4H SCIENCE PROGRESS 



bend is connected to the flask D which acts as a receiver. 

 D is connected in series with the large aspirator G by 

 means of a U-tube E, tightly packed with soda lime, and a 

 tower of caustic potash F. The U-tube H, also containing soda 

 lime, and the caustic potash tower K are connected with the 

 air reservoir L containing sticks of moistened potash. When 

 the aspirator G is working, air enters the apparatus through a 

 minute orifice at the upper part of the tube M, which is filled 

 with soda lime. From the stopcock N to the side tube joining E 

 and F all parts of the apparatus are fused together, so that when 

 reasonable precautions are taken, leakage of carbon dioxide 

 from the air into bend C is entirely prevented. The other parts 

 of the apparatus are securely joined together by pressure 

 india-rubber tubing wired in place and having its surface 

 covered with vaseline. 



In an actual experiment a small cylinder of nearly pure 

 polished iron about 40 mm. long and 2 mm. in diameter was 

 placed in a bent piece of dry glass tube containing sufficient 

 of a 1 per cent, solution of chromic acid just to cover the 

 iron. A slow current of air was drawn through the apparatus 

 for about three weeks so as to remove all traces of carbon 

 dioxide. The dilute chromic acid solution served to keep the 

 iron clean and free from rust while the carbon dioxide was being 

 removed. Water was then distilled from the flask A, which 

 contained a 1 per cent, solution of barium hydroxide, until 

 all the chromic acid was washed into the receiver D. During 

 the distillation the cock N was closed and, with the object 

 of preventing carbon dioxide from finding its way into the 

 apparatus through a sudden inrush of air, care was taken to 

 cool the apparatus very 'slowly after distillation. Air was 

 then drawn slowly through the apparatus during about six 

 weeks. 



In the earlier experiments it was found that after this period 

 the iron remained perfectly bright with the exception of those 

 parts which rested on the glass, where a slight discoloration was 

 visible. As interaction between the glass and iron appeared to 

 take place, precautions were taken to avoid contact between 

 these substances. The ends of the small iron cylinders were 

 therefore covered with small blobs of purified paraffin wax : in 

 this way the metal was caused to lie in the bend of the tube 

 without touching the glass, the position being such that as each 



