The estimation of phenol and cresol by a biological method

M. Wynter Blyth, Leonard Goodban
1907 The Analyst  
THE estimation of phenol and the cresols is a matter of considerable importance, and one which is not easy to carry out unless the substances are pure and unmixed with each other. The estimation of phenol in commercial ( ( carbolic acids " and in creasote, etc., is particularly difficult. I n the present paper we record some observations made upon the germicidal powers of pure phenol, pure ortho-, meta-and paracresol, and mixtures of these on cultures of B. coli communis under defined
more » ... r defined conditions. The principal object of our investigation was to obtain a method which can be applied to the estimation of the amount of phenol and cresylic acid in commercial carbolic acids and powders. I t has been shown by a number of observers that the germicidal value of cresylic acid is considerably greater than that of phenol; and it has been further shown by one of us (Jozmz. SOC. Chem. Ind., 1906, 25, 1183 that this difference in germicidal value between cresylic acid and phenol is very much reduced in the presence of organic matter containing either fat or albumin. I t became evident to us during these experiments that to ensure consistent results when working with micro-organisms two factors, in addition to the precautions usually taken, are of importance : (1) Temperature ; (2) previous history of the organism. (1) The temperature usually laid down is a room temperature of from 16" to 18" C. I n exact work we find that we cannot allow any range of temperature, and our method of procedure is to make the necessary dilutions in fest-tubes, which are then placed in a water-bath at the exact temperature required for at least fifteen minutes before the experiment. The bath may have its side covered with felt, and the temperature is maintained by a small jet of gas and a thermostat in the ordinary way. During the experiment, when a test-tube is withdrawn to make an inoculation, it is replaced as rapidly as possible.
doi:10.1039/an9073200154 fatcat:byfho5mhlbhhnlcxz4bsptpwt4