ROSE ON THE ANHYDROUS SULPHATE OF AMMONIA. 557 



baiytes and lead and other reagents, and more particularly with 

 tartai'ic and racemic acids ; the sulphat-ammon is more spa- 

 ringly soluble than the parasulphat, and does not so readily 

 become acid when moistened ; these, however, are circumstances 

 of too little importance to allow of our regarding with certainty 

 the parasulphat as a distinct substance from sulphat-ammon, 

 and isomerical with it. 



The following facts led me, however, to adopt this opinion : 

 when a neutral solution of chloride of barium is added to a cold 

 solution of pure sulphat-ammon, and the sulphate of barytes is 

 allowed to precipitate for an hour, the filtered solution, without 

 being heated again, deposits sulphate of barytes, and this occurs 

 again after repeating the filtration ; this is not the case with the 

 parasulphat-ammon ; its solution, after the addition of chloride 

 of bai'ium, remains for months perfectly clear in the cold, when no 

 acid has been added; in performing these exjjeriments equal 

 portions of the isomerical salts were dissolved in similar quan- 

 tities of water. 



I consider these different actions as an essential difference be- 

 tween these substances ; and the following series of experiments 

 is also decidedly in favour of this difference : 100 parts of sul- 

 phat-ammon weighed 91*42 after drying in a water-bath; it 

 was dissolved in cold water, without any acid, and mixed in the 

 cold with a solution of chloride of barium ; in an hour after 

 mixing, the sulphate of baiytes was separated by the filter and 

 washed, towards the end of the operation, with warm-water ; it 

 weighed 51-71 parts, equivalent to 18-16 of sulphuric acid. 

 Hydi-ochloric acid was added to the filtered solution, and it was 

 evaporated to dryness ; the residue, moderately heated, treated 

 with water and a little hydrochloric acid, gave 145*7 of sulphate 

 of barytes, equivalent to 51*16 of sulphuric acid; the whole 

 quantity of sulphuric acid, therefore, in 100 parts, amounts to 

 69*32 parts, approximating very closely to the quantity con- 

 tained in the sulphat-ammon by calculation. 



In supposing that the 18*16 of sulphuric acid precipitated in 

 the cold, might be derived from an admixture of sulphate of am- 

 monia with the sulphat-ammon, they would be equivalent to 

 30*01 of the former salts, and the 51*16 of sulphuric acid ob- 

 tained by evaporation indicate 73*08 of sulphat-ammon, giving 

 an excess of 3*06, which the analyses will not admit of. 



