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 D i c k s o n , Otterson, ani1 L i n k . J . A 4 ~ nC./ L P I RS o. c . , 52, 77; ( 1 F o r e m a n a n d I h g l i s , ISD, ESG. ( ' H h x . , 23, 41;-16 [,19:31I . . F o r e s t P r o d u c t s 1,aboratory Nethocls. Palm, Trade J . , 87, So.
2 3 , 59 (19%). 4 ' H s a r , -4.K.1-an d e r , " l n l c i t i i n g z u i n h - a r h w u n d R e s t i m m u n g der reinen u n d a u s Gluko t e n e n M o n o s a c c h a r i d e u n d ~ ~ l i l e l i ~ i l s I i u r e n11.. " 124, Gclirii~li r B o r n t r a e g e r , Berlin, 1920. (.j) S e u b e r g a n d Wohlgemuth, %. 2 h p i o l . f'hw!., 35,31 ilC302)). (Cj, Schorger a n d Sinirh, J . ISD. ESG. ( ' H E ~ I . 8 , , 494 (191(j). ( 7 1 \Vise a n d 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 and, as more is added to a gasolinc, relationship befueen the concentrut ion qf teiraits 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 m e t e r s of tetmethylleatl adder1 E-3.5 type, variable vnmpresqion fuctors wltose proper r d a tionships are incorper gallon of gasoline. ~wg~iie, and tlie result.. of these 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 n u m l i e r scale of the blendiiig hi?ity of a gusoline from fhe ocfane numbers of 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 factor 1, is a property of isooc\ 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~eadi. 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 OCTAKEXUVBER Sc ILE cowideralily improved, and that from this chart tlie lead usceptibility of the base gasoline could be conveniently I n order to determine factor 1 (the dimensions of the 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. the factors that affect the accurarv of the compression ratio 2 . The effectiveness of tetraethyllead at diderent concentra-
D
II
INDUSTRIAL AND ENGINEERING CHEMISTRY
188
Vol. 25, No. 2
the circles), showing the agreement between Equation 1 and the observed data. A reproducible relationship between the compression ratio and the octane number can now be obtained by integration of Equation 1: R
=
r
+ 0.005~+ 0 . 0 0 0 1 3 ~+~ 9.4 X lo-''
X y8.2
(2)
The integration constant, T , represents the compression ratio of heptane, and is consequentJy a term whose value is not satisfactorily reproducible. However, the quantity ( R - T ) serves the purpose, for, as previously pointed out, it is reproducible, and its value is now given by Equation 2.
TETRAETHYLLEAD SCALE Since the compression ratio-tetraethyllead curves' on different gasolines all extended to 0 cc. per gallon, it was possible to use a simpler method for solving factor 2 than t h a t used for factor 1. Table I1 shows the increases in compression ratio on twelve different gasolines, caused by the addition of different concentrations of tetraethyllead.
TABLE11. INCREASES IN COMPRESSION RATIOCAUSEDBY ADDITION O F VARIOUS CONCENTRATIONS OF TETRAETHYLLEAD OF:
Cubtc Cen/,mefers of Te/ruethy/ L e o d per Ga//on
FIGURE1. ETHYLBLENDING CHART (Data obtained on several gasolines using C. F. R.engine at 212O F. (looo C.) jacket temperature and 600 r. p. m.) 1. Stabilized natural gasoline 4. West Texas straight-run gaso2. Cracked gasoline line 3. 50 per cent cracked 50 per 5. Midcontinent straight-run gasocent West Texas atraight-run line gasoline
+
--
4 . 5 cc. 0.79
GASOLINE 3 4
1:io
6
7
0.79
a
0.85 0.68
9 10 11 12 13 14 15
1.11
1:oz 0.63
However, the increases in compression ratio shown in Table I1 depend partly on the lead susceptibilities of the gasolines (factor 4), and, before an average solution of factor 2 can be obtained, the former must be eliminated. This was done by adjusting the "steepness" of the compression TABLEI. CHANGE IN COMPRESSION RATIOPER UXITCHANGE ratio increase-tetraIN OCTANE NUMBER ethyllead curve for (Slopes of compression ratio-octane number curves) e a c h g a s o l i n e to r OCTANENUMBERS p a s s t h r o u g h 0.5 85 60 70 75 80 CURVE" 40 50 0.048 ratio a t 2.0 cc. per 0.112 0.024 0.033 0.070 0.053 1 0.016 ... ... 0.031 2 ... ... 0.020 g a l l o n , the other 0:Ok 0.042 3 0.024 0:075 0.036 0.050 0:067 4 o:oi7 o:ois 0.025 p o i n t s b e i n g in0.073 ... 0.058 0.038 5 0.018 0.022 0.030 0.100 creased or decreased 0.062 0.040 6 . . . ... 0:04s ... .. 0 :020 0.033 7 0.050 .. in the correct proo:ois 0.027 0.037 8 o:oi2 0:059 .. portion. 0.045 0.033 9 ... 0:024 0.031 io o:oi7 0:oio When this is done, 0:oiz 0:092 ... 11 ... ... ... 0 043 0.064 0.094 ... 12 ... ... ... ... t h e s h a p e s of the ... ... 0.080 13 ... 0:0i4 0:oio ... ... 14 ... ... curves are practiOcfunr N u m A e i ( y ) 0:067 ... 0.038 ... 0.025 15 0.068 ... cally identical, 16 o:ois 0:024 0.029 0.040 FIGURE2. RELATIVEEFFECTIVENESS 17 ... ... 0.024 0.038 0:052 0.062 . . . cating that factor 2 OF ISOOCTANEAT DIFFERENTCONMean 0.016 0,021 0.025 0.037 0.051 0.065 0.090 is a p r o p e r t y of CENTRATIONS a Each of these curves was constructed from the octane numbers and compression ratios obtained during one day's testing, by plotting the comtetraethyllead quite pression ratios against the corresponding octane numbers. independent of the gasoline with which it is mixed. The average values for the solution of factor 2 are shown a t This change in compression ratio per octane number is the bottom of Table 111. The particular values, 0.5 ratio related to the octane number according to the following and 2 cc. per gallon, were chosen arbitrarily as representing empirical equation: approximately a typical gasoline and a typical concentration, though any other pair of values would have served equally as d R = 0.005 0.00025y 7.7 X 1O-le X y7.* (1) well. & where R = compression ratio of any gasoline The averages shown in Table I11 may be expressed by the y = its octane number. following relationship:
-._/-
are not ordinarily apparent from test to test; their influence usually becomes measurable only after running a few days. Therefore, the change in compression ratio, corresponding to a change of one octane number is fairly reproducible, as shown in Table I.
I
+
+
The values of d R / d y calculated from Equation 1 for various octane numbers (y) are shown by the curve in Figure 2 in comparison with the average values from Table I (indicated by
where R
A'
(R
-~o~~.,~= ~ i 0.34 . ) o N - 0.058 N'.82
= =
compression ratio lead concentration
(3)
Stilwript (L is intended to indicate tlint the ijoantity i!? - roc..,r.i.) has been adjusted to 0.5 ratio a t 2.0 cc. per
liqiiiit,iims 2 ami 4 then reduce to:
It R
pillon (1”igiire 3).
+J(Y)
=
T
=
ro m
(2.4
+ SdN
(4a)
. , ~ ~ .
.. 1 lie
two vimsiants, r (the coiiipression ratio of heptane) r,, ,.~., yi,t, (that uf the nudoped gasoline as before), iiirist i h p out in the solution of S .
:id
,.n 40 9
z
e
0.8 2 ‘,
$
3k
LEADSurcm~,riniLirySCALE
E
Ileturniiig to Table IT, me can now reproduce the data on of the gasoline8 sho~vnin that table by Equation 3, if insert an additional term, S , called the “lead susceptil,ilit,y” of tho gasoline. This term regulates the “steepness”
