118 Messrs. Hughes and Wilson on the Action of 



We wish it to be distinctly understood that these experi- 

 ments are only of a preliminary character, and that the 

 method adopted for drying this exceedingly hygroscopic gas 

 was probably not sufficient to insure absolute freedom from 

 moisture. 



The apparatus which was used in these investigations was 

 as follows : — 



To two of the branches of a three-way tube were attached 

 respectively a Kipps' apparatus for the production of carbon 

 dioxide, and a flask in which was generated the hydrochloric 

 acid (the hydrochloric acid being made either from concen- 

 trated sulphuric acid and sodium chloride or by dropping 

 concentrated sulphuric acid into a saturated solution of 

 hydrochloric acid in water). The current of gas was regu- 

 lated by means of stopcocks. 



The gas passing from the three-way tube bubbled through 

 concentrated sulphuric acid, whence it was conducted through 

 the purifying and drying apparatus, which was made up of, 

 firstly, a tube filled with copper turnings to remove any 

 chlorine that might be present, next through four straight 

 tubes containing small lumps of pumice moistened with 

 concentrated sulphuric acid previously boiled, each of which 

 tubes was about a foot in length, then it passed through two 

 tubes containing pumice and phosphorus pentoxide, of lengths 

 respectively 6 and 18 inches. 



Finally, the gas was led through a series of four pentoxide 

 bulbs, to which was attached the experimental tube contained 

 in an air-bath, beyond which was placed a drying-tube of 

 calcium chloride ; the issuing gas was passed into a wash- 

 bottle containing sodium hydrate. 



The method of experiment was this : — 



Carbon dioxide having been passed through the apparatus 

 for a sufficient length of time to remove the air, the 

 experimental tube, being maintained at a temperature of 

 about 130° Centigrade, was sealed and weighed. 



The tube was replaced, the ends were cut off, and a stream 

 of hydrochloric-acid gas was passed through for about an 

 hour ; the current of hydrochloric -acid gas was then stopped 

 and carbon dioxide was driven through to remove the hydro- 

 chloric acid. It was, however, found so difficult to remove 

 the hydrochloric acid from the sulphuric-acid drying-tubes, 

 that these were replaced by a series of calcium-chloride tubes, 

 with the result that in a short time the last traces of hydro- 

 chloric acid were removed. 



The tube was again sealed, it having been raised to a 

 temperature of about 130° Centigrade before sealing. It was 

 then weighed together with the ends previously cut off. 



