28 Dr. W. Ramsay onJPicoline and its Derivatives. 



give whitish blue precipitates. With ferric chloride, the /3- and 

 y-acids give a white precipitate, which is changed to ferric 

 hydrate on addition of ammonia; the a-acid gives no preci- 

 pitate with ferric chloride, even after addition of excess of 

 ammonia, showing that ferric hydrate is soluble in the 

 ammonium salt of the acid. The methyl-ether of the a-acid 

 forms thick isolated crystals ; that of the /3-acid consists of 

 deliquescent needles. The chloride of the a-acid boils at 

 284°, that of the /3-acid at 269-270°, and the chloride of 

 the 7-acid at 265°. The melting-points of the chlorides are 

 respectively :— a, 60*5-61° ; /3, 49° ; 7, 88-89°. 



I may anticipate that the acid obtained by oxidation of 

 quinine, and since found to result from the four chief alka- 

 loids of the cinchona-bark, and described by Mr. James Dobbie 

 and myself in the ' Journal of the Chemical Society ' for 

 April of the current year, has the formula C 7 H 5 N0 4 ; but, 

 from its crystalline form and properties, it appears to be dis- 

 tinct from any one of the acids described in this memoir. 

 This subject, however, demands a more complete examination 

 than we have as yet bestowed on it. It is my intention, 

 should it prove different, to publish a table giving the charac- 

 ters of the isomeric acids. 



It is also possible that the bitter substance, which, like these 

 acids, gave off pyridine when heated, is also an isomeride ; but 

 of this I have no proof. 



Dipyridine. — In purifying some oils, afterwards to be de- 

 scribed, I obtained a considerable quantity of dipyridine, 

 C 10 H 10 N 2 ? an( i purified it by crystallization from hot water. 

 It presented the appearance of long hair-like w T hite needles. 

 As its vapour-density had only been once determined, it was 

 deemed of sufficient interest to redetermine it, by means of 

 Meyer's apparatus. 



The amount taken was 0*0247 gram. The formula by which 

 it was calculated is 



0*0247 x 1543500 x 14*47 



>°K 86 *!)}»MKf)r ' 



Reference is made to the previous example for the meaning 

 of the numbers. The theoretical density of dipyridine vapour 

 compared with hydrogen is 79. 



Isodipyridine. — Some test tubes full of oil, left by the late 

 Professor Anderson, and labelled " Bases forced over from the 

 residue on distillation of dipyridine," were submitted to ex- 

 amination. When heated at the ordinary atmospheric pressure, 

 these bases boiled at a temperature above that at which 



