120 II. E. Merwin — Per oxidized Titanium Solutions. 



Suljdiuric acid 95-1/2 per cent, sp. g. 1'SIO. 



Hydrogen peroxide of ordinary strength. 



The standard colored solution was made from the above 

 solutions. It contained 5 ec of the standard titanium solution, 

 2 CC of hydrogen peroxide and approximately 3 - 5 cc of sulphuric 

 acid (including the free acid in the titanium solution), and was 

 made up to 50 cc . 



The test solutions each had the same volume as the standard, 

 and contained the same amounts of titanium and hydrogen 

 peroxide besides varying amounts of sulphuric acid, alkali sul- 

 phates and fluorine. 



Methods of comparing the colored solutions. — During the 

 early part of the work the comparisons were made by placing 

 the test and standard solutions each in one of two parallel- 

 sided glass containers of equal diameters placed side by side. 

 The standard was then diluted to match the test. By this 

 method the ratio of the coloring matter in the solutions is 

 directly proportional to the final volumes of the solutions. 

 Certain discrepancies appeared in the results of this method 

 which were found to be due to a tendency on the part of the 

 observer to overestimate the color in the left glass. The 

 amount of overestimation varied considerably, but sometimes 

 amounted to 6 per cent. For this reason all the later tests 

 were made with JSTessler tubes 6 CI " long and 2*7 cm in diameter 

 held over a white surface illuminated by diffused light. In 

 making the comparisons the depths of the liquids in the tubes 

 were so adjusted that when the tubes were changed right for 

 left that the left one appeared uniformly darker. A close 

 comparison could best be made by focusing the eyes on the 

 surface six or eight inches in front of where the tubes were 

 standing, and then lifting the tubes and bringing them momen- 

 tarily within the field of vision. Solutions thus compared 

 were first made up to equal volumes, then sufficient amounts of 

 each were run into the J^essler tubes and the depths noted. 

 Four to six comparisons were usually made for each set of 

 solutions. The degree of coloration is inversely proportional 

 to the depths of the liquids. 



The temperature of the solutions was maintained at 21 1/2°- 

 22 1/2° C. while they were being matched, except when the 

 effects of temperature change were being investigated. 



Agents Affecting the Coloration of Peroxidized Titanium 



Solutions. 



Free acids. — Colored titanium solutions that have been 

 bleached have their color restored as the acidity of the solution 

 is increased. Sulphuric, nitric, and hydrochloric acids, and 

 probably others, produce similar effects. The amount of the 

 effect in the case of sulphuric acid is shown in detail further 



