51 



4- The effect on vegetation of a number of isolated roastings of 

 arsenical ore will depend on the concentration of the fumes, and the 

 period between the roastings, but even if the vegetation is not com- 

 pletedly killed, growth will naturally be retarded. 



In confirmation of these results it might be of interest to quote 

 the following extract from Nature," February 20th, 1908, page 376 : 



" It has been found that not only are the trees and grass in the 

 vicinity of the works injured by the sulphur dioxide and sulphuric 

 acid of the smoke (Note : from a copper smelting works in America 

 which is stated to produce II^ per cent, of the world's supply of 

 copper), but the gass is rendered poisonous by arsenic (Note by B. J. 

 E. — Cattle would feed on such grass as the arsenic would be taste- 

 less ; grass sprayed with Sodium Arsenite in the F. M. S. some time 

 ago was the cause of poisoning of a number of cows on an estate.) 



Large settling chambers were found to be much less effective 

 than long flues for the arsenic — the loss of animals became much 

 greater with the former. 



In the above works, arsenic escaped in considerable quantities 

 from flues 300 feet high and caused considerable damage to forests 

 and crops. Sulphuric acid was also found in the flues and near the 

 furnace. 



The article continues : — " To this sulphuric acid, together with 

 the arsenic with which it is associated, is probably due much of the 

 spotting of the leaves:which is so common in the vicinity of the works. 



N. B. — The action of the flue dust is of far less importance than 

 that of the sulphur dioxide in affecting the growth of plants but the 

 arsenic may affect to a greater degree the value of the grass, since it 

 renders it poisonous." 



B.J. Eaton, 

 Government Chemist^ F.M.S. 



ANALYTICAL NOTES. 



OF RUBBER PLANTS IN THE BOTANICAL GARDENS, 

 SINGAPORE. 



Hevea brasiliensis. 



The latex was obtained from one 32 year old tree, tapped 

 at 6-30 a.m. No water was added to the latex, and the formaHn 

 added was carefully measured, so that the amount of pure latex 

 is known. In the figures given below this formalin has been correct- 

 ed for so that they refer to pure latex. . . . 



