T H E J O U R N A L O F I N D U S T R I A L A N D ELVGINEERING C H E M I S T R Y
210
aene. From t h e partial pressure of the gasoline its volume is computed. W A T E R V A P O R IX AIR can be determined in t h e same manner as gasoline or benzene vapor. A temperature of -78' C. (the temperature of liquid carbon dioxide) can be employed. At this temperature t h e vapor pressure of ice is practically nil. APPLICATION
OF
?JETHOD
TO
OTHER
MIXTURES-
Aside from t h e separation of natural gases, illuminants in coal gas, gasoline, benzene and water vapor in air, t h e method should be useful in examining t h e various mixtures produced in t h e destructive distillation of different fuels, concerning which a large amount of experimental work is performed each year. The authors are cooperating with Dr. W. F. R i t t m a n , of the petroleum laboratory of the Bureau, in t h e cracking of oils. T h e different gases produced b y cracking oils and t h e pure liquid paraffins are being examined b y t h e method of fractional distillation. I n this may facts of fundamental importance regarding t h e "cracking" of oils will be learned. I n the case of fractional distillation of liquids a t ordinary or elevated temperatures, t h e distillations have t o be repeated several times in order t o obtain t h e diEerent fractions in a fairly free condition. T h e same is true of t h e fractional distillation of gases in a vacuum a t low temperatures. T h e Bureau has redistilled some fractions four and five times t o obt a i n gases t h a t were analytically pure. T h e apparatus required is such as can be easily obtained b y many laboratories. 4 vacuum p u m p for withdrawing the gases, glass vessels for trapping them, a gas burette for measuring them, a n d pentane thermometers for measuring temperatures are easily procurable. Liquid air can be obtained a t several different places in t h e Cnited States, and liquid carbon dioxide in all large cities. T h e only special part of the apparatus is the liquefaction bulb a n d this is very simple. Precise thermometric measurements are not necessary and pentane thermometers accurate t o I or 2' C. can be used.
T'ol. 7, NO. 3
nitrogen were obtained pure. The same procedure was followed in fractionating coal gas. At t h e temperature of liquid air, the first fraction consisted of methane, nitrogen, carbon monoxide, hydrogen, and oxygen with small quantities of ethane and ethylene. Also the residue contained some of t h e five gases first mentioned. Hence the distillate and residue were refractionated until the distillate was freed of ethane and ethylene, and none of t h e five gases remained in t h e final residue. T h e procedure now adopted, which is faster a n d more economical of liquid air, consists, in t h e case of coal gas, for instance, of first removing as much gas as possible a t t h e temperature of liquid air. Call this fraction A . The residue is then subjected t o distillation a t a temperature n o t higher t h a n ----140' C. Call the distillation so obtained B. S e x t fractionate t h e residue from B a t a temperature not higher t h a n -120' C. Call the distillate so otained C. T h e n fractionate t h e residue from C a t a temperature not higher t h a n -78' C. and call t h e distillate so obtained D . There are thus obtained four fractions, A , B , C and D , each containing some gases t h a t belong properly t o other fractions and which must be purified by further fractionating. A s each distillate was obtained i t was removed from the pump and transferred t o another container. The residue in each case was left in t h e liquefaction bulb. For instance, after the first distillate was removed ( a t the temperature of liquid air): t h e liquid air was removed and t h e bulb surrounded with light gasoline of a temperature not higher t h a n - - - I ~ o ' C., and so on. The following d a t a show the results of fractionating t h e artificial illuminating gas of New York City: FRACTIONATION ANALYSISOF hTEw YORKILLUMI~-ATIKG Gas
. .............. . ., .. . . .. .
Original volume of g a s . . . . . . . . . . . . COS removed by caustic p o t a s h . . . . . .
I
,
,
cc. 1007.6 32.3 _ I _ _
Volume taken for fractionation
975,3
975.3 cc. Liquefied a t temperature of liquid air
I
A-
Residue
CHEMICAL LABORATORY BUREACO F M I R E S , P I T T S B U R G H
A RAPID METHOD OF FRACTIONATING GASES AT LOW TEMPERATURESi By G. A. BURRELLA N D
I.
w.
C
'
Residue ~-_ 26 1 cc. Giquefied a t -78' C
_ _ _ I -
ROBERTSON
Received December 9, 1914
I n this paper is shown a more rapid method of fractionating gases in a vacuum a t low temperatures t h a n hitherto used by t h e Bureau of Mines. T h e particular gas worked with was t h e artificial illuminating gas of New York City. I n previous experiments t h e authors continued t o refractionate a particular fraction until the gases obtained were analytically pure. For instance, in working with natural gas, t h e first distillate was obtained at t h e temperature of liquid air. T h e distillate a n d residue were then refractionated until methane a n d 1
Published by permission of t h e Director of t h e Bureau of Mines
~I"l
I cc.
The above diagram s h o n s t h e method of obtaining t h e first four distillates, A , B , C and D . Next the distillate A was reliquefied a t t h e temperature of liquid air a n d t h e distillate from i t removed. The residue, which was very small, was left in t h e liquefaction bulb and t h e distillate B added t o it. The latter was t h e n refractionated a t a temperature not C. The distillate and residue higher t h a n -140' so obtained were both refractionated again, because t h e pressure manometer showed t h a t one fractiona-
Mar., 1915
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 C H E M I S T R Y
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thermometer should be about I inch from t h e surface of t h e liquid, so as t o get t h e vapor temperature only, which should never go above 108' C. Connect t h e delivery t u b e t o t h e figure S condenser (C) which has one of its curves nearly filled with water a n d submerged in cold water in a 500 cc. beaker, a n d i t s other free end dipping into about 75 cc. of water i n a 300 cc. beaker. T h e S condenser is about 18 inches long a n d l / ~ inch inside diameter b u t tapers t o about '/4 inch a t t h e ANALYSIS OP NEWYORK CITY ILLUMINATSNG GAS upper, a n d 1 / 8 inch at t h e lower end t o facilitate washPer cent Per cent ing and make the bubbles of gas small as t h e y emerge COz ................... 4.7 C2H4................. 9.8 02..................... C8H6 ................. 2.7 into beaker. This makes a perfect condensing apCO.. .................. 2918 C4Hs. ................ paratus i n this case; it is very simple, easy t o handle, COHO ................. 1.6 1.5 Hz ..................... 32.0 Nz ................... 1.7 CHI ................... 13.1 has only one rubber connection besides t h e rubber CrHs ................... 2 . 8 C3H8. .................. 0.3 Total.. ............. 100.0 stopper, a n d no cocks or corks t h a t leak. Nothing The various fractions were analyzed as described in a is lost through i t except air from t h e flask a t t h e very previous communication t o THIS J O U R N A L . ' start. CHEMICAL LABORATORY, BUREAU OF MINES Distil from I O t o 1 5 minutes, boiling gently, a n d PITTSBURG keeping t h e vapor temperature at 107' for a t least 5 minutes. The arsenic, as AS Cla, is all distilled over RAPID ANALYSIS OF ALLOYS FOR TIN, ANTIMONY even if t h e alloy contains 5 per cent, which is rare. AND ARSENIC ARSENIC-Wash out t h e condenser into t h e 300 cc. By F. A. STIEF~ a n d a d d a n excess of about 2 g. sodium bibeaker, Received December 14, 1914 carbonate t o this solution which should now have a The iodine a n d permanganate titrations in t h e volume of about 2 0 0 cc., a n d be warmed t o a temperafollowing method are well known, a n d used with many ture of about 2 7 " C. Titrate with standard iodine variations i n many laboratories, b u t this combination solution and starch t o deep blue, which color will t a k e method of determining tin, antimony a n d arsenic all 0 . 2 cc. of iodine solution in a blank under t h e conon t h e same sample a n d without filtering, as well as ditions used. many important details, is original. Equivalent in grams of 1 cc. of solution TIN ARSENIC IODINE STANDARD SOLUTIONS METHOD-DiSSO1ve 0 . j gram of t h e finely divided Iodine .......................... 0.010672 0.005000 0.003150 alloy, best in t h e form of thin foil-like shavings KMn04 IRON ANTIMONY (sawings or very small drillings will do), in exactly Permanganate ................... 0.0026315 0.004650 0.005000
tion was not enough. The final residue was left in t h e liquefaction bulb and t h e distillate C added t o it, and so on. The last residue obtained a t -78" C. was allowed t o evaporate at room temperature a n d its pressure read. Previous experimentation had shown t h a t at -78' C. practically t h e only gas remaining in coal gas is benzene. There follows a n analysis of t h e artificial illuminating gas of New York City as made by this method.
ANTIMONY-Coo1t h e solution left in flask, a d d about 130 cc. cold water a n d titrate with standard perman-
8 cc. concentrated sulfuric acid in a 300 cc. Florence flask covered with a small watch glass: boil t h e solution. Cool, a d d exactly 5 cc. of water; cool, a d d a bulk of about 0.5 cc. clean, granulated pumice stone, and exactly 2 0 cc. concentrated hydrochloric acid. Now insert in t h e flask a clean rubber stopper, carrying a centigrade thermometer (A) a n d a delivery t u b e (B). T h e 1 Burrell, G. A. and Robertson, I. W., "The Separation of the Illurninants in Mixed Coal and Water Gas," THIS JOURNAL, 7 (1915), 17. 2 Chemist, Hoyt Metal Company, Granite City, Illinois.
ganate solution. T h e blank is 0.1 cc. About 4 cc. of hydrochloric acid must be present during this titration; usually enough is left in t h e flask from t h e distillation. TIN--If t h e antimony was found t o r u n below 14 per cent or 0.07 g., a d d enough dissolved SbCls t o t h e solution t o make i t contain just about 0.07 Sb. This is done t o insure perfect reduction of t h e tin, a n d for t'he sake of making uniform t h e effect of t h e antimony on t h e titration of tin with iodine. Then a d d exactly 6 cc. concentrated sulfuric acid, 6 0 cc. concentrated hydrochloric acid a n d about 6 inches of clean, soft, No. 14,pure F e wire ("hay" wire is best, used in a-inch lengths, a n d cleaned with dilute hydrochloric acid just before using). Boil gently one-half hour, a d d 4 t o 6 inches more wire, a n d boil one-half hour longer. Take off heat, wash down t h e inside of t h e flask with distilled water, fit a clean rubbei stopper loosely in t h e flask, a n d allow about two minutes for all air t o be expelled from t h e flask a n d replaced b y hydrogen, water a n d hydrochloric acid vapors; then cork tightly, a n d quickly place in cold water. When cold (about 20' C. is best) pour t h e solution into a 500 cc. beaker (leaving t h e iron wires i n t h e flask); p u t 1 5 0 cc. cold, recently boiled distilled water into t h e flask a n d pour this into t h e beaker. This should give a final volume of between 300-350 cc. Titrate quickly with standard
