But facts accumulated. By the action of chlorine on alcohol Liebig obtained _chloroform_ and _chloral_, substances which have since been so largely applied to the alleviation of human suffering; but it was Dumas who correctly determined the composition of these two compounds, and showed how they are related to alcohol and to one another. Liebig's reception of the corrections made by Dumas in his work furnishes a striking example of the true scientific spirit. "As an excellent illustration," said Liebig, "of the mode in which errors should be corrected, the investigation of chloral by Dumas may fitly be introduced. It carried conviction to myself, as I think to everybody else, not by the copious number of analytical data opposed to the not less numerous results which I had published, but because these data gave a simpler explanation both of the formation and of the changes of the substances in question." One of the most important contributions to the new views was made by Dumas in his paper on the action of chlorine on acetic acid (1833), wherein he proved that the product of this action, viz. _trichloracetic acid_, is related to the parent substance by containing three atoms of chlorine in place of three atoms of hydrogen in the molecule; that the new substance is, like the parent substance, a monobasic acid; that its salts are very analogous in properties to the salts of acetic acid; that the action of the same reagents on the two substances is similar; and finally, that the existence of many derivatives of these compounds could be foretold by the help of the new hypothesis, which derivatives ought not to exist according to the dualistic theory, but which, unfortunately for that theory, were prepared and analyzed by Dumas.