GREEN ARSENOID - SCHEELE GREEN. 25 



ner, and linally weigh the arsenic acid as magnesium pyro arsenate, 

 after having ignited with the precautions mentioned in Fresenious. 

 The results will be slightly low in both cases. 



GREEN ARSENOID. a 



[Serial No. l%2f>.] 



Composition of Green Arsenoid. 



Per cent. 



Moisture ............................................ 2. 56 



Sand ................ .- .............................. 1. 30 



S< xlium sulphate .................................... 2. 02 



Arsenious oxid ...................................... 61 . 48 



Copper oxid ........................................ 29. 67 



Blue coloring matter ( by difference) .................. 3. 02 



100.00 

 Arsenious oxid, soluble by water extraction ........... 5. 88 



Copper oxid, soluble by water extraction .............. 50 



This sample has as much copper oxid as the ordinary sample of 

 Paris (iiven and even more arsenious oxid, so that it is as strong or 

 stronger in those constituents which kill insects. 



It is high in both sand and sodium sulphate, faults which could easily 

 be remedied by more careful handling and more washing. 



As to the free arsenious oxid, this is above the standard used in 

 California and the Kast, l>ut below the (\ percent standard. Since this 

 compound has been used in practical experiments with good results 

 by a number of the experiment stations, this is only one more point 

 in favor of adopting the 6 per cent rather than the 4 per cent limit 

 for free arsenious oxid in Paris greens and other compounds. 



SCIIKKLK ,I;KK.\. 

 [Serial No. 19535.] 



<>f Xchrele Green. 



Per cent. 

 Hygroscopic moisture ........ ........................ 5. 27 



Water of constitution that should be present to form 



CuIIAs() :! ......................................... 4.32 



Arsenious oxid ....................................... 51. 33 



Copper oxid ......................................... 38. 14 



99.06 



Arsenious oxid extracted by water in 10 days 15. 00 



Arsenious < >\id extracted by water in 36 days 17. 70 



o See correspondence with manufacturers, page 59. 



Since Green Arsenoid is often spoken of as Scheele Green in publications by ento- 

 mologists, it might be as well to call attention to the fact that these two compounds 

 are not identical. Scheele Green is copper hydrogen arsenite and contains less arsen- 

 ious oxid and more copper oxid than Paris Green, while Green Arsenoid is one of 

 the copper arsenites not containing any hydrogen, but being richer in arsenious oxid 

 than Paris Green and containing about the same amount of copper oxid. It is this 

 neutral arsenite tha* has been recommended by the Department of Agriculture. 



