6So TRANS. ST. LOUIS ACAD. SCIENCE. 



On plate 13 is shown the cadmium coat before and after treat- 

 ment with the vapor of ammonic sulphide. The blue molybde- 

 num coat is not an iodide, but the pentoxide, and is permanent. 

 The coat as given by the simple iodide of sulphur is also shown 

 (plate 13), which for an instant or so is apt to mask the iodide 

 coats, but it disappears completely on a few minutes' ex- 

 posure. 



It will be noted, that close to the assay in the tablets illus- 

 trated there is more or less of a black film, due to the formation 

 of sulphides from the excess of sulphur that is requisite to insure 

 the decomposition of all compounds. 



As one of the most valuable features of the blowpipe outfit is 

 portability, and as liquids are most undesirable members in a 

 traveling outfit, we have now secured the benefit of the very 

 delicate and valuable reactions of the iodides in this cheap and 

 simple reagent. 



Laboratory Washington University, May, iSS6. 



