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
Analytical Data for Trialkyltin Hydroxides and Bis(trialky1tin)oxides Trimethyltin Bis(tri-n-propylhydroxide tin)oxide Bis(tri-n-butyltin )oxiden Sn (calcd.), % 65.60 46.38 39.83 65.35 46.29 39.73-40.09 (range) Sn (found), 7% 3.02 H20 apparent (calcd.), 7' 9.95 3.51 H20 apparent (found), yo 9.88 3.68 3.12, 3.08, 3.14, 3.07 Mole 12/Sn (calcd.) 1.oo 0.500 0.500 0.992 0.509 0.523, 0.510, 0 . 5 2 0 , Mole 12/Sn (found) 0.508 Various commercial samples, minimum purity 96%.
Table It.
0
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
