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The viscosity, η, of 97.6 percent deuterium oxide and six more dilute mixtures with water, as well as that of nearly pure protium oxide, has been determined by comparison with ordinary water, and found to be almost but not quite a linear function of the specific gravity. The relative fluidity, Φ, has been related to the density by an equation of the type φ=1/η=1+A(Δs)+B(Δs)2, where (Δs) is the increase in the specific gravity over ordinary water. This equation has been found valid to 0.006 percent over the entire concentration range. Bingham's equation concerning the law of additive fluidities in binary systems, and containing but one arbitrary constant, has been tested and found valid to 0.01 percent.

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The Viscosity of Methanol 1683 is an orthoquinone, there is no steric restriction on forming these bonds. In a paraquinone, however, the two bonds can be formed only by putting the planes of the two six-carbon rings flatly one upon the other. This will be easily possible in benzoquinone, but in duroquinone the voluminous side chains prevent a sufficiently close approach. It may be briefly and preliminarily mentioned that the ease with which a solid quinhydrone is formed by mixing a quinone with the corresponding hydroquinone, decreases with the number of CH3 groups which substitute the H atoms. In the tetramethyl compound, duroquinone, no quinhydrone is formed at all at room temperature.The authors are deeply indebted to Columbia University for the use of their facilities. SummaryDuroquinone in a strongly alkaline solution forms a free paramagnetic semiquinone radical of brown color as intermediate step of the reduction. There is no dimeric form of this radical; in other words, no compound corresponding to the ordinary crystalline benzoquinhydrone, which is a dimeric diamagnetic molecule, is formed from duroquinone and durohydroquinone either from alkaline or acid solutions. Solid benzoquinhydrone is a compound formed from quinone and hydroquinone by two hydrogen bonds. These bonds cannot be formed in duroquinone due to steric hindrance.The maximum percentage of the duro-semiquinone radical in equilibrium with its parent substances continuously increases with increasing pH. At pH 13 this maximum is about 50%, a result which is the same whether derived from potentiometric or magnetic observations. New York, N. Y.