318 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



fluence on the determination of the arsenic could be predicated from 

 the foregoing investigation. 



To sum up, then, yre think that small amounts of arsenic can be 

 determined by our method without danger of interference from sul- 

 phur, phosphorus, and antimony, provided the solution to be tested is 

 freed as carefully as possible from these substances and the additional 

 precaution is taken to place a strip of lead acetate paper in front of 

 the test paper. 



From the comparative rarity of the hydrides of selenium and tellu- 

 rium and the unlikelihood of their occurrence in ordinary practice, we 

 have made no study of their action on mercuric chloride paper. One 

 would suppose from analogy, also, that the reactions in small amount 

 would be similar to that of hydrogen sulphide. We note in this con- 

 nection that Rosenheim -^^ states that hydrogen selenide has no influ- 

 ence on the Gutzeit test, unless in large quantity, if lead acetate paper 

 is used. 



The results of the above experiments are tabulated for comparison 

 as follows : 



TABLE II. 



Eeactions of Color Bands within the Range of the Arsenic Standards 



FROM ApPROXIxMATELY EQUIVALENT AMOUNTS OF ArSINE, StIBINE, PhOSPHINE, 



AND Hydrogen Sulphide. 



Element. 



As 



Sb 



Amounts 

 taken for 

 Reduction. 



30 mmg. 

 (AS2O3). 



200 mmg. 



(SboOg). 



200 mmg. 

 (P)- 



Initial 

 Band. 



Orange 



yellow 

 to red 



Faint 

 gray 



Pale 

 yellow 



50 mmg. Dull 

 (S). yellow 



Action of 

 Air. 



Slightly 

 faded 



Un- 

 changed 



Pale 



brown 

 where 

 exposed 

 to light 



Un- 

 changed 



Cold 

 Water. 



Consid- 

 erably 

 bleached 



Bleached 



Consid- 

 erably 

 bleached 



Un- 

 changed 



Hot 

 Water. 



Grayish 



white 



Grayish 

 white 



Faint 

 yellow. 



Un- 

 changed. 

 Onstiind- 

 ing, light 

 brown. 



Hydro- 

 chloric 

 Acid. 



Dark 



red 



Grayish 



Bright 

 lemon 

 yellow 



Brighter 

 yellow 



Auric 

 Chloride. 



Bright 

 purple 



Dull 

 purple 



Red 

 brown 

 to 

 purple 



Slightly 

 brown 



Ammonia. 



Dense 

 black 



Dull 

 black 



Gray 

 black 



Pale 

 brown. 



31 Chem. News, 83, 277 (1901). 



