ANALYTICAL CHEMISTRY
890
+
tation velocity, k , k l , call be calculated. I n the equations drrived by Hudson for the maximum rates of solution and crystallization, common logarithm is employed. If the rate constants are to be applied to kinetics problems, they must be inultiplied t)!the logarithmic conversion factor 2.3026. In Table I1 results on thr a- and @-lactose dietributioii in different dry products of milk i i drttsrniined ~ from d e s of crystallization are presented along with some datu obtained by the solubilit,y method ( 1 ) . The valuw for nonf:it dry milk solids :ire in agreement Fyith those reportcd 1)y 81inrp and Doob ( 7 ) :ind 11y the present authors using the, w1ul)ility method ( I ) . The ratio of pto ol-lactosc is very clow t o that found in fresh fluid milk a t ordinary temperature, a fact which indic,atc:: that the drying opei'ations cause very Mtle r1isturl):inw i n the equilibrium of the two forms of lactose. This is a k o truv of dry whey solids Pamples 1. 2 . iind 3. I n the remaining sninplw of d q - whey solide. in n-hic.11
crystallization of the lactose had Ixrn induced in the proces8ing. the alpha modification predominnten. In general, results obtained by t,lie solubility method ( 1 ) and by the crystallization method are in good agreement. The techniques employed and the length of time required per analysis are very eimilar in hoth methods. LITER.ATtiRE CITED
( I ) Choi, R. P., T a t t e r , C . IT'., O'Slalley. ., and Fairhaiiks. R . IT.,J . Dair,u Sci.. 32, 391 11949). 12) Hrrrington. B. I,.. Ihid., 17, 659 (1934). I:{) Hinton. C . L., and Macara. T., A n a l y s t , 52, 668 (1927). 4)Hudson, C. S.,J . Am. C h o n . Soc.. 26, 1065 (1904). 1.5) Hunziker, 0. F., and Sissen, B. H.. -1.Dairy Sci., 9, 517 (1926). 4)Kendrew. J. C.. a n d hloel~vr-yn-Hughes,E. .L,Proc. R o y . Soc. (London), A176, 352 (1940). ( 7 ) Sharp, P. F., and Dooh, H., . J r , , .I. D a i r y S c i . , 24, 589 (19411.
RECEIVED.January 6,
1951.
'Potentiometric Analytical Methods for Hydrazino Compounds Hydrazine Sulfate W l l , l , J A J I H . McBHIUE, RONALD A . HENRY, AND SOL SKOLNIK Chemistr.s Diaision, 17. S. .Vavnl Ordnance Test Station, China Lake, Calif. 'l'his poteiitioiiietric s t u c l ~o f the oxidation of hj dr.1Line to nitrogen was made in order to develop general procedures for the quantitative determination of hydrazine nitrogen in organic compounds. Experimental conditions are systematically varied, so that the reduction of iodate ion proceeds to the three distinct equivalence points: the iodine monochloride, the iodine, and the iodide ion. The relative erect of hydrogen ion and chloride ion roncentra-
T
HE quantitative oxiclntioii ot' Iiydr~~ziiieto niti.ogcii u i t h various oxidants has led to numerous analytical methods for the determination of hydrazine. A comprehensive review of quantitative methods is given by Peniiem:in and Audrieth ( 2 , 8). Jamieson (6) applied the Andren-s method ( I ) , rrsmtiall>titration with potassium iodate in a strong hydrochloric acid solution x i t h formation of iodine monochloride, to several hj-drazincl salts. The potentiometric study of this reaction in at least 4 b' hydrochloric acid was found b y Singh (IO) to give accurate anti reproducible results with a sh:irp inflect,ion point whew using :I platinum foil electrode versus a calomel cell. Stelliny (11) reported that the potentiometric titration of hydrazine n i t h iodic acid gave iodine as an end product in sulfuric acid solutions :tnd iodine monochloride in hydrochloric acid solutions. Bray and Cuy (3) found that the oxidation of hydrazinc t o nitrogen in 0.5 to 2.0 N eulfuric acid was complete in 3 minut(+ when treated with a known excess volume of iodic acid. The excess iodic acid was determined by reduction t o iodine n-itli potassium iodide and titration with potassium thiosulfate. T h r oxidation of hydrazine by iodine (5)was found t,o be rapid i n alkaline solution and slow in acid solution. I n the presence of sir in alkaline solution hydrazine undergoes slow decomposition due to a reaction with oxygen. By proper addition of reagent:: this decomposition was minimized t o give agreement within 0.2YG of theory.
tions on the iodate reduction is studied i u both the presence and absence of chloroform. Recommended potentiometric procedures for the quantitative determination of hydrazine sulfate are described. Because potentiometric procedures may be varied to a greater degree than most generally accepted methods allow, it is probable that the hydrazine nitrogen in other compounds may be determined by a proper choice of one o f the procedures described.
l
