174 Thornton — Separation of Titanium from Iron. 



It has been known for a long time that certain organic acids, 

 containing both hydroxy! and carboxyl groups, such as tartaric 

 acid and citric acid, have the power to prevent the precipitation 

 of certain metals when their solutions are made alkaline with 

 sodium or potassium or ammonium hydroxide. This principle 

 was made use of by Gooch* for the separation of titanium from 

 iron; for, if the solution contain sufficient tartaric acid, the iron can 

 be precipitated by ammonium sulphide as ferrous sulphideandthe 

 titanium will then be found entirely in the iron free filtrate. The 

 next step is to oxidize the tartaric acid; for titanium is not precip- 

 itated in its presence by any of the reagents previously used for 

 its gravimetric estimation. This was accomplished by Gooch,f 

 after strongly acidifying with sulphuric acid by adding potas- 

 sium permanganate to the boiling aqueous solution. This 

 process is open to the objection that a great deal of manganese 

 is thus introduced into the solution and is coprecipitated in 

 some measure when the titanium is subsequently thrown down 

 by hydrolysis of titanic acetate. A second precipitation is 

 therefore necessary, which must be preceded by fusion with an 

 appropriate flux and solution of the melt in acid. The author's 

 experiments show that, after acidifying the filtrate from the 

 ferrous sulphide, the titanium can be quantitatively precipitated 

 by the "cupferron" reagent, notwithstanding the presence of 

 tartaric acid. 



Two solutions of titanic sulphate were employed for these 

 experiments ; which were prepared by warming potassium 

 fluotitanate with concentrated sulphuric acid until all the 

 hydrofluoric acid had been volatilized, pouring into cold water, 

 and making up to known volume. The quantity of sulphuric 

 acid used was such that the resulting solution contained about 

 10 per cent .of absolute acid. In the case of the second solu- 

 tion, the trace of platinum was removed by saturating the 

 solution with hydrogen sulphide, filtering off the platinic sul- 

 phide, boiling out the Irydrogen sulphide, filtering again, and 

 making up the solution to definite volume. The first solution 

 was standardized by taking weighed portions of 25 cm3 and pre- 

 cipitating the titanium by hydrolysis of the acetate. The solu- 

 tion was made nearly neutral with redistilled ammonium 

 hydroxide — until a faint permanent turbidity appeared. One 

 cm 3 of a strong solution of ammonium hydrogen sulphite was 

 added, followed by 15 grams of ammonium acetate and 20 grams 

 of glacial acetic acid, and the solution made up to 400 cm3 . This 

 solution was brought rapidly to boiling and maintained in ebul- 

 lition for one minute. The precipitate was washed twenty 

 times — first with boiling 5 per cent acetic acid, and finally 



* Proc. Am. Acad. Arts arid Sci., n. s., vol. xii, p. 435 ; Chem. News, Hi, 

 55, 68. 



f Loc. cit., p. 445. 



