884 Prof. H. Rose on the Isomeric Modifications 



In a solution oi sulphate of nickel a greenish- white preci- 

 pitate is produced, which is readily soluble in the soda salt. 

 The solution is not rendered turbid by heat. With chloride 

 of nickel the same reaction occurs, except that the solution of 

 the precipitate in excess of the soda salt is rendered turbid 

 when heated and does not become clear on cooling, Sul- 

 phuret of nickel is immediately thrown down from this solution 

 by sulphuret of ammonium. 



Solution of sulphate of cobalt is precipitated of a pale red 

 colour; the precipitate is readily soluble in the soda salt. 

 The solution is red, and when heated becomes perfectly blue, 

 but not turbid ; on cooling it reacquires the red colour. Sul- 

 phuret of ammonium immediately causes the formation of sul- 

 phuret of cobalt in it. 



Solution of alum produces a white precipitate, soluble in 

 the soda salt. No precipitate is caused in this solution either 

 by ammonia or sulphuret of ammonium. But the preci- 

 pitate is soluble in excess of the solution of alum. 



Solution of nitrate of bismuth, although it contains free 

 acid, produces a white precipitate, soluble in the soda salt. 

 On applying heat a precipitate is formed. Sulphuret of am- 

 monium produces sulphuret of bismuth in it. 



No precipitate is caused in a dilute filtered solution o^ albu- 

 men by solution of pyrophosphate of soda, even after the addi- 

 tion of acetic acid. 



As is well known, aqueous solution of pyrophosphoric acid 

 is best obtained by decomposing the pyrophosphate of lead, 

 suspended in water, by a current of sulphuretted hydrogen. 

 In this manner the conversion of the pyrophosphoric acid into 

 the c-phosphoric acid is avoided, which, as we know, ensues 

 after the lapse of some time even by repose, but much more ra- 

 pidly when the acid is heated. If however the solution of pyro- 

 phosphoric acid has been saturated or supersaturated by a 

 strong base, it may be keptin it without undergoing any change. 

 Neither by ebullition nor by long repose is the ^-phosphoric 

 acid converted into the c, and a solution of the pyrophosphate 

 of soda may be preserved for many years without change. 

 With excess of alkali, the solution of pyrophosphoric acid is 

 not converted into the c-phosphoric acid, until the mass, after 

 evaporation to dryness, has been completely fused. But even 

 in this case, according to Weber, the entire conversion into 

 the c-phosphoric acid does not take place, until the pyro- 

 phosphate has been completely decomposed by fusion with 

 excess of alkali, especially an alkaline carbonate. As this does 

 not occur completely on fusing pyrophosphate of lime with 

 excess of an alkaline carbonate, the ^-phosphoric acid of the 



