hNhLYTICAL EDITIOI-
SEPTEllBER 1 5 , 1938
oxide mixture containing up to 9 per cent by volume of carbon monoxide. The diffusion- rate bf hydrogen through palladium decreases rapidly if more than 4 per cent by v o h m e of carbon monoxide is present in the gas Sample. Gas mixtures containing less than 1.5 per cent by volume of carbon monoxide and less than 5 per cent by volume of methane n.ith a large amount Of hydrogen can be accurateb analyzed b y the described method. If higher percentages of carbon monoxide and methane are present, however, the results for hydrogen are high and those for carbon monoxide and methane are lon-.
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Literature Cited ( 1 ) Coquillon, J. J., Cmnpt. rend., 77, 444 (1873). ( 2 ) Dennis, L. XI,,"Gas dnalyais," New T o r k , RIacmillan CO., 1918. (3j Lombard, v., and Eichner, c o ~ ~ prend., t. 1 9 5 , 3 2 2 4 (1932). ( 3 ) Mulders, E. M. J., and Scheffer, F. E. C., Rec. traw. chim., 49,105765 (1930). ( 5 ) Paneth, F., and Peters, K., Z . p h y s i k . Chem., 134, 353-73 (1928). (6) Rassfeld, p., Gas- u. Wasserf&, 72, 344-7 (1929). (7) Sabatier, P., and Senderens, J. B.,Con~pt.rend., 134, 514, 689
c.,
(1902). (8) Thompson, J. G.1 ISD. ESG. CHELI.2 21, 389 (1929). RECEIVED May 2 7 , 1938.
A Continuous Extractor Using Hot Solvent T. R. P. GIBB, JR., 3Iassachusetts Institute of Technology, Cambridge, >lass.
I
N THE course of a series of experiments on the constitution of cert.ain resins, i t became necessary to carry out an extraction wibh hot solvent upon several kilograms of tarry material. 9cursory search of the available literature failed to disclose any suitable type of extractor capable of handling large quantities of material and a t the same time using boiling solvent. The apparatus described herein is designed to meet the very real need for such an extractor. This type of extractor possesses the following advantages over the conventional designs : It may be attached to any flask, thus eliminating the transfer
of material from another vessel.
It uses solvents at temperatures as high as the boiling point, where frequently the dissolving power is greatly enhanced. It increases the surface of contact between solvent and material to be extracted, by reason of the act of boiling and because of the rapid influx of hot vapor. Channeling and filter clogging are entirely avoided for the same reasons, permitting the apparatus to be used in the extraction of adhesive, semisolid tars, or gelatinous substances. The flow of solvent is rapid, varying from 20 to 50 cc. per minute. It is capable of handling much larger quantities of material than the conventional types of extractors. It is inexpensive, and may be constructed from ordinary laboratory materials by the most inexperienced glass blower. The action is continuous and entirely automatic, requiring no attention whatsoever. The operation of the extractor will be made clear by the accompanying diagram. Solvent, boiling in flask 8,produces vapors lyhich are forced up tube B into flask C which contains the material to be extracted together with a suitable quantity of solvent. The level of the solvent is controlled by the height of tube E above the bottom of the flask. The rapid influx of vapor, which is under a slight pressure, violently agitates the contents of flask C and soon heats them to the boiling point. The hot solution of extract is forced through the filtering device, J , and proceeds through tube E to side-arm vessel F . Excess vapor which has not been condensed by the microcondenser, K , or by passage through the solution, is condensed in G, and descends, together with the solution of extract, into flask A , where the extracted material accumulates. Filtering device J consists of a length of large-diameter glass tubing sealed at the bottom, and perforated along the lower half of its length. A close-fitting extraction thimble is slipped over the perforated portion and the whole is placed over tube E as shown. The filter paper may be protected by a wrapping of cloth, for use with alkaline or corrosive solutions,
Dimensions Dimensions of the apparatus may be varied to suit the needs of the moment. It is necessary, however, to have tube H of sufficient length t o ensure an ample hydrostatic head
for the descending solution. A length of 53 cm. with a n attendant difference of 32 cm. in level of the liquid in the two flasks was found advisable. The hydrostatic head, of course, depends on the density of the liquid, the height necessary being here governed by the fineness of the filter. Tubes E and B should rise several centimeters above the stopper of flask C, permitting ready adjustment to a larger flask. The tm-o condensers should have as large a condensing surface as possible, and a t the same time not be too large for convenience. A microcondenser, I
