IMIDOSULPHONATES. 



75 



Pentasodiwn ammonkim hmdosulphonate. — From dilute solution this 

 «alt f.Tystallises with seven molecules of water, NagAmNg (803)4, (OH..)';, 

 but from concentrated saline liquors it crystallises with less water. To 

 prepare the fully hydrated s^alt, strong ammonia- water is added in large 

 excess to a solution of disodium imidosulphonate, which must be free 

 from sulphate or other salt. Separation of the salt begins at once or 

 very soon and continues ibr some time if the liquor is kept nearly ice- 

 cold. The salt forms minute prisms which bear moderate washing, 

 with concentrated ammonia-water, and can be drained on a tile un- 

 changed if under close cover. W]ien dry, the salt does not smell 

 noticeably of ammonia. The numbers obtained l)y calculation and 

 experiment are as follows : — 



Sodium 



Ammonium 



Sulphur 



A salt with ^^^H./) only, falls as a crystalJine precipitate on 

 adding strong ammonia-water to a solution of trisodium imidosul- 

 phonate and its equivalent at least of ammonium nitrate (3 mois.). 

 l^)eing but very little soluble in ammonia-water, it can be properlv 

 washed with this, and niay then be drained dry on a tile under cover 

 without change. Heated it loses water and ammonia without suffer- 

 ing aqueous fusion. It contains no nitrate. Analysis gave — 



Calc. Found. 



Sodium 21-8G 99.01 



Ammonium 3-42 3-40 



Sulphur 24-34 24-40 



For notice of a monohydrogen sodium ammonium imidosul- 

 phonjite, one in which the ammonium greatly predominates over the 

 sodium, see p. 77. 



