May, 1917
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
I n view of the order of magnitude of L / R , as compared with t h a t of R’/R in these experiments (see previous section) it appeared probable t h a t a correction of the linear form, as used by Ladenburg, would be satisfactory; t h a t is, the values of K found are multiplied by the terms (I b.R/L) where b is a constant and R / L is t h e particular value of the ratio of radius of sphere t o height of liquid column, t o give the corrected value K. I n this caqe three equations are obtained, for two unknowns, b a n d K. The mean value of b by solution of these was 11.65, and the corresponding values of K’ were:
+
Sphere Diam. l / k in. ‘ / 8 in. i/a in.
K
R/L 1/126 1/84 1/63
358 339 330
K’ 391.2 386.0 392.0
Mean
K’
389.7
On t h e other hand, by plotting K (uncorrected for height) as ordinate, R / L as abscissa, and extrapolating the closest fitting straight line t o cut the K-ordinate, giving the value K for R / L = o or L / R = w , t h e value K = 386.5 was obtained. Hence, the corrected values are: Ht. correction applied B y formula.. . . Graphically.. ,
R
.......... ... .. 389.7 386.5
k (viscosity relative to water at 20’) 3 9 x 10‘ 3 87 X 10‘
The correction for the length of height of the tube appears rather large, and further work is planned using a wider range of values of L / R , t o test the validity of the linear correction more precisely, as well as a comparison of t h e method with the “shearing” type of viscosimeter. While the viscosity found is very high, it is less t h a n t h a t of t h e turpentine solution of colophony used by Ladenburg (K 1343) a n d was shown t o be of the right order by a comparison with castor oil, a t the temperature given 2 0 ’ C., which made our medium t o be 3.1 times the viscosity of castor oil which, a t 20’ = 10,000K,,,.l Hence by this the viscosity of our medium would be some 31,000 times water. The viscosity of “castor oil” varies considerably but the comparison shows t h e result is of the right order. SUMMARY
I-The application of Stokes’ law t o viscosimetry is discussed, particularly for very viscous media, and with special reference t o the influence of the wall or boundary of the containing vessel. 11-An empirical formula correcting for the influence of t h e wall of a cylinder is obtained which is valid over a wide range. III-uSing this formula and a linear correction for t h e influence of the total height of the liquid column, determinations of the absolute viscosity of very viscous media may be made with relatively simple apparatus, by application of Stokes’ law. T h e author’s thanks are due t o Mr. W. H. Davis for help in t h e experimental work, a n d t o Mr. S. Tompkins for assistance in the computations. RESEARCH LABORATORY EASTMAN KOUAKCOMPANY ROCHESTER, NEW YORK 1
Landolt-Bornstein, 4 Auflage, p. 75.
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A SIMPLE DEVICE FOR THE AUTOMATIC AND INTERMITTENT WASHING OF PRECIPITATES B y ELBERTC. LATRROP Received January 31, 1917
The accompanying illustration shows a simple and efficient form of apparatus for the automatic, intermittent washing of precipitates. The feature which distinguishes this apparatus from the well-known constant level device is the capillary tube (represented in the figure by heavy black lines), the function of which is not only t o permit air t o enter the inverted flask, but also t o produce a n intermittent flow of solvent from the flask. The principle underlying the use of the capillary tube may perhaps be best explained by a description of the operation of t h e apparatus. Suppose t h a t the apparatus is set up as shown, with t h e end of t h e capillary tube, which is full of solvent, just touching t h e surface of t h e solvent in the funnel, and the other tube, which in the apparatus used has been about 5 mm. in diameter, just touching the surface of the settled precipitate. As the solvent passes through the precipitate and out of t h e funnel the level of the liquid above the precipitate will fall below the end of t h e capillary tube. Air will not pass into t h e inverted flask, however, until the level of liquid in t h e t’ a point such that the has differences of hydrostatic pressure in t h e two tubes is sufficient t o overcome the force of capillarity, \ which tends to keep the capillary tube filled with water. In the apparatus as drawn, this point lies just above t h e end of the large tube, so t h a t the precipitate is almost bare of solvent thus permitting each addition of solvent t o drain from t h e precipitate, t h e most efficient method of freeing a precipitate from soluble substances. When this point on the large t u b e is reached t h e air rushes into t h e flask through the capillary tube, the funnel fills again with solvent, which finally reaches the end of t h e capillary tube a n d cuts off t h e air supply, the tube filling with liquid due to diminished pressure within the flask. The process then repeats itself. Experiment has shown t h a t the vertical distance from the end of the capillary tube t o the point on the other tube, a t which the pressure just overbalances the capillarity, is just a little greater t h a n the height of capillary rise. The pressure required t o pull air through a capillary tube full of liquid depends on t h e size of the capillary opening and on the nature of the liquid. I n practice, the author, after allowing the precipitate t o settle on the filter, measures the vertical distance from t h e lowest point on the surface of this precipitate t o t h e top of t h e filter paper, and selects - for use a capillary tube having a capillary rise for the given solvent equal in length t o this distance. T h e total length of the capillary tube should be a little greater t h a n t h e capillary rise. The author has
T H E J O U R N A L OF I N D C S T R I A L A X D ENGI-VEERING C H E M I S T R Y
528
used this apparatus for the past two and a half years with entire success in washing large amounts of gelatinous precipitates, working with as much as three pounds of precipitate in one funnel and washing with ten liters of water a t one filling of the flask. BUREAUOF PLANT INDUSTRY DEPARTMENT O F AGRICULTURE WASHINGTON. D. C.
u. s.
1’01. 9 , NO. 5
face when breaking the contact and t o prevent deterioration of the battery. compensation should always be made with a rising mercury column a t point of contact. I n practice this compensator checks the gas volume consistently and accurately and does i t in less time than the old optical method of adjusting the height
AN IMPROVED COMPENSATOR’ FOR GAS ANALYSIS By E. T. GREGG Received February 10, 1917
An improved compensator, described below, has been used with most satisfactory results in connection with t h e Hempel apparatus for gas analysis in the fuels efficiency laboratory of the Federal Bureau of Mines. As shown in t h e accompanying drawing, two platinum wires are sealed into t h e compensator side of the mercury manometer. The upper wire which is sealed about 3 / ~ in. above t h e mercury when level, is bent downwards a t right angle and just touches t h e surface of t h e mercury. The lower platinum wire enters far enough t o make electrical contact with the mercury. I n series with the two platinum wires are a small dry cell, switch and miniature lamp. To use t h e compensator for adjusting t h e volume of a gas before making a reading, the contact between t h e mercury and upper platinum wire is broken by means of t h e leveling bulb containing mercury, the switch is then closed and the compensator adjusted till t h e break in the circuit a t t h e mercury platinum contact is just closed, whereupon the lamp lights and t h e compensation is completed. Rough adjustment is made b y sliding t h e mercury bulb and its support upon t h e iron rod b y hand. The fine adjustment is made b y taking u p t h e sag in the arm supporting t h e bulb b y means of t h e t h u m b screw. The switch is then opened t o prevent sparking a t t h e mercury sur1 Pettersson, “ 0 . Luftanalyse nach einem neuem Princip,” 2. anal. Chem., 2S (1886), 467; also Hempel’s “Gas Analysis,” translated by I,. M. Dennis from 3rd German Edition, 19011, 59.
I
of the mercury t o a mark. It removes t h e difficulty of adjustment due t o poor or changing light a n d decreases the strain upon t h e eyes of the operator. Where many analyses are made it removes one of t h e chief sources of fatigue. U.
s.
ADDRESSES ONE BILLION GALLONS OF SYNTHETIC GASOLINE IN 19181 By WALTERF . RITTMAN Received April 9 , 1917
The market value of synthetic gasoline produced by cracking in the United States during 1917 will be sufficient to supply the navy with ten superdreadnaughts. In other words, one-fifth of the 3,000,000,000 gallons t o be produced will be made by cracking. By July I of the present year there will be in operation in the United States 4,000,000 automobiles. Financial men, in considering the investment value of motor stocks, have for several years been dwelling upon the saturation point, but despite this consideration the demand for machines still keeps well ahead of the 40 per cent average yearly increase of past years. When the saturation point will be reached nobody knows. Responsible and successful automobile men maintain that the present increase in rate of production will keep up for years, and that 1 Paper read at the Spring Meeting of the American Chemical Society, Kansas City, April 10-14. 1917.
BUREAUO F MINES
EXPERIMENT STATION. PITTSBURGH
I
after the present high prices of materials the price of cars can be so reduced that every family having an income over $1,000 may own a car. On this basis, the United States will have in the neighborhood of IO,OOO,OOO automobiles, two and one-half times the present number. Assuming an annual life of five years per machine, IO,OOO,OOO cars means an annual replacement number equal to z,ooo,ooo;i. e., our present rate of production. When one questions the correctness of the opinion of the automobile man who suggests the above figures, one is answered with the statement that every prediction which the automobile man has heretofore made has been too conservative. An important consideration is the greatly increasing number of motor trucks necessary to replace the shortage in horses. As to the influence on this industry of the United States’ entrance into the European war, time will tell. Only the steel, lumber, and clothing industries exceed the automobile business in importance today. Detroit, the center of this new industry, has risen as a manufacturing center from sixteenth place in 1900 to sixth place in 1914. In the United States over 500 factories are to-day engaged in making different
