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Communications to thb Editor 2167 on mannose indicate that the changes in the compositions of the solutions may involve changes in the proportions of the ring isomers. Rapid measurements at 0°of the optical rotations of a-tZ-gulose-CaC^I^O show that the mutarotation previously reported is preceded by a short period in which the change in rotation is less rapid than later on. This is evidence that the mutarotation is more complex than the reversible interconversion of only two isomers. It is noted that a new guióse calcium chloride compound has been separated. It corresponds to the formula (CeHiaOe^CaCh, and gives [a]|> +34°(1.4 minutes after solution in water), constant -167°( 3.3292 g./100 cc.

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Cobalt and nickel may be determined in the same solution by precipitating them as the complex salts as outlined above, determining the nickel by the dimethylglyoxime method and calculating the cobalt by difference. The reliability of the method was tested by mixing standard solutions of cobalt and nickel sulfates to make two solutions, then analyzing for both by the volumetric method and determining nickel by the dimethylglyoxime method and calculating cobalt by the difference. The results are given in Table III.An examination of the tables shows that this method gives excellent results for cobalt and nickel separately, and that results in the presence of each other compare reasonably well with accepted methods. The method is very rapid and requires no expensive apparatus, as does the method of Spacu for nickel.