ANALYTICAL CHEMISTRY
674
The mixtures of methyl deuteride and methane were obtained from the reaction of deuterium oxide-water mixtures with methyl magnesium iodide (ca. 3 LV in dibutyl ether), carried out in a vacuum system. The water samples ranging in size from 20 to 200 mg. were distilled in vacuo onto the previously degassed and frozen Grignard reagent. The methane liberated after warming was transferred by a Toepler pump, past a dry ice trap, into the gas ~ ~ 1 1The . total methane pressure in the cell was recorded.
If the rates of reaction of deuterium oxide and water with the Grignard reagent are the same, the per cent methyl deuteride in the methane is equal to the atom per cent deuterium in the water. Orchin, Render, and Friedel ( 2 ) showed this to be the case in connection with their work on the analysis of deuterium oxidewater mixtures. Their method was based on mass spectrometric examination of the methyl deuteride-methane mixtures formed after the water reaction with the Grignard reagent in a nitrogen atmosphere. In the present study five different concentrations of deuterium oxide were used, ranging from 4 to 98 atom % ' deuterium For each sample of mixed isotopic methanes thus produced, several points of the calibration curve of Figure 1 could be obtained, by successive reductions of the total pressure. Coggeshall and Saier ( I ) , who studied the dependence of the absorbancy of the 7.65 fi band of methane upon the partial pressure of nonabsorbing foreign gases, found a considerable pressure-broadening effect. In the present study the presence of air as a foreign gas was found to cause an appreciable increase in apparent absorbancy, as
anticipat,ed from their results. Although no systematic study was carried out to determine the pressure-broadening effect due to methane, the data of Table I suggest that this may be small. No trend or scatter associated with the variation of total methane pressure is evident from Figure 1. The minimum limit of detectability of methyl deuteride in methane (and thus of deuterium oxide in water) was investigated using samples of approximately 1% deuterium oxide. For a 100mg. sample, 0.4 atom % deuterium may be detected with certainty. The ultiniat,e sensitivity of the method appears limited by the instrumental noise-to-signal ratio. Under the conditions used, this was generally about 0.5%. It would appear that the infrared method described would lie suitable for estimation of deuterium in small quantities of water. ACKNOWLEDGhIENT
The deuterium oxide was procured through the courtesy of the Atomic Energy Commission. The aut,horsappreciate thc assistance of S. Kxta and D. rr. Kniebes of the Institute of Gas Technology. LITERATURE CITED ( 1 ) Coggeshall, S . D., and (1946).
Saier, E. L., J. A p p l i e d P h y s . , 17, 450
(2) Orchin, ll.,\Vender, I., and Friedel, R. A., ANAL.C m x , 21, 1072 (1949). RECEIVED .June 23, 1550.
Microdetermination of Total Phosphorus by Amperometric Titration RICHARD N. BOOS AhD JOHN B. CONY Research Laboratories, Werrk & Co., Inc., Rahway, .V. J .
METHOD for the determination of total phosphorus in
Li organic compounds based on the Kolthoff and Cohn ( I ) amperometric titration of phosphate ion with uranyl acetate hap been developed, and is now in routine use. Bolthoff m d Cohn ( 1 ) showed that the concentration of SUIfate in the solution to be titrated must be less than 0.01 .%I This limitation forces the abandonment of wet combustion methods using sulfuric &id. Fusion of the organic compound with sodium carbonate is satisfactory f i om the standpoint of speed, accuracy, and ease of handling. The total phosphorus content can be determined within 45 minutes by the proposed procedure, the economy in time being a matter of many hours in comparison with the gravimetric method. It was observed that when the concentration of phosphate in the solution to be titrated was in the range of 0.0005 M , the curve obtained was irregular in the vicinity of the equivalence point. This difficulty wm caused by crystallizrttion of the initially amorphous precipitate of uranyl potassium phosphate, and was eliminated by the addition of a few crystals of uranyl potassium phosphate to saturate the solution before the start of the titration. Cocarboxylase was used as a standard compound in testing the feasibility of the method. The cocarbovylase was found pure by solubihty analysis and the analytical results for the anhydrous material were as follows: Carbon Hydrogen Nitrogen Chlorine Phosphorus
Calcd.
Found
31.25 4.16 12.16 7.69 13.20
31.50 4.27
12,25
flask with 300 ml. of water and 6 to 10 ml. of glacial acetic acid, I t is diluted with water to 1 liter. Standard Phosphate Solution. Potassium Phosphate Monobasic Merck (Soerensen's potassium phosphate) is dried a t 110' C. for 1 hour and a 0.001 M solution is prepared by dissolving 136.14 mg. in water and diluting to 1 liter. Potassium chloride, 2 -If. Acetic acid, 0.1 M . Sodium carbonate anhydrous, Nerck. Bromocresol green indicator solution, 0.04% (Clark and Lubs solution). Hydrochloric acid, 5 -V and 0.5 dV. Cranyl potassium phosphate is prepared by mixing 50 ml. of 0.01 M potassium dihydrogen phosphate, 5 ml. of 0.1 M acetic acid, 5 ml. of 2 M potassium chloride, 20 ml. 95% ethyl alcohol, 20 ml. of distilled water, and 4.83 ml. of 0.1 M uranyl acetate. The precipitate is allowed to stand overnight, after which it is filtered and washed with 0.1 M acetic acid, distilled water, and acetone. The precipitate is dried for 1 hour in a vacuum desiccator. PROCEDURE
The sample is weighed into a 5-ml. platinum crucible and covered with approximately 100 mg. of sodium carbonate. The Table I. Sample Cocarboxylase Cocarboxylase Cocarboxylase A
7.63 1 3 . 0 1 (gravimetric)
Samples A, B, C, D, E, and F listed in Table I represent samples of other organic compounds that were submitted by chemists in these research laboratories. REAGENTS
Uranyl acetate, 0.1 31, is prepared by dissolving 42.422 grams of uranyl acetate monohydrate in a 1-liter volumetric
B C
n E
F
Determination of Total Phosphorus Sample
W L ,J l g .
Volume UO~(Ac)~, MI. Calcd.
3.455" 0.0568 0.0480 1.188 0.0244 0.622 5.9~32~ 0.684 1.029 0,0289 0.664 0.0175 2 108 0,0288 586 0.0511 - , 410 0,0521 4.680 0.01896
;: 8p;;
$,
13.20
...
Gravimetric
dmperometric
13.01
13.16 12.95 12.60 i.05
...
,.. 6.80
6.94
9:06
8.69
i.35 9.00
4.43
8.62 4.38 16.61
...
4.59 16.85 6.82 2.23
, . .
...
...
... ...
...
6.g3 2.28
Xeutral solution was diluted t o 10 ml., 4 ml. of which wae transferred t o titration cell 0.1043 .II 'ZTOn(Ac)*. Other resulta n'ere obtained using 0.1034 ,If UOi(Ac)s. a
*
V O L U M E 23, NO. 4, A P R I L 1 9 5 1
675
buret increment corrections t o the observed diffusions current8 are negligible. Results obtained by this procedure are shown in Table I. CALCULATION
V X M X 30.98 X 100
s
%P= where
V M S
= volume of uranyl acetate solution = molarity of uranyl acetate solution = weight of sample in milligrams
The uranyl acetate solution is standardized according to the described procedure except that 5 ml. of 0.001 M potassium dibydrogen phosphate and 2 ml. of water are substituted for the neutral solution of phosphate and the two 1-ml. portions of wash water. LITERATURE CITED
(1) Kolthoff, I. M., and Cohn, Gunther, IND.ENQ.CHEM.,ANAL ED., 14, 412 (1942).
43. Sodium Stannate, Na,Sn(OH), Contributed by JOHN KRC, JR.. Armour Research Foundation, Illinois Institute of Teohnology, Chicago 16, 111.
OOD crystals of sodium stannate ( 1 ) can be obtained on
B
G macro sesle from water solutions after prolonged evapora-
tion. C~yatalsprepared on a microscope slide are extremely small and poorly formed. Other investigators have reported sodium stannate as crystallizing a8 rhombohedra and ditrigonal scalenohedra (2, 8).
CRYSTAL MORPHOLOGY
Crystal System. Hexagonal. Form and Habit. Plates lying on basal pina_eoid, 0001, and showing firsborder hexagonal bipyamics, [ 10111, and o c w sianally firstorder hexagonal prisms, (1010). Asia1 Ratio. a:c = 1:2.373 (hexagonal).
Figore 2.
Crystals of Sodium Stannate
Principal Lines d
I/II
d
otii
~ n t e r i a c i ah~g l e s (polar).
iiotAiioi
= 69' 56'.
Figure 1. Orthographic Projection of Typical Crystal of Sodium Stannate
X-RAYDIFFRACTION DATASpace Group. C:i-R3
@).
=
40' 8';
iioinaooi
L
