280
ANALYTICAL CHEMISTRY
has been devised that is as satisfactory for this purpose as the more coniplicated machines. APPARATUS
The eluate from the column is introduced into the flared upper end of a glass manifold equipped with outlet tubes a t 4-inch intervals. The manifold is held a t a slope of 1 in 12 inches so that the eluate flows down the manifold into the first outlet which is connected by tygon tubing to a 500-ml. Erlenmeyer flask. When the first flask is filled, eluate rises in its exhaust tube until the pressure head formed equals that of the incoming eluate. The eluate then bypasses the first outlet and flows into the second one until the second flask is filled. In this manner, as many fractions can be collected as there are outlets in the manifold. The volume of the fractions can be varied by using flasks of different capacities. Stationary air bubbles that automatically form in the Tygon tubes after each flask is filled ensure the collection of clean fractions. The filled flasks are removed after the screw clamps have been tightened to avoid contamination of the fractions with the small amounts of eluate trapped above the air bubbles. If contact between the eluate and the rubber stoppers is undesirable, the exhaust tubes may be extended into the flasks.
Adaptation of Existing Potassium Bromide Disk Press for Microdisk Pressing in Vacuo
All die parts are made of stainless steel tooled to fit the press, making slight allowances for evacuation, with the die surfaces properly hardened and polished to optical flatness. The sleeve is beveled on the lower edge for greater ease of removal after pressing. One procedure used is t o put the powder mixture on the sleeved lower die, distributing the powder smoothly with a tamper pin before placing the bored cylinder over the die. Next the upper die and the plunger are inserted. The assembly is then carefully inverted while the dies are held in place (an operation made easier by the fact that the cylinder is magnetized) t o put it in the outer shell. Variations are possible, such as using a loading tube to place the powder on the sleeved lower die after assembly in the cylinder and the outer shell, in which case the upper die and the plunger are then merely slid into place. ACKNOWLEDGMENT
The services of John Stupka and Robert Henry of the machine shop in the construction of the microdie are gratefully acknowledged. Prepublication information from Don H. Anderson and Richard G. Smith facilitated the design descrihed. LITERATURE CITED
(1) Anderson, D. H., and Miller, 0. E., J . O p t . SOC.Amer. 43, 777 (1953). (2) Anderson, D. H., and Smith, R. G., prepublication communica(3)
tion to W. G. Brown. Anderson, D. H., and Woodall, N. B., Ax.4~.CHEST. 25, 1906
(4)
Beckman Instruments, Inc., Beckman Bull. 16, 6 (1955).
(1953).
Roger A. Pickering, Spectroscopy laboratory, Argonne Cancer Research Hospital, Chicago 37, 111.
recent commercial development of silver chloride infrared beam condensing optics ( I ) by the Eastman Kodak Go., Rochester, N. Y., led to an interest in potassium bromide microdisk pressing in this laboratory for possible use in infrared microanalysis. Although some easily constructed microdies have been described ( 2 , s), and a die based on the design of Anderson and Smith ( 2 ) is to be available from the Beckman Co., Fullerton, Calif. (4), no mention has been made apparently of adaptation of existing commercial 0.5-inch disk presses to do microdisk pressing. The simplicity of an adaptation devised in this laboratory for pressing microdisks permits a convenient conversion of a commercially distributed press supplied by the Research and Industrial Instruments Co., 30, Langton Road, Brixton, London, S.W. 9, England. The adaptation utilizes the existing die shell with comparable evacuation through the use of a sleeve holder suggested by Anderson and Smith's description of their microdie ( 2 ) . In this method the disks are pressed directly into a steel sleeve, which then serves as a convenient ring holder for mounting and handling. A disk die 6 mm. in diameter is illustrated in Figure 1. The same principles have been used to construct a die pressing 3 x 10 mm. rectangular pellets.
T
HE
Evaporator Feeder W. 0.Phillips, laboratory Division, Goodyear Atomic Corp., Portsmouth, Ohio
operations of analytical and spectro chemistry, it is Iexamination frequently necessary to evaporate solutions to dryness for of the residue. Large quantities of liquid samples N THE
must often be used to obtain an adequate residue for handling. However, the evaporating dish should be small to reduce contamination and to facilitate removal of the residue.
ROD SUPPORT
0
4hW
a-rs
n
Figure 1. Adaptation for pressing 6-mm. potassium bromide disks in vacuo From left. Cross-sectional view of press. showing position of microdie, lower die, s,leeve, upper die, and tamper pin
-
4 3/0"
-
Figure 1. Automatically controlled evaporator feeder
The two aims can be reconciled by an automatically controlled feeder of sufficient reservoir capacity. A device providing these features has been described by Telang [Telang, bl. S., IND. ENG. CHEM.;ANAL.ED. 18, 454 (1946)]. In the laboratories of the Goodyear Atomic Corp., Telang's design has been modified for ease of handling and operation as shown in Figure 1. The re-
