Abstract
In a previous paper 1 it was shown that the specific substance of the tubercle bacillus, soluble in lipoid solvents, can be prepared from ether, ethyl and methyl alcohol extracts in a similar grade of purity; the potency and the chemical composition of the preparation is very similar. With the further purification of the product as described in the paper mentioned, and with the separation of it into different fractions by precipitation from warm methyl alcohol, from acetic acid and from chloroform solution, etc., we never obtained markedly more potent preparations. The bulk of the purified substance, which is supposed to contain a large percentage of the specific substance, is composed of fatty acids. Besides these, it contains quite a large amount of P. (2.6 per cent), home reducing sugar (in one case only 4 per cent), and it contains only traces of N. (0.3 per cent).
During further work with this preparation a fortunate chance helped us to separate the antigenically active part of the preparation from the lipoidal part. Quite a large amount of the specific substance was prepared from an alcohol extract of tubercle bacilli as formerly described. The preparation showing the maximum potency was dissolved in ether, and the ether solution was washed with diluted HCl for the elimination of the substances containing N, then several times with distilled water, and kept for 24 hours over anhydrous Na2SO4. The perfectly clear solution, which after this procedure has shown unchanged potency for several weeks, first developed a turbidity, then deposited a heavy precipitate and simultaneously with the appearance of the precipitation its potency decreased. The container during this time was opened several times, but after every opening filled with CO2.
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