Ph = 



Methyl- 

 Violet, 



Tropaolin 00 



Butter yellow 



5 



.03% 



.03% 



Methyl orange, .02% 

 4Br — phenolsulfophthaleiii 



Methyl red, .04% 

 p — nitrophenol, .5% 

 Neutral red, .02% 



Phenolsulphonepthalein, .05% 

 6 P„ 7 



.15% 

 a — napthol — phthalein 



Thymolsulfophthalein, 05^^ 



2 Br thymolsulfophthalein, .05% 



a — naptholsulfophthalein 



Phenolphthalein, .2% 



Thymolphthalein, .05% 



Fig. 3. — Conversion table for roughly determining the Ph of any aqueous solution. The solution is 

 placed in a test-tube of 1 cm. bore together with 0.1 c.c. of the indicator solution of the indicated 

 concentration and the color is compared with the chart while looking downward into the tube. 

 In many cases two attempts to match the color were made, the continuous scale being made with 

 the aid of water colors and the discontinuous scale with the aid of aniline dyes. About O.'S must be 

 subtracted from the Ph of sea-water as determined by this chart if sulfophthalein indicators are 

 used, to correct for the salt error. For finer work the tubes described in this i)aper are recommended. 



