86 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



EATIO OF SILVER TO BARIC CHLORIDE. 

 Third Series : Second New Method. 



During a large part of the considerable time consumed by these 

 analyses, experience with the comparison of opalescence was gradu- 

 ally being acquired. The details of this method have been so fully 

 given by Stas that further mention of them need not be made here. 

 For the final experiments the baric chloride was dissolved in a large 

 amount of water, and decomposed by a very slight excess of argentic 

 nitrate in very dilute solution, the silver having been weighed and 

 dissolved with the greatest care. After the mixture had been shaken 

 occasionally for a number of days, it was allowed to settle, and two 

 portions of twenty-five cubic centimeters each were taken out with a 

 pipette. A little hydrochloric acid produced a more evident opales- 

 cence in one of these portions than an equivalent amount of silver did 

 in the other, showing that too much silver had been taken. Known 



* The last two of these determinations formed a continuation of Experi- 

 ments 28 and 29 already given, and the calculation of the amount of anhydrous 

 baric chloride need not be repeated. The actual weight of ignited baric chlo- 

 ride taken in Experiment 39 was 2.64851 grams (in vacuum) ; but this was 

 found to require a correction due to loss of chlorine amounting to 0.00025 

 grams. The corrected weight is given in the table. Since the salt used in 

 Experiment 38 was ignited in hydrochioric acid gas, no correction was neces- 

 sary. In Experiment 38 the weight of silver given in the third column is 

 0.00020 gram less than the amount actually weighed, because 0.20 cubic centi- 

 meter of standard hydrochloric acid was added to determine the neutrality of 

 the baric chloride before the precipitation. 



