Auric. Dent
OCl ^ i 1 GIFT
Issued September 22, 1911.
United States Department of Agriculture,
BUREAU OF CHEMISTRY— Circular No. 80. H. W. WILEY, Chief of Bureau.
TWO NEW PIECES OF CHEMICAL APPARATUS.
I. Apparatus for the continuous extraction of liquids with immiscible solvents lighter
than -water.
II. Apparatus for quantitative reactions which depend on the measurement of an evolved gas.
R. F. BACON and P. B. DUNBAK, Assistant chemists, Division of Foods.
I. CONTINUOUS LIQUID EXTRACTOR.
This apparatus was designed originally for use in the extraction of lactic acid from ketchup and other fruit products. Its principal advantages are compactness, the elimination of ground joints and stoppers, and practically complete condensation. Seven of the ex- tractors may easily be placed side by side on a 24-inch hot plate. They have been made for the authors at a cost of $1.50 each, but may be constructed in the laboratory by anyone having ordinary skill in glass blowing.
The apparatus consists of four parts: (1) A jacket flask; (2) an extractor thimble; (3) an ordinary Gooch funnel; (4) a condenser.
(1) The jacket flask (fig. 1, A) -is made of glass tubing 2 inches in diameter and approximately one-sixteenth of an inch thick; it is 20.5 inches long and is enlarged to a diameter of about 3 inches at its lower or sealed end, as shown in the illustration. (2) The ex- traction thimble (fig. 1, B) is an ordinary test tube having a diam- eter of 1.5 inches and a capacity of 100 cc when filled to within 1.5 inches of the top. One-fourth of an inch from its top and on op- posite sides of the tube are placed two holes about one- fourth inch in diameter. (3) The Gooch crucible funnel is figure 1, C; those used in this laboratory are 8.5 inches long. When dense liquids are to be extracted it is sometimes necessary to increase the length of the funnel. The lower end of the stem is ground at an angle of 45 degrees. (4) The condenser (fig. 1, D) is designed to hang loosely in the jacket flask. Its details are evident from the drawing. A simpler form of condenser, which is just as efficient, may be made by
5873°— Cir. 80—11
sealing one end of a If-inch tube and drawing it to a point. The open end is flared somewhat to permit the tube to hang in the jacket. The condenser tube is closed by a two-holed rubber stopper, through which pass the inflow and outflow tubes.
OPERATION.
Place from 100 to 150 cc of ether in the jacket flask (A) ; put the liquid to be extracted (100 cc) in the test tube (B), insert the funnel in the same tube and suspend it in the jacket flask, about 3 inches above the bottom, with a copper wire which passes through the holes in the test tube and is hooked over the rim of the jacket flask. Insert the condenser in the top of the jacket flask. The condensation is usually so perfect that no ether vapors escape into the room. The condensed ether drops from the point of the condenser into the fun- nel and is carried to the bottom of the test tube whence it flows up through the liquid and over- flows at the top.
The efficiency of the extractor may be in- creased by the use of a glass spiral attached to the stem of the Gooch funnel, as described by Kempf.1
II. APPARATUS FOR THE MEASUREMENT OF AN EVOLVED GAS.
The apparatus represented in figure 2 was devised to give in a compact and easily ma- nipulated form an apparatus which will allow of the measurement of an evolved gas with- out first sweeping out all air or other indiffer- ent gases. It consists of a graduated funnel tube (A), a reaction chamber (B), an absorp- tion tube (C), filled with glass beads, a eudi- ometer (D), and a leveling tube (E). A heating coil may be wrapped around the reac- tion chamber (B) when desired. The absorp- tion tube (C), which is sealed onto the eudiometer, fits into the reaction chamber (B) by means of a ground joint at (F).
The manner of using the apparatus may best be illustrated by one of the reactions which can be advantageously carried out in it. Spica 2 estimates citric acid from the carbon monoxid evolved by decomposing
[Cir. 80]
FIG. 1. — Continuous liquid extractor in operation.
. Ztg., 1910, 34: 1365; Chem. Abst., 1911, 5: 1350. 2Chem. Ztg., 1910, 34: 1141.
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this acid with strong sulphuric acid at 100° C. He runs air-free
carbon dioxid through a flask containing the citric
acid until all air is displaced from the apparatus.
He then adds concentrated sulphuric acid, heats to
100° C., drives over the evolved carbon monoxid with a
stream of air-free carbon dioxid, and collects the gas in a
eudiometer over a sodium hydrate solution. The method
as carried out by him is accurate, but requires consider-
able care and attention to remove the air from the appa-
ratus completely, to insure that all evolved carbon mon-
oxid is swept over into the eudiometer, and to prevent
the strong sodium hydrate solution from sucking back
into the reaction flask containing carbon dioxid and sul-
phuric acid. In the apparatus proposed by us no attempt
is made to remove the air before reaction, the volume of
evolved gas being simply measured by the increase in
volume of the total gases after reaction. Thus the Spica
method as carried out in this apparatus is as follows :
Place about 0.2 gram of citric acid in the reaction chamber (B), open the stopcock (X) and bring the liquid (in this case a strong sodium hydrate solution) to the zero mark (G) in the eudiometer tube by raising or lowering the leveling tube (E). The air in the appa- ratus is then at atmospheric pressure. Close (X). To (A) add about 15 cc of concentrated sulphuric acid. Lower the leveling tube so that the air in the apparatus is under reduced pressure. By carefully opening the stopcock (X) run in exactly 10 cc of the sulphuric acid. Close (X) and heat to about 100° C. by means of the heating coil until the reaction is complete. Let the apparatus stand until the absorption of other gases (sul- phur dioxid, etc.) is complete and it has reached room temperature. Bring the gas in the apparatus to atmos- pheric pressure by means of the leveling tube (E). The gas reading in the eudiometer minus 10 cc (for the added sulphuric acid) equals the volume of the evolved gas at the existing temperature and pressure. The apparatus has been used in this laboratory with accurate results to estimate citric acid by the Spica method and for the estimation of amino acids by the Van Slyke method,1 FIG.S.— Appara- which depends on the evolution of nitrogen by the action of nitrous acid on the amino acids. The appa- ratus is readily cleaned by taking it apart at the ground joint (F).
tus for meas-
[Cir. 80]
d. chem. Ges., 1910, 48(3) : 3170.
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FORM NO. DD6
UNIVERSITY OF CALIFORNIA, BERKELEY BERKELEY, CA 94720
YC 69407
U. C. BERKELEY LIBRARIES
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