288
ANALYTICAL EDITION
preliminary to evaporation and weighing. In the new apparatus, the weighing bottle is not moved until all the solvent has been evaporated. Possible mechanical loss is avoided. The fact that the new weighing bottle weighs only 4 grams probably improves the chances of weighing with a precision of A0.001 mg. In the micro-Soxhlet apparatus, the extraction thimble was made by sealing an alundum disk into a section of glass tube X. It was difficult to select an alundum disk whose pores were sufficiently small to retain finely divided sample and a t the same time allow the ether to flow through a t a reasonable speed. The straight walls of the original thimbles also allowed occasional small sample losses due to creeping. The new thimbles eliminated the first difficulty by the sub-
Vol. 5, No. 4
stitution of the paper disk and the second difficulty by a constriction of the walls of the thimble T. There is little doubt that operation a t reduced pressure also prevented creeping of the solvent to some extent. Upon condensation the ether flows into the thimble and directly into the weighing bottle. No ether collects in the bottom or a t the joint of the extractor. If ether is lost during the extraction, an additional aliquot may be added a t the top of the condenser without disturbing the sample. While ether is the only solvent mentioned in this investigation, it is possible to use other reagents effectively. RECEIVED February 13, 1933. Presented before the Division of Physica and Inorganic Chemistry at the 84th Meeting of the American Chemical Society, Denver, Colo., August 22 to 26, 1932.
A Simple Laboratory Tachometer W. A. SPERRY,11th and Washington Sts., Wilmington, Del.
A
TACHOMETER, or angular velocity indicator, can occasionally be used to excellent advantage in the laboratory-for instance, in the control of high-speed agitators in process work, to give warning of viscosity changes in the contents of autoclaves, or to secure reproducible agitation’conditions in analytical procedures.
*
clutch end of the latter with a short piece of rubber tubing. The instrument is then operated by a belt and a properly selected set of pulleys. This arrangement provides for a wide range of angular velocities falling within the limits of the speedometer scale. It has been found that under ordinary conditions belt slippage is practically undetectable. The scale reading may be correlated to the angular velocity of the driving shaft by the use of a variable-speed motor or some other method for changing the velocity of the driving shaft. Measurements of the angular velocity of the motor shaft are conveniently taken with a revolution counter, a t the same time noting the tachometer reading a t different speeds, and the data SO obtained are plotted on coordinate paper. The velocity of the drive shaft may then be picked from the curve at corresponding tachometer readings. An alternative scheme is to adjust the pulley diameters so that the speedometer scale may be read directly in revolutions per minute, or in decimal multiples thereof. For example, on a high-speed agitator used by the writer a scale reading of 40 indicated a shaft velocity of 4000 r. p. m. LITERATURE CITED (1) Holder, L. F.,Gen. Elec. Rev., 34, 141 (1932). RECEIVED April 24, 1933.
FIGURE1. CONNECTIONOF TACHOMETER TO DRIVESHAFT A , old sp-eedometer with mileage counter removed B inverted agitator drive C: shaft of high-speed agitator, line shaft, or other mechanism D,rubber tubing
WORLDNITROGEN PRODUCTION CAPACITY for 1932-33, according t o a German nitrogen director was: Per Cent
There are commercial instruments adaptabIe to these uses but they are complicated, expensive, and of unnecessary precision for this type of work (1). It has been found that a very inexpensive device can be constructed from a salvaged automobile speedometer. The magnetic type of instrument is convenient to convert, as it is merely necessary to remove the mileage counter to avoid excessive drag on the drive shaft, thereby rendering the instrument more sensitive. If the tachometer is to be attached to a permanent set-up, it may be connected directly to the shaft whose velocity it is desired to obtain by means of flexible shafting and suitable gears. A more useful method is to invert an ordinary agitator-drive, connecting the speedometer shaft to the
Atmos heric nitrogen: SyntKetic ammonia process: Haher-Bosch Caaale Fauser Claude N. E. C. Mont-Cenis Shibeta (Japan) F. N. R. L. Unknown Cvanamide Aic B -product ammonia CXilean nitrate
33.16 10.00 8.10 4.40 3.90 3.80 0.05 0.10 0.16
66.1
10.3 0.7 11.9 11.0
The plants employing the major processes are: Haber-
Bosch, 8; Casale, 26. Fauser, 16; Claude, 19; N.E.C. 15;
Mont-Cenis, 7; and dyanamide, 59.
.
