PREFACE TO FOURTH EDITION.

The Committee on Standard Methods of Bacteriological Water Analysis was

reorganized in 1918 with the following membership: F. P. Gorham,

chairman, L. A. Rogers, W. G. Bissell, H. E. Hasseltine, H. W. Redfield,

with M. Levine as adjunct member. This committee made a report in 1918

which was not acted on by the Laboratory Section, and in 1919 made a

revised report, recommending certain changes in Standard Methods, which

were adopted by the section and which are now incorporated in this

present fourth edition.

Following are the more important changes:

New brands of peptone authorized.

Phenol Red Method of Hydrogen-ion Concentration.

Five-tenths per cent of sugar specified for broths instead of 1 per

cent.

Sterilization of sugar is media specified in greater detail.

Preparation of Endo Medium.

Synthetic Medium for the Methyl Red Test.

There are no changes in the chemical methods in this edition.

AMERICAN PUBLIC HEALTH ASSOCIATION.

_LABORATORY SECTION._

STANDARD METHODS FOR THE EXAMINATION OF WATER AND SEWAGE.

Compiled and revised by committees of the American Public Health

Association and the American Chemical Society and referees of the

Association of Official Agricultural Chemists.

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