CHEMICAL PRINCIPLES UNDERLYING THE INVESTIGATION. ^ 



part of the sulphur. It is then fused with a siliceous flux, which 

 removes more of the sulphur and a large part of the iron. This proc- 

 ess is repeated until a product quite rich in copper is obtained. 

 Finally, the impure copper is placed in a blast furnace with a sili- 

 ceous lining, where the remainder of the impurities, consisting of iron, 

 sulphur, etc., are either fluxed or burned oft 2 . 



In practically all of these processes the sulphur originally present 

 in the ore is burned and given off into the air, principally as sulphur 

 dioxid, but to some extent as sulphur trioxid. For each pound of sul- 

 phur burned 2 pounds of sulphur dioxid are formed and given off into 

 th'e atmosphere, a part of which acts directly on the foliage of the 

 trees. Sooner or later, however, all of the sulphur dioxid is changed 

 by the action of the oxygen of the air into sulphur trioxid, and it is 

 in this form that we may expect to find it in the foliage of trees. 

 The moisture present in the air unites with this sulphur trioxid to 

 form the highly corrosive compound sulphuric acid, which in its turn 

 acts upon the delicate foliage. 



One other point should be mentioned. The foliage of all plants 

 naturally contains some sulphur trioxid that the tree has absorbed 

 from the ground through its roots. The sulphur trioxid thus absorbed, 

 however, is not in the free state, as it is when formed in the air by 

 the burning of sulphur, but is combined with other substances which 

 render it entirely Harmless. The sulphur trioxid absorbed from the 

 air is in a free and very corrosive state. It will thus be seen that all 

 trees examined will contain sulphur trioxid, and that this sulphur tri- 

 oxid may be derived either from the harmless form in the earth or 

 from the harmful form in the air. If two trees grow near each other 

 in the same soil and are about equalty vigorous, the sulphur trioxid 

 absorbed from the earth is apt to be about the same in both trees. 

 While this may fail in individual cases, it will be true in the majority 

 of cases. Now, if the percentage of sulphur trioxid both in the dry 

 foliage and in the ash of the dry foliage of one tree of a certain species 

 is much higher than it is in another of the same species standing close 

 by, there is an indication that this may have come from the sulphur 

 trioxid or dioxid of the air; if the percentage of sulphur trioxid both 

 in the dry foliage and in the ash of the dry foliage of many trees of a 

 certain species is higher than it is in near-by trees of a like species, it 

 is almost absolute proof that it must have come from the sulphur tri- 

 oxid or dioxid of the air. Going one step further, if the trees con- 

 taining the larger amounts of sulphur trioxid have been injured, 

 .while those containing the smaller amounts of sulphur trioxid have 

 not been injured, it is more than probable that the former trees have 

 been injured by fumes containing sulphur dioxid or trioxid. The 

 results of the investigation, to determine this point, are given in the 

 following pages. 

 1473205 2 



