Dried Hydrochloric- Acid Gas on Iceland Spar. 119 



Experiments were undertaken at the temperature of the 

 laboratory and at about 100° Centigrade. 



The weight of the Iceland spar taken in an experiment 

 conducted at the temperature of the laboratory was 

 •8705 gram. 



The weight after the passage of the hydrochloric-acid gas 

 was '8712 gram. 



The difference shows an increase of weight equal to 

 •0007 gram, 

 or a percentage increase of '08. 



Another experiment, conducted at the temperature of 

 95°-110° Centigrade, gave the following results : — 



The weight of Iceland spar taken = *6196 gram. 



The weight after passage of hydrochloric- 

 acid gas = '62025, 



which shows an increase = *00065, 



or a percentage increase = *1. 



The theoretical increase is 29 per cent. 



Tn order to compare our experiments with the dried gas 

 with the case in which the gas was not dry, the hydrochloric 

 acid before passing over the carbonate was caused to take up 

 moisture by passing through a tube in which moist glass 

 wool had been placed. This showed a very considerable 

 action, and the numbers are as follows : — 



The weight of calcium carbonate taken . = '68735 gram. 



The weight of the carbonate after the 



passage of the hydrochloric-acid gas = '70735. 



The increase shown is '02. 



Comparing this experiment with moist hydrochloric acid 

 with those in which the dried gas was used, we find that if 

 the action on the carbonate when moist hydrochloric-acid gas 

 was used be 100, then the action on the carbonate when dried 

 hydrochloric-acid gas was used becomes 2*66 and 3. 



If a piece of dry blue litmus-paper was placed in the tube 

 through which the dried gas was passing, no change of colour 

 was observed ; but if the gas was allowed to take up a small 

 quantity of moisture, then an immediate change to a red 

 colour was noticed. 



Glacial acetic acid was shown by Marsh to have no action 

 on litmus, and Gore showed the same for the liquefied dried 

 hydrochloric acid. 



An experiment was undertaken on the action of dried 

 hydrochloric-acid gas on witherite at the temperature of the 

 laboratory. 



The conditions of the experiment were the same as those 

 under which the experiments with calcium carbonate were 

 made. 



