T H E J O U R N A L OF I N D U S T R I A L AiVD E N G I N E E R I K G C H E M I S T R Y
7 50
Vol. 7 , NO. 9
temperatures employed are here concisely shown. For example, Yo. 2 9 7 7 is more soluble in benzol t h a n No. 2847, although heated at a temperature lower b y over 100' C., b u t on t h e other hand being heated 11 hours longer. The same is true of Nos. 3369 and 2 8 2 2 , using heavy benzine as solvent, in t h e proportion of one part solvent t o one part resin. R i t h two parts solvent t o one part resin, we see t h a t 204' for I z hours,
saturated bodies. Temperatures above 6 j o o F. exert a marked influence both as t o solubility and chemical and physical properties. 111-Pontianak rubber resin is very inert to alkalies and, practically speaking, may be regarded as substantially unsaponifiable.
TABLE 111-SOLUBILITIESOF P O ~ T I A ~ RUBBER A K RESIKWITH RBFEREXCE TO TREATMENT 4 . r ' ~ SOLVENT USED
THE QUANTITY OF GASOLINE NECESSARY TO PRODUCE EXPLOSIVE MIXTURES IN SEWERS
P E R C E N T OF
RESINI N
C L E A R SOLUTIOX
MONTCLAIR. N E W JERSEY
By G. A . BURRELL ATD
No. N o . No. N o . No. No. No. N o . 2728 2977 2991 2974 2832 2847 2822 3369 SOLVEXTS AND PARTS
USEDI N EACHCAS= TO 1 P A R T OF RESIN
. , . 38 .. . . . . . . .. . . . . . . .. . . . . . . .. . . . . . .. . . . . . . .. . . . . . . .. . . . . . .
..
..
.. .. .. .. .. 1
..
..
1'/2
2
..
.. .. .. ..
.. 1
..
11/z
2
...... . . . . .
1
.. .. ..
'/Z
. . . . . . 56 . . . . 48 . . . . . . . .
49
. . . . . . . .
. . . . . . . . . .. ,, .. ,,
, ,
40
. . . .
40 3i
36
39
40
..
42 37
42 39
38
3i
3i
45
::
. . . . . . . . . . . . . . . . . . 45 58
. . . . . . . . . . . . '54 . . 42 . . . .
The Bureau of Mines and the City of Pittsburgh are cooperating in an endeavor t o determine the causes of explosions in sewers and means for their prevention. The results of the investigation are being published in reports of the Bureau of Mines. I n this report are shown the quantities of gasoline which must be introduced into sewers in order t o produce explosive mixtures of gasoline vapor and air under certain conditions. hiany different conditions affect this quantity, such as size of t h e sewer, velocity of t h e sewage, temperature of the sewer air, volatility of the gasoline, rate of inflow of the gasoline, etc., so t h a t only under identical conditions of tests are duplicate results obtained.
. . . . . . . .
E XPE RIJIENT A L
. . . . . . . . . , .. , . , , . . . . 38 . . . . 36 . . , .
The particular sewer wherein the tests here recorded were conducted is one of the largest of t h e Pittsburgh sewers. I t is 8 ft. 3 in. wide and 8 f t . 6 in. high. I n Fig. I is shown a plan of the sewer, with conditions such as existed when the first test was conducted on September 3 0 , 1 9 1 4 . At the points I , 2 , 3 , 4 , j and 6 are shown the manholes where samples of gas were collected. The distance from No. I manhole, where the gasoline was dumped into t h e sewer, t o the sewer outlet, the Allegheny River, is 2706 feet. The distance between the different manholes is marked on the diagram. The velocity of the sewer was established as follows: Pine floats 6 in. square were dropped into the upper manhole No. I a t a given signal. Stop-watches were set a t the same instant, and as the floats passed each succeeding manhole (which fact was determined by a man standing a t the foot of a ladder in each manhole) the time was caught on a stop-watch. As a result of these tests it was established t h a t the average velocity of the sewer was 6 . 4 j linear f e e t per second. The depth of the flow was about 8 in. The amount of flow was 19.6 cu. f t . per second and t h e grade of the sewer 0.90 per cent. The temperature of the water in the sewer was 21' C. (69.8' F.). The temperature of the air just above the water was 20.3' C. ( 6 8 . j 4 ' F.), and of the air above ground 20' C. ( 6 8 " F . ) .
. . . . . . . .
.,
...
. . . . . . . .
44
... ...... . . . 29
1/2
41 36
43 41
38 46
2
. 52(a) . . . 46 .. . , . 52(a) 1 .. . . . . . . .. 1 ... 1 . . ' / z 40,. . . 1/2 35 11/2 ..
59 50
H.T. BOYD
Received June 4, 1 9 1 5
. . . . . . . . . .
. . . . . . . . . . . . . . . . . . 38
( a ) Upon evaporation, the residue was very granular and had the odor
of benzine, hence it 1s very probable that some solvent was still in the resin, thus making these results too high.
232' for I O hours, 264' for 9 hours, and 3 1 6 ' for hour give practically t h e same results, while heating t o 2 6 4 " for I hour affords a degree of solubility less t h a n any of these. On heating t o 321'. however, t h e greatest amount of resin was in solution. The mixtures of various solvents did not in many cases seem t o be more active t h a n each one taken separately. The influence of alkali on the plastic resin in thin layers is shown by the following: Samples, made u p of equal parts of plastic resin and heavy benzine and in some cases with additions of I O t o 2 0 per cent of various saponifiable siccative oil, were flowed in thin layers on glass plates and allowed t o dry for several days. The plates were then immersed in an aqueous 5 per cent caustic soda solution for j days. Upon removing the plates and rinsing, the samples containing 2 0 per cent of drying oil were found quite badly decomposed, those containing I O per cent were only slightly affected, while those containing only the dried plastic resin were scarcely softened, the resin when again dried, being in apparently as good condition as before the test.
TEST K O .
CONCLUSIOXS
I-Of t h e solvents or thinners commonly used in varnish and paint oil making, benzol is the most energetic on Pontianak rubber resin. 11-Heating the resin for an extended period makes it more soluble and increases the proportion of un-
I
At 2 . 1 0 P.M.: j j gallons of refinery gasoline, sp. gr. 6 7 . j ' BaumC, were rapidly dumped from an open barrel into t h e sewer a t manhole N o . I , by turning the barrel on end, allowing the gasoline t o run in all a t once. 1
Published with the permission of the Director of the Bureau of Mines
T H E J O r R N A L OF I S D C S T R I A L A S D EiVGISEERISG C H E M I S T R Y
Sept., 191j
T h e fractionation analysis of this gasoline appears in Table I. TABLE I-FRACTIONATION ANALYSIS(U)OF GASOLINE USED I N TESTNO. 1 F i r s t d r o p . . . . . . . 3 1 O C. u p to , . , 6 5 . 5 per Cent U p to 40' C . . . . . 1 . 4 6 per cent U p t o 130O.. . . . . . 7 6 . 5 Up Up Up Up Up u p up
,
...... 3.4 ...... 7.0 t o 7 0 ° . . . . . . . 13 . O to 80°. . , . . , . 20.5 t o 90'. . . . . . . 2 9 . 5 to 50'.
U p t o 140'.
......
Over 1 6 0 O . .
. . . .
84.0
up t o 1500. . . . . . . . 91 .0 U p t o 1 6 0 ° . ., . . 9 7 5
to 60'.
1.9 ~
to 1000 . . . . . . 4 1 . i t o 1100.. . . . . 5 4 . 5
T o t a l . . . . . . . . . 99 4 per cent LOSS . . . . . . 0 . 6 ~ e r ~ ~ (a) M a d e b y hl. S. Evans, Chief, Bureau of T e s t + , City of Pittsburgh.
Combustible gas, trace (too small for identification)
hence. no allowance was made in other analyses. Samples of sewer air T-vere collected on schedule time. from 2 . 1 2 P.M. t o 4.4: P.M. as shown in Table 11. T.¶BLE
11-TIMES
SAMPLE KO. AIanhole S o . hlanhole N o . Manhole S o . Manhole N o .
'
perfect mixing of t h e sewer air and gasoline vapor. It will be noted how far theoretical conditions differ f r o m t h e conditions of the test: (I) The gasoline flowing with t h e sewer water was rapidly carried past a n y particular point; ( 2 ) only the lighter portions had a chance t o evaporate a t a n y point; ( 3 ) gasoline vapor is about three times as heavy as air, so t h a t mixing n of t vapor with air a t an appreciable distance above the sewer water lvould be slow. Sample 1-0, I (manhole S o . z ) , taken 2 minutes after the introduction of the gasoline, shows 0.89 per cent of gasoline. Sample K O . I (manhole S o . 3) shows 2 . 1 9 per cent, and was taken 3 minutes after t h e gasoline n-as poured in.
Samples of gas were collected b y lowering exhausted, glass sample tubes on t h e end of long poles and breaking off their tips b y striking them against t h e sewer wails. The sewer air immediately rushed into t h e giass containers through the very small opening t h u s afforded. The arrangement of this device is sh0n.n in Fig. 2 . h1. S. Evans, chief of the Bureau of Tests, City of Pittsburgh. worked out t h e details and made the del-ice for holding t h e vacuum bottles. This was the arrangement FIG. 1 - P u s adopted for t h e first test. On the subsequent tests samples of the sewer air were drawn from t h e sewer into bottles by means of a small p u m p with a long hose attachment. This arrangement is shown in Fig. 3 , Before t h e gasoline was dumped. a sample of sewer air was taken at Station N o . 2 . This m-as done t o determine whether a n y gasoline was already in t h e sewer. The sample analyzed as follows: C O S , 0.06 per cent.
751
b
C.15R
SECTION
UP
SEWERWHERE TESTSRIERE CONDGCTED
I n other words, the relation between-the movement of the gasoline down t h e sewer and the distance between t h e manholes and time of collecting samples was such t h a t a t manhole KO.3 there was more gasoline vapor 3 minutes after t h e introduction of t h e gasoline t h a n a t KO. z manhole, 2 minutes after the gasoline was poured in. T h e significant fact is t h a t 2 . 1 9 per cent was t h e largest quantity of gasoline vapor found in a n y sample. Only very small proportions were found a t a n y manhole I O minutes after the introduction of
AIR ITERE C O L L E C T E D 5 6 7 8 9 2.52 3.25 4.25 . . . . . . . . 2.53 3.30 4.25 . . . . . . . . 2.41 2.51 3.01 3.45 4.30 3.00 3.50 4.15 . . . . . . . .
A T XYHICH S A M P L E S O F S E T E R
1 2 . . . . . . . . . . . . 2.12 3 . . . . . . . . . . . . . 2.13 4 . . . . . . . . . . . 2.16 6 . . . . . . . . . . . . . 2.20
2 2.22 2.23 2.21 2.30
3 2.32 2.33 2.26 2.40
4 2.42 2.43 2.31 2.50
The analysis' of these samples gave the results shown in Table 111. One gallon of gasoline. if entirely vaporized, produces about 3 2 cu. ft. of l-apor a t ordinary temperature and pressure. Adopting 1 . j per cent2 as t h e low TABLEI I I - . 4 N A L Y S E S hfAKHOLE S O .
Time P.M.
2.12 2.22 2.32 2.42 2.52 3.25 4.25
2
YCb y vol.
GasoCO? line 0.05 0.89 0.05 0.27 0.12 0.25 0.10 0.18 0.08 0.136 0.06 Trace 0 0 1 h-one
OF SAMPLES
hfANHOLE N O .
3
R b y vol.
TAKEN DURISG
MANHOLE N O .
7;b y
4
TEST
So. 1
h1ASHOLE S O .
vol. Time GasoTime Gaso- Time P.M. COz line P . M . COz line P.M. 2.13 0.05 2.19 2.16 0.08 0.67 2.20 2.23 0.10 0.23 2.21 0.10 0.28 2.30 2.33 0.06 0.10 2.26 0.07 0.12 2.40 2.4,3 0.06 0.04 2.31 0.05 0.11 2.50 2.53 0.06 Trace '2.41 0.05 Trace 3.00 3.30 0.05 Trace 2.51 0.05 Trace 3.45 4.25 0.05 Trace 3.01 0.10 S o n e 4.35 3.45 0.05 None 4.30 0.05 Xone
6
ccGaqob y vol.
CO, 0.04 0.05 0.09
.... .... . . . ....
line 0.20 Trace Xone Sone Kone h-one >-one
explosive limit of gasoline-vapor-air mixtures, j j gallons of gasoline would produce enough vapor t o render explosive t h e air in 1900 ft. of a 9-ft. sewer, assuming 1 Methods of analysis are shown in a previou3 report. THISJ O U R N A L , 5 (1913), 1 1 2 . See THISJ O U R N A L , 7 (1935), 414.
Sample tube
FIG. 2-DEVICE
Broid strap tube support FOR
HOLDING EVACUATED S A M P L E TUBES
the gasoline. It is evident t h a t I barrel of gasoline (jg gallons) poured all a t once in a manhole of a fastflowing sewer renders t h e air explosive for only a few minutes a t a n y particular point. TEST SO. 2
There follows a description of the second test made t o determine t h e quantity of gasoline necessary t o render sewer air explosive under certain conditions. I n this test the covers of the manholes were not removed (as was the case in the previous tests). The hose connection t o the p u m p was let down in some
752
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
cases t o within z in. of t h e sewer water and in other cases t o within z f t . The most important difference over t h e first test was in t h e fact t h a t the gasoline, instead of being dumped into t h e sewer all a t once, was allowed t o dribble down manhole No. I a t the rate of j gallons per minute, requiring 1 1 minutes for the barrel of jj gallons t o empty itself. The temperature of the sewer air a t 11.40 A . M . vias z o o C. ( 6 8 " F.). The temperature of the outside air was 24OC. ( ; s o F.). A sewer-air sample, collected a t station No. z before the gasoline was dumped, contained 0.20 per cent of carbon dioxide and FIG. 3-hIETHOD O F COLLECTING SEWER no traces of comAIR SAMPLES bustible gas. The results of the analyses of samples of sewer air collected a t t h e four manholes appear in Table IV. Some interesting results were obtained b y alternately raising t h e hose from z inches above t h e water t o 2 feet above. As will be noticed, the highest percentage of gasoline obtained from the samples taken z feet
1701.
7, No. 9
gallons of gasoline per minute introduced into t h e sewer under t h e above conditions would produce a dangerous condition as long as the flow lasted. TEST K O . 3
In order t o better understand what effect on t h e vaporization of gasoline a sewer outlet entirely submerged (by high water of the Allegheny River, for instance) would have. Test No. 3 was conducted on October 26, 1914. X bulkhead was built in the sewer a t manhole S o . 3 on the map. Part of the flow was diverted into the old sewer adjacent by means of sandbags placed farther up, and then the water in t h e sewer was allowed t o back u p gradually. The gasoline was dumped into t h e 5th manhole a b o w a t the rate of 5 gallons per minute. T h e effect of having t h e sewer outlet submerged b y high water in Allegheny River would be a slowing-up of t h e velocity of the sewer, and consequently v i t h t h e same inflow of gasoline there would result greater evaporation of gasoline in the sewer over a given length of time t h a n if the gasoline were rapidly swept away b y a fast current. I n other words, there should be required a smaller quantity of gasoline t o produce a dangerous condition, or t h e same quantity of gasoline would stay longer at a given spot. Samples were taken a t the four other stations on regular schedule, alternately z inches and z feet above, from 1 1 . 1 0 A . X . until 3.30 P . U . T h e results given in Table V were obtained. T h e results of this test prove t h a t with a sewer submerged by high water extremely dangerous conditions can result from a small amount of gasoline -4s will be noted from these analyses. there existed, be-
T A B L EIV-AICALYSES OF SAMPLES COLLECTED D U R I X G TESTN o 2 ' DATE-Oct. 8, 1914. Velocity of Sewer Water, 5.38 f t . per sec. Amount of Flow. 10 95 f t . per sec Surface of Area of Flow, per second, 31 53 sq. it. MANHOLEKO. 3 MANHOLENo. 4 MANHOLENo. 6 MANHOLENo. 2 Per Time a f t e r Height of Per Time after Height of Per T i m e after Height of Per Time after Height of entrance of hose above cent entrance of hose above cent entrance of hose above cent entrance of hose above cent water of of gasoline Easoline water water of of gasoline gasoline water Minutes Inches gasoline Minutes Inches gasoline Inches gasoline Minutes Minutes Inches gasoline 2 1.28 0.26 3.0 1.63 1.01 4.5 2 1.67 6.5 2 1.51 0.46 8.5 24 0.27 7 10.5 1.17 1,07 0.40 12.5 24 0. I? 14.5 0.83 1.14 0 . I6 19.5 24 0.10 Traces 29.5 2 Traces None 39.5 24 None 2 None 49.5 None
above was only 0.70 per cent. I t will also be noted t h a t t h e sewer rapidly cleared itself of gasoline vapor a t any one point in a very short time. There were required 1 1 minutes to d u m p in the gasoline; 13 minutes after t h e inflow of gasoline had ceased there was found ( S o . 2 Station) 1.14 per cent of the vapor, 2 in. above t h e water; 18 minutes after t h e inflow of gasoline, only a trace of vapor was left in the sewer air. At N o . 4 manhole, t h e gasoline vapor was not swept out so quickly. I n 16 minutes t h e amount was 1 . 1 0 per cent ( z in. above), and in 3 1 minutes 0 . 1 2 per cent. During certain periods, a t z inches above t h e water, very dangerous atmospheres existed, but in all cases, a t z feet above the water, the quantities discovered could not propagate flame. Upon ignition of t h e gasoline a t any time extending over a period of, say, 1 5 minutes after t h e gasoline was dumped in, a rapid sheet of flame would have swept along the sewer. The test shows, therefore, t h a t 5
tween Stations KO. 3 and N o . 4, a distance of about j o o feet, a dangerous condition j hours after t h e gasoline was run in. I t will also be observed t h a t t h e percentages of gasoline were gradually b u t noticeably increasing a t Stations No. I and S o . 2 above them. I t can be readily seen t h a t if, a s might happen, a sewer were submerged for several days or a week a t a time, a very dangerous condition would result if j gallons of gasoline were t o escape (through t h e carelessness of employees) into it from garages and drycleaning establishments or other places located on its drainage basin. TEST KO.
4
The last of the four tests was carried out November 6th. Conditions were kept t h e same as on October 26th with t h e exception t h a t one-half t h e quantity of gasoline was used ( 2 7 l / 2 gallons) and samples were not taken till the gasoline had been entirely dumped. One-half barrel of gasoline was dumped into the sewer
T H E JOGRiYAL OF I S D C S T R I A L A N D E N G I S E E R I N G C H E M I S T R Y
Sept., 1915
753
TABLE \'-h'ALYSES MANHOLENo. 1 Height of Per hose above cent of water Time Inches gasorine
OF SAMPLES COLLECTED D U R I N G TESTNO. 3 MAXHOLENo. 2 MANHOLEh'o. 3 Per Height of Per Height of cent hose above cent hose above of of water water Time Inches gasoline Time Inches gasoline
....
.. 2
0.86
12.00 12.30
24
0.81 0.86
1.00 1.30 2.00 2.30 3.00 3.30
24 2 24
0.82 0.63 0.53 0.55 0.50 0.68
11 30
.....
1.00 1.30 2.00 2.30 3.00 3.30
..
....
24 2 24 2 24
0.10 0.10 0.13 0.12 0.14 0.20
7
....
1.00 1.30 2.00 2 70 3 00 3.30
24 2 24 2 24 2
a t 11.45 A . U . and samples were collected every half hour, starting a t 1 2 &I.% until 4.30 P . M . , a t four manholes intervening between this point and thc bulkhead. The analyses are shown in Table 1-1. TABLE VI-ANALYSES 'Time 12.00 12.30 1.00 1.30 2.00 2.30 3.00 3.30
4.00 4.30
OF
Height of hose above water Inches 2 247 24 24 2
24 2 24
.....
....
0.11 0.04 0.09 0.13 0.14 0.20
SAMPLES COLLECTED DURISC; TESTA-o. 4 PERCENTAGES OF G.4sor.rsE VAPOR Manhole hlanhole Manhole Manhole No. 1 hTo. 2 So 3 KO.4 0.58 0.50 0.81 0.30 0.06 0.35 0 . 14 0.07 0.36 0.51 0.08 0.06 0.08 0.05 0.33 0.33 0.07 0.06 0.2; 0.42 0.23 0.39 0.07 0.02 0.08 0.0; 0.22 0.54 0.08 0.18 0.38 0.08 0 21 0 52 0.09 0.11 0.08 0.07 0.14 0.14
2
.... , . .
7
24
2
MANHOLENo. 4 Height of Per hose above cent water of Time Inches gasoline 11.10 2 0.96 11.20 24 0.76 7 11.30 1.15 12.00 0.95 24 2 12.30 1.15 24 0.90 12.40 1.00 2 1.05 1.30 24 0.89 2 2.00 1.02 24 2,30 0.36 7 I .24 3.00 2? 1 06 3.30
into a ~j cc. glass bulb connected with a mercury vacuum pump and a mercury manometer. First t h e glass bulb containing t h e gasoline was cooled a t a temperature of - ; S o C. (the temperature of solid carbon dioxide and acetone) and the air removed from the system by means of the pump. At a temperature of - ; g o C. none of t h e gasoline samples had an appreciable vapor pressure. Next t h e bulb with its
Several samples were taken a t a manhole above the point where the gasoline was emptied. The samples analyzed as follows: Percentages in Sample So. 1 Carbon dioxide (COz), . . . . . . . . . . . . 0 . 0 7 Gasoline., . . . . . . . . . . . . . . . . . . . . . . Sone
Sample No. 2 0.10 Sone
These two samples were taken t o ascertain whether or not the gasoline vapor has a tendency t o travel u p the sewer when the outlet is submerged. I t seems probable from t h e results of these two samples t h a t the vapor moT-ed b u t very few feet u p the sewer above t h e point where the gasoline entered. I t will be noticed, on comparing Test 3 0 .4 with Test K O . 3 , especially manhole No. 4 of October 26th: t h a t the results of t h e analyses are almost in the same ratio as t h e quantities of gasoline used, i. e . , t h e samples collected on November 6th, when one-half barrel of gasoline was used, show only approximately one-half t h e percentage of gasoline vapor as compared with t h e samples collected October 26th, when one barrel of gasoline w a s utilized. T h e gasoline used for both tests was of the same grade. Consequently, since one barrel contained twice the volume of lighter hydrocarbons in one-half barrel, i t should furnish in t h e sewer about twice t h e percentage of vapor.
tc >
a
w
b L
z
3
L I
Y
ciE
VAPOR P R E S S C R E S O F D I F F E R E K T GRADES OF GASOLINE
Of much importance on the question of explosions in sewers caused b y gasoline is the volatility of t h e gasoline, or the rate of evaporation. Gasoline of high volatility, when dumped into a sewer, evaporates much more rapidly, and other things being equal will make explosive a greater volume of sewer air in a given time t h a n gasoline t h a t is not so volatile. T o obtain information regarding this matter, vapor pressure determinations were made of five different grades of gasoline. The results are shown in Fig. 4. The determinations were made b y introducing t h e gasoline
TEMPERATURE-DEG CENT
FIG YA VAPOR PRESSURE C U R V E SOF DIFFERENTGRADESOF GASOLINE
gasoline was surrounded b y a stirred constant temperature b a t h and the pressure in millimeters of mercury noted a t different temperatures. Sufficient time was allowed before taking readings for equilibrium t o take place. Pressure readings could be made with a n accuracy of * I millimeter of mercury and ternperGLture readings with a n accuracy of * 0 . z O C
7 54
T H E J O U R h T A L OF I N 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
Great differences will be noted in t h e results. For instance, a t ordinary temperature, 1 7 . j" C., t h e vapor pressure of cleaners' naphtha is 4 0 mm. of mercury; of 61' BC. gasoline, 8 2 m m . ; of 69' Bi..gasoline, I I O mm.; and of 73' Bi.., 2 1 2 mm. When these vapor pressures are expressed in terms of t h e percentage by volume of gasoline vapor t h a t will mix with air a t the temperatures given, t h e results become: Cleaners' n a p h t h a , 6 4 O Be. gasoline,
69' BC. gasoline, 73' Be. gasoline,
401760 X 100 = 5 . 0 per 8 2 / 7 6 0 X 100 = 1 1 , O per 11OIi60 X 100 = 15.0 per 212/760 X 100 = 2 8 . 0 per
cent cent ce,nt cent
I n other words, air will uniformly mix with almost 6 times as much vapor from 73' B4. gasoline as from cleaners' naphtha a t a temperature of I 7 . j O C . Gasoline is not a definite compound and the specific gravity test is a poor criterion of t h e nature of a particular distillate; hence, t h e above figures are only approximate t o what t h e vapor pressure of different distillates from gasoline of the specific gravities given must be, b u t they indicate t h e relative danger of explosions due t o dumping into a sewer gasoline of different grades. S L- M M A R Y
One barrel ( 5 j gallons) of gasoline dumped into the sewer, all a t once, resulted in t h e formation of a n explosive mixture for a few minutes only a t any one particular point. This condition existed close t o t h e surface of t h e sewer water and did not extend very far into t h e upper sewer air. When one barrel ( j j gallons) of gasoline was dumped into t h e sewer a t t h e rate of j gallons per minute, t h e highest percentage of gasoline vapor z feet above the sewer water was 0 . 7 0 per cent. The gasoline vapor was practically all swept past the manholes in Under these same conditicns from 18 t o 30 minutes. of test, except with t h e velocity of the sewer mater much less, dangerous atmospheres existed in t h e sewer 5 hours after the gasoline was poured in. A C K Ii0 W L E D G M E N T S
T h e authors wish t o acknowledge the valuable assistance rendered t h e m in conducting these tests, b y hIr. W. H. Coster, Superintendent of t h e Board of Fire Prevention, Dept. of Public Safety, hIr. XI. S. Evans, Chief of the Bureau of Tests, and hlr. J. Chas. Palmer, Division Engineer, Bureau of Highways and Sewers, all of the staff of the Department of Public m'orks, City of Pittsburgh. They were present at all tests, made numerous suggestions and helped in many ways. XIr. X. S. Sprague, Superintendent of t h e Bureau of Engineering, City of Pittsburgh. also rendered valuable assistance. 1;.
s.
BUREAZ:O F MIXES. PITTSBURGH
THE ANALYTICAL DISTILLATION OF PETROLEUM-11' By W. F. RITTMANA N D E. W. DEAN Received June 26, 1915
I n a previous paper2 attention was called t o the need in t h e scientific and in t h e commercial petroleum world of an accurate and satisfactory method for the quantitative distillation of crude oil and its products. 1
2
Published with the permission of the Director of the Bureau of Rlincs. R i t t m a n and Dean, THISJOURNAL, 7 (1915), 185.
Vol. 7 , No. 9
T h e results of a series of redistillation experiments showed t h a t a method of efficient separation, involving the use of a Hempel column of moderate dimensions, attained a degree of separation of 56 per cent, on t h e arbitrary and empirical scale fixed by experimental conditions. The Ubbelohde-Engler method, representing moderate separation, was rated a t 26 per cent on the same scale. T h e Allen-Jacobs method of minimum separation obtained a degree of separation of 14 per cent. I t was shown also t h a t a single Hempel distillation was more efficient t h a n t w o successive open flask distillations. SCOPE O F THE P R E S E N T P A P E R
The experiments described in the present paper deal chiefly with a comparison of results attained by t h e use of various types of fractionating apparatus. Crude oil distillations have been made with representatives of nearly all types of still-heads nov.7 in use and figures are given which should be readily intelligible t o t h e petroleum technologist. Attention has been given in the experiments both t o degree of efficiency attained and t o mechanical details. I n the earlier paper no attempt was made t o determine t h e relative advantages of various specific methods. I t mas, however, clearly indicated t h a t the class involving efficient fractionation seemed most promising, as they attained most nearly the desired end, which is the separation of the oil into its constituents. The method of minimum separation seems t o have advantages for t h e examination of emulsified or difficultly distillable oils b u t i t involves rather tedious manipulation, and for t h a t reason a s well as o n account of its inherently inefficient fractionation, it is not t o be recommended for general use. The whole problem, except for the matter of "cracking," seems t o resolve itself into applying t h e principle of efficient fractionation in some way which will be satisfactory t o t'he laboratory worker. A further series of experiments has been outlined which should furnish definite and conclusive evidence v-ith regard t o the matter of cracking. I t seems improbable, however, t h a t the results obtained will alter in any way the conclusions drawn from t h e present investigation. With Pennsylvania crude oil there is strong evidence t h a t no cracking occurs a t temperatures up t o a t least 3 0 0 ' C. and in addition it has been shown t h a t the possibility of cracking is b u t slightly greater with efficient t h a n with moderate separation. G E S E R A L OTJTLISE O F PROCEDURE
I t was decided t o make first a comparison of stills from as comprehensive a list as would in any possibility be available to the petrole\um chemist. Stills were not. however, purchased indiscriminately but consideration was given in most cases t o t h e possibility of too efficient condensation. At temperatures ranging betxl-een . 2 j o o and 300' C. any moderately long tube mill act as an air condenser and, on this account, few still-heads of excessive length were secured. Still-heads of all types listed in t h e catalogues of chemical supply houses were purchased and. i n
