2 



chemical on a large scale in these islands. On large areas on the 

 rubber plantations plowing has been entirely replaced by the 

 arsenical spray in the last five years. A further extensive test has 

 been made by the Parker Eanch as a means of eradicating such 

 weeds as thimble berry and German ivy from their pasture lands. 

 Since these successful applications the use of this spray has 

 increased until it has entirely replaced hoeing on some plantations 

 and partially replaced plowing, even in the dry sections. 



Object of the Work 



The status of arsenite of soda as a weed destroyer is firmly 

 fixed, from both a practical and an economical standpoint. But 

 there still remains to be considered the effect of this chemical 

 upon the soil and the growth of plants. Comparatively little work 

 of this nature has been done but it is quite generally conceded that 

 plant growth is materially affected by the presence in the soil of 

 this chemical. The Colorado Experiment Station 2 has made some 

 investigations upon the death of fruit trees excessively sprayed 

 with insoluble arsenical compounds, and the Bureau of Chemistry 

 of the U. S. Department of Agriculture 3 has investigated the 

 death of plants as a result of arsenic settling from smelter fumes. 

 In all cases arsenic has been found in both the soil and the plants 

 in appreciable amounts. 



In view of the above facts and the increase in use of arsenite 

 of soda in the Hawaiian islands, the Station undertook an exhaus- 

 tive studv of the effect of this chemical upon plant growth and its 

 physical, chemical and biological activities in the soil. While no 

 deleterious effects have appeared through its use thus far, vet it is 

 highly essential that we should be able to recognize them immedi- 

 ately should they appear. 



Preparation of the Stray. 



Several formulas have been recommended for the preparation 

 of this spray. They all involve the boiling of white arsenic with 

 sal soda or caustic soda, the two being added in sufficient quan- 

 tities to combine, forming soluble sodium arsenite. ^Yhen thus 

 boiled there are two salts of sodium arsenite possible of forma- 

 tion the acid salt fXa 2 0. 2 As 2 O s 2 H 2 0) and the neutral salt 

 (Xa,0. As 2 0 3 ). Therefore the resulting compound depends upor 

 the proportion of the two ingredients. The following equations 

 illustrate : 



Withdrawn 



