80 



WORK OF J. N. PEARCE. 



HYDROCHLORIC ACID. 



Having investigated fifteen salts, attention was next turned to the study of some 

 of the more common acids. 



An approximately 3 normal solution of hydrochloric acid was prepared. Dilute 

 portions of the mother-solution were then titrated against a standard solution of 

 potassium hydroxide free from carbonate. This, in turn, had been standardized by 

 means of a 0.1 normal solution of freshly prepared oxalic acid. The results are 

 given in table 61. 



Table 61. Hydrochloric Acid Data for Freezing-point and Conductivity Measurements, 



Specific Gravity, and Hydrates. 



A glance at table 61 shows that, for the more dilute solutions, the corrected ob- 

 served freezing-point lowering (Z/) is less than that calculated from the dissociation. 

 This is due to one of two causes the very high migration velocity of the hydrogen 

 ion or its inability to form hydrates. 



The minimum in the freezing-point lowering occurs at about 0.25 normal. For 

 dilutions greater than 0.5 normal, there is no evidence of hydration. At 0.5 normal, 

 however, the hygroscopic property of the molecular hydrochloric acid begins to pre- 

 dominate over the effect of decrease in dissociation. From this point the amount of 

 combined water increases with increase in concentration. The corresponding values 

 of H differ from those of the other electrolytes thus far studied in that they, also, 

 increase as the concentration increases. 



The values of H and M, for hydrochloric acid, are plotted in figs. 22 and 23, p. 62. 



