112 Sir Charles A. Cameron and Mr. J. Macallan. [^P r - 



V. u On the Compounds of Ammonia with Selenium Dioxide." 

 By Sir Charles A. Cameron, V.P.I.C., F.K.C.S.I., and John 

 MACALLAN, F.I.C. Communicated by Professor Dewar, 

 F.R.S. Keceived March 19, 1888. 



The following experiments were undertaken with the object of 

 determining the action of ammonia npon selenium dioxide. They 

 have resulted in the discovery of two new componnds, which, from 

 what has been ascertained regarding their constitution, may, perhaps, 

 be best designated by the term selenosamates or ammonium salts of an 

 acid — selenosamic — yet to be isolated. 



Preparation of Neutral Ammonium Selenosamate. 



Ammonia, which had been carefully dried by passing through a 

 series of potash tabes, was led into a solution of selenium dioxide in 

 absolute alcohol. After being absorbed for some time, minute 

 crystals commenced to deposit, and when complete precipitation had 

 taken place, the liquid portion was filtered off, the crystals washed 

 with, alcohol, and dried over sulphuric acid in a vacuum. 



The compound formed as above described is a deliquescent salt, 

 which separates from its solution in alcoholic ammonia in minute, 

 but very well-defined hexagonal prisms and pyramids — both forms 

 often occurring in combination. It is a very unstable substance, con- 

 tinuously liberating ammonia, and tending to the formation of a 

 more stable acid salt. Some of the crystals which had been placed 

 in a large stoppered bottle were found after some weeks to be entirely 

 converted into large crystals of the acid salt. It also loses ammonia 

 when treated with alcohol or water ; and when its aqueous solution 

 is evaporated in a vacuum, crystals of the acid salt remain. When 

 heated, it is at once converted into the acid salt. On account of its 

 instability, it is best prepared in a partial vacuum, and when dried 

 placed in a stoppered bottle, which should be quite full and kept in a 

 cool place. In this way it may be preserved of definite composition 

 for a considerable time. It is with difficulty, and only partially, con- 

 verted into ammonium selenite by the action of water upon it. When 

 barium chloride is added to its neutral aqueous solution, only a faint 

 cloudiness is produced, until it is heated, when a slight precipitate 

 forms, but even after standing for weeks and long-continued boiling, 

 only a portion of the selenium precipitates. Addition of excess of 

 ammonia to the solution, however, precipitates a basic barium salt. 

 It is but sparingly soluble in cold alcoholic ammonia. l"6658gram of 

 solution from which crystals had deposited, left a residue of 

 0*0134 gram, reduced to acid salt, which is equivalent to a solubility 



