Humic acids

[ref. ID; 7182]
Humic acids were prepared from anaerobic and activated sludge digests as follows. The pH of sludge, which contained about 2% solids w/w, was brought to pH 11 with 40% NaOH, centrifugated and the supernatant reduced to pH 2 with 6N HCl. The resulting precipitate (humic acids) was collected by centrifugation, resuspended in alkali, reprecipitated and resuspended twice, dialyzed exhaustively against distilled water, and lypophilized.
Test organisms;
Oligochaeta: Eisenia foetida (ref. ID; 7182)