Nr. 47 - CHEMICAL REACTOR 1985, Schott Mainz

diam 80 cm, borosilicate glass

This chemical reactor, made of borosilicate glass, was used in the 1980ies at the University of Ghent (BE) to study the impact of air pollution on climate. An example of how, in order to study a part of nature, that part was separated from the rest of nature. (see also Cat. Nr. 12)

The reactor was filled with ultra pure air, i.e. 78,09% of nitrogen (N2), 20,95% of oxygen (O2) and 0,93% of argon (Ar), and with controlled amounts of water vapour (H2O), sulfur dioxide (SO2) and nitrous acid (HONO). The reactor was then irradiated with UV lamps, simulating sunlight, to trigger a series of chemical reactions in the gas mixture: UV light would split HONO into OH and NO, and two OH’s would react with SO2 to form sulfuric acid (H2SO4). The aim of the experiment was to quantify the rate at which these H2SO4 molecules would further nucleate and condense into nanometer sized H2O-H2SO4 droplets.

The hypothesis was that humans  could change the properties of clouds and therefore climate, by emitting SO2 into the atmosphere that would provide more H2O-H2SO4 droplets  for water to condense on.

In the experiment the real atmosphere was reduced to its simplest form: O2, N2, Ar, H2O, HONO. Pollution by humans was reduced to just one compound SO2. 

The experiment showed that droplets were indeed formed. But what did this tell about the real atmosphere? When taking an aircraft and flying thorough the air, with its smokes, dust and hazes and its clouds forming on and in them, it was quickly realized that it was impossible to recreate that complexity in a laboratory reactor. And in fact during the first experiments in the real atmosphere no nucleation of H2O-H2SO4 droplets or of any other droplets was observed.