W. M. Thornton, Jr. — Estimation of Titanium. 215 



process. This makes no difference when the amount of alu- 

 minium is relatively large ; for, although titanium can be com- 

 pletely thrown clown in a solution containing up to 11 per cent 

 of absolute acetic acid and thereby separated from most of the 

 aluminium (not from all of it), at least a second precipitation is 

 required. 



It seemed probable to the author that some oxidizing agent 

 could be found by means of which the tartaric acid could be 

 broken down and at the same time introduce no substance that 

 would contaminate the titanic acid ; so that in cases where 

 the aluminium was small in amount relative to the titanium 

 one precipitation would suffice. After several unsuccessful 

 experiments with different oxidizing agents, the plan of using 

 a mixture of sulphuric acid and fuming nitric acid was tried 

 with very gratifying results. 



Two standard solutions containing titanic sulphate were 

 employed in the following experiments. The first was pre- 

 pared by fusing Merck's titanium dioxide with sodium pyro- 

 sulphate, extracting the melt with 10 per cent sulphuric acid, 

 filtering, and making up to a definite volume. The second 

 was prepared by treating twice crystallized potassium fluo- 

 titanate with concentrated sulphuric acid — the sulphuric acid 

 being kept at the fuming point for several hours, poured into 

 cold water, and filtered. In either case the solution contained 

 about 10 per cent of absolute sulphuric acid. Duplicate por- 

 tions of 25 cm3 each were taken for standardization. Ammonium 

 hydroxide was added until the solution was nearly neutral 

 (the approach to neutrality being determined by the formation 

 of a turbidity which disappeared but slowly after vigorous 

 stirring). About l cm3 of a strong solution of ammonium bisul- 

 phite was added as a precaution to prevent the precipitation of 

 any iron that might accidentally have found its way into the 

 solution. Five 5 cm3 of glacial acetic acid and 15 grams of 

 ammonium acetate were also added and the volume was made 

 up to about 350 cm \ The solution was then brought rapidly to 

 boiling and maintained in ebullition for about two minutes. 

 The titanium came down in flocculent and readily filterable 

 condition. The precipitate was washed first with water con- 

 taining acetic acid and finally with pure water. Ignition in 

 contact with the paper was performed in the usual manner, 

 and finally the heat of a Meker burner was applied for 20 

 minutes. Duplicate determinations agreed to within 0*0001 

 grm. 



The first series of experiments were carried out with a view 

 to determining whether or not the titanium could be com- 

 pletely recovered after destruction of the tartaric acid in a 

 solution containing the same constituents as the acidified and 



