Thornton, Jr. — Separation of Titanium from Iron, etc. 409 



great deal. Two hours was found to be satisfactory ; but no 

 doubt a shorter time would suffice, and in a few cases the pre- 

 cipitate was allowed to stand about twelve hours with no harm- 

 ful consequences. The precipitate was filtered on paper with 

 the aid of very gentle suction, washed twenty times with water 

 containing 20 cra3 of hydrochloric acid of sp. g.=l - 20 per litre, 

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

 at first very carefully with the cover on, then with the crucible 

 inclined and open until all the carbon had been consumed, and 

 finally brought to constant weight over the Meker burner. 

 From experiments (1) and (2) it is evident that if the concen- 

 tration of free sulphuric acid be too small, very serious errors 

 are made in the direction of gain of weight on the titanium. 

 Since, after the separation of the iron, the filtrate from the 

 ferrous sulphide contains already tartaric acid, it was considered 

 advisable at this point to learn the effect of tartaric acid on the 

 next operation in the analysis, viz., the separation of titanium 

 from aluminum. Since the conditions in experiments (3) and 

 (4) are the same as those in experiments (1) and (2) respectively, 

 excepting the presence of tartaric acid, it is obvious that 

 if this acid be present in the solution, the concentration of 

 free sulphuric acid necessary to bring about a clean separation 

 can be greatly diminished. In experiments (5) and (6) it will 

 be noticed that with small increments in acidity the error is 

 very slightly lowered. If the original solution for the analysis 

 occupy a volume of 100 om3 the author has found that in his 

 experience the filtrate and washings from the ferrous sulphide 

 will occupy a volume of about 350 cm \ An absolute volume of 

 400 cm3 was therefore chosen as a convenient one in which to 

 make the precipitation of titanium. Accordingly experiments 

 (7) and (8) were performed with the object of learning the 

 quantities of sulphuric acid and of tartaric acid necessary to 

 effect a good separation in the above given absolute volume. 

 In these two experiments the concentration of sulphuric acid 

 was the same as in experiments (4) and the tartaric acid in- 

 creased somewhat over the amount previously used. Since 

 the results of experiments (7) and (8) were satisfactory it was 

 not thought necessary to carry the series further. 



The second series of experiments was begun with the object 

 of determining how great a concentration of sulphuric acid 

 could be employed in the presence of tartaric acid without any 

 resultant loss of titanium. The mode of procedure was the 

 same as in the separation of titanium from aluminum except 

 that in experiment (9) the precipitate was washed with water 

 and in experiments (11) and (12) with hydrochloric acid (made 

 by diluting 100 cm3 of acid of sp. g.=l*20 to one liter). Since 

 in experiment (12) the concentration of sulphuric acid was 



