A too free application of tar mixtures and other preparations containing phenols is liable to cause poisoning; hence care should be observed in this regard.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
All the colouring matters of this class possess either a distinctively acid character, or belong to the class of phenols, which, while not being true acids, still possess weak acid functions that enable them to combine with bases like acids.
"The Dyeing of Woollen Fabrics"
Franklin Beech