ANALYTICAL CHEMISTRY
1506 method for the complete oxidation of the compound to carbon dioxide (6, 6). For example, after oxidizing, according to the authors' method, phenylglucosazone-carbon-14 labeled in the glucose portion of the molecule, the authors found that the specific activity of the glucose carbon averaged 95% of that obtained by direct plating of the osazone on paper (Table 11),even though in some cases only 90% of the theoretical yield of carbon was obtained (Table I ) . This might be taken to indicate that preferential oxidation of carbon atoms may not be a major source of error here. However, since evenly labeled glucose was used in preparing the osazone, it is possible to obtain such a high recovery of the theoretical specific activity even if one or more of the glucose carbons were only partially oxidized to carbon dioxide. Hence, before using the method for the determination of specifically labeled glucose, the suitability of this oxidation technique should first be established.
ACKNOWLEDGMENT
The authors gratefully acknowledge the technical assistance of C. L. Hannum, Jr. LITERATURE CITED
Barker, H. A., in Calvin, If.,Heidelberger, C., Reid, J. C., Tolbert, B. &and 'I. Yankwick, , P. E., "Isotopic Carbon," p. 93, New York, John Wiley & Sons, 1949. (2) Claycomb, C. K., Hutchens, T. T., Van Bruggen, J. T., and Cathey, W. J., Nucleonics, 7, 38 (1950). (3) Katz, J., Abraham, S.,and Baker, K.,Aa.4~.CHEM., 26, 1503 (1)
(1954). (4)
Michaels, G. D., Margen, S., Liebert, G., and Kinsell, L. W.,
J . Clin. Invest., 30, 1483 (1951). ( 5 ) Van Slyke, D. D., and Folch, J., J . BioZ. Chem., 136, 509 (1940). (6) Van Slyke, D. D., Gteele, R., and Plazin, J., I b i d . , 192, 769 (1951). RECEIVED
for review July 9, 1953.
Bccepted March 29, 1954.
Thermolysis of Zinc Monosalicy laldoxime JOSEPH RYNASIEWICZ
JOHN F. FLAGG
and
General Electric Co., Knolls Atomic Power Laboratory, Scbenectady, N. Y.
P
EARSON ( 4 ) attempted to precipitate zinc as zinc disalicylaldoxime, Zn(C,H602X)2,from solutions of pH 7 t o 8, but the result was a salt of variable composition. On the other hand, Flagg and Furman ( 3 ) found that if such a precipitate were digested for 10 minutes between 90" and 100" C., zinc monosalicylaldoxime, Zn( CrH,OzN), was formed. The compound came to constant weight when dried a t 110" C. for 1 hour and remained stable for several hours thereafter a t the same temperature. The dry zinc salt contained 32.5'% of zinc compared with the theoretical 32.6% of zinc found in Zn(C7H602S). Furthermore, this compound was used successfully as a weighing form for the analysis of zinc in a National Bureau of Standards brass sample. Duval (1) and coworkers obtained thermolysis curves for a zinc complex which they believed was Zn(C7H502iY), but they were unable to determine a satisfactory drying temperature for the compound. As a result they proposed that the method be abandoned.
The correct drying temperature for zinc monosalicylaldoxime lies between 25' and 285" C., depending on the moisture content of the sample and the heating (drying) rate. Practically, drying to constant weight a t 110' C. is recommended. As observed by Duval ( I ) , the wet sample starts to lose moisture a t -60" C., and decomposes very rapidly a t 290" C.
Table I.
Curve, Fig. 1
I 11
I11 IV
b d e
OC
I
0
1
100
ZW
Dc,
,
100
I
I
100
700
900
I
1000
Figure 1
Using the same type Chevernard thermobalance employed by Duval (1, 3), this laboratory obtained thermolysis curves which confirmed the drying temperature and the composition of the zinc salicylaldoxime complex proposed by Flagg and Furman (3). The data for five thermolysis curves (Figure 1) are summarized in Table I. The following conclusions were made.
Reagent Added for P p t n . of Zn Excess Deficiency Deficiency Deficiency Excess
a
Thermolysis" of Zinc Salicylaldoxime hfoisture in P p t . a t Start of Thermolysis, % None
Discontinued Heating for 1 %ur at C.
Temp. Range for Zn(X),
Zn in Zn(X)b,
110
-5Od
115
25-285 115-240 135-290 2 15-29 0
32.0 43.0 37.4 40.5
245-315
33.0
-5Od 250e 63OC
135
Heating uninterrupted Heating uninterrupted
c.
%
Heating rate 5' C. per min. Zinc in Zn(CrHa0zX) is 3 2 . 6 % . Air-dried for -70 hours a t 25' C. Air-dried for -24 hours a t 25' C. Wet precipitate immediately after filtration
A zinc complex of variable composition (probably a mixture of zinc hydroxide and zinc salicylaldoxime) resulted when less than the stoichiometric amount of salicylaldoxime reagent was used for the precipitation of zinc. When a 20% excess of reagent was used, zinc monosalicylaldoxime, Zn(C7HsO*N), was formed. In all cases, a constant weight for the final ignition residue w ~ t s obtained between 500' and 1000' C. This observation is a t variance with the Duval's thermolysis data ( I ) , which showed that the zinc salicylaldoxime complex is converted to zinc oxide a t 950' C. LITERATURE CITED
(1) Duval, C., "Inorganic Thermogravimetric Analysis." p. 283, Kew York, Elsevier Publishing Co., 1953. (2) Duval, C., et nZ., A N ~ LCHEM., . 23, 1271-85 (1951). (3) Flagg, J. F., and Furman, H. N , IWD.ENG.CHEM.,ANAL. ED., 12, 663-5 (1940). (4) Pearson, Th. G., 2. anal. Chem., 112, I79 (1938). RECEIVED for review January 15, 1954 Accepted May 24, 1954 The Knolls Atomic Power Laboratory is operated b y the General Electric Co for the Atomic Energy Commission T h e work reported here was carried o u t under Contract TV-31-109 Eng-52
