March, 1927
I,VDUSTRIAL 81VD ENGINEERING CHEMISTRY
425
An Apparatus for Circulating Gases' By H. N. Stephens UNIVERSITY OF
?rfINNESOTA,
A
R E C E S T articale2 describes a magnetic pump for circulating gases. The apparatus descritled herein was designed for a similar purpose and hits been in use for about three years. Although it in no way supplants the all-glass pump, when corrosive gases are absent it may be used in some cases where the magnetic pump would not be satisfactory. The circulator described herein is able to operate against practically any head, while the magnetic pump can overcome a head of a t most a few Centimeters of water. Again, the apparatus is neither so difficult to construct nor so fragile as the magnetic pump and it has been allowed to run continuously for a period o f about 3 months without attention. Finally, if constructed with the end in view of obtaining a high capacity it will be more efficient than the magnetic pump. For example, if the bulbs B and B1 have a capacity of 500 cc. and the reaction chamber To reaction chamber
MINNEAPOLIS, MI".
Dimensions and Capacity
I n the apparatus used in this laboratory the capacity (which is about 12 liters per hour) was not an important factor and the lag in the circulator is relatively great. By using larger tubing to connect B and B1 and also larger traps, A and Ai, this lag would be largely eliminated. It will be seen also that the capacity depends on both the absolute and relative sizes of B and the reaction chamber. For maximum working efficiency the mercury from B ought to be completely transferred to B I just a t the top of the expansion stroke. To insure this, the correct dimensional relationship between Ha, H1, B , and the reaction chamber ought to be determined. This may be done by means of a very simple calculation. Let PI = pressure (cm. Hg) in circulator a t top of expansion stroke. Let PZ = pressure (cm. Hg) in control a t top of expansion stroke. Pn = Pi - Hi (1)
Assuming atmospheric pressure to be 76 cm., H3 = 76
-
Pz=76-(P1
-
HI)
(2)
P1may be calculated from the relative volumes of B and the reaction chamber. Flexibility
By adjusting the positions of B and B1, pressures above or below atmospheric may be employed. If it is desired to work over a range of pressures, while maintaining maximum capacity. B and B1 may be connected with rubber hose. Thus, in equation ( 2 ) HI may be varied with P I , so that H3 remains constant.
A Modified Adapter'
1 liter, a circulating capacity of 25 to 30 liters per hour
By G . N. Quam
could be obtained. This could be further increased by using a large reservoir to the left of the reaction chamber, Tyhich might then be of any size. Description and Operation
The circulator itself consists of two leveling bulbs, B and B1, and two reversed mercury traps, A and AI. The mercury is raised in BI by means of an aspirator and then. when air is admitted through the automatic control, it is allowed to flow back into B. On the compret;sion stroke the gas can pass only through the trap A and into the reaction chamber, and on the expansion stroke it flows back through 3 1 into B. Compartment C contains cotton or glass ~vool to prevent mercury from being carried over mechanically. The tube 0 is used in sweeping out the apparatus, after breaking the sealed tip. The automatic control is simply an adaptation of the control used on the hlaass automatic Topler pump.3 Evacuation by the aspirator raises the mercury in B I , D, and F until the contents of G are drawn over into D, a t which point air rushes into the apparatus through F. Before the levels in D and E are equalized, mercury siphons into G and evacuation is resumed. Stopcock K controls the flow of air into the apparatus and L the flow of mercury from D to E. 1
Received December 6, 1926. Bardwell, and Lind, THIS JOURNAL, 18, 1086 I 1926). Maass, J A m Chem S O L ,37, 2654 (1925).
* Porter, 3
COS COLLEGE, CED%RRkPIDS,
IOW4
URISG the preparation of a supply of absolute alcohol in this laboratory, the following modification of a curved adapter suggested itself: A curved adapter, -4, with a diameter of about 12 mm. a t the outlet was selected. ,4 tube of length CD and inside diameter of 9 mni. was sealed on a t C. A 5-mm. tube was sealed on a t E and bent as shown in the accompanying figure. The drying tube, F , was fitted to tube E B and a stopper of a size to fit the small bottles used for storage of the absolute a l c o h o l TTas fitted to the d e l i v e r y tube a t R. With this modification the necessity for transferring the distillate can be avoided. The receiving bottle can be quickly replaced with a dry one and stoppered and sealed a t once for storage, thus lowering the time of exposure of the anhydrous product to a minimum. 1
Received December 17. 1926.
