igo 5 .] 



HALL AND SMITH— COLUMBIUM. 199 



Known amounts of the two hydrates were next treated together 

 as in the following experiments. 



6. 0.2816 gram of K 2 TiF 6 , containing .0939 gram of Ti0 2 , and 

 0.5078 gram of K 2 CbOF 5 H 2 0, containing 0.2255 gram Cb 2 5 , 

 were treated with 50 grams of water and 15 grams of sulphuric acid 

 (sp. gr.= 1.435) f° r f° ur hours. The amount of oxfde remaining 

 insoluble was only .07 gram. It was not examined as to its titan- 

 ium content. 



7. The hydrate from o. 2420 gram K 2 TiF 6 , containing .0807 gram 

 Ti0 2 , and that from 0.3454 gram of K 2 CbOF.H 2 0, containing 

 0.1537 gram of Cb 2 5 , were covered with 70 grams of water and 5 

 grams of sulphuric acid of sp. gr. 1.435. The amount of oxide in 

 solution after four hours was 0.0800 gram, corresponding well with 

 the weight of the oxide of titanium present, but the insoluble portion 

 was found to contain 0.0350 gram of Ti0 2 , determined colorimet- 

 rically ; so that only about one-half of the titanium hydrate had 

 been dissolved out while nearly as much columbium hydrate had 

 gone into solution. The acid used would not have dissolved any 

 columbium hydrate had it been free from titanium hydrate ; further 

 it would have dissolved out all of the titanium hydrate had it not 

 been mixed with the columbium hydrate. It may, therefore, be 

 concluded that this method of separation is worthless. It remains 

 to be seen how haloid acids would act. 



THE CHROMOTROPIC ACID TEST FOR TITANIUM. 



Geisow (Dissertation, 1902) observed that the color developed 

 by chromotropic acid with titanium solutions offered a very deli- 

 cate test for that element. In concentrated solution it gives a deep 

 red, in dilute solutions, a pink color. The color-giving compound 

 was isolated by Geisow and found to have the following composi- 

 tion : one molecule of chromotropic acid to four of Ti0 2 and nine 

 of H 2 0. 



As it was most important to find some means of estimating the 

 amount of titanium in columbium we were induced to study this 

 reaction of Geisow, using solutions of titanic hydrate in oxalic, 

 sulphuric and hydrochloric acids. 



Solutions used : 



(A) 0.53 gram of Ti0 2 dissolved in 3.42 grams of oxalic acid 

 and diluted to 500 c.c. 1 c.c. = .00106 gram of TiO, and con- 

 tained .00684 gram of oxalic acid. 



