630 AGRICULTURAL ANALYSIS 



precipitate appears, then proceed as directed in the last two sen- 

 tences of Method II. 



Sodium-Acetate-Soluble Arsenious O.rid. 1 Solutions Re- 

 quired. Prepare the same solutions as are used in Method II 

 for total arsenious oxid, with the exception of the sodium po- 

 tassium tartrate solution. 



Determination. Proceed as described in the first three sen- 

 tences of Method II for total arsenious oxid, except that a paper 

 filter is used, instead of asbestos. 



Water-Soluble Arsenious Oxid. Method I. 2 Solutions Re- 

 quired. Prepare starch and standard iodin solutions as de- 

 scribed under Method II for total arsenious oxid. 



Determination. Treat one gram of paris green in a large 

 flask with 1,000 cubic centimeters of water previously boiled to 

 xpel carbon dioxid and then cooled to room temperature. Stop- 

 per the flask and shake eight times each day for ten days. At 

 the end of this time filter the solution through a dry filter. Treat 

 200 cubic centimeters of this filtrate with sodium bicarbonate 

 and titrate with the iodin solution. 



Water-Soluble Arsenious Oxid. Method II. 3 Solutions Re- 

 quired. The same solutions are required as are used in Method 

 I for water-soluble arsenious oxid. 



Determination. Digest one part of paris green in 1,000 parts 

 of water for twenty-four hours with occasional shaking. At the 

 end of this time filter through a dry filter, treat an aliquot with 

 sodium bicarbonate and titrate with iodin solution. 



Water-Soluble Arsenious Oxid. Method III.* Solutions Re- 

 quired. The same solutions are required as are used in Method 

 I for water-soluble arsenious oxid. 



1 Avery and Beans, Journal of the American Chemical Society, 1901, 

 23 : in. 



Bureau of Chemistry, Bulletin 107, 1907 : 27. 



2 Haywood, Journal of the American Chemical Society, 1900, 22 : 568, 

 705 ; 1901, 23 : in. 



Bureau of Chemistry, Bulletin 67, 1902 : 98. 



s Cathcart, New Jersey Agricultural -Experiment Station, Bulletin 205, 

 1905 : 9. 



* Colby, California Agricultural Experiment Station, Bulletin 151, 1903 : 

 18. 



