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VOL. 9, NO. 4
INDUSTRIAL AND ENGINEERING CHEMISTRY
As soon as the sodium hydroxide digestion is started, a 2liter vessel of distilled water is connected to the line from the bottom of the distributor, suction is applied t o the T-tube line, and the whole distributing system is rinsed and drained by suction from below. This removes the caustic soda and prevents freezing of the glass stopcocks. The inverted filters are also washed thoroughly and soaked in several changes of water. A 12-liter bottle two-fifths full of water is placed in the line to the suction pump to receive the hot acid filtrate and washings, and suction is applied through this reservoir at all times. An &liter tinned copper tank placed over a flame on the shelf above the apparatus su plies hot distilled water by gravity for all washin%mrposes. $his vessel is filled from the storage tank through a ock-tin pipe, by either gravity or pressure. Ordinary 9-mm. glass funnels with cut-off stems are fitted to
the 25-cc. Gooch crucibles by means of No. 7 rubber stoppers to aid in the transfer of material from the Erlenmeyer flasks. By this means the hot extract is removed immediately with two quick pourings. Table I shows a comparison of the results obtained with this apparatus and the average of the results from 53 feed laboratories throughout the country on check samples sent out by the Association of Feed Control Officials. These samples show a wide variation in fiber content. RECEIV~D November 26, 1936. Published with the approval of the Director of the West Virginia Agricultural Experiment Station .as Scientific Paper No. 178.
Gas-Tight Laboratory Stirring Device for Pasty Materials A. H. MAUDE, Hooker Electrochemical Company, Niagara Falls, N. Y.
T
H E apparatus described below was developed for the purpose of reacting and distilling pasty materials under vacuum. Where materials are of such consistency that ordinary stirring devices fail to give effective mixing, the only alternative types of apparatus known to the author are the kneading machine and the ball mill. These are not available for small charges, of the order of 100 grams, and they have other disadvantages, such as the difficulty of determining changes in weight and of maintaining perfectly vacuumtight glands, time consumed in opening and closing for charging or discharging, and relatively high cost. A method of mixing thick masses by affixing wire loops to a stirring rod was described by Hershberg ( I ) , and a method of
making a glandless stirrer for a flask was described by Powell (2). The apparatus now described combines these two ideas and develops them into a form of wide utility. The a p p a r a t u s is shown in Figure 1. A 500-CC.3necked Pyrex distilling flask, i, was used. The middle neck, g, was cut down to about 1.25 cm. (0.5 inch) in length and slightly flared. A stirring rod, e, was introduced t h r o u g h a stopper attached to the flask by a 5om. (2-inch) length of thick-walled 2.5om. (I-inch) inside d i a m e t e r rubber t u b i n g , j , wired FIQURE 2 f i r m l y in place. The glass stirring rod was 0.9 om. (0.375 inch) in diameter. very sli htly drawn out at the two points where the wires were bounf on. After several trials it was found that steel music wire 0.6 mm. (0.024 inch) in diameter (music wire, gage 10) or phosphor bronze wire of about double this thickness was of a suitable springiness and stiffness to stir any paste encountered, yet not to endanger the glass flask. Twenty of these wires, j , were attached by twisting them around soft iron wires, k, as shown in Figure 2. The iron wires were then twisted around t h e constricted portions of the glass stirring rod. The steel wires were to scrape the spread out and cut off t o suitable lengths - against walls of the flask. The stirrer was driven at 30 revolutions per minute, by a speedreducing gear, a, which was furnished with a disk wheel, b, drilled for the floating pin, c. Several drill holes were provided to permit adjustment of the width of sweep of the stirrer. As it ie necessary to mount the flask very firmly, it was clamped by suitably shaped wooden ieces, h, across its three necks. The stirring rod was attachefby a heavy rubber tube d, wired in place. All connections to the flask may be cemented with shellac or collodion. Use of this device reduces to a fine powder a paste which would become a solid hard lump if distilled without stirring.
Literature Cited
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(1) Hershberg, IND. ENQ.CHEM.,Anal. Ed., 8, 313 (1936). (2) Powell, Ibid., 8, 488 (1936). FIGURE
1. APPARATUS
REC~IVED January 13, 1937,
