176 Thornton — Separation of Titanium from Iron. 



The supply of "cupferron" for these experiments was pre- 

 pared in this laboratory according to the directions given by 

 Baudisch.* An approximately 6 per cent solution of the salt 

 was made by dissolving it in cold water and filtering from any 

 insoluble residue that remained. 



The first series of experiments was carried out with a view 

 to ascertaining whether or not titanium could be completely 

 precipitated and accurately determined in the presence of tar- 

 taric acid. To a solution containing a known quantity of titan- 

 ium a little more than three times the weight of the titanic 

 oxide present was added of tartaric acid. The solution was 

 made neutral to litmus with ammonium hydroxide, then acid 

 again with 5 cm3 of sulphuric acid (made by diluting acid of 

 sp. g. = 1*84 with an equal volume of water), and the volume 

 made up to 200 cm3 . A little more than the calculated amount 

 of " cupferron " solution was added and the beaker set aside 

 for the precipitate to settle. The supernatent liquid was tested 

 by adding a few drops of the reagent, which were made to run 

 down the wall of the beaker. The formation of a white pre- 

 cipitate of nitrosophenylhydroxylamine indicates that the re- 

 agent has been added in excess, while the formation of a yellow 

 turbidity shows that the titanium had not been completely 

 thrown out. It is well also to test the filtrate. The precipi- 

 tate was filtered on paper using very gentle suction and washed 

 twenty times with cold water. During the washing the suction 

 should be almost stopped to prevent the wash water from run- 

 ning through too fast to accomplish much solvent work. The 

 precipitate is very prone to develop mud cracks and should 

 therefore be agitated with the stream of water from the wash 

 bottle as much as possible. After having been sucked free 

 from drainage water, the precipitate along with the filter was 

 placed in a tared platinum crucible, dried at 110° C, very 

 carefully heated until the volatile products of destructive distil- 

 lation had escaped, the inclined open crucible ignited till all 

 carbon had been consumed, and finally brought to constant 

 weight over the Meker burner. If it is desired to save time, 

 the precipitate can be dried by inclining the crucible, support- 

 ing the lid tongue downward on the triangle and edge of the 

 crucible, and applying a small flame beneath the lid. The heat 

 is thus deflected downward and the precipitate gradually dried 

 from above with little danger of spattering.f It is unadvis- 

 able to dry the precipitate in the funnel ; for at a low tempera- 

 ture the substance melts, or at least assumes a plastic condition, 

 and penetrates the pores of the filter ; moreover, the dried 



* Chem. Zeitung, xxxv, 913, 1911. 



\ See Analytical Chemistry, Treadwell [translated by Hall], vol. ii, p. 29, 

 1910. 



