Sanger and Black.— Arsenic by Gutzeit Method. 



Plate 2. 



■ I 



ll 



2 5 10 15 20 25 35 40 50 60 70 



Fig. 3. 



Standard Arsenic Bands in Micro-milligrams of As 2 3 



Ammon;a Development. 



Proc. Amer. Acad. Arts and Sciences. Vol. XLI 



