Alcohol 'evaporation' from samples in open containers

Systematic investigations on the problem of alcohol loss in unclosed stored blood samples have been performed. The decrease of alcohol concentration in unclosed blood samples depends mainly on temperature, extent of sample surface, and circulation of air. Storage of filled 8 ml venules at 21(degrees)C causes a loss of about 50% of the alcohol concentration within 5 to 7 days, whereas storage at 5(degrees)C causes only a diminution of about 20%. During the first days of storage the loss of alcohol in the samples was found to be proportional to the extent of sample surface. The percentage of alcohol loss in the samples is independent of the level of the initial concentration. Therefore, conclusions as to the initial concentration in unclosed stored blood samples seem to be possible, if the conditions of storage are known. The possibility of proving such conclusions is discussed.