Color Stability of Gasolines Effect of Mercaptans, Alkyl Disulfides, and Sulfur GUSTAVEGLOFT, J. c. M O R R E L L , w. L. BEKEDICT, A N D CHARLESWIRTH,TI1 Universal Oil Products Company, Riverside, Ill. formation without the appearLTHOUGH much progColor stabilities of Midcontinent and Pennance of haze. Haze is sometimes ress has been made in the sylvania gasolines were determined in a carbon preceded by a small color ,drop, stabilization of gasolines arc lamp. Mercaptans added to the gasolines but when it forms the major drop in r e s p e c t to gum and color had little effect on color stability but sulfur in color usually follows. Haze formation in storage, the stabiliand/or alkyl disul$des caused color and haze appears first as a faint bluish cast zation of color of some motor by reflected light and approaches fuels, when exposed to direct formation. Their combined efects were greater a maximum intensity rapidly, sunlight, is still a problem. In than the effect of either substance separately. In the Saybolt colorimeter the addition to color depreciation of Sulfur was more harmful to cracked than to gasoline a t this point has a redthe gasoline on exposure to sunstraight-run gasolines, but disulfides were more dish brown cast which increases light, there is haze and in some detrimental to the straight-run gasolines. The in intensity with further exposure cases sediment formation. A to light. Preliminary work on light-stable gasoline is of particucolor instability of Midcontinent gasolines sweethaze indicates that it is a suspenlar value in connection with the ened with sodium plumbite and sulfur was due sion or dispersion of p a r t i c l e s use of glass d i s p e n s i n g bowls to excess sulfur and disulfides resulting f r o m caused by a chemical change commonly employed in filling sweetening, and not to the plumbite solution when the gasoline is exposed to stations. Their use is of doubtitself. Improved stabilities were obtained by actinic rays. The d i s p e r s i o n ful value as it increases the cost may be of an emulsoid characof refining gasolines w i t h o u t removing either disulfides or sulfur, but complete ter-i. e., extremely small drops compensating advantage and for stabilily was had only by removal of both. Fuller’s of a liquid in the gasoline which this reason many companies have earth treatment did not improee color stability. appear as a haze because of the e l i m i n a t e d or never adopted The color in straight-run gasolines was due io difference in the index of refracthem. suspended particles but in cracked gasolines was tion of the dispersed liquid and The present study was made to determine the independent the gasoline, and the reflection largely due to soluble colored compounds. of light from t h e i r s u r f a c e s . and combined effects on color These drops gradually become stability and haze formation of mercaptans, disulfides, and elementary sulfur when present in darker, coalesce, and ultimately deposit on the walls of the constraight-run and cracked gasoline and their blends. taining vessel. Accumulation of this material may result in a Brooks (8) offers the suggestion that color deterioration of separate bottom layer of dark, tarlike material. The composigasolines containing no free sulfur may be due to the oxidation tion of the particles has not as yet been determined. of mercaptans to disulfides as the first step in their transforAPPARaTUS AND MATERIAL USED mation to sulfonic acids. Bennett and Story (1) found that a gasoline to which 2 per cent of butyl disulfide was added beColor determinations were made with the Standard Saycame color-unstable upon exposure to diffused light. The bolt Colorimeter (A. S. T. M. designation D156-23T) and the presence of excess free sulfur added during the sweetening re- appearance of haze was observed by looking through the action has long been known to decrease color stability. The bottle on a black base toward northern sky light. deleterious effect of sulfur dioxide, particularly in the presIn the present work, color stabilities were determined beence of moisture, on color stability has been recognized, and fore and after sweetening, and after addition of mercaptans, the presence of alkyl esters of sulfuric acid is known to be ob- disulfides, and sulfur to the gasolines. The mercaptans and jectionable. Rue and Espach (4) report the effect of sulfur disulfides were obtained from the Eastman Kodak Company. compounds upon color stability during 6-month dark storage. They were added to a sulfur-free cleaner’s naphtha; a sour It is known that poor color stability often results when gaso- Cutbank (Mont.) straight-run gasoline with mercaptans both lines have been sweetened with sodium plumbite and sulfur. present and removed; and to Midcontinent (Healdton, Okla.) In the sweetening reaction the mercaptans are converted straight-run and cracked gasolines. Another set of tests was t o lead mercaptides by treatment with sodium plumbite. made employing gasolines from a Pennsylvania stock. Disulfides are formed upon the addition of elementary sulfur The color stabilities of the gasoline were determined by exwith precipitation of lead sulfide. The effect of excess elethem to light from a carbon arc lamp, type C3A, of the mentary sulfur on the color stability of the resulting sweetened posing National Carbon Company. It is a 60-ampere, 50-volt lamp, gasoline has been observed, but much less is known about the utilizing alternating current and equipped with an automatic carbon feed. The lamp operates in a vertical position. As influence of the disulfides. manufactured it is intended to use two pairs of carbons burning alternately, but for purposes of testing color stabilities it was COLORAND HAZE modified to burn a single pair of carbons continuously. Eveready Color stability may be divided into (1) color drop or forma- Sunshine carbons designed to produce a spectrum of approxition of color and (2) development of a milky cloud or haze. mately the same distribution as natural sunshine are used. The The actual mechanism of color formation has not been satis- lamp unit is suspended in a vertical, cylindrical, sheet metal factorily explained and is being investigated further in the shell (Figures 1 and 2). The vapors and fine ash formed when the arc is in operation are led through a line under suction from laboratories. The haze may be either accompanied or fol- the interior of the apparatus. Around the middle circumference lowed by color, whereas there are many examples of color of this housing and directly opposite the flaming arc is a water
A
323
IXDUSTRIAL AND ENGINEERING
324
jacket for holding and cooling the samples. The test bottles are placed in nine semi-cylindrical recesses in the jacket which open toward the arc and are so spaced that the distance between the center of the sample bottles and the center of the carbon electrodes is 30.5 cm. Care is taken that no shadows from the interior of the apparatus fall on the samples. The bottles used are fused quartz cylinders 15.24 cm. long and 3.5 cm. in outside diameter, with a wall thickness of 1.2 to 1.6 mm. A charge of 100 cc. of gasoline is used. They are stoppered but are vented with 0.25-mm. capillary tubing extending through the corks. The temperature of the gasoline approaches 50" C. by the end of the test period. Fifteen-minute exposure of gasoline in quartz bottles to this apparatus has been found t o be equivalent to 2-hour exposure in Pounce glass oil sample bottles to noon June sunlight in the Chicago area.
the carbon arc, no greater color drop and a slightly increased rate of haze formation for the straight-run gasoline, and no greater color instability and no haze formation for the cracked gasoline and blend. Similar mercaptan experiments, shown in Table 111, were made with the Pennsylvania gasolines. TABLE111. EFFECTOF MERCAPTANSON COLORSTABILITY OF PENNSYLVANIA GASOLINES GASOLINE Straight-run
EXPERIMENTAL WORK Work was carried out using straight-run and cracked gasolines from Midcontinent and Pennsylvania crude oils and their blends. The properties of the gasolines, including an analysis for sulfur compounds according to the methods of Faragher, Morrell, and Monroe (3) are shown in Table I.
Cracked
Blend
TABLEI. ANALYSIS OF MIDCONTINENT AND PENNSYLVANIA GASOLINE s PA.GASOLINE
MIDCONTINENT GASOLINE STRAI QHT-RUN
Sour Sweetened Gravity, A. P. I. 58.1 Sp. gr. 0.7463 A. S.dr,M. distn., I n i i G i ' ~ .P. Distilled over,
%:
10 50 90 End B. P. 25 Color, Saybolt 0.06 Sulfur, % Positive Do_otortest None H;Y Free sulfur, % Trace Mercaptans, % 0 . 0 0 3 0.03 Bisulfides, %
CRACKED
STRAIQHTRUN CRACKED
Sour Sweetened 58.3 62.2 0.7455 0.7305
47
40
74 120 167 191 25 30 0.00 0.15 Ejigative Positive Nigative Negative None None None None None Trace 0 . 0 1 0.01 None None 0.006 None Present Trace Present None 82 135 187 225 25
68 125 182 214 26
51
+
63.9 0.7242 57 7s 113 152 182 30 0.01 Negative None None None None
+
EFFECTOF MERCAPTANS IN GASOLINE Since disulfides are formed from mercaptans during sweetening, it was thought advisable to determine their effect on the color stability of straight-run and cracked gasolines and their blends of equal proportions. The gasolines used were treated, previous to the addition of the mercaptans, with metallic mercury and silver nitrate solution to remove the sulfur and mercaptans originally present. Table I1 shows the results obtained on Midcontinent gasolines. ON COLOR STABILITY OF TABLE 11. EFFECTOF MERCAPTANS MIDCONTINENT GASOLINES
CARBON.kRC LAMP TEsr Color ORIQINAL a t 15 Remained Haze GASOLINE MERCAPTAN ADDED@COLOR min. b clear appeared
Min.
Straight-run
Min.
23, hazy
12.5
15.0
16,hazy 18, hazy 18 hazy 19: hazy
12.5 10.0 10.0 10.0
15.0 12.5 12.5 12.5
22, clear
15.0
23, clear 22, clear 22, clear 21, clear
15.0 15.0 15.0 15.0
None (sour) 25 22, clear None (sweetened with 21, clear AgNOs s o h ) 25 22, clear Ethyl 23 22, clear 24 n-Propyl 23 22. clear n-Amyl Equivalent to 0.1 per cent sulfur. b Equivalent to 2 hours of noon June sunlight,
15.0 15.0 15.0 15.0
Cracked
Blend
None (sour) 25 None (sweetened with 25 AgNOs soln.) 23 Ethyl 25 n-Propyl 25 n-Amyl 25 None (sour) None (sweetened with 25 AgNOs s o h ) 23 Ethyl 23 n-Propyl 23 n-Amyl
15.0
.. .... .. ..
The addition of mercaptans to straight-run and cracked Midcontinent gasolines and their blends showed, when compared with corresponding control samples upon exposure to
Vol. 27, No. 3
CHEMISTRY
a
b
CARBON ARCLAMPTEST MERCAPTAN ORIQINAL Color a t 15 Remained Haze ADDED* COLOR min. b clear appeared Min. Min. None 30f 27,clear 15.0 n-Propyl Ethyl 30+ 19 19, haze 10.0 1l 22:.5 n-Butvl Amyl
30+ 30+
20: haze 20; haze
10.0 10.0
None Ethyl n-Propyl
30+ 30+
25, clear 27. 24, clear
1 5 . 00 15.0
n-Butyl Amyl
30+
23, 25, clear
16 5.0
None
30+
Ethyl
"3:
23,faint haze 20 haze 20: haz
264
19, haze
--,
12.5 12.5
.. .. ..
_.-I
10.0
Equivalent to 0.1 per cent sulfur. Equivalent to 2 hours of noon June sunlight.
I n regard to the effect of the addition of mercaptans to Pennsylvania gasolines, the presence of mercaptans in the straight-run gasoline caused color and haze formation upon exposure to light. The cracked gasoline containing mercaptans did not haze but was slightly less color-stable than the original gasoline. Mercaptans in the blend did not hasten the appearance of haze but did decrease the color stability by 3" to 4' Saybolt.
EFFECT OF ALKYLDISULFIDES Ethyl, n-propyl, n-butyl, and isoamyl disulfides were added in amounts equivalent to 0.10 per cent sulfur to the sulfurfree cleaner's naphtha, and to the sour and silver-nitratesweetened Cutbank (Mont.) straight-run gasoline. The gasolines were exposed to the carbon arc for 15 minutes. A plumbite-sweetened Cutbank gasoline was also exposed for comparison. The results are shown in Table IV. TABLEIV. EFFECTOF DISULFIDES ON COLORSTABILITY (Appearence of gasoline after 15-minute exposure t o carbon arc lampa) SULFUR-FREE CUTRANK STRAIQET-RUN QASOLIN~ DISULFIDE CLEANER'S AgNOaPlumbiteADDEDb NAPHTHA Sour sweetened sweetened None Clear Clear Clear Cloudy Cloudy Cloudy .... Cloudy Ethylb C1 oudy Cloudy .... Cloudy n-Propylb Cloudy Cloudy Cloudy n-Butyl Cloudy Cloudy .... Clear Isoamyl a Equivalent to 2 hours of noon June sunlight. b Equivalent to 0.10 per cent sulfur.
....
Table IV shows that the addition of alkyl disulfides to a naphtha and straight-run gasoline, both sour and sweetened (with and without mercaptans present), caused them to become cloudy after exposure to the carbon arc. The plumbitesweetened gasoline became cloudy, even after shaking with mercury to remove excess elementary sulfur. The exposed samples were not only cloudy but also had a brown color. The straight-run Cutbank gasoline containing naturally occurring mercaptans did not cloud on exposure to the arc. I n a further study of the effect of disulfides on color stability and haze formation, portions of the Midcontinent and Pennsylvania straight-run and cracked gasolines were agitated with mercury to remove free sulfur and then shaken with silver nitrate solution t o remove the mercaptans in order to eliminate any color-depreciating effect which might be caused by these compounds, The straight-run gasoline contained the disulfide sulfur originally present.
I N D U S T R I A L -4 N D E N G I N E E R I N G C H E M I S T R Y
March, 1935
325
ment on the Midcontinent T o t h e s e treated gasogasoline was studied. The lines several disulfides were straight-run and c r a c k e d added; their e f f e c t u p o n g a s o l i n e s were sveetened color stability in the carbon with sodium plumbite soluarc lamp test is noted in tion] using an excess of sulTable V. Each sample was fur of 0.01 per cent. The e x a m i n e d for the appears u l f u r was dissolved in a ance of haze at 2.5-minute portion of the gasoline and intervals. added to the r e m a i n d e r . T a b l e V s h o w s that in Part of this product was exthe case of the M i d c o n posed to light, while the extinent gasoline there was a cess sulfur was r e m o v e d definite decrease in Saybolt from a second portion with c o l o r o n exposure to the m e r c u r y . A part of the carbon arc. The drop in original sour gasoline was c o l o r was especially protreated with silver nitrate nounced in the straight-run to remove mercaptans] and gasoline and blend but was e l e m e n t a r y s u l f u r was m u c h l e s s in the cracked added up to 0.01 per cent. g a s o l i n e alone. A haze The cracked gasoline and a was produced on exposure b l e n d of equal parts of of the straight-run gasoline c r a c k e d and straight-run to the light in from 2.5 to gasolines were treated in a 10.0 m i n u t e s , b u t t h e s i m i l a r manner. The recracked gasoline showed no sults appear in Table VI. haze within 15.0 m i n u t e s T h e d a t a in Table VI except with isoamyl disulshow the effect of the addifide in the Midcontinent t i o n of e x c e s s sulfur in c r a c k e d g a s o l i n e . The sweetening. I n the case of blend showed somewhat less the straight-run g a s o l i n e pronounced haze formation there was only 1" Saybolt than the straight-run gaso7%8N5f ORMER d i f f e r e n c e in color drop line. I n the straight-run w h e t h e r the excess sulfur and blended Midcontinent gasolines, ethyl disulfide and FIGURE1. C,ARBONARC APPARATUSFOR DETERMINING was p r e s e n t or removed. However, there was an inn-propyl disulfide showed COLORSTABILITY OF GASOLINE crease in the time required s r e a t e r tendencv to form Laze and color than the other disulfides, I n the Pennsylvania for haze formation when the excess sulfur was remove-d imcracked gasoline there was only a slight decrease in color and mediately after sweetening. no haze formation. The extent of drop of color in all of the I n the case of the cracked gasoline the drop in color with Pennsylvania gasolines was decidedly less than in the Mid- excess sulfur on exposure to the arc was from 25" to IO0 Saycontinent upon addition of disulfides. The rate a t which haze bolt, whereas with the excess sulfur removed the color dropped appeared in the Midcontinent gasolines varied with different to 20" Saybolt (a difference of lo"), proving that excess sulfur disulfides but was the same in the Pennsylvania gasolines. was highly deleterious to the color stability of the cracked gasoline. The removal of the excess sulfur prolonged the EFFECT OF EXCESS SULFUR time for the appearance of haze by 50 minutes. Similar reSince the use of a n excess of sulfur over that required for sults were noted with a mixture of cracked and straight-run the sweetening reaction has been generally observed to de- gasolines; in fact, the effect on the blend was greater than in crease color stability of gasoline] the specific effect of this ele- either the straight-run or cracked gasoline alone. TABLE V. EFFECT OF ALKYLDISULFIDES ON COLOR STABILITIES OF GASOLINES PENNSYLYANIA GASOLINES
MIDCONTINENT GASOLINEB
GASOLINE Straight-run
Cracked
Blend
DIBULFIDE ADDED~
ORIGINAL COLOR
--CARBON
ARC LAMP TEST-
Color at 15 min.b
Remained clear Min. 12.5
None Ethyl n-Propyl n-Butyl n-Amyl Isoamyl
25 23 21 22 21
16,faint haze -3, very cloudy -6, clolldy -6, cloudy 1. very hazy 3, hazy
None Ethyl n-Propyl n-Butyl n-A my1 Isoamyl
25 25 25 24 23 23
23, clear 19, clear 18, clear 20, clear 16, clear 17, faint haze
15.0 15.0 15.0 15.0 15.0 12.5
25 24 21 22 22 22
21, clear 4, cloudy 8, cloudy 13, clear 10,hazy 8, hazy
15.0
None Ethyl n-Propyl n-Butyl n-Amyl Isoirmyl Equivalent to 0.10 per cent sulfur. b Equivalent t o 2 hours of noon June
19
sunlight.
5:0 7.5 7.5 7.5
2:5 15.0 10.0 10.0
-CARBON
Haze appeared Min. 15.0 2.5 7.5 10.0 10.0 10.0
.. ..
.. ..
15;o
i:5 5.0 l2:5 12.5
ORIQINAL COLOR
30f
30+
$:30+
..
::: 30+ 30+
..
30f 30+
30+ 30+
*.
Color at 15 min. b
27, clear 17, hazy 17 hazy 16: hazy 16, hazy
....
ARC LAMP TEST----
Remained clear Min. 15.0 2.5 2.5 2.5 2.5
..
Haze appeared Min. 5:0
5.0 5.0 5.0
..
..
27, clear 26, clear 26, clear 25, clear 24, clear
15.0
..
23, faint haze 21 hazy 21: hazy 19, hazy 19, hazy
10.0 5.0 5.0 5.0 5.0
12.5 7.5 7.5 7.5 7.5
....
....
15.0 15.0 15.0 15.0
..
..
.. ..
.. ..
..
INDUSTRIAL AND ENGINEERING CHEMISTRY
326
With the straight-run gasoline the same amount of excess sulfur added had a more deleterious effect after sweetening with silver nitrate than when sweetened with sodium plumbite solution. The reverse was true in the case of the cracked gasoline. The possible effect of sodium plumbite solution on the removal of part of the excess sulfur must be considered in the first case.
Vol. 27, No. 3
sulfides were removed by refluxing the gasoline with zinc dust and glacial acetic acid for 3 hours; followed by removal of the mercaptans formed. Free sulfur was removed with mercurv. Tabl;! VI11 shows the relative effects of disulfides and sulfur on the color stability of Midcontinent gasolines, both straight-run and cracked. The effect of these substances on the straight-run gasoline is clearly shown COMBINED EFFECT OF DISULFIDES as follows: With disulfides alone, and AND EXCESS SULFUR only a trace of sulfur, the drop in color I n view of the deteriorating effect is from 25" to 22" Saybolt; with sulof the alkyl disulfides it seemed probfur alone (0.01 per cent), the drop in able that the combined effects of excolor is from 24" to 12" S a y b o l t ; cess sulfur and disulfides would be whereas with both disulfides and sulgreater than either taken separately. fur (0.01 per cent) present, the drop T o the silver-nitrate-treated gasolines in color is from 25" to 0" Saybolt. the various disulfides and elementary With disulfides present in the gasosulfur mere added. The color stabililine, and only a trace of sulfur, 15.0 ties upon exposure to light are shown minutes were required for haze to apin Table VII. pear. T h e p r e s e n c e of sulfur, both In all of the Midcontinent gasolines with disulfides present and abscnt, and in the Pennsylvania straight-run caused haze appearance in 2.5 minand blended gasolines (Table VII) the utes. The renioval of both disulfides and sulfur caused the s t r a i g h t - r u n combined effect of sulfur on color and gasoline to remain the same color after each of the disiilfidcs was greater than exposure of 15.0 minutes to the carbon the separate effects of any of these arc and no haze was formed during substances. The addition of the dithis period. sulfides to the Pennsylvania cracked When the straight-run gasoline was gasoline contnining sulfur showed no treated with plumbite solution and greater effect on the color than the FIGUHE 2. PHOTOGRAPH OF CARBON . . . 0.01 per cent excess sulfur with the ARC APPARATUS sulfur alone. disulfides resulting from the treatment In the Midcontinent cracked and in the Pennsylvania straight-run and blcnded gasolines the present, as well as those originally contained in the distillate combined effect of sulfur and disulfides on haze formation present, the color dropped from 25' to 18" Saybult and haze appeared a t the end of 5.0 minutes. With the excess sulfur was greater than for sulfur alone. removed, the color droppcd from 25" to 18" Sttybolt, and 7.5 minutes were required for haze to appear. Upon the renioval T~~~~VI, EFFECTOF SULFUR ON coLoR STABILITY OF of both the disulfides and the excess sulfur, there was a 1" MIDCONTINENT GASOLINES drop in color only (from 27' to 26" Saybolt), and no haze apL~~~ T~~~ cARBON lor at ma,ned ReHaze peared in 15.0 minutes. When this sample was treated to remin.a clear appeared move the sulfur and disulfides, it was reduced in color to 22' .. % Min. Min. and was therefore further treated with fuller's earth to bring Straiaht- None. aour None 25 23,faint 12.5 15.0 it up to 27" Saybolt. However, the 22"color sample rcniaincd run haze Plumbite + 0.01% stable after exposurc to the arc light. The addition of 0.01 exvee.8 S 0.01 25 16, hazy 2.5 5.0 per cent of sulfur to the cracked gasoline following thc treatPlumbite + 0.01% exceaa Y (excess mcnt with silver nitrate to sweeten caused a drop in color S removed None 25 17!faint 5.0 7.5 haze from 25" to 15" Sayljult, with haze appearing in 10.0 minutes. AgNOa None 25 16, faint 12.5 15.0 When the cracked gasoline was treated with plumbite soluhaze 0.01 25 0, hazy 2.5 AgNOa tion and 0.01 per cent escess sulfur, it was reduced in color AgNOa 0.0025 25 6, hazy 2:5 5.0 from 2G" to 10" Sayholt, and haze appeared in 5.0 minutes. Cracked None aour None 25 22, clear 15.0 .. When the excess sulfur mtls removed with the disulfides pres~~umbi+ t e 0.01% eyi'es~S 0.01 25 10,hary 2.5 5.0 ent, the reduction in color was from 26" to 20" Saybolt, and Plumbite + 0.01% 10.0 minutes were required for haze to appear. When both eyvesa s (excess 26 20, hazy 7.5 10.0 S removed) None the excess sulfur and the disulfides were removed, the drop 15.0 None 25 23, clear AaNna 25 15, hazy 7.5 1O:O AgNO; 0.01 in color was 1" only (from 26" to 25" Saybolt), and haze did 25 20,clear 15.0 .. AgNOa 0.0025 not appear after 15.0 minutes of exposure to the arc. As a Blend None, Bour None 25 22, clear 15.0 .. general conclusion, the color and haze stability of the straightPlumhite + O . O l ~ o run and cracked gasolines could be improved by the removal excess S 0.01 25 0,cloudy .. 2.5 Plumbite + 0.01% of disulfides or sulfur, but complete stability could be obexcess S (excess S removed) None 25 17, hazy 5.0 7.5 tained only by the removal of both. 25 21 clear 15.0 AuNOa AgNOa
0
None 0.0025
25
9: hazy
..
2:5
Equivalent to 2 hours of noon June sunlight.
Table VI11 shows the effect of separate and consecutive A removal of disulfides and elementary sulfur from the plumbiteand the silver-nitrate-sweetened Midcontinent gasoline. Di-
f
EFFECT OF PLUMBITE SOLUTION ON COLOR STABILITY Since it has been demonstrated that the color instability of the plumbite-sweetened gasolines was due to the presence of excess sulfur and of disulfides formed during the reaction, it remained t o be shown what effect the plumbite
INDUSTRIAL AND ENGINEERING CHEMISTRY
March, 1935
327
OF GASOLINES TABLE VII. EFFECTOF SULFURAND ALKYL DISULFIDESON COLORSTABILITY
PENNSYLVANIA GASOLINES
MIDCONTINEKT GASOLINES GAEOLINE Straight-run
Cracked
ORIQINAL COLOR
Color a t 15 mime
% None None Ethyl n-Propyl n-Butyl n-Amyl Isoamyl
None 0.0025 0.0025 0 0025 0.0025 0.0095 0.0025
25 25 23 19 21 22 21
-7 cloudy -2: cloudy 0, cloudy 1, cloudy
None None Ethyl n-Propyl n-Butyl n-Amyl Isoamyl
None 0.0025 0.0025 0.0025 0.0025 0.0025 0.0025
25 25 25 25 24 23 23
23, clear 20, clear 16, faint haze 16. faint haze 16, clear 15, faint haze 13, haze
None None Ethyl n-Propyl n-Butvl n-Amyl ISoamjl Equivalent to 0.10 per cent
Blend
0
SULFUR ADDED
16,faint haze
6, hazy -8, cloudy
Remained clear Min. 12.5 2.5
..
7:s 5.0 5.0 15.0 15.0 12.5 12.5 15.0 12.5 7.5
Haze appeared Min. 15.0 5.0 2.5 2.5 10.0 7.5 7.5
.. 15:o 15.0 15: 0 10.0
None 25 21 15.0 i:5 0.0025 25 9 .. 2.5 0.0025 24 5, cloudy 6 , cloudy 2.5 0.0025 21 cloudy z2.5 .4 0.0025 22 5. CloUdy 0.0025 22 2:5 5.0 0.0025 22 sulfur. b Equivalent to 2 hours of noon June sunlight.
..
..
c,
ARC L A M P TEST-
-CARBON
A R C L A M P TEST-
-CARBON
DISULFIDE ADDED
