National Research Council of Canada. NRC Institute for National Measurement Standards
Analytical and Bioanalytical Chemistry invites its reader to participate in the Analytical Challenge, a series of puzzles for readers. Mendeleyev's solution theory is the topic for this issue and reader can win Springer book of their choice worth €75. Reader can access to the complete collection of published problems and their solutions on the website at http://www.springer. com/abc. Mendeleyev's work includes investigation of aqueous solutions of ethanol and determining how the density of alcohol and water mixtures changes with mass fraction of the alcohol. He claims that the biggest volume contraction occurs when 1 mol ethanol is mixed with 3 mol of water. Readers need to answer that what strength of vodka Mendeleyev considered a candidate for the 'perfect' vodka based on his theory of solution and is vodka of that particular strength available commercially.