I9 o 5 .i HALL AND SMITH— COLUMBIUM. 201 



EFFECT OF THE PRESENCE OF HYDROCHLORIC ACID. 



The solution of hydrochloric acid used was one part of concen- 

 trated acid to five parts of water. 



With i c.c. of hydrochloric acid (1:5) and 1 c.c. of chromo- 

 tropic acid in 50 c.c, .0000795 gram of Ti0 2 gave a distinct pink 

 color. 



With 2 c.c. of hydrochloric acid (1:5) .00017 gram of Ti0 2 was 

 required to give the color. 



When 5 c.c. of hydrochloric acid (1:5) was used .000424 gram 

 of Ti0 2 gave a pink color to 50 c.c. 



10 c.c. of hydrochloric acid (1:5) required .000848 gram of 

 Ti0 2 for the color. 



20 c.c. of hydrochloric acid (1:5) required .00169 gram of 

 Ti0 2 in 50 c.c. to give a definite test for titanium. 



It may, therefore, be concluded that the destruction of the color 

 given by chromotropic acid is in proportion to the amount of acid 

 present, so if this test is used hydrochloric acid should be absent. 



EFFECT OF SULPHURIC ACID. 



With 1 c.c. of sulphuric acid, specific gravity, 1.435, 0.000318 

 gram of Ti0 2 was required to give a pink color in 50 c.c. of 

 solution. 



With 2 c.c. of sulphuric acid 0.000742 gram of Ti0 2 was required 

 to give the titanium test. 



While more dilute solutions of sulphuric acid were not tried it is 

 evident that the effect of the sulpuric acid is roughly proportional 

 to the amount of acid present, and that any appreciable amount of 

 this acid seriously interferes with the delicacy of the test. The 

 same is true of hydrofluoric acid. 



In the presence of oxalic acid in any appreciable amount chromo- 

 tropic acid will show .000025 gram of Ti0 2 in 50 c.c. very dis- 

 tinctly. Half that amount could be detected but the color is very 

 faint and its similarity to the color possessed by the solution of 

 chromotropic acid itself renders the detection of this amount uncer- 

 tain. In making the test it is best to avoid the presence of free 

 mineral acids, as they interfere and generally in direct proportion 

 to the amount of acid present. The neutral chlorides and sulphates 

 are without effect, as Geisow has stated. It is probable that the 

 color developed in oxalate solution could be used to determine the 



