INDUSTRIAL AND ENGINEERING CHEMISTRY
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The precision attainable by the use of these four formulas is as follows : I11 Mean error, per cent Maximum error, per cent
No. of cams v 26 30 45 50 70'7' 90%
kl9.0 +85.9 -29.6 10 19 32 38 49 54 65 66 57 59
t33
IV v VI h11.3 2~10.5 111.6 4-38.4 f40.1 +48.l -23.1 -33.4 -22.8 17 19 26 35 32 37 43 43 44 61 54 50 56 55 68 67 59 60 60 61 60 61 61 62 61 62 62
..
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It is interesting to note that the precision of the turbidity for the red is somewhat better than that for the green. This is probably due to the fact that the slope of the spectral curves is much smaller a t the red than a t the blue end. Summary and Conclusions The formulas developed in the previous paper (6),for calculating the concentration of coloring matter and turbidity in a certain raw sugar from the transmittancy and Tyndall beam intensity of its solution, have been applied to 62 other raw sugars. It has been found that the results obtained by this method check with those of Balch's method only in those cases where the properties of the particles causing the turbidity are the same as in the standard sugar. Conversely, the discrepancy between the results of the two methods serves to characterize the particle properties. Determinations of the transmittancy and Tyndall beam intensity of unfiltered
VOL. 7, NO. 3
and filtered solutions of raw sugars make it possible (1) to express the concentration of the filterable turbidity, Nu N,, and also of the total turbidity, Nu,in terms of an arbitrary standard turbidity particle, whereas the difference between the absorptive indexes of the unfiltered and filtered solutions represents merely an optical measure; (2) to estimate the deviation from standard particle properties by the "quality index"-i. e., the ratio between Nu - N/ and the turbidity according to Balch-at one wave length, preferably in the green; and (3) to characterize the absorption quality of the particles by the ratio between N u - Nf a t one wave length and that at another wave length. Value 1 above is analogous to Peters and Phelps' Characterization of color concentration by the -log t a t a specified wave length; values 2 and 3 correspond to the characterization of the quality of the coloring matter by the Q or R ratios. It is of course fully realized that neither the color nor the turbidity problem in sugar products can be completely solved without further fundamental knowledge of the chemical and physical properties of the constituent dispersoids present as turbidity or coloring matter, and the procedure outlined in this paper is presented merely as a step in that direction.
Literature Cited (1) Balch, IND.EXQ.CHEV.,Snal. Ed., 3, 124 (1931). (2) Landt and Witte, 2. Ver. deut. Zuckerind., 84,450 (1934). (3) Peters and Phelps, Bur. Standards Tech. Paper 338 (1927), (4) Teorell, Kolloi&Z., 53, 322 (1930); 54, 55, 150 (1931).
(5) Zerban, Sattler, and Lorge, IND. ENQ.CHEM..,Anal. Ed.,6, 178 (1934). RECEIVPD March 5,1936. Presented before the Division of Sugar Chemistry at the 88th Meeting of the Amerioan Chemioal Society, Cleveland, Ohio, September 10 t o 14, 1934.
An Emergency Stopper for Nitric Acid Bottles DARWIN HARRIS, 854 Madison Ave., Grand Rapids, Mi&.
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EQUIRING a stopper for a bottle containing 98 per cent nitric acid, the author at a venture tried using a cork covered with four thicknesses of ordinary aluminum foil, thinking it would serve for a short time a t least until the acid could be transferred. After a few days, it was found that the device was in perfect condition, there being practically no corrosion of the aluminum, and the cork was thoroughly sound. Moreover, it was superior to a glass stopper, since it was air-tight, allowing no leakage of fumes which sometimes occurs with glass-stoppered bottles containing fuming nitric acid. I n order to determine the efficacy of this method in the case of weaker acid as well, a bottle holding 80 per cent acid was closed with a stopper made in the same way as the original one, four thicknesses of foil over cork, and set away with the first bottle, After six months' storage at temperatures ranging from 60" to 80" F., both stoppers were in satisfactory condition. The aluminum in the bottle containing the 98 per cent acid was bright and completely intact, although it was removed several times to withdraw acid. There was some corrosion around the upper part of the stopper, where it did not extend into the bottle, due probably to the action of diluted acid. The foil in the other bottle, containing 80 per cent acid, was dulled somewhat on its inner surface, and was corroded around the circumference, where it was in contact with the glass and remained wetted with the acid. No acid had penetrated to the cork in either case.
This suggests that ordinary bottles with aluminumcovered corks may satisfactorily replace the more expensive glass-stoppered bottles for storing commercial fuming nitric acid. The foil from certain types of candy is easily available and is satisfactory, although a foil having a somewhat greater thickness is preferable. At least four thicknesses of the thinner material should be used. At intervals, the foil may be replaced if it shows corrosion. The corrosion of aluminum by nitric acid is less the stronger the acid. Dilute acid attacks aluminum rather easily, so it is advised that the stopper be not used for acid weaker than 80 per cent, although it will serve for a short time. Eighty per cent acid in direct contact with aluminum penetrates the metal at the rate of about 0.006 inch per year, while 95 per cent acid penetrates about 0.0025 inch per year (1). The slight corrosion of aluminum in contact with the vapor of nitric acid from mixtures containing up to 20 per cent or more water is probably due to a relatively low water concentration in the vapor. Mixed nitrating acid could be stored in bottles stoppered with aluminum without trouble, since the vapors from such acid consist of nearly anhydrous nitric acid, even if the water concentration in the mixture is as high as 25 per cent.
Literature Cited (1) Frary, IND.ENO.CHEW,26, 1231 (1934). R B C E I V February ~D 23, 1935.
