220 DR T. ANDERSON ON THE PRODUCTS OF THE 
law that the boiling points of homologous substances rise by 34° of Fahrenheit 
for every addition of C, H, to the atom, and from which the boiling points of 
pyridine, picoline, and lutidine do not greatly differ, I directed my attention to 
the portion of mixed bases boiling about 340°, in which it was reasonable to ex-— 
pect that the next base of the series should be found. But even after repeated 
rectifications, the base distilling at this temperature still gave a very powerful 
reaction of aniline, with chloride of lime, and the percentage of platinum in its 
double compound was but little lower than that of the lutidine salt, or at all 
events never reached the number required by theory for the higher base. Being 
convinced that the separation of two bases approximating so closely in their boil- 
ing points as aniline and the substance I expected to find, could not be effected 
by fractionated distillation, or at least only by an expenditure of time, labour, and 
material, altogether out of proportion to the importance of the object to be at- 
tained, I endeavoured to accomplish it by crystallization. Having observed that 
the other members of the picoline series gave highly soluble and even deliquescent 
oxalates, I conceived that by converting the mixed bases into salts of that acid, it 
would be easy to separate the rather sparingly soluble and highly crystallizable 
oxalate of aniline, and obtain the oxalate of the other base in a state of purity. 
But this expectation was not confirmed by experiment; for neither from the por- 
tion boiling about 340°, nor even from that collected at 360°, and corresponding, 
therefore, with the boiling point of pure aniline, could the slightest trace of crys- 
tallized oxalate of aniline be obtained, although both fractions gave the reaction 
of that base in the most powerful manner. The experiment was varied in every 
possible way, by the use of water, spirit, and absolute alcohol, but by allowing 
these fluids to evaporate spontaneously only a thick syrup was obtained, without 
the slightest indication of crystallization. Even the addition of ether to its alco- 
holic solution gave only a syrupy fluid, and no crystals; and I was forced to con- 
clude, that even in the portion of the mixed bases corresponding to the boiling 
point of aniline, its quantity was so small in proportion to the other substances, 
that the properties of its salts were entirely masked by them. 
Not succeeding in obtaining the pure aniline, and so separating it from the other 
base, the question came to be, how to get rid of the former substance in the best 
possible way. For this purpose I availed myself of the extreme stability of the 
bases of the picoline series mentioned in my former paper, which is so great that 
they resist even the action of strong nitric acid, by which aniline is entirely de- 
stroyed. When the base, boiling between 340° and 345°, is mixed rapidly and in 
large quantity with nitric acid, much heat is evolved, and a brisk action takes place ; 
and if the portion boiling about 360° is employed, the action is so violent as to be 
almost explosive, and it is requisite to add the base drop by drop to the acid, which 
must be kept carefully cool. The acid fluid acquires a deep red colour, and on boil- 
ing, red fumes are abundantly evolved, accompanied by an odour resembling that of 
