of very small amounts of BcHIO can be found in the two plots of BIHIOvs. time of photolysis for a diborane pressure of 0.08 cm. These are depicted elsewhere (6). The B,HI0 varied between 0.02 and 0.15 pmole, and the two curves n-ere straight lines which extrapolated to within 0.02 pmole of the origin. LITERATURE CITED
( 1 ) Bragg, J. K., hlcCarty, L. V., Korton, F. J., J. Am. Chem. SOC.73,2134 (1951).
(2) Burwasser, H., Pease, R. N., J . Phys. Chem. 60, 1589 (1956). (3) Hamlen, R. P., Koski, W. S., ANAL. CHEM.28, 1631 (1956). (4) Hirata, T., Gunning, H. E., J . Chem. Phys. 27, 477 (1957). (5) Kaufman, J. J., Todd, J. E., Koski, W7.S., ANAL.CHEM.29, 1032 (1957). (6) Kreye, W. C., Ph.D. thesis, Polytechnic Institute of Brooklyn, 1960. (7) Kreye, W. C., Marcus, R. A., J . Chem. Phys. 37, 419 (1962). (8) LeRoy, D. J., Can. J . Research, B28, 492 (1950). (9) McCarty, L. V., Smith, G. S., McDonald, R. S., ANAL.CHEM.26, 1027 (1954).
(10) Stenart, R. D., .Idler, R. G , 134th
Meeting, ACS, Chicago, September
1958. (11) Stock, A , , “Hydrides of Boron and Silicon,” Cornell University Press. Yew York. 1933.
W. C. I i m m R. A . .\liacus
Department of Chemistry Polytechnic Institute of Brooklyn Brooklyn 1, S. Y. Work supported by grants from the Allied Dye and Chemical Corp. and from the
Office of Naval Research.
Karl Fischer Reagent for Determination of and Differentiation between Trialkyl (Aryl) Organotin Hydroxides and Corresponding Oxides SIR: A rapid and satisfactory method has been developed for the quantitative determination of trialkyl and triaryl organotin oxides and hydroxides using the Karl Fischer reagent. It is extremely useful in differentiating beta-een members of this class of organotin compounds where both the oxide and the hydroxide exist in stable forms. The reagent has been employed in a number of cases and the determination is general for this class of compound. Mitchell and Smith (b), who discuss the applications and limitations of the Karl Fischer reagent a t length, state that the quantitative reaction of this reagent with inorganic oxides and hydroxides is fairly general in nature and, therefore, serves as the basis for a method of analysis. The following reactions were proposed by Mitchell and Smith (2), ignoring the salt-forming function of pyridine in the reagent to simplify formulation:
-
+ Ia+ SO2 + CHaOH ZnIl + HSOaCHa NaOH + Iz + SO2 + CHIOH KaI + HI + HS04CH3 ZnO
(R3Sn)ZO (1)
+
Table 1.
Gilman and Miller (1) referred to similar reactions with organic silanols and silanediols. While attempting to determine the water content of these materials using the Karl Fischer reagent, they found that consistently high results were obtained. Investigation led to the conclusion that not only was the water content being determined, but also that the silanol was reacting quantitatively with the reagent. The method was then extended by them to other organometallics-namely, triphenyl lead hydroxide, triphenyltin hydroxide, and phenyl boric oxide. We have found that the Karl Fischer reagent not only is effective in the quantitative determination of triaryl and trialkyltin hydroxides, but is also applicable to bis(trialky1tin)oxides and bis(triary1tin)oxides. Reactions analogous to those proposed by Mitchell and Smith (2) can be postulated.
(2)
+
+ IZ + SO2 + CHIOH
+ H S O ~ ~ H(3)S R3SnOH + 1, + SO2 + CHaOH R3SnI + HS04CHs HI (4) 2R3SnI
Comparative Analytical Data for Triphenyltin Hydroxide and Bis(tripheny1tin)oxide
Triphenyltin hydroxide Calcd. Found
...
32.37 58.69, 58.74 4.52; 4 . 4 5 118.5-120
4.90 1 .oo
4.83 0.984
32.36 58.90 4.39
HzO (apparent), Ip/Sn atom, moles%
(decomp.)
Bis(tripheny1tin)oxide Calcd. Found 33.15 60.37 4.22
...
33.10, 33.20 60.22, 60.17 4.40; 4 . 3 3 122-123.5
2.52 0.500
2.60, 2.62 0.506
The similarity between Equations 1 and 3 and 2 and 4 is apparent. Although in each reaction l mole of iodine is consumed for each mole of organotin compound, it is helpful to base the iodine consumption on the number of tin atoms. Thus, the RdnOH class of compounds consumes 1 mole of iodine for each tin atom; whereas with the (R3Sn)ZO type of compound, the ratio is 0.5. As the Karl Fischer procedure is already employed routinely by our Analytical Group for water determinations, a method of interpretation of data in the form normally reportedLe., as per cent HzO was worked out. A theoretical figure for apparent water was arrived at by employing the following formula:
% HzO (apparent) = moles of 1 2 er male of compound (theo.) X 18 ?mol. wt. of H20) X 100 mol. wt. of compound In the case of triphenyltin hydroxide: HzO (apparent)
=
1 X 1800 367 ~
0
ANALYTICAL CHEMISTRY
4.90%
while in the case of bis(tripheny1tin)oxide
The purity of the compound can then be determined by comparing the per cent of water found (apparent) with the theoretical value. Conversely, a value for per cent HzO can easily be converted to moles of Iz per atom of tin for compounds of the type RanOH as follows: Moles of 1 2 = mol. wt. of compound X % HIO (found) 1800
1666
=
and for the type (R3Sn)20: Moles of 11=
The divisor 2 in the case of the (R3Sn)20 class of compounds takes into account that two atoms of tin are involved in each mole of material. Table I illustrates the usefulness of this determination to differentiate between a triorganotin hydroxide and its bis(triorgan0tin)oxide equivalent where both exist. As shown, the difference in carbon analysis between triphenyltin hydroxide and bis(tripheny1tin)oxide is only 1.47%; the difference in tin is 0.79% and the difference in hydrogen is 0.17%. The melting points of the materials are so close that they cannot be used to differentiate between the compounds. However, the difference in magnitude of the value determined by Karl Fischer titration is in the order of 100% and one compound is easily distinguished from the other. The above example is particularly
Table It.
Analytical Data for Trialkyltin Hydroxides and Bis(trialky1tin)oxides
Trimethyltin hydroxide Sn (calcd.), % 65.60 65.35 Sn (found), 7% H20 apparent (calcd.), 7' 9.95 H20 apparent (found), yo 9.88 Mole 12/Sn (calcd.) 1.oo Mole 12/Sn (found) 0.992 0
Bis(tri-n-propyltin)oxide 46.38 46.29 3.51 3.68 0.500 0.509
Bis(tri-n-butyltin )oxiden 39.83 39.73-40.09 (range) 3.02 3.12, 3.08, 3.14, 3.07 0.500 0.523, 0.510, 0 . 5 2 0 , 0.508
Various commercial samples, minimum purity 96%.
useful because triphenyltin exists in both the hydroxide and bis oxide form. Karl Fischer values falling between 0.500 and 1.000 mole of I2 per tin atom would indicate mixtures of both compounds as the addition of water to bis(tripheny1tin)oxide would convert it to the corresponding hydroxide, leaving no free water available for titration. The method, therefore, is also useful in determining the composition of a mixture of the two compounds. Typical analytical data for other
trialkyltin hydroxides and oxides are shown in Table 11. LITERATURE CITED
(1) Gilman, H., Miller, L. S., J. Am. Chem. Sac. 73,2367 (1951). (2) Mili;t,chell, J., Smith, D. M., "Aquametry, p. 249, Interscience, New York, 1948. B. G. KUSHLEFSKY ALEXANDERRoss Metal & Thermit Corp. Research Laboratory Rahway, N. J.
Determination of Impurities in Aluminum Oxide Whiskers SIR: The analysis of whiskers in quantities of a few milligrams introduces many problems, particularly when the matriv and impurities are refractory and fairly inert. The whiskers were grown from commercial grades of alumina in an argon atmosphere containing
