lO Thomson, Detection of Arsenic in Beer. 



EXPLANATION OF PLATES. 

 Plate I. 



Fig. I. Apparatus employed. 



Fii;. 2. Pholograpliic production of mirrors, -^oth gr. per gallon 

 of AS4OG when using 50 c.c. 



(a) With the naked tube, heated directly with Bunsen 



flame. 



(b) With the heated portion of the tube wrapped in 



wire gauze. 



Fig. 3. Showing the effect of temperature on the formation of 

 the mirrors and arsenic deposits in a solution con- 

 taining g^g- of a grain per gallon of AS4O6, when 

 using 50 c.c. 



1. Ordinary Marsh test method (without special 



cooling). 



2. Enclosed in a steam jacket from (a) to (I?), and 



cooled with cold water at (c). 



3. With current of water at 5o°C. passing over the 



outside of the tube between (d) and (e). 



4. With current of water at i5°C. passing over the 



outside of the tube between ( f) and (g). 



Plate II. 



77\'. 4. Standard bore tubes, using 50 c.c. with different ijuanlities 



of As^Oe. Cooling method. 

 Fig. 5. Arsenic mirrors before exposure to the light, .^outh gr. 



per gallon AS4O6 using 50 c.c. 



Fig. 6. The same mirrors seen in Fig. 5, after exposure to the 

 light for six weeks. 



Fig. 7. Photographs of five pairs of arsenic deposits, made by 

 old method, respectively unsealed, and sealed in air, 

 hydrogen, nitrogen, and carbon dioxide. ^ Jo^h gr. per 

 gallon using 50 c.c. 



Fig. 8. Photogra|)hs of same after the right hand one of each 

 pair had been exposed to the light for six weeks. 



