34 Agricultural Chemistry. 



laws restricting its escape. It is now condensed in the factory 

 as a by-product of the industry. 



Sulphur dioxide is an accidental gaseous constituent of the 

 air, the effects of which are of economic importance. It is ex- 

 pelled from the stacks of smelters roasting ores which contain 

 sulphur. It is also produced in small amounts wherever the 

 combustion of coal takes place. It may be partially converted to 

 sulphur trioxide and brought to the soil by rain as a supply of 

 sulphur for plants. The amount in the rain at Rothamsted was 

 found to be about 17 pounds of sulphur trioxide yearly per acre. 



Experiments have demonstrated that sulphur dioxide injures 

 plants through their leaves. Fumigation with one part of the 

 gas to 100,000 parts of air has been fatal to scrub pines. In- 

 vestigations have shown it to be the cause of serious injury to 

 the vegetation in the vicinity of copper smelters in California, 

 Montana and elsewhere. The foliage of injured trees in these 

 vicinities was found to contain more sulphur than that of normal 

 trees. Peach trees in an exposed position nine miles from a 

 smelter at Redding, California, and red firs at a distance of fif- 

 teen miles from the Washoe smelter, Anaconda, Montana, were 

 badly injured. Analysis of the smoke from the latter smelter 

 showed an output of 5,000,000 pounds of sulphur trioxide per 

 day. Haywood, of the Bureau of Chemistry, concludes that these 

 fumes can be condensed and the products probably readily mar- 

 keted. Legislation in the interests of forestry should restrict 

 the escape of this gas as it has in the case of hydrochloric acid. 



