“COLOR STANDARDS” FOR THE COLORIMETRIC MEASUREMENT OF H-ION CONCENTRATION pH 1.2 TO pH 9.8

Abstract

I. H-ION CONCENTRATION METHOD OF ADJUSTING CULTURE MEDIA BY THE USE OF " COLOR STANDARDS" * This table was prepared from an antilogarithm table by using the antilogarithmic value of 0.9 for pH 1.1, that of 0.8 for pH 1.2, etc.-since pH 1.1 is pH 0.9 stronger than pH 2, and pH 1.2 is pH 0.8 stronger than pH 2, etc.

The Reactions of Culture Media

“…We like the color shades produced by B. T. B. better than those produced by P. R. when color standards prepared after Medalia are used in the comparator block which will be described in a later section of this paper. In this connection Medalia (1920) observed that:…”

“…were used in the Miraflores, Mt. Hope and Agua Clara laboratories until the latter part of 1920 when an article by Medalia (1920) on "'Color Standards' for the colorimetric measurement of H. 1. C. pH 1.2 to pH 9.8" was published.…”

“…The blocks provided with the sets were made up with slits. Medalia (1920) uses slits in his block. Clark (1920) shows round holes in the block illustrated in figure 7 of his book, Cox and Wood (1920) use round holes of two thirds the size of those in which the test tubes arc set.…”

“…of this Society, the initial contribution having been made by and continued intermittently by them as well as others up to the present time; the latest article of great practical value being that of Medalia (1920). We can not expect the younger men, recently out of school, who are starting out on a modest salary, immediately to join the Water Works Associations, the Society of American Bacteriologists, the American Chemical Society, and to subscribe to the Engineering News-Record, The American City, Engineering & Contracting, and others.…”

“…To those men who wish to determine the hydrogen-ion concentration of culture media and to adjust the reaction of the latter to definite concentrations we strongly advise the purchase of (1) Clark's book (1920) on The Determination of Hydrogen Ions, which contains an indexed bibliography of 1100 references; and (2) No.5, volume 5 (September, 1920), of the Journal of Bacteriology, which contains an excellent article by Medalia (1920) on "Color Standards for the Colorimetric Measurement of H-ion Concentration pH 1.2 to pH 9.8. " This article gives a practical method of preparing color standards for use in bacteriological laboratories and we have quoted quite extensively from it in this paper.…”