7 research outputs found
Some Observations on the Dropping Mercury Electrode
In the course of an investigation of the oxidation reduction potentials of some organic systems, it was found impossible to obtain concordant measurements by the ordinary methods. Accordingly, we turned to the polarographic method first developed by Prof. J. Heyrovsky of the University of Prague and recently gaining favor in this country. The polarographic method consists of applying, by means of a dropping mercury electrode, a steadily increasing electromotive force to a solution of some substance which can be reduced. Current and voltage are measured and recorded graphically. There is little current increase with respect to voltage until a point is reached where the voltage is sufficient to reduce the substance. The current then rises suddenly until the rate of the reaction becomes steady, when the curve again flattens out to a gentle slope as before. A whole series of reducible substances may be determined from the same solution in this way if their reduction potentials differ by as much as .2 volt
Recommended from our members
Global climate change and soil carbon stocks: predictions from two contrasting models for the turnover of organic carbon in soil
Enhanced release of CO2 to the atmosphere from soil organic carbon as a result of increased temperatures may lead to a positive feedback between climate change and the carbon cycle, resulting in much higher CO2 levels and accelerated lobal warming. However, the magnitude of this effect is uncertain and critically dependent on how the decomposition of soil organic C (heterotrophic respiration) responds to changes in climate. Previous studies with the Hadley Centre’s coupled climate–carbon cycle general circulation model (GCM) (HadCM3LC) used a simple, single-pool soil carbon model to simulate the response. Here we present results from numerical simulations that use the more sophisticated ‘RothC’ multipool soil carbon model, driven with the same climate data.
The results show strong similarities in the behaviour of the two models, although RothC tends to simulate slightly smaller changes in global soil carbon stocks for the same forcing. RothC simulates global soil carbon stocks decreasing by 54 GtC by 2100 in a climate change simulation compared with an 80 GtC decrease in HadCM3LC. The multipool carbon dynamics of RothC cause it to exhibit a slower magnitude of transient response to both increased organic carbon inputs and changes in climate. We conclude that the projection of a positive feedback between climate and carbon cycle is robust, but the magnitude of the feedback is dependent on the structure of the soil carbon model