February, 1924
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Table I1 gives results comparing the action of monocaleium phosphate with that of calcium carbonate on nine different crops. Corn, radishes, rye, and barley seem to he more affectedby aluminium toxicity than by hydrogen-ion toxicity. Wheat and o a k are affected by both, while red beets, huckwheat, and red clover seem to be affected by hydrogen ions more than by aluminium ions. These results were obtained in three tests on corn, three on red beets, two on buckwheat, and two on wheat-all in duplicate pots. It is obvious that an investigation of soil acidity should include a study of the response of different crops as well as of diffcrent types of soils. The soil used in these pot tests contains a large amount of active (soluble) acidity, much exchange acidity, and much hydrolytic acidity (organic). Just how phosphorus prevents aluminium toxicity is not definitely known. Analyses of corn plants grown on six acid
175
so& were made hy Hoffer and Trost.? The average of the analyses showed 0.37 per cent aluminium oxide in the corn on untreated soils, 0.27 per cent on soils treated with 3 tons of lime, and 0.23 per cent on soils treated with 500 pounds of acid phosphate. It would appear that phosphate might act partly in preventing the intake of aluminium and partly in correcting its toxicity wyithin the plant. It is a well-known fact that acid soils need phosphate as well as lime. Undoubtedly, much of the benefit due to phosphate on such soils is to help correct aluminium toxicity. No doubt there are acid soils vrhich may a t times be unproductive on account of iron or manganese compounds, hut it is thought that in the majority of soils aluminium is more prevalent as a toxic agent in connection with the hydrogenion toxicity. 3. Am. See. A r m . , 16, 323 (1923).
A Special Slide Rule for Apparent Purity Calculations' By H. J. Bastone Tns AYRRSCINSUEAI RZPZNINO Co., BBOOHLYN.N. Y.
T H L,'laboratory of the sugarhouse is liable to be overrun by the drudmrv of common-dace work unless every means is utilized io simplify and systematize the testinb. of the numerous samples which are received daily. Tests of the apparent purities of the various liquors, sirups, and magmas in process are a heavy burden on the laboratory and at t.he same time are exceedingly inkportant and necessary to the refiner. Anything, therefore, which speeds up the determinatidn of such tests not only increases the efficiency of the laboratory,, but makes the work much more valuable to the refiner. Among the various irnprovements used in this laboratory is a special slide rule for purity calculations which eliminates t.he iise of factor tables. The rule is of the 20-inch Mannheiui type with two scales placed in proper logarithmic relation to each other. Inasmuch as polarity and purity are percentage figures, it is obvious that one scale should answer for both. A second scale is constructed based on the logs of the Brix factors, and both scales are made to read in direct percentage and Brix numheks, respectively. The polarity and purity scale is niounted on the movable part of the rule and 1 Presented before t h e Division of Sugar Chemistry a t the 66th Meeting of the Ameiican Chemical Society, Milwaukee, Wis., September 10 to 14. 1923.
is the ordinary A scale of the hlannheiin rule with t . 1 nrain ~ divisions renumbered to read from 0.8" to 100". with subdivisions ranging from 0.01' at the lower end tob.5° at the upper end of the scale. The Brix, or fixed scale, reads from 0.2" to 23.7*, with subdivisions of 0.1'. This gives the density range required for any apparent purity determination and covers all grades of materials. To operate the rule one arranges the movable part so that the division thereon corresponding to a given polarization coincideswith its proper Brix division on the fixed scale. Thus the required purity is shown directly on the movable scale hy an indicating arrow which is a t the right of the fixed scale. The slide rule is compactly housed in a polished mahogany box and is operated by an extension bar projecting through the right-hand end of the box. The scale is covered with glass, making the whole unit dust and dirt proof. The outfit is arranged to mount on a t.able arid its sturdy construction permits constant use. The slide rule may he operated by a school boy without difficulty; i t t.akes up little space; it eliminates charts and factor tables; i t saves time, and gives accurat,e results. In short, the apparatus is thought to be the simplest and most complete yet devised for apparent purity calculations.
