Abstract
A number of miscellaneous experiments has been undertaken using the apparatus described in previous papers. An anthracite has been oxidized at the copper cathode and, as is to be expected, much smaller yields were obtained than from a similar treatment of a vitrain. The amount of water‐soluble acids was much less than that of the ulmic acids. An attempt to oxidize two durains, in order to isolate the plant remains, proved unsuccessful, for it was found that unless the coal was ground to pass a 240 B.S. sieve; little oxidation took place. The durains could not be. ground to this fineness since the original structure of the plant entities would be destroyed.
Fractions obtained from coal by treatment with pyridine followed with chloroform, i.e., the β‐fraction and the γ‐fraction have been oxidized at the copper cathode and yield ulmic acids. The molecular weights were similar to those of ulmic acids obtained from the direct oxidation of coal. This accords with the work of Biggs who similarly examined the fractions obtained by pressure‐benzene extraction, followed by nitric acid oxidation, and supports his theory that the difference between the various fractions is one of molecular size rather than of chemical type.
Reduction of the vitrain at a copper cathode appeared to effect little change. However, reduction of the ulmic acid appears to increase its adsorptive power for electrolytes. It was not found possible to free the reduced ulmic acids from electrolyte by prolonged washing and they were no longer soluble in furfural and other solvents. It was thus not found possible to obtain a pure sample of the reduced ulmic acids.
A general summary of the work is given and suggestions made for further work.