Dr. W. Ramsay on Picoline and its Derivatives, 21 



liberated as usual by treatment with sulphuretted hydrogen. 

 The lead sulphide was well washed with boiling water ; the 

 filtrate and washings were evaporated ; and on cooling, a white 

 substance deposited mixed with spear-like crystals. After a 

 long series of fractional crystallizations from water three dis- 

 tinct acids were obtained, of which I have investigated two ; 

 the third was unfortunately lost. As these two have the same 

 percentage composition as Dewar's dicarbopyridenic acid, I 

 propose to name that acid u-dicarbopyridenic acid. 



The white substance, mentioned above, consisted chiefly of 

 a sparingly soluble acid, which I shall call fi-dicarbopyriclenic 

 acid. 



The acid depositing from the mother liquor of the /3-acid, 

 in groups of spear-like crystals, shall be distinguished as 

 y-dicarbopyridenic acid. 



$-Dicarbopyridenic acid, C 7 H 5 N0 4 .— This acid, as has 

 already been mentioned, separates out as a white crystalline 

 powder when its aqueous solution is allowed to cool. It was 

 purified by repeated crystallization from water. When viewed 

 under the microscope it presents the appearance of truncated 

 octahedra, grouped together in masses. The acid dried at 

 100° decomposes at 244-245°, frothing up, and giving off 

 gas. It is very sparingly soluble in water; 02 gram, dis- 

 solved by boiling with about 200 cubic centimetres of water, 

 crystallized out after standing for some hours. It is rather 

 more soluble in alcohol, and dissolves sparingly in ether. 

 When heated on platinum-foil it melts, effervesces, and gives 

 off a smell resembling that of pyridine. It was analyzed, with 

 the following results : — 



I. Taken, 0'4012 gram of air-dried acid. Loss at 100°, 

 0'0532 gram; C0 2 obtained on combustion, 0'6611 gram; 

 H 2 0, 0-1045 gram. 



II. Taken, 0*4233 gram of air-dried acid. Loss at 100°, 

 0-0560 gram; C0 2 , 0'6935 gram; H 2 O, 0*1025 gram. 



Calculated for 

 I. II. 7 H 5 N0 4 .liH 2 O, 



H 2 O... 13-26 per cent. 13-20 per cent. 13'91 per cent. 



For C 7 H 5 N0 4 . 



C 51-81 „ 51*49 „ 50-30percent, 



H 3-33 „ 3-10 „ 3-00 „ 



To ascertain if this acid, when heated, splits up into carbonic 

 anhydride and pyridine, thus, 



C 7 H 5 N0 4 = C 5 H 5 N + 2C0 2 , 

 its vapour-density was taken at the boiling-point of sulphur 

 (446° C.) by means of the beautiful arrangement devised by 



