336 Hileman — Alkalimetric Estimation of Silicon Fluoride. 



A Specially Devised Apparatus for use at High Temperatures, 



Owing to the lack of success with the silicon fluoride pro- 

 cesses in which the decomposition was effected at temperatures 

 between 150°-160°, an attempt was made to devise a simple 

 and convenient form of apparatus in which the acid mixture 

 might be heated to boiling to facilitate the removal of the 

 silicon fluoride to the absorption system. 



After a number of experiments with this end in view the 

 following model of apparatus was found to be the most satis- 

 factory : a glass stopper, made by drawling out a glass tube 

 l cm in diameter and sealing a small glass tube on each end, is 

 ground into a 70 cmS side neck flask. To one end is sealed 

 a glass stop-cock. The other end extends to the bottom 

 of the flask. The side neck is sealed to a Yoit flask. The 

 length of the tube between the two flasks is 17 cm , and it is 

 bent at right angles, 12 cm from the Yoit flask. The tube lead- 

 ing from the Yoit flask enters a large empty U-tube through 

 a rubber stopper. A tube from the other limb of the U-tube 

 enters a trap loaded with phosphorus pentoxide. A rubber 

 connection joins the trap with the delivery tube of the absorp- 

 tion apparatus described above. Connected with the absorp- 

 tion tube is a pressure regulator. This consists of a T-tube, 

 one opening of which enters a test tube of mercury through 

 a rubber stopper. Another perforation is closed with a glass 

 tube which may be raised or lowered in the mercury. The 

 third opening of the T leads to the aspirating pump. 



Preparatory to making a determination the apparatus is 

 carefully dried. The tip of the delivery tube is then placed 

 beneath the surface of the mercury in the absorption tube and 

 distilled water is added, care being taken that enough space 

 remain for the rise in level when air bubbles are in the liquid. 

 The pressure regulator is then connected with the absorption 

 tube and adjusted so that a rise of pressure in the apparatus 

 should be relieved but no appreciable vacuum created. The 

 U-tube is then immersed in a vessel of cold water and connected 

 with the trap. Next, the mineral, together with quartz powder 



