128 DR ANDERSON ON THE COMPOSITION AND PROPERTIES OF PICOLINE, 
gravity of picoline is less than that of water. I found it to be 0:955 at 50°, while, 
according to Horrman, that of aniline is 1-020 at 68°. 
Picoline mixes with water in all proportions, and forms a transparent and 
colourless solution. It is insoluble, however, in solution of potass, as well as in 
most alkaline salts, the addition of which causes its immediate separation from 
the water. It dissolves also readily in alcohol, ether, pyroxylic spirit, and the 
fixed and volatile oils. It is a powerful alkaline base: a rod dipped in hydro- 
chloric acid, and held over it, is immediately surrounded by a copious white 
cloud of hydrochlorate of picoline. It restores the blue colour of reddened litmus, 
but does not affect the colouring matter of red cabbage. It does not coagulate 
the white of eggs as aniline does. 
The reactions which it produces with other substances are also quite distinct 
from those presented by aniline. When brought in contact with the solution of 
chloride of lime, it does not produce, in the least degree, the violet colour which 
is so characteristic of aniline; on the contrary, the solution remains perfectly 
colourless, unless, indeed, the picoline has not been well separated from pyrrol; 
in which case a slight brown makes its appearance, but no violet. Picoline is also 
incapable of producing the yellow colour in fir wood and the pith of the elder, 
which is so readily obtained with aniline. When treated with chromic acid, even 
when very concentrated, and after boiling, no change takes place in the colour of 
the solution, and only a small quantity of a yellow powder is deposited; while 
Aniline gives an abundant precipitate, which has, according to the degree of con- 
centration of the fluid, a green, blue, or black colour. 
Picoline precipitates from solutions of chloride of copper a portion of the oxide 
of copper, while the remainder forms a pale blue solution, which, when evapo- 
rated to a small bulk, deposits a congeries of prismatic crystals, which seem to 
be a doubie salt. No blackening of the solution takes place, as is the case with 
aniline. When an excess of hydrochloric acid is present there is obtained, on 
evaporation, another double salt in large crystals, apparently derived from the 
rhombohedral system. Picoline produces also double compounds with the chlo- 
rides of mercury, platinum, gold, tin, and antimony. With chloride of gold it gives 
an exceedingly characteristic compound, in the form of a fine lemon-yellow pre- 
cipitate, which is soluble in a considerable quantity of boiling water, and is depo- 
sited, on cooling, in delicate yellow needles. Aniline, under similar circumstances, 
gives a reddish-brown precipitate resembling the ferrocyanide of copper. It gives, 
with infusion of nut-galls, a copious curdy precipitate of a pale yellow colour, 
which dissolves in hot water, and is deposited again on cooling. It does not pre- 
cipitate the solutions of nitrate of silver, chlorides of barium and strontium, or 
sulphate of magnesia. 
The properties of picoline, as now detailed, are obviously different from those 
of aniline. They recalled, however, strongly to my mind those of a base called 

