.4R ~ ~ I X T U R E S
DETERMIKATION O F
A series of determinations was run on sugar mixtures containing known amounts of galactose, arabinose, and in some instances sucrose, in order to ascertain the limitations of the methods from the standpoint of manipulation and the effect of other sugars. GALACTOSE,In all quantitative determinations of galactose the van der Haar-Tollens method (4) was used, with the modifications suggested by Wise and Peterson ( 7 ) . The results of these analyses indicate that the presence of arabinose in an arabinose-galactose mixture does not affect in any way the interpretation of the figures given in van der Haar's table which is based on galactose-sucrose mixtures. In six analyses of known mixtures of galactose and arabinose, the percentage of galactose recovered, as calculated from the weight of mucic acid, varied from 97.4 to 102.3. In four experiments in which galactose-sucrose mixtures were analyzed, the percentage of recovery of galactose fluctuated from 91.8 to 100.5. In eleven analyses of known mixtures of arabinose, galactose, and sucrose, from 93.1 t o 98.9 per cent of galactose was recovered. The greatest source of error in individual analyses seems to lie in the slight unknown differences in conditions of oxidation, cooling, etc., rather than in the mere presence of arabinose. Evidently the method leaves much to be desired. A correction factor of 1.04, based on data collected from the analyses of the known mixtures, was applied to the analysis of the hydrolyzed galactan. This factor was derived statistically from the average percentage recovery of galactose in the case of twenty-one determinations. ARABINOSE.Here, as in the determinations of galactose in known mixtures, conditions were adopted similar to those which would be encountered in the analysis of hydrolyzed arabogalactan. The method employed was that of Neuberg and Wohlgemuth (6) as modified by Wise and Peterson (7).
The mixture of sugars (arabinose and galactose) was dissolved in 5 cc. of water and treated with diphenylhydrazine reagent, prepared just prior to use from 0.76 gram of carefully purified diphenylhydrazine hydrochloride and 0.73 gram of sodium acetate. Ten cubic centimeters of a 50 per cent alcoholic solution saturated with arabinose diphenylhydrazone were then added, and the mixture allowed to stand overnight. Subsequently the diphenylhydrazone was filtered off on a weighed Gooch crucible, washed with eight 10-cc. portions of the saturated 50 per cent alcoholic solution of arabinose diphenylhydrazone, and dried to constant weight a t 105" C. The weight of arabinose diphenylhydrazone multiplied by the factor 0.4747 gives the corresponding weight of arabinose. In one series of analyses the amounts of arabinose taken ranged from 0.0702 to 0.0922 gram. This represents approximately the range which might be expected in the portions of concentrated hydrolyzate used for arabinose determinations. The mean of seven determinations indicated only 90.3 per cent recovery of arabinose (with an extreme variation of 78.2 to 103 per cent).
I iX D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
186
In another series tlie arabinose content was increaied t o approximately 0.1500 gram as recommended by Wise and Peterson (7). The other conditions of the analysis were the same as in the first series, except that a slightly larger amount of reagent was used (one gram of the diphenylhydrazine hydrochloride and one gram of sodium acetate). Here the average of six determinations (fluctuating from 95.2 to 110.8) indicated a recovery of 101.1 per cent. It is apparent from these data that the percentage of arabinose recovered by this method is dependent in a large measure on the amount of the sugar present, owing presumably to a solubility factor. When the arabinose content is approximately 0.150 gram or is increased to this amount by the addition of the pure sugar (as in the case of the hydrolyzates), a correction factor becomes unnecessary. Here, too, the analytical procedure gives only approximate results, and the data must be handled statistically.
DETERUISATIOS OF GALACTOSE IX HYDROLYZED GALACTAN 4 number of quantitative galactose determinations were inade on hydrolyzed portions of the galactan, in which 30 cc. of the hydrolyzate (corresponding to approximately 0.9 gram of the original polysaccharide) were used for each determination, and the qame procedure was followed as in the analysis for galactose in the known mixtures. The results of sixteen determinations indicated an average anhydrogalactose content of 78.9 per cent. The corrected percentage (using the factor 1.04) gives a mean value of 82.1 per cent anhydrogalactose in eastern larch galactan (Table 11). TABLE 11. +~YHTDROGALACTOSE IS G ~ L ~ C T A N (Determined after h q d r o l ~ s i u ) .\VHl-
CORRF-
CORREDRT .\&H-
FREE
MUCIC
ACID
l\lCCIC
ACID
IICCIC
Ga~ac-
OB-
TLN
TAIXED
Gram 9721 9721 9721 9938 9938 9938 9938 9938 8964 8964 8964 8964 8964 8964 8964 8964
Gram 0.7275 0.7167 0.z130 0.,397 0.7725 0 . 7825 0,8038 0.7988 1.0489 1.0448 1.0611
ACID ADDED Gram 0.0992 0.0993 0.0992 0,0998 0,0992
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
1.0671 1.0670 1,0745 1,0749 1.0740
FROM
SPOSDISG
SPOSDISG
DRO~~~
GAL-LCT O S E IS
\TEIGHT ORIGIOF
X.\L
WEIGHT ANHY- G.LL.~cOF
DRO
T\N
GALAC- OALLC- G a ~ a c - (UsTOBE
Gram 0.6283 0.6175 0.6142 0.6399 0.6733 0.6815 0 .io35 0,6990 0.5716 0.5675 0.5739 0,5900 0,5899 0.5977 0.5975 0.5961
T O ~ E
TOSE
Gram Gram 0.8314 0.7483 0.8194 0.!375 0.8158 0.1342 0.8443 0.i599 0.8814 0,7933 0,8905 0.8014 0.1010 0.9150 0.8235 0.1003 0,9100 0,8190 0.0998 0 , 7 6 8 4 0.6916 0.4773 0,7639 0.6875 0,4773 0.7710 0 . E939 0,4772 0.,189 0.7988 0.4771 0.7887 0.7098 0.4771 0.7974 0.7177 0.4768 0 7972 0.7175 0.4774 0.7956 0.7160 0.4779 Average (uncor.1 .Iverage ( c o r . ) using factur 1.04
CON.)
% 77.0
75 9 75.5 76.5 i9.8
was required, the volume was reduced to 5 cc. by gentle heating on a steam bath. The results of ten analyses, in d i c h the calculated arabinose content was increased to approximately 0.150 gram by the addition of the pure sugar, showed an average anhydroarabinose content of 12.0 per cent. The average anhydroarabinose content calculated from the yield of furfural was 12.6 per cent. The agreement in the data obtained by the tjTo methods indicates t'hat the entire furfural yielding complex is due to the arabinose linkage. TABLE 111.
OSE
DRY
GAL\(-
PHESYLHYDROZOSE
OSE .%DDED
T.AS
Gram 0.5298 0.5298
FOCSD
Gram 0 0790 0.0754
0.5298 0,5298 0.5298 0,5298 0,5298 0,5298 0.5298 0.5298
Gram 0.3179 0 2936 0.3185 0.3402 0.3191 0 3244 0,3212 0.3071 0,3202 0.31'32
0.0805
0.0797
0.0814
0.0753 0.0809 0,0752 0.0804 0.0804
SPOSDISG
SPOZIDIXG
ARIBIN- WEIGHT ~~~
YEIGHT
OSE
ASHYDRO- I N A R A B I N - GILIC-
OF .\R.LBINOSE
GALICTAN
OSE
Gram 0,1509 0.1394 0.1512 0.1615 0 . 1515 0.1540 0.1525 0.1458 0 1520 0.1534
Gram 0.0719 0.0640 0.0707 0.0818 0.0701 0.0787 0,0716 0.0706 0.0716 0,0730
Gram 0.0633 0.0563 0.0622 0.0720 0.0617 0.0693 0.0630 0.0621 0.0630 0.0642
FROM
DROARA-
~~
BIKOSE
OF
T.AK
% 12.0 10.6
11.7 13.6 11.7 13.1 11.9 11.7 11.9 12.1
NETHOSYL ASD UROXICACID GROUPS The apparatus used for determining the methoxyl group by Zeisel's method was of the type recommended by the Forest' Products Laboratory ( 3 ) . Analysis of the unhydrolyzed galactan indicated a methoxyl content of only 0.25 per cent, which was probably due to impurities. Whether or not the arabogalactan molecule contains a small number of anhydrouronic acid linkages is still a moot question. By the method of Dickson, Otterson, and Link ( I ) nearly the same amounts of carbon dioxide were obtained froin galactose as from corresponding amounts of the arabogalactan under similar conditions of distillation with hydrochloric acid. This indicates that uronic acid residues are probably absent. In Table IV the data on eastern larch galactan are compared with those obtained by previous investigators on the arabogalactan of western larch. ' ~ B L EIv.
. ~ V E R A G E CO31PARATIvE D A T A ON L
~
~
~
DERIYED FROM ESTERS AXD KESTERX LARCH TTOOD
52.4 8 , . ?
DETERRIISATIOS O F ARhBIXOSE IN HYDROLYZED GAL.&CTAX Arabinose was quantitatively determined in the hydrolyzed galactan by the method already described. The concentration of the hydrolyzate was usually such that 5 cc. were sufficient for a determination. If more than this amount
DI-
.ISH- PCRE F I f ~ AR.ABIS~
82.9
h hydrolyzate of western larch galactan was analyzed for galactose by the same method. The average of six determinations showed an anhydrogalactose content of 79.3 per cent, which, when multiplied by the factor 1.04, gives 82.5 per cent. This value is 2.1 per cent lower than the mean anhydrogalactose content obtained by Wise and Peterson (who, however, did not use the correction factor in their determinations).
ASHYDROARABINOSE I N G.4LACTAT
(Determined after hydrolysis: arabinose content increased t o a b o u t 0.150 gram b y addition of pure sugar) .IR.ABISCORRECORRE- ASHY-
80.6
76.; 7i.4 80 2 79.2 80.1 so.0 is 9 i8 9 82.1
Vol. 23, 3-0.2
.\R.LROG
DIT.\
l-ield, %
Aeh, Yo Cul0 g e r 500 nip. galact a n , gram
[~12Do
0,74
o , 0327 +13.02O
.\nhydroarabino~e (furiura1 m e t h u d ) . 70 , 12.6 Anhydroarabinose (diphenylhydrazone m e t h o d ) , 70 12.0 Anhydrogalactose, 53 82.1 Carbon, % Hydrogen,
70
ILLCTkS
From eastern F r o m western ISVE?TIGITORS, larch larrli O F TT-, L.LHCH ,,-4 {&lo Schorger ITise and aPeterson n d Smith ( 7 )( 5 )
4 4 . 40a 6 . 31a
{
0.0359 0.0350 +12.113
Wise and Peterson
11.5 11.95 84.6 82.5
1
Wise a n d Peterson Schorger a n d Smith Wise a n d Petersqn Schorger a n d Smith Schorger a n d Smith
1
Wise a n d Peterson IVise a n d Peterson Hanier Schorger a n d Smith
9774hkurs Wise a n d Peterson Hydrolysis with H:JOI, 97-3 in , hours , 9 9 8. 0hours in 70 Schorger a n d Smith a Owing t o its marked hygroscopicity, t h e galactan x a s dried in C o\.er €'?Ob a t 100' C . prior t o analysis.
~ C U O
S U M X I R Y A S D CONCLUSIOSS
1. The mood of eastern larch contains a water-soluble polysaccharide having the same physical characteristics as the +galactan originally described by Schorger and Smith and more recently by Wise and Peterson. 2. The polysaccharide was purified by three different
i
Fcbruar>-, 1933
I N D U S T R I A L A N D E N G I S E E R I N G C €1 E 31 I S T R Y
nietl:ocl-. The pureqt product was obtained from extract; decolorized by treatment with ethyl alcohol. 3 . Quantitative methods of analysis for gJactose and arabinose were applied to known sugar mixtures. and variou' cnnditionb of the analyses vere investigated. 4. The arialysiq of tlie polysaccharide in( luded deteriiiinati~nqof ash, reducing value, rotatory power, furfural. aral iiiio'e3 galactoqe. methoxyl group, and carlion and hydrogen. .i Tlie poly-accharide n-as s l i o ~ nto be an arabogalactaii containing 12.0 1)er crnt anhydroarabinose and s'2.1 per ( eiit nnliydrogalactoie ti From the analytical data obtained, it i i probable that the arabogalactan froin eaqterii larch is cheniically the qanie :is that from western larch. 7 The agreement in data on +galactan iiolated from t $1o different specie-- of larch pointq favorably tonard the
187
liypotdiesis that this substance is a homogeneous chemical compound. 8. Investigations on the arahogalactan obtained from coniferous woods are being continued. LITERATURE CITED Dickson, Otterson, ani1 Link. J . A 4 ~ nC./ L P I RS o. c . , 52, 77; ( 1 Foreman and I h g l i s , ISD,ESG. ( ' H h x . , 23, 41;-16 [,19:31I . .Forest Products 1,aboratory Nethocls. Palm, Trade J . , 87, So. 2 3 , 59 (19%). 4 ' H s a r , -4.K.1-an d e r , "lnlcitiing z u i n h-arhw und Restimmung der reinen und aus Gluko tenen Monosaccharide und ~ ~ l i l e l i ~ i l s I i u r e 11. n . "124, Gclirii~lir Borntraeger, Berlin, 1920. (.j) S e u b e r g and Wohlgemuth, %. 2 h p i o l . f'hw!., 35,31 ilC302)). (Cj, Schorger and Sinirh, J . ISD. ESG. ( ' H E ~ I . 8 , , 494 (191(j). ( 7 1 \Vise and Peterdoll, I h i d . . 22, 302 (1930). R E C E I V E D -4UgUSt
2 5 , 1932.
EEec-t of Tetraetlhyllead on Octane Number L. E. HCI~L, T. B. RESDEL,
ISD
F. L. G ~ R T O K
IT-ood Rix-er Refinery, Shell Petroleum Corporation. FYood River,
I11
tionr. Thi- compound i ni o .- t An empirical analysis hus been made qf' the U R I S G tlie past few effective in small concentration.. years a large amount of relationship befueen the concentrut ion qf teiraand, as more is added to a gasolinc, its effect gradually diminishes. data on knork ratingi of ethyllead a n d ihe octane riuniher qf n gasoline, 3. The octane number of the \ arious gasolines coiitaining difbase gasoline tiefore tetraethyl lead and a rlejinition is deteloped f o r the "lead ferent quantities of tetraethylii added. susceptibility" of any gasoline. If i s shoiin that lead lias been collected by the 4. The lead susceptibility of the gasoline. the ociane number of an eihylized gasoline is a II t 11 o r s . Tlie earlier experi5.- The numher of cubic centinieiita were made on a Ricardo deelermined b y a combination qf fire disiiricf meters of tetmethylleatl adder1 E-3.5 type, variable vnmpresqion fuctors wltose proper r d a tionships are incorper gallon of gasoline. and tlie result.. of these ~wg~iie, poraied in a n Ethyl blending chart. T h i s chnrt Factors 1 and 2 are considered te-ts h a l e been described in a niay be u'pd f o r determining ihe lead susceptirelative to each otlier; the octane previous publication ( 2 ) . T1ie.e hi?ity of a gusoline from fhe ocfane numbers of numlier scale of the blendiiig eywimeiit.. brought out the fact chart, n.2iicli c o r r e s p o n d s trJ that, in addition to its antiknock lico b l m d s corifairiirzg different concentrations of 1, is a property of isoocfactor \ d u e , every gaqoliiie h a s a tefrnethyllend. Lead suscepiibilif ies of gasolines tane-heptane mixtures, and simiproperty n liich may be defined as mrLdeIroni rarioas crudes and by several processes larly the scale showing the conit. lead suwmtibilit\r and which are git'e7z. ceiitration of tetraet~ij.l~ead i. a detrrmines t,Eie a i n k n t of inproperty of t h a t (> o n i p o u ii d , rrease in antiknock value for any piven concentration of tetraethyllead. Tlie resi-ilts reported Tlieqe two factor. ilia>-be modified by varying the coiiditioiiiirrewith form a continuation of the above work using the of test. Factor' 3 and 4 are properties of the gasoline t o be etliylized iimi-ly standardized form of reporting ailtiknock values in terms of octane number as determined on the C. F. R . engine. and therefore need to be determined separately for each -1nalysis of t'he results of ant'iknock tests on et hylized gaso- gaqoliiie. In the case of blend; made from gasolines who-e lines leads to the conclusion that there are five distinct factors octane numbers and lead su.ceptibilities are kiio~vn,t h e v values may he calculated for the hlends n i t h fair accuracy. n liicli, together, are sufficient to determine the octane number (if' aii ethylized gasoline. Factor 5 may be tlie arbitrary variable, or, iu the inanu11s constructing a special chart, 17-liich has been called an facture of Ethyl gasoline, all the otlier factors are often lrnonn ,'Et!iyl blending chart" (Figure 1), embodying these five or specified and ( 5 ) is the quantity to he determined, called factors in t,lieir proper relation, it TVRS found that the reliability the "lead requirement" of the gasoline. of estimated octane numbers of ethylized gasolines could be OCTAKE XUVBER Sc ILE cowideralily improved, and that from this chart tlie lead I n order to determine factor 1 (the dimensions of the usceptibility of the base gasoline could be conveniently detrrni ined. octane number scale) , the octane numhers of gasolines were The following are the five factors which determine the oc- compared with the compresqion ratios a t which these octane tane iiumber of any ethylized gasoline: numbers were determined. Tlie compression ratio on the C. F. R. engine, per qe, is not a reproducible measure of anti1. The effectiveness of isooctane at different concentrations knock value because mechanical conditions (especially the in raising the antiknock value of isobctane-heptane mixturescondition and adjustment of the bouncing-pin contact points) I . e., the relative "dimensions" of octane numbers in different have a marked effect on the compression ratio. However, parte of the scale. 2 . The effectiveness of tetraethyllead at diderent concentra- the factors that affect the accurarv of the compression ratio
D
II
