and the third three parts of saturated alcoholic solution to 10 parts of 0.01 per cent 

 NaOH. Prepare three slides of a fresh culture of a diphtheria organism; stain one 

 slide in each of these three solutions for two or three seconds only, i. e., just as 

 briefly as the stain can be poured on and poured off, and wash each slide im- 

 raediatly. Examined under the microscope all three of these preparations should 

 show deeply stained bacteria with the characteristic metachromatic granules 

 suflSciently distinct to insure accurate diagnosis. 



5. The sample should prove satisfactory for histological use. Xo exact method 

 for determining this can be given, but the sample must be submitted to one or two 

 experts in histological technic in order to get their judgment. 



6. It must be understood that these standards refer to samples to be used for 

 ordinary bacteriological and histological staining. Special standards for methylene 

 blue used in vital staining will undoubtedly be necessary. These standards, how- 

 ever, have not yet been determined. 



SPECIFICATIONS FOR SAFRANIN' O 



1. Samples of safranin O must be of the t^-pe represented by Colour Index 

 No. 841 and on spectrometric analysis .should have an absorption curve maximum 

 at approximately olou/x as determined in a one cm. layer by a spectrophotometer. 

 Other dyes must not be present. 



2. Safranin samples to be certified by the Commission must contain at least 75 

 f>er cent total color as determined when reduced V>y titanous chloride in an atmos- 

 phere of carbon dioxide. One gram of the dye must consume at least 4.195 cc. 

 normal titanous chloride solution. 



3. The samples should prove satisfactory for histological use. No exact method 

 for determining this can be given, but the samples must be submitted to one or two 

 experts in histological technic in order to get their judgment. Their judgment 

 must be based to a considerable extent upon the behavior of the stain in the Flem- 

 ming triple staining technic, in which it is used together with orange G and gentian 

 violet. In other words, the stain must be of such a shade as to contrast well with 

 both of these two other dyes. 



SPECIFICATIONS FOR BASIC FUCHSIN 



1. Basic fuchsin designed for staining and indicator purpo.ses must be ro.saniliu 

 or new fuchsin (Colour Index No. 678) or else a mixture of rosanilin and para- 

 rosanilin containing at least half of the former (that is, c-orresponding to Colour 

 Index No. 677). 



2. Fuchsin samples to be certified by the Commission must be of such a strength 

 that, when reduced by titanous chloride in an atmosphere of car])on dioxide, one 

 gram of the dye will consume at least 46.5 cc. normal titanous chloride solution. 

 A sample of this strength will be between 76 and 85 per cent total dye content, the 

 exact dye content varying according to the relative amounts of the higher and the 

 lower homologs present. 



8. The sample should prove satisfactory for staining the tuhercle organism and 

 should retain its color sufficiently when treated by the Ziehl metliod t» be diagnostic 

 when staining tubercular discharges. This must be determined by an investigator 

 skilled in this particular technic. 



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