Abstract
Winkler's method for quantitative determination of dissolved oxygen may be applied to 10 c.c. or even 5 c.c. samples of water in the following way. One tenth of a cubic centimeter of each of the two solutions MnCl2 and NaOH — KI are added from 1 c.c. burettes graduated to 0.1 c.c. or less. The thiosulfate solution of the usual concentration is diluted to ten times its volume. The iodine is titrated in a tall dish using a 5 c.c. burette. The end joint is just as definite as that in the ordinary procedure. The percentage error is also the same, about 1 per cent. The distinct advantage in the micro method lies in the possibility of greatly shortening the duration of the tests, thus making it possible to follow the time course of respiratory exchange over relatively short periods of time. Owing to the small volumes used, temperature adjustment is rapid.
With good manipulation the maximum error is less than 0.005 c.c. of O2 gas. The method is being used in studies on oxygen consumption by small organisms such as protozoa, eggs and certain kinds of tissues.
Get full access to this article
View all access options for this article.