26 INSECTICIDES AND FUNGICIDES. 



Although this sample contains large quantities of arsenious and 

 copper oxids, it is worthless as an insecticide, since it contains such 

 large quantities of soluble arsenious oxid. 



PARAGRENE. 



[Serial No. 19714.] 



Composition of Paragrene. 



Per cent. 



Sand 0. 25 



Water of crystallization and hygroscopic moisture 10. 05 



Ferric oxid 20 



Calcium oxid 12. 13 



Copper oxid 20. 50 



Sulphur trioxid 16. 15 



Arsenious oxid 33. 14 



Acetic acid.. 6.66 



99.08 



Arsenious oxid soluble by water extraction 6. 12 



Copper oxid soluble by water extraction 90 



This compound consists essentially of a mixture of Paris Green with 

 about 35 to 36 per cent gypsum. The principal use of the gypsum 

 appears to be to weaken the compound and add weight. It may also 

 be of value in mitigating the injurious effects of the free arsenious 

 acid. Since this compound contains even more than the 6 per cent 

 limit of arsenious oxid, it can not be recommended as a high-grade 

 insecticide. If the amount of soluble arsenious oxid could only be 

 reduced to a slight extent this would doubtless be a good insecti- 

 cide, since it contains enough poison to kill insects; it is at the same 

 time in a very fine condition and will consequently stay in suspension 

 in water better than the ordinary sample of Paris Green. 



LAUREL GREEN. 



[Serial No. 19017.] 



Composition of Laurel Green. 



Per cent. 



Sand 0. 49 



Ferric oxid 3. 25 



Copper oxid i 12. 53 



Calcium oxid 27. 50 



Magnesium oxid 2. 29 



Arsenious oxid 6. 92 



Sulphur trioxid 24. 65 



Carbon dioxid 5. 73 



Water of crystallization, composition, and hygroscopic 



(by difference) 16.64 



100. 00 



This substance consists of large amounts of gypsum, calcium car- 

 bonate, and magnesium carbonate, amounting in all to about 65 per 



"See correspondence with manufacturers, page 62. 



