CHEMISTRY. 455 



ill water, the latter being more effective than the Ibrnier. In the pres. 

 euee of one of these 1 part of barium sulphate is soluble in about 

 400,000 parts of water. 



(2) {(t) Fifty mg. barium sulphate remains permanently dissolved in 

 500 CO. of an 8 per cent solution of ammonium chlorid, corresponding 

 to 1 i)artof the barium salt to 10,000 i)arts of the solution, {h) Barium 

 chlorid or free sulphuric acid reduces the solubility of the barium salt 

 in ammonium chlorid solution, its solubility in 10 per cent ammonium 

 chlorid solution with moderate excess of sulphuric acid being- 1 part in 

 400,000 parts (same as in water), while in presence of barium chlorid 

 the solubility is 1 part in r)0,000 parts of solution, (c) From (a) and {b) 

 the conclusion is drawn that while ammonium chlorid in large amounts 

 does not hinder the precipitation of barium by sulphuric acid, which is 

 always added in excess, it does interfere with the coiii])lete ])recipita- 

 tion of sulphuric acid by barium chlorid. 



(8) {<() While barium sulphate dissolves in dilute solutions of ammo- 

 nium chlorid to a far greater extent than in pure water, it is less soluble 

 ill them than in more concentrated solutions, {h) In the presence of 

 moderate quantities of ammonium chlorid (2.5 parts in 100 cc. of liquid) 

 the precipitation of barium by sulphuric acid is practically complete, 

 whilQ the precipitation of sulphuric acid by barium chlorid is suflB- 

 ciently complete for quantitative purposes. 



(4) (a) In a 2.3 per cent solution of sodium chlorid 20 mg. of barium 

 suljihate remained dissolved in 440 cc. of the solution, corresponding 

 to 1 part in 22,000, which is practically the same result as obtained 

 with ammonium chlorid, though the latter is remarked to have some- 

 what more solvent power than the former, (b) The solubility of barium 

 sulphate in stronger sodium chlorid solutions corresponds with its 

 solubility in ammonium chlorid solutions of like strength; and barium 

 chlorid or sulphuric acid acts in the same way in reducing its solubility 

 as they do in ammonium chlorid solution, (c) The presence of barium 

 sulphate in mineral waters containing chlorids is explained on the basis 

 of the above facts. 



(5) (a) About 1 part of barium sulphate is dissolved by 7,300 parts 

 of nitric acid (7 to 8 per cent). (/>) Barium chlorid and free suli)huric 

 acid reduce very materially the solubility of barium sulphate in dilute 

 nitric acid, sulphuric acid reducing the solubility to 1 part in 400,000, 

 while 30 cc. of barium chlorid reduces the solubility from 3 mg. in 

 100 cc. to 1 part in 33,000. (c) From (a) and (/>) the authors conclude 

 that barium and sulphuric acid can be estimated with sufficient accu- 

 racy for analytical purposes in nitric acid solutions of 10 per cent or 

 less by the addition of an excess of sulphuric aci<l or of barium chlorid, 

 as the case may be. 



(6) (a) The solubility of barium sulphate in 7 to 8 and 10 i)er (!ent 

 hydrochloric acid is practically the same as in nitric acid of the same 



11008— No. () 2 



