of Phosphoric Acid. 333 



phosphate of soda. The solution is of a blue colour ; on the 

 addition of ammonia it becomes of a darker blue, sulphuret of 

 ammonium immediately produces in it a brown precipitate of 

 sulphuret of copper. The pyrophosphate of copper is also 

 soluble in a very large excess of sulphate of copper. Heat 

 produces a precipitate in the solution which does not dis- 

 appear on cooling. 



Solution of acetate of lead causes a white gelatinous preci- 

 pitate, readily soluble in the pyrophosphate of soda. Sulphuret 

 of lead is immediately thrown down from this solution by 

 sulphuretted hydrogen. 



Solution of protosulphate of manganese produces a white 

 precipitate, which is insoluble in excess of the protosalt of 

 manganese, but is soluble in the pyrophosphate of soda. This 

 solution is not troubled by ammonia ; sulphuret of ammonium 

 does not produce a precipitate of sulphuret of manganese in 

 it (which certainly deserves special notice), even when set 

 aside for a considerable time. 



Solution of protosulphate of iron produces a white preci- 

 pitate, soluble in excess of the pyrophosphate of soda. A 

 black precipitate of sulphuret of iron is immediately formed 

 in the solution on the addition of sulphuret of ammonium ; the 

 solution is not however rendered turbid by ammonia; it 

 merely renders it of a dark colour. The pyrophosphate of 

 iron is also soluble in excess of the solution of the proto- 

 sulphate of iron. 



Solution of perchloride of iron causes a white precipitate, 

 readily soluble in excess of the pyrophosphate of soda. Sul- 

 phuret of ammonium immediately produces in the almost 

 colourless solution, a black precipitate of sulphuret of iron, 

 which deserves particular notice, because Persoz denies the 

 production of sulphuret of iron in the solution by sulphuret of 

 ammonium. Ammonia however does not render the solution 

 turbid ; it immediately turns it of a blood-red colour. 



Solution of sulphate of zinc produces a white precipitate, 

 soluble in the pyrophosphate of soda. The solution is neither 

 precipitated by ammonia nor by boiling, but sulphuret of am- 

 monium throws down sulphuret of zinc. The precipitate is 

 also soluble in excess of the solution of sulphate of zinc. 

 On boiling, the solution becomes turbid ; the turbidity does 

 not disappear on cooling. 



Solution of sulphate of cadmium produces a precipitate 

 which is soluble in pyrophosphate of soda. The solution be- 

 comes turbid when heated, the turbidity not disappearing as 

 the solution cools. Sulphuret of cadmium is immediately 

 precipitated from it by sulphuret of ammonium. 



