12 Thomson, Detection of Arsenic in Beer. 



Beer contains sugar and other organic compounds 

 which might also influence the results, and the next series 

 of experiments were made to find what influence different 

 kinds and quantities of sugar would have on the resulting 

 mirrors. The first of this series was made strictly in 

 accordance with the instructions of the Committee, but 

 using 50 c.c. of a solution containing y^oth of a grain per 

 gallon, instead of 25 c.c. The first tube Plate IX., Fig. i, 

 was a blank (made with -the reagents alone), and shows no 

 mirrors ; for this reason the tube is scarcely visible in the 

 print. The mirror in the second tube was produced from 

 the solution without either amyl alcohol or sugar, and shews 

 a well-marked deposit. The mirror in the third tube was 

 produced whilst using 2 c.c. of amyl alcohol alone, and 

 shows a trace of a mirror. The fourth and fifth tubes 

 were obtained when using 2 c.c. of amyl alcohol, but the 

 former contained also 5 grammes, and the latter 10 

 grammes of invert sugar. In neither of these was any 

 trace _ of an arsenic mirror produced, and yet there is 

 present double " the permissible quantity" of arsenic in 

 the apparatus, according to the Committee's instructions 

 to use 25 c.c. of the beer. 



The fifth and sixth tubes show the effects of the 

 invert sugar alone, and indicate that invert sugar in 

 moderate quantity does not so seriously interfere with the 

 test as amyl alcohol ; 5 grammes, however, prevent 

 the formation of the full-sized mirror, and 10 grammes 

 seriously interfere with its production. 



The fifth series, Plate IX., Fig. 2, was made to ascertain 

 what influence different quantities of glucose each with 

 2 c.c. amyl alcohol would have on the production of the 

 mirrors when using 50 c.c. of a solution containing y^th 

 of a grain of As40ri per gallon, and cooling the tubes at 

 the point at which the mirrors were formed. 



