INDUSTRIAL AND ENGINEERING CHEUISTRY
July 15, 1931
Two of these washings are usually sufficient for transfer of the solid to the paper, as this transfer does not need to be quantitative. The time required for this filtration may be very materially reduced by using 9-cm. rapid filter paper fitted to a long narrow stem funnel by wetting with distilled water. The filter paper is freed from water by washing with two portions of alcohol wash solution before the filtration is begun. After filtration and washing, the potassium acid tartrate is dissolved in nearly boiling distilled water and titrated with 0.12 N sodium hydroxide. Procedure I1 aliquot later diluted to 25 cc.) contains 0.08 to 0.22 gram of potassium. If more than 0.40 gram of sodium chloride or nitrate is present, the method is not recommended. Twentyfive cubic centimeters of a solution containing 104 grams of MgC4H4064Hz0,95 grams of NaHC4H40~Hz0, and 264 grams of tartaric acid per liter are then added to the sample and mechanical agitation started. Subsequent steps are exactly the same as those outlined for procedure I. Comparison of New Method with Hicks Method Procedure I has been used extensively for over a year by this laboratory for analysis of water extracts of the mineral polyhalite. These extracts contain nearly equivalent amounts of potassium and magnesium sulfates and small amounts of sodium chloride and calcium sulfate. A comparison of results obtained by this method with analysis by a modification of the chloroplatinate method of Hicks (4) is given in Table I. Table I-Comparison of New Method a n d Hicks Method MAGNESIUM POTASSIUM SULFATE FOUND IN Hicks New DIFSULFATE SAMPLE method method FERENCE
SUBSTANCE ANALYZED
Polyhalite extract Polyhalite extract Polyhalite extract Polyhalite extract Polvhalite extract Polvhalite extract Polyhalite extract Rali magnesia Potassium sulfate
A comparison of the results of analysis of synthetic potassium chloride and potassium nitrate solutions by procedure I1 with analyses by the method of Hicks (4) is given in Tabla 11. In the case of the potassium chloride solution used, the chloride content was also determined by Mohr's method, and the titer calculated as potassium checked the chloroplatinate procedure to 0.1 per cent. Table 11-Comparison of Procedure I1 w i t h Hicks Method --POTASSIUX FOUND--FORMOF SODIUM PROCEDURE IT POTASSIUMCHLORIDE Calcd. by Calcd by IN IN Hicks theoretical empirical DIFFERENCE SAMPLE SAMPLE method factor factor"
Gram
A sample is taken so that a 25-cc. aliquot (or a smaller
Grom
Gram
Grom
0.20 0.24 0.24 0.27 0.24 0.28 0.32 0.17 0.01
0.3156 0.3358 0.3494 0.3912 0.3392 0.4118 0.4648 0.2368 0.2257
0.3136 0.3330 0.3510 0.3872 0.3372 0.4084 0.4644 0.2380 0.2260
Gram
Gram
KC1 None 0.1038 0.1015 KC1 None 0.1038 0.1022 KC1 None 0.1038 0.1023 KCI None 0.2076 0.2040 KCl None 0,2076 0,2027 KC1 0.40 0.1038 0.1023 KC1 0.40 0.1038 0.1016 KC1 0.40 0.2076 0.2040 KC1 0.40 0.2076 0,2050 KNOs None 0 1960 0 1933 KNOI None 0 1960 0 1933 0 0983 0 0974 KNOa None KNOa None 0 0983 0 0972 KNOs None 0 0983 0 0970 KNOa None 0 0983 0 0968 a Empirical factor used IS 1.016 times theoretical
Gram
%
0.1032 0.1038 0.1040 0.2074 0.2060 0.1040 0.1032 0.2074 0.2083 0 1964 0 1964 0 0990 0 0988 0 0986 0 0984 factor.
-0.6 -0.0 +0.2 -0 1 -0.8 +o 2
-0.6. -0.1 +0.3 $0 2 +O 2 +O 4 +O 3 +O 2 +O 1
Reference to this table shows that if the empirical factor of 1.016 times the theoretical is used, the results of the procedure agree fairly satisfactorily with the results of the chloroplatinate procedure. Acknowledgment The authors wish to acknowledge the valuable suggestions of Nathan Fragen, junior chemist, of this laboratory. Literature Cited (1) Ajon, A n n . slue. sper. d i ogrumicoltura c frutlicoltura di Acirsale, 3, B t
% -0.7 -0.8 $0.5 -1.0 -0.6 -0.8 -0.1 $0.5 +0.1 Mean - 0 . 3
325
(2) (3) (4) (5) (6) (7) (8) (9)
(1915). Bayer, Chem.-Ztg., 17, 686 (1893). Bokernuller, Chem. Zenlrolblatl, 1918, 11, 764. Hicks, J. IND.END.CHEM.,5, 650 (1913). Marshall, Chem.-Zlg., 88, 585 (1914). Meurice, Ann. chim. m a l . oPPl., 7 , 161 (1925); 8, 130 (1926). Okada, Mcm. Coll. Sci. Kyoto I m p . Uniu., 89 (1914). St. Minovici and Kolla, Bul. SOC. chim. Romdnio, 8 , 25 (1921). Touaritske and Slezak, Zhurnab Sokharnoi Prom., 2, 462 (1928).
Method for Increasing Sensitivity of Certain Chemical Test Reactions' Irwin Stone 360 WADSWORTR AvE., NEWYORK,N. Y.
H E general class of organic precipitant reagents used in qualitative inorganic analysis includes some of the most sensitive chemical tests for metals known. Some, such as the dimethylglyoxime test for nickel, are well known, whereas others, such as the p-nitrobenzeneazoresorcinol test for magnesium (4),or the p-dimethylaminobenzylidenerhodaninetest for silver (9) have not such widespread recognition. The usual reaction that takes place in this class of tests is one where the metal enters the molecule of the organic compound to form a very insoluble, highly colored precipitate. This precipitate, composed of a generally water-insoluble organic residue coupled to a metal, which is more or less repelled by organic solvents, forms a typical polar molecule. This polar precipitate, if shaken with a mixture of water and 1 Received
April 27, 1931.
some immiscible organic solvent, will tend to collect at:the water-solvent interface, the molecules probably orienting themselves similar to the polar molecules described by Harkina and his co-workers (1) and Langmuir (3), the organic portion jutting into the immiscible solvent phase while the metallic portion points toward the water. This fact may be applied to extending the range of sensitivity of these tests by collecting a t the interface the small amount of precipitate which would be undiscernible suspended in the large bulk of test liquor. It may also be utilized to make faint reactions more easily and surely recognizable. As a general method for performing this sensitization, one may conduct the test in the usual manner and when completed add a few cubic centimeters of ether and shake thoroughly. When the ether has separated, note any color or precipitate that has collected a t the water-ether interface.
ANALYTICAL EDITION
826
of Organic Precipitant Reagents SENSITIVITY usual Interface REAGENT method method Mg. per 5 CC. Dimethylglyoxime 0.02 0.005 Alizarin 0.6 0.01 p-Nitrobenzeneazoresorcinol 0.07 0.01 p-Dimethylaminobenzylidenerhodanine 0.001 0 00008
Table I-Sensitivity METAL Nickel Aluminum Magnesium Silver
Table 1shows the increase in sensitivity for a few organic precipitant reagents. The figures in the table are not to be
Vol. 3, No. 3
construed as accurate sensitivity figures, but merely the limits of an easily discernible reaction under similar conditions. Literature Cited (1) Harkins et al., J . A m . Chem. Soc., 39, 354 (1917); 39, 541 (1917); 43. 700 (1920): 43. 35 (1921). (2) Rolthoff, Ibid., 62, 2222 (1930). (3) Langmuir, I b i d , , 39, 1848 (191,). (4) Ruigh, z b i d . , si, 1466 (1929).
Studies on Turbidity in Sugar Products I-Relation between Intensity of Tyndall Beam and Depth and Concentration of Solution' F. W. Zerban and Louis Sattler NEW YORKSUGARTRADELABORATORY, INC., 80 SOUTHST.,NEWYORK, N. Y.
T
Previous work on the optical measurement of turbe determined more easily by URBIDITY p l a y s an bidity in general, and with respect to sugar products a simple turbidity determinaimportant part in the in particular, is briefly reviewed. The Pulfrich photion than by filtration and manufacture of c a n e tometer, with which both the transmittancy and the weighing, as is the c u s t o m sugar. The juice expressed Tyndall-beam intensity of turbid solutions can be a t p r e s e n t . As a f u r t h e r from the cane contains susdetermined, is described. Several series of such example, t h e p r o b l e m of pended m a t t e r i n v a r i o u s measurements have been made on a raw sugar solution degrees of dispersion, from color d e t e r m i n a t i o n s in at varying depths and concentrations. It was found sugar products may be mencoarse, through fine particles, that with colored turbid solutions the Tyndall-beam to those of colloidal diment i on e d. Various investigaintensity is affected to such an extent by absorption t o r s h a v e f o u n d that i n sions. One of the objects of that the latter must be corrected for. The ratio beorder that the Lambert-Beer clarification is to remove the tween Tyndall-beam intensity and transmittancy is law may be applied to such suspended matter as far as within a certain range, a power function of the depth measurements, the turbidity possible. Even if this obor the concentration, according to the formulas R = must be reduced to a certain ject has been attained, the R1 X bn, and R = R, X cn, where b is the depth, c the m i n i m u m by careful filtrajuice becomes cloudy once concentration, R1the ratio for unit depth or concention. It is not known exmore upon c o n c e n t r a t i o n , tration, and R the ratio at any depth or concentration; actly w h a t t h a t minimum and the sirup m u s t a g a i n n is a constant which, at constant depth and varying be settled before crystallizashould be, except that there concentration, or vice versa, is independent of wave tion, because any suspended should be only a faint Tynlength. In the formula R = R1 X bn, the value of n dall beam. Opinions differ matter is partly adsorbed on varies approximately as the logarithm of the concenas to what is the best filterthe crystals, partly retained tration. The work is being continued to test the above ing medium to use. A careon them while the sugar is beformulas further and combine them into one equation. ful studv of turbiditv and ing centrifuged, and another transmittancy of s o l u t i o n s important part goes into the runoffs. When these are boiled to grain, the cycle is repeated, may be expected to throw more light on this disputed point. These few examples will suffice to show the importance of and when a low-grade sugar in which suspended matter has accumulated is used as seed, the resulting sugar gives a very turbidity measurements in the sugar industry. turbid solution. I n raw sugar manufacture, the juices, Available Radiometric Procedures sirups, and molasses are not filtered, but only settled, and The radiometric procedures available for this purpose fall the care with which this is done largely determines the filtering quality of the raw sugar. Turbidity in the liquors into three classes. In the first of these, the measurements are made by transof the refinery causes similar difficulties as in the raw sugar factory, and the suspended particles must be removed in order mitted light, using a photometric null device and comparing that a product of high quality may be obtained which must either with a standard dispersion in the same dispersion be free not only from color and dissolved impurities, but medium (turbidimeters of the Duboscq colorimeter type), or must also give a clear solution, If turbidity is t o be controlled comparing with the intensity of the light transmitted by the dispersion medium or a standard dispersion in a second abin the factory, we must be able to measure it. Turbidity measurements would also prove of value in sorption cell of the same characteristics (photometers, various analytical operations. The suspended matter in spectrophotometers). This group of methods is especially juices, sirups, and molasses affects the specific gravity of the adapted for measuring visible turbidity. The second group is based on measurements with a photolatter. To correct for this, it is customary to let the solution sfand until the suspended matter has settled out. The non- metric null device of the intensity of the Tyndall beam emitted settling particles should also be allowed for because they in- by the dispersed particles, in a manner similar to the one fluence the specific gravity. Their quantity can probably used in transmittancy measurements. If the comparison is made with a standard dispersion, the instruments are 1 Received April 14, 1931. Presented before the Division of Sugar termed nephelometers; if the comparison is made directly Chemistry at the 81st Meeting of the American Chemical Society, Indianwith the intensity of the incident light they are called tyndallapolis, Ind., March 30 to April 3, 1931.
