73-1
T H E J O U R N A L O F i.'iDS7STRIA L A N D E S G Z ~ V E E R I N GC H E M I S T R Y
found difficult t o make this vacuum chamber absolutely tight so a petcock was soldered on and frequently t h e vacuum was attained again b y means of t h e pump. This trough saved considerable cost in CO: and alcohol. preventing t h e former from being melted b y the heat in t h e room t o a considerable extent and 'enabling one t o collect all of t h e alcohol after t h e determination b y allowing t h e COS t o vaporize off. 111-The P?OS, which soon ceased t o be active in respect t o water vapor, necessitated cutting t h e tube leading from this bulb and connecting the two pieces by means of rubber tubing. I n this way fresh P 2 0 s a n d glass wool could be easily inserted. Several other points of operation may be of interest. A n ordinary Gerylr vacuum p u m p , single stroke, was used and found effective. I t might be well t o state t h e well-knovn method of making C02-snow economically. A cylinder containing j o lbs. C 0 2 a t high pressure is inverted t o an angle of about 4j O and the snow which issues forth when t h e valve is opened quite Ti-ide is caught in a canvas bag about 1 2 X 18 in. in size. The snow keeps vel1 in a cardboard box, I t was found t h a t more constant results were obtained by bringing the bulb up t o room temperature after immersion in the freezing mixture. by means of inserting it in water for I O min. I. more careful control of the temperature can thus be maintained. Although this article is intended only t o give certain suggestions for t h e operation of Burrell and Robertson's apparatus it might be of interest t o show some results obtained with it using coke-oven gas, t o supplement the results obtained a t t h e Bureau of Mines on Pittsburgh illuminating gas.
Yol. 8,No. 8
series) there appears t o be little ltnown and with reason as its composition varies in different plants. With an actual recovery during the period of one month of 2 . 2 0 gals. per net ton of coal carbonized of benzol toluol solvent naphtha, t h e average of many results determined b y this apparatus indicated an amount equal t o 1.70 gals. per ton coal or 2 2 . 7 per cent lorn. The recovered hydrocarbons in practice consisted in t h e following:
+
+
HYDROCARBON: 90Y0 Benzol Per cent recovered..
.,.,
67.5
Crude Toluol 29.3
Solvent A-aphtha 13.2
This would seem t o indicate t h a t all of the benzol, part of the toluol and little if a n y of t h e solvent naphtha C.: but was condensed a t the temperature of -78" this is merely a suggestion as it has not been as yet thoroughly investigated. In conclusion i t might be added t h a t this method is more difficult of operation t h a n it appears. The apparatus is delicate and t h e conditions as stated above must be rigidly adhered t o in order to obtain consistent checks. As a method for determining benzol scrubber efficiency i t is of some value; as a method of absolute determination of benzol, toluol and solrent naphtha it is of doubtful value, giving results apparently 24 per cent lower t h a n those obtained in actual practice. Furthermore, the operation of the method requires a man skilled in handling such apparatus. LABORATORY OF
& C O A L PRODCCTS CHATTANOOGA, TENXESSBE
CHATTANOOGA G A S
COMPANY
AN AUTOMATIC PIPETTE] By XLEXAXDERLOWY
Received March 28, 1916 Gas d (dup!icates) Bar. pressure, m m . , , . , . . . , . . 742 . 0 742.0 Partial press. benzol vapors.. . . 5,4 5.2 Per cent benzol in gas.. . . . . , . , 0,729 0.702
Gas B (duplicates) 741.0 541.0 1.8 1.9 0.243 0.256
These are typical determinations made b y this machine. Benzol scrubber efficiency does not call for absolute benzol determinations, comparative results before a n d after scrubber being sufficient. Therefore it is not necessary t o have t h e manometer. as carefully leveled as otherwise. Efficiency of scrubbers with t h e above results averaged would be determined zhus:
The extreme results on the above tests would indicate 66.7 and 6 3 . 7 per cent efficiencies, which is as good as can be expected with this apparatus. The resulL using this method as a determination of absolute benzol, toluol and solvent naphtha is somewhat lower t h a n t h a t obtained b y absorption methods and averaged 2 4 per cent less t h a n the amount obtained in actual practice. Benzol it is kcon-n has a sufficiently low vapor pressure at --78" C. t o assert t h a t it is completely condensed; about toluol there appears t o be some doubt, and about solvenx naphtha < amixture of xylol and higher homologues of the benzene
Fig. I shows the entire pipette with t h e modified stopcock adaptable t o any given volume. Fig. z shows the position of the stopcock while t h e liquid is being drawn up. Line A B is the mark of graduation. H shows the chamber below stopcock and G t h e chamber above the stopcock. F is a cylindrical bore through the stopcock connecting chambers I; and H during the process of suction. E is a cylindrical bore ending back of F a t an angle of 9 0 ' . of which C is a continuation and ends a t a slight elevation a t D. Fig. 3 shon-s t h e position of stopcock after it has been turned clocltrvise 90' t o t h a t shown in Fig. z. D shows place closed by thumb. In this position channel C is connected with chamber H through opening E . I n this position channel G is shut off from channel H . TT'ith suction applied a t end of chamber G (Fig. 2 ) . the !iquid is drawn u p through chamber H until it just passes t h e graduated mark A B . The t h u m b is then placed on D so as t o close opening D air--tight.. The stop-cock is then rotated clockwise through 90' thus bringing opening E (the continuation of tube C and D ) t o line of graduation A B and directly in contact with the upper opening of chamber ZI. The t h u m b is then released. -air pressure now forces the exact 1
Patent applied for
Aug., 1916
T H E JOURNAL OF I N D C S T R I A L A N D ENGINEERIXG CHEMISTRY
measured volume of liquid out of chamber H . Any excess liquid drawn u p beyond line A B will be ent r a p p e d in either bore F , or in bore F a n d in chamber G. This excess is returnable b y revolving t h e stopcock counter-clockwise through 90". T h e advantages of this pipette may be summarized as follows: I-It enables t h e operator t o automatically control a n exact measured volume of liquid drawn into t h e pipette. 2-It obviates t h e necessity of adjusting, maintaining a n d manipulating t h e exact volume of t h e liquid once it has passed t h e graduation mark, placed
Frs. 2 S e c t i o n at y - y
FIG.1
FIG.3 - S e c t i o n at x-x
where t h e stopcock meets t h e lower end of t h e valve of t h e pipette. 3-It permits t h e discharge of t h e exact measured volume of liquid from t h e pipette. is exceedingly easy t o manipulate. 4-It CHEMICAL LABORATORY, COMXERCIAL HIGH SCHOOL BROOKLYN NE , W YORK
THE DETERMINATION OF AIR, WATER VAPOR AND NITROUS OXIDE IN MIXTURES OF THESE THREE CONSTITUENTS1 By G. A. BURRELLA N D G. W. JONES Received M a y 19, 1916
T h e authors of this report h a d occasion recently to examine some samples of nitrous oxide (dentists' "laughing ,gas") for t h e presence of water vapor a n d Published with the permission of t h e Director of t h e Bureau of Mines.
735
air. The mixture was first liquefied by means of liquid air, t h e air being t h e n withdrawn with a Topler mercury p u m p , a n d measured. The residual gas was C., t h e nitrous subjected t o a temperature of -78' oxide being then withdrawn and measured. Finally t h e partial pressure of t h e water vapor was measured. This analysis is one of t h e many gas analyses t h a t can be performed by means of t h e apparatus shown in Fig. I . The apparatus is first exhausted of i t s air by means of a Topler mercury pump. and t h e sample of "laughing gas" is introduced a t atmospheric pressure. Next t h e bulb A is immersed in a Dewar flask containing liquid air. After about I O min. t h e air is withdrawn from t h e mixture through t h e pump and measured. T h e vapor pressure of t h e air a t t h e temperature of liquid air is of course very high, a n d t h e air can be readily removed from t h e mixture. T h e vapor pressure of nitrous oxide is I m m . a t a temperature of -144. I " C.,l hence its pressure a t t h e temperature of liquid air is practically negligible. After t h e air has been removed a n d measured, the bulb A is immersed in a mixture of solid carbon FIG.I dioxide and acetone. This mixture Apparatus for t h e gives a temperature of -78 " C. Determination of Air, T h e bulb A is exposed t o this tem-Water Vapor a n d Niperature for about I O min., a n d of t r othe u s oThree x i d e i n Mixtures t h e nitrous oxide is withdrawn through t h e pump a n d measured. The normal boiling point of nitrous oxide is -88. 7 " C . 2 so i t can be readily removed from t h e mixture a t a C. On t h e other h a n d , t h e temperature of -78" vapor pressure of water is practically nil a t a t e m perature of -78" C. so t h a t it freezes a n d remains in t h e bulb A . After t h e nitrous oxide has been withdrawn and measured, t h e Dewar flask containing t h e solid carbon dioxide a n d acetone is removed from around t h e bulb A . The frozen water vapor t h e n vaporizes a n d exerts its partial pressure on t h e mercury in t h e manometer t u b e C. This pressure is, of course, proportional t o t h e percentage of water vapor present. T h e results of t h e analysis of three samples of gas taken from t h e same t a n k follow: PERCENTAGE ANALYSESOF NITROUSOXIDE CONSTITUENT Sample I . . . . . . . . . . . . Sample 2 . . . . . . . . . . . . Sample 3 . . . . . . . . . . . .
AIR 2.0 2.1 2.0
NzO 95.9 95.6 96.2
Ha0 2.0 2.0 2.0
TOTAL 99.9 99.7 100.2
BUREAUO F MINES, WASHINGTON 1 G. A . Burrell and I. W. Robertson, "The Vapor Pressures of Sulliir Dioxide and Nitrous Oxide a t Temperatures below Their Normal Boiling Points," J . A m . Chem. SOC.,37 (1915), 269. 2 G. A. Burrell and I. W. Robertson, LOC. rit.
