d S A L I'TICd L EDI T I O S
106
modifications of the above method and also hy the regular -4.S.T. 11. method. T a b l e I-Sulfur
C o n t e n t of C a r b o n Disulfide a n d T h i o p h e n e by R e g u l a r a n d Modified M e t h o d s SULFUR FOVND Lam ABSORBER CHIXISEY
SULFUR PRESEKT
CARBOX D I S U L F I D E
Pcr c e n t
Per cenl 0.195 0.188 0.185
0.19s 0 198 0.198
4-b 2-b
2
4-b
3 Standard A . S. T. 31.standard
T-ol. 2, s o . I
I t \Till be noted that, the two methods give very close results, with a slight tendency for the modified method to give higher results. The average of twenty determinations shows a value about 0.003 higher. llthougli this difference is small enough bo be within the limit, of accuracy, its tendency to be always in t,he same direction is probably not accidental. It can probably be att,ributed to the greater efficiency of absorption in the filter tube than in the bead absorber. Discussion
THIOPHENE
0 100 0,100 0.100 0.257 0.257 0,257
0 096 0.097 0 101 0,255 0 257 0,255
A . S. T . A I . standard 3 Standard 3 Standard A . S. T. SI. standard 3 4-b 3 Standard
2-b 4-b 4-b 2-b
The results, shown in Table I, agree very well with each other and with the theoretical. It should be noted that all the data on solutions of thiophene are closer t o the theoretical values than those on solutions of carbon bisulfide. Thib suggests t h a t solutions of pure thiophene would serve excellently for the calibration of any sulfur lamps. Since the method was designed primarily as a practical substitute for the A. S. T. AI, method, i t is of greater interest to compare the results obtained by both methods. A number of determinations were run simultaneously on samples of commercial gasolines, one determination being made by the standard A. S.T. AI. method, and one by the modified method, using lamps 2-a and 2 4 , without the entirely enclosed chimney. Blank determinations were run for each method and corrections made accordingly. The determinations were made in a routine way with no special precautions. Characteristic results are shown in Table 11. T a b l e 11-Comparison of S u l f u r C o n t e n t of C o m m e r c i a l Gasolines b y E t h y l Gasoline a n d A . S. T. M. M e t h o d s KO.
A . S.T. h f , I~ETHOD Per cent 0.126 0.113
0,079 0.082
0 0 0 0 0 0
034 068 103 134 129 101
ETHYL
ETHYL
A. S. T. 31. G.ASOLISE
GASOLINE LfETHOD
S O .
Per cent 0.136
11
0.109 0.085 0,086 0.034 0.068 0.1Oi 0.141 0.135 0.099
12
13
14 15 16 17
18
19 20
AfETHOD
Per cenl 0 05s 0 096 0,0i6 0.075
O.Oi6 0.085 0 087 0 009 0 150 0 082
AlETIiOD Per cent 0 05; 0 100 0 084 0 083 0 090 0 094 0 083 0 012 0 144 0 0i6
A Laboratory Shaker' Henry E. Bent CHEXZICAL LABORATORIES, HARIA R D UNIVERSITY, CAMBRIDGE, S14sq
HE shaker shon n in the accompanying figure has been in continuous uae for the last two years, during aliich time it has required no attention aside from occasional oiling. It consists of a 6-foot (1.8-meter) 0.5-inch (1.3-cm.) steel rod, pivoted a t one end, the other being held by six heavy screen door springs. The rod with attached appaiatu; vibrates with its own period, a small impulqe approximately in phase being imparted by a sniall spring actuated by a constant-speed motor. The period of the shaker is made to approximate that of the crank by means of an adjustable 1%-eightwhich slides on the steel rod. $pparatus is attached directly to the rod by ordinary clamps. The shaker is noiseless, the slight noise from the motor being tlie only sound. Rapid shaking of delicate glass apparatus is possible inasmuch as the drive is not direct but through springs. The amplitude may easily be varied by a 1
Received November 8, 1929
The following advantages may be claimed for the devices described above over the standard apparatus: (1) Lamp 1 permits ready adjustment of the flame d u i h g the progress of the determination. ( 2 ) Lamps 2-a and 2-b permit ready adjustnient of tlie flame during the determination and also allon- tlie amount of fuel burned to be determined by volume rather than by weight'. thus saving considerable time when a nuniber of determinations are made simultaneously. They are also more readily adaptable for use with the special chimney (Figure 4) than the standard lamp Jvould be. (3) The absorption tube (Figure 3 ) gives very excellent contact between the air and the soda solution which should make for very efficient absorption of the sulfur trioxide. The air flow through it, is entirely free from pulsations, making the flame burn more steadily than it does with the standard set-up. Titration of the soda at' the end of the deterniination is effected in a flask, and is much more comfortably made than in tlie standard absorption tube. (4) The modified chimney permits the elimination of tlie lilank determination, which is not only advantageous from tlie standpoint of saring time, but, also increases the accuracy of the determination, since with the standard apparatus there is no way of knoning whether the volume of air passing through the blank is identical with that passing through the actual determinations, and this makes the correction for blanks somewhat uncertain if quite pure air is not available. .is pointed out above, these devices may all be uaed together or any one or more of them may be coniliined vMi parts of the standard apparatus. Sote-The complete apparatus described abox-e, consistingof I d m p 4 - b , chimney 4 - b , and absorption system 3, may now be obtained from the Vonkers Laboratory Supply Co., 515-132nd St., S e w York, PI'. 1 ' .
slight shift in the sliding weight which changes the natural period. A4tthe pivot the angular motion is about 3 degrees. Connections for gas, water, or even a glass line may be made a t this point, in the latter case using a spiral. A 'jao-hp. c o n s t a n t - s p e e d m o t o r n-as found to supply inore than sufficient power. The other materials are easily obtained and require very little time for assembling. The frequency of shaking was about 200 r. p. ni., the amplitude 4 inches (10 em.); and t,he weight 3 kg. Aside from stiffening of the rod, which is necessary a t higher frequencies, a wide range of speed and amplitude is possible.
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