Buret for Titrants Requiring an Inert Atmosphere.
Application to Quadrivalent Uranium Solutions
David J. McEwen’ and Thomas De Vrles, Department of Chemistry, Purdue University, Lafayette, Ind.
some experiments oii the polarography of uranium(IT’), a buret was required for storing and dispensing 0-q-gm-sensitiye uranium(1V) stock solutions. Although three types were used for this purpose, only one was completely satisfactory. This is a modification of the sealed burets proposed by S t o w (.?) and was made of borosilicate glass in this laboratory. DURIKG
filled siniply by tipping the entire assembly. i l n example of the uranium(1V) solutions stored in the buret is a solution
For use the buret is flushed n-ith nitrogen, tlien half-filled ivith titrant either through tube D (which is then scaled) or through the stopcock. Because of the narrou- opening a t the tip of the buret. it is easier to fill through tube D. -1positive pressure of nitrogen is introduced into the storage bulb through the stopcock. The buret is
of 0.01.U uraniuni(1V) perchlorate in 0.1X perchloric acid. After being sealed in the buret, this solution was allowed to stand for a day or two to react with a n y traces of oxygen remaining in the buret, then standardized with potassium dichromate ( 2 ) . After many months of standing no change in the original titer of the solution could be detected. This type of buret has also been used for storing and dispensing moisture-sensitive solutions of organoaluminum compounds (1). LITERATURE CITED
(1) Jensen, F. R., Ph. D. thesis, Purdue University, 19%. (2) Rodden, C. J., ed.-in-chief, “Analyti-
cal Chemistry of the XIanhattan Project,” N.N.E.S., Div. VIII, p. 68, XlcGran--Hill, Kern York,
l Present address, Central Research Laboratory, Canadian Industries Limited, Mchlasterville, Quebec, Canada.
Microsyringe for Small liquid Volumes Stanley H. Langer and Peter Pantages, Central Experiment Station, Bureau of Mines, U. S. Department of the Interior, Bruceton, Pa.
course of gas-liquid chromatogIraphy studies, i t was desirable to modify the microsyringe described by \ THE
Lichtenfel5, Fleck, and BuroTr- [AKAL. CHIX. 28, 1376 (1956)]. The modified syringe asheniblj- can be used to inject 3-11. ianiples reproducibly within =tlt o 37; (1.47, standard deviation for 10 injections) arid is convenient to use. Largcr saniple. are injected n-ith greater prclci-ion. This microsyringe requires miiiiiiuni sample. is easy to clean, and enil)loyF interchangeable measuring sections. The assenihlr consists of a microsyringe control and needle measuring section. The latter is pressure-fitted to the microsyringe control through a metal adapter in the sanie way as a conr-entional syringe needle. The microsyringe control incorporates a niicronieter screw seated in a threaded Teflon plunger. The end of the screw is a solid, close-fitting cylinder n-hich m o w s up and down in the thin part (end) of the Teflon plunger. The Teflon plunger fits snugly in a graduated standard glass syringe barrel (tuberculin syringe. 0,5-m1., Becton, Dickinson and Co.. Rutherford, h-. J.). Other details of construction are shown in the figure. The iiecdle nieasuring section consists of a syringe aclapter, a piece of gradu-
ated glass capillary tubing, a needle support and a hollow needle. d uniformly tapered hole is ground in tlie
tainless -steel mmomefer screw . . l o c k not --.__
Teflon plunger
. -Syringe
b oo rr rr ee l ld d’
I
EPOXYresin gloss to-metal seal
Stainless-steel needle support sleeve eve1 ground cone for needle seal
25 goge stainlesssteel needle
-
-
glass capillary with grinding coiiipound and the needle is wedged in the glass capillary. The cone is filled with a room temperature curing epoxy resinfor example, Bakelite 2795 resin with ERL 2793 hardener, available in small quantities from IT’. B. Klliams, Inc., 150 Pine St., Ilontclair, h-. J.-as indicated. Then. the needle-support sleere is placed in position. For sample injection the Teflon plunger is placed around the 0.1-ml. mark. The needle tip is immersed in the sample. and the steel plunger is mored with the micrometer screw arrangement so that saniple is pulled up to a graduation in the capillary tubing. The needle is nithdrawn from the sample solution, without jarring, and the sample is d r a n n up from the tip of the needle a t the same time. After the sample is d r a n n a short distance into the capillary tubing, the outside of the needle tip is wiped clean. The gas chromatography equipment is depressurized, and the sample is injected through a rubber septum into a plug of glass 001 above the chromatographic column. The 0.1 ml. of air in tlie syringe serves as a flush for the needle assembly and gives a marker peak from m-hich to measure zero time. The needle measuring section is cleaned by forcing a suitable solvent through i t from a nash bottle tip placed against the capillary opening in the VOL. 30, NO. 11, NOVEMBER 1958
1889
metal syringe adapter. The robust c o n s t r d o n of the adapter Permits easy connection to a water aspirator in order to remove the volatile solvent.
F~~ greater
capacity,
enlargement can be blown in the glass capillary tubing. If the Teflon plunger begins to fit loosely in the syringe barrel,
it can he roughened up by rubbing lightly with emery cloth. More sensitive control might be achieved by using a micrometer screw with a finer pitch, though the authors did not find this neCessarY. A magnifying glass can be mounted in front of the syringe assembly if there
is dfficulty in matching sample meniscus against the glass graduation. ACKNOWLEDGMENT
Grateful acknowledgment is made to Alvin Hedrick and Louis Perinetti for fabricating the components described here.
Automatic Starter for Chromatograms S. M. Martin, Division of Applied Biology, National Research Council, Ottawa, Canada many paper chromatographic technique is the chromatogram, which takes 9 to 15 hours for development. This necessitates returning to the laboratory a t odd hours to start chromatograms,or changing to a slower running solvent system whlch is often less satisfactory. This annoyance can be overcome bv the use of the simple automatic starting device shown in the figure.
Friday to be started Sunday. When the solenoid is energized, the movable jaw opens, and the solvent flows slowly into the cabinet. Should it be advisable to avoid the use of rubber or plastic tubing, the starter might be used to open the solvent reservoir to the a& mosphere, thereby allowing the solvent to siphon into the tank through an allglass setup.
in A laboratories annoyance employing the CONTINUAL
The apparatus consists of two jaws, one stationary, A , and one movable, B, and a trigger latch, C, operated by a continuous-duty solenoid, D, all mounted on a base plate, E. When assembled, a short length of rubber or plastic tubing leads from a solvent reservoir through the jaws of the “starter,” to a glass capillary tube, which in turn passes through a cork in the lid of the
chromatography cabinet. When the descending technique is used, the tip of the tube is placed just above the paper in the trough, and alongside the weight. If two troughs are to be used, a capihry $‘-tube is employed. For the ascending technique, the tube is run to the bottom of the cabinet. The starter is connected to an on-off timer, set to go on at the appropriate time. A 6C-hour timer is most satisfactory, as it allows chromatograms set up
I n several years of operation, this starter, parts for which cost less than $10, has not failed to operate satisfactorily. ACKNOWLEDGMENT
The author wishes to thank James
Ross for constructing the apparatus. N.R.C. No. 4818.
Stopcock for Gas Chromatography D. N. Glew and D. M. Young, Exploratory Research laboratory, Daw Chemical of Canada, Ltd., Sarnia, Ont., Canada
FOUR-Way double oblique bore T capillary stopcock drawn to scale in Figure 1 has proved valuable in this HE
atm.) pressures in D, interchangeable U-tubes of varying sizes may he at-
laboratory for transferring liquid or condensable gas samples directly from a vacuum system to a gas chromatography unit. Initially, the helium stream from the gas chromatography unit enters a t A , passes through a hole into the hollow barrel of the stopcock and out through a second hole, returning to the gas chromatography unit along tube B. Meanwhile the 2-mm. bore U-tnhe, D, is evacuated, through the T-shaped, T-bore capillary stopcock, C, leading to the vacuum system, and the liquid or gas sample transferred quantitatively to D by cooling the latter in liquid nitrogen. Stopcock C is turned through 180” and U-tube D brought to room temperature. The sample may he swept rapidly into the gas chromatography unit by turning the fourway stopcock through 180”. To handle large gas samples without building up prohibitively high (>2
1890
ANALYTICAL CHEMISTRY
I
0
5
10crn.
Figure 1. Capillary stopcock A. B. C.
Copiliory tube Capillary tube Capillary stopcock 1-shaped
D. Capillary U-tube E. Spose for ball and rocket joints
tached with hall and socket joints a t E. Leads A and B are connected to the gas chromatography unit by KovarPyrex seals. Both stopcocks are springloaded and lubricated with Dow-Corning silicone grease. The addition of a second T-shaped, T-bore stopcock opposite C would allow the sample to be introduced into D by a flow method if desired. This arrangement is identical in principle with the devices described by Harvey and Chalkley [Harvey, D., Chalkley, D. E., Fuel 34, 191 (1955)l and by Craats [Craats, F. van de, Anal. Chim. Acta 14, 136 (1956)], but is more convenient, inasmuch as, at the moment of admission of the sample, only one stopcock need be manipulated. The four-way stopcock was made by the Decar Laboratory Glass Co., 1397 Indian b a d , Sarnia, Ontario. OONTRIBUTIONNo. 1, Exploratory Research Laboratory, Dow Chemical of Canada, Ltd.
