378 Gooch and Howland—lodometvic Method, etc. 



potassium iodide and estimated by standard sodium thiosul- 

 phate. In handling the larger amounts of tellurium we found 

 it desirable to make the preparation of the telluric acid in 

 the distilling flask and to boil out the oxygen and ozone set 

 free in the preparation before proceeding with the operation. 

 The apparatus which we used consisted of a Voit's gas-wash- 

 ing flask, with sealed-in inlet tube and ground-in outlet tube, 

 used as the distillation flask, to which was joined by a sealed 

 joint the inlet tube of a Drexel washing bottle to the outlet 

 tube of which was sealed a Will and Varrentrapp absorption 

 apparatus. The washing bottle and attached bulbs contained 

 a solution of 3 grams of potassium iodide and the former was 

 kept cool by standing it during the distillation in a vessel of 

 cold water. The absorption of the bromine took place almost 

 entirely in the bottle, only traces of iodine being, set free in 

 the bulbs. The results of our experiments are recorded in the 

 accompanying statement ; Te = 127, = 16. 





Initial 



Final 



Te0 2 



Te0 2 







volume. 



volume. 



taken. 



found. 



Error. 





cm 3 . 



cm 3 . 



grm. 



grm. 



grm. 



(1) 



50 



20 



0-0102 



0-0098 



0-0004 — 



(2) 



50 



20 



0-0102 



0-0099 



0-0003 - 



(3) 



50 



20 



0-0102 



0-0098 



00004 — 



(4) 



50 



20 



0-0102 



0-0098 



0-0004-- 



(5) 



100 



40 



o-iooo 



0-0994 



0-0006 — 



(6) 



80 



40 



o-iooi 



o-iooi 



o-oooo 



(?) 



100 



20 



01002 



o-iooi 



o-oooi — 



(8) 



50 



20 



01000 



0-1003 



0-0003 + 



( 9 ) 



50 



25 



0-5011 



0-5008 



0-0003 — 



(10) 



50 



25 



0-5002 



0-5006 



0-0004 4- 



(11) 



50 



25 



0-5000 



0-4998 



0-0002 — 



(12) 



50 



20 



0-5000 



0-4994 



0-0006 — 



The results of experiment agree fairly well with one another 

 and with theory based upon the assumption that the atomic 

 weight of the tellurium which we employed was 127. It is 

 evident that the reducing action of the hydrobromic acid 

 developed in the distillation is regular and that that agent is 

 well adapted to the reduction of telluric acid to tellurous acid. 

 The formation of tellurium tetrabromide in the concentrated 

 acid liquid makes it impossible to tell by the color when all 

 the bromine has been distilled, but the evidence of the experi- 

 ments goes to show that the boiling of the liquid from a 

 volume of 50 cm 3 to 25 cm 3 is sufficient, while concentration 

 from 100 cm 3 to 20 cm 3 apparently does no harm. 



