246 Dr. W. Ramsay on PlcoUne 



needle-shaped crystals. It is very slightly more soluble in 

 hot than in cold water, and cannot be obtained in large crystals 

 by cooling a hot solution, nor by allo^Ying a solution to eva- 

 porate over sulphuric acid. It contains no water of crystal- 

 lization. 



0-2510 grm., dried at 100°, gave 04198 grm. CaCOs,^ 

 0-0479 grm. Ca,=: 18-63 per cent, of Ca. C5 H3N(COO)2 Ca 

 requires 19*51 per cent. 



The neutral salt does not dissolve in excess of the acid. It 

 may be prepared either by boiling a very dilute solution of the 

 acid with calcium carbonate, or by mixing very concentrated 

 solutions of calcium chloride and the acid ammonium salt 

 of dicarbopyridenic acid. 



Barium Salts.— The neutral salt, C5 H3 N (C00)2 Ba + H2 

 (Ba found, 42-81 per cent.; calculated, 42-54: Hg found 

 6-24 per cent. ; calculated, 5*62), is formed by dissolving 

 barium carbonate in a very dilute solution of the acid. In its 

 properties it closely resembles the calcium salt. It crystal- 

 lizes in microscopic plates. The acid salt is a very insoluble 

 white powder. 



The neutral zinc salt crystallizes from a dilute solution 

 allowed to stand over sulphuric acid in well-defined octahedra. 



The lead salt is sparingly soluble in water, and crystallizes 

 out, when a hot solution of the ammonium salt and lead 

 acetate are mixed, in short small prisms, w^hich are without 

 action on polarized light. 



There are two copper salts, one of which forms light-blue 

 needles with a satin-like lustre ; the other crystallizes in 

 dark blue prisms. The former is sparingly, and the latter 

 easily, soluble in water. 



The cadmium salt, prepared by adding cadmium chloride 

 to the acid, is a white, very sparingly soluble precipitate ; it 

 contains no water of crystallization. 



Y'^ii]! ferrous salts, dicarbopyridenic acid, or any one of its 

 soluble salts, gives a red colour, closely resembling, that of 

 ferric sulphocyanide. This forms an excellent test for the 

 presence of the acid. Ferric scdts produce no change of 

 colour nor precipitate. 



The manganese salt, C5 II3 IST (000)2 Mn. Hg 0, ^^^as pre- 

 pared by adding manganese carbonate to the acid. The car- 

 bonate dissolved at first ; but a white salt of the above formula 

 came down after some time. It is sparingly soluble in water. 



0-2212 grm. lost at 110° 0-0164 grm., = 7-41 per cent. 

 Theory demands 7-56 per cent. 0-2212 grm. gave 0-07090 

 grm. Mn3 0.i, = 23-05 percent. Mn. Theory requires 23*10 

 per cent. 



