ANALYTICAL EDITION
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1 B A(tar single rueighing I with the rnodilied Bolonce I 4 I I
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t?S receivad
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5 %
Under weight Figure 5-Distribution Curves after Adjustment with Modified Balance of Underweight Blocks
Vol. 3, No. 1
to bring the weight up to the comparison standard. The balance scale is now in terms of length, say of the stock to be added. An illustration of this is given in Figure 5, where the blocks as delivered for checking are represented by the distribution curve A. The resultant distribution after the adjustment has been made with a single weighing is represented by curve B. The “weigh-by” in the case of Figures 4 and 5 was 1.7 kg. The variation in weight of blocks as delivered was so great that two springs were used t o extend the offweight scale. It is to be remembered that in making these weighings only a single laying upon the pan is necessitated by the modified balance with the single deflection method, whereas in the usual method, a t least two, sometimes three or four weighing operations are required before the sample has been brought within limits. Not only is the distribution curve more favorable with the former method from the standpoint of elimination of waste, but it also consumes considerably less time. To make the weighings represented in Figure 4 required at least 10 per cent less time using the modified balance in the first deflection manner than when the customary method is employed. On another occasion 6 blocks per minute were adjusted by the new as compared with 5.04 by the customary method, or 19 per cent faster. If a comparison be made on the basis of the time required to bring about the same distribution, a much neater difference is brought out. I
Apparatus for Continuous Leaching with Suction’ J. F. Fudge TEXASAQRICULTURAL EXPERIMENT STATION, COLLEGE STATION, TEXAS
ANY laboratory methods require the continued leaching or washing of material. The addition of the leaching solution may become very tedious and time-consuming if a wash bottle or aspirator bottle be used. Schollenberger and Dreibelbis (1) describe an apparatus for continuous leaching. It is not, however, adopted to use with suction, and hence is unsuited to many laboratory operations. For example, in the determination of the base exchange capacity of a soil, as conducted in this laboratory, 10 grams of soil in a 35-00. Gooch crucible are leached with 250 ml. of a neutral, normal solution of ammonium acetate. The excess ammonium acetate is then washed out with 95 per cent alcohol until the leachate gives no test with Nessler’s solution. Suction is applied in order to reduce the time required for leaching and washing. Many soils leach very slowly, and without some self-operating apparatus a great deal of time may be lost in adding the leaching solution. For this reason, a number of different arrangements of apparatus were tried and the one described below finally selected. This has been found very satisfactory. The sizes and dimensions of the materials used are those adapted to the work described above. They may, of course, be varied a t will to meet the requirements of other work. The diagram gives all the essential characteristics of the apparatus. A few points should, however, be noted. The glass tubes are flush with the bottom of the stopper allowing
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Received October 11, 1930. Technical Article 127 of the Texas Agricultural Experiment Station.
for the complete removal of the measured volume of solution. The rubber tubing enables slight adjustment of the height of the glass tips. Tip B is drawn to a small hole in order to prevent splashing of the soil in the crucible. The tip of tip B should be a t least 1/4 inch below the tip of tip A. This difference is necessary in order to keep the solution flowing from tip B when tip A is in the air; if A and B are a t the same height, both tubes fill up with solution and the flow stops. The entire a p p a r a t u s is inverted after filling with the solution, and supported by a wooden s u p p o r t , with the b o t t o m of both tips w i t h i n a n d below t h e edge of t h e crucible. Figure 1-Diagram of Apparatus v
Literature Cited
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(1) Schollenberger and Dreibelbis, Soil Science, 80, 166 (1930).
