A photometric method for the comparative evaluation of disinfectants

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Abstract
1. Attention is called to the widespread dissatisfaction with the standard of reproducibility attained with the existing disinfectant tests.2. It is suggested that this lack of reproducibility is inherent in any 100% mortality test.3. The trend in all recent disinfectant developments appears to be towards greater specificity than was the case with the older products.4. Where a comparison is being made to ascertain the true relative efficiency of two or more disinfectants, this possible specificity necessitates their examination under a wider range of conditions than has been catered for in the past.5. A technique is suggested for use in those cases where a more limited examination will provide all the information that is required. It employs a simple culture medium, uses a measured quantity for the transfer from the medication tube, and makes use of a compensated photo-electric circuit to determine the amount of growth produced by the organisms which have survived the contact with the disinfectant.I wish to acknowledge my grateful thanks to the directors of Messrs Cooper, McDougall and Robertson Ltd. for permission to publish this paper, and to my colleagues of the Cooper Technical Bureau for assistance in various directions.