An investigation of the accuracy of the Barcroft differential manometer in respiration studies

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Abstract
The authors have made a critical analysis of the use of the Barcroft differential manometer in respiration studies. Expts. were set up in high replication (13-15) and the results examined statistically. Most of the expts..were done at 20[degree]C and the results showed that deductions from single, or even duplicate, expts. should be accepted with caution and that a higher degree of replication is desirable. The following procedure is recommended: (a) Expts. are planned in triplicate, quadruplicate, or even with higher replication, according to the standard error expected and the probable magnitude of the differences to be examined; (b) expts. are continued for a period appropriate to the number of replicates used so as to give a standard error not appreciably greater than 5%; (c) the actual values of the pressure differences found at hourly intervals are plotted on double logarithmic paper and results of any expts. giving anomalous curves are rejected; (d) after conversion of the pressure differences to volumes, the arithmetic means are found, the standard errors calculated and the differences between the means investigated statistically. If such a procedure is adopted the apparatus can be employed usefully in the investigation of small or large differences in many biological oxidations.