What is "contact process"

n. (context inorganic chemistry English) The industrial process for the manufacture of sulfuric acid from sulfur and oxygen

The contact process is the current method of producing sulfuric acid in the high concentrations needed for industrial processes. Platinum used to be the catalyst for this reaction; however, as it is susceptible to reacting with arsenic impurities in the sulfur feedstock, vanadium(V) oxide (VO) is now preferred.

This process was patented in 1831 by British vinegar merchant Peregrine Phillips.On March 21, 1831, Peregrine Phillips, Jr., a vinegar manufacturer in Bristol, England, received British patent 6096 for "Certain improvements in manufacturing sulfuric acid, … " See:

• The Repertory of Patent Inventions … , no. 72 (April 1831), page 248.
• (Anon.) (1832) "English patents: Specification of the patent granted to Peregrine Phillips, Jr. of Bristol, in the county of Somersetshire, Vinegar Maker, for an improvement in manufacturing Sulphuric Acid. Dated March 21, 1831." Journal of the Franklin Institute, new series, vol. 9, pages 180-182.
• Ernest Cook (March 20, 1926) "Peregrine Phillips, the inventor of the contact process for sulphuric acid," Nature, 117 (2942) : 419-421.
• George Lunge, Theoretical and Practical Treatise on the Manufacture of Sulphuric Acid and Alkali, with the Collateral Branches, 3rd ed., vol. 1, part 2 (London, England: Gurney and Jackson, 1903), page 975. In addition to being a far more economical process for producing concentrated sulfuric acid than the previous lead chamber process, the contact process also produces sulfur trioxide and oleum.

The contact process is a model of an interacting particle system. It is a continuous time Markov process with state space {0, 1}, where S is a finite or countable graph, usually Z. The process is usually interpreted as a model for the spread of an infection: if the state of the process at a given time is η, then a site x in S is "infected" if η(x) = 1 and healthy if η(x) = 0. Infected sites become healthy at a constant rate, while healthy sites become infected at a rate proportional to the number infected neighbors. One can generalize the state space to {0, …, κ}, such is called the multitype contact process. It represents a model when more than one type of infection is competing for space.