THE DENSITY OF ZINC AMALGAMS. 



II 



THE DENSITY OF AMALGAMS. 



Previous investigators appear to have mixed a weight, W , of amalgam of 

 concentration c x with a weight nW of mercury to form a new amalgam of 

 concentration, c 2 , and written 



= n -f- i. 



c n 



This assumption is not permissible in accurate work, as is shown by the 

 following investigation of the densities of zinc and cadmium amalgams. 



The zinc used for this purpose was electrolyzed from the " chemically 

 pure " zinc sulphate of commerce, in ammoniacal solution, and washed with 

 dilute ammonia, distilled water, alcohol, and ether ; it was dried in a vacuum 

 desiccator over strong sulphuric acid, to absorb all the ether vapor. The 

 mercury was shaken with strong sulphuric acid, and passed through a 

 tower 32 containing dilute nitric acid. The materials were weighed out into 

 a stoppered tube, covered with dilute sulphuric acid, and shaken until all the 

 zinc was dissolved. The sulphuric acid was pipetted off", neutralized with 

 ammonia, and its zinc content determined by titration 3S with a solution of 

 K 4 Fe(CN) 6 , i cc. == 0.003 gram zinc. The proper correction was then 

 applied to the weight of zinc taken. 



The pycnometer was of the Sprengel type, as modified by Ostwald ; S4 its 

 capacity was 5 cc, and its tubes 1 mm. in diameter. It was treated with 

 cleaning solution, and after washing thoroughly, dried with alcohol and 

 ether, followed by suction. When all was ready, the amalgam was hastily 

 dried with filter paper and drawn into the pycnometer ; the resulting oxida- 

 tion was too small to affect the density of the product. The pycnometer 

 was hung in a large beaker of water at a fixed temperature for a quarter 

 of an hour, after which the surplus amalgam was withdrawn through an 

 exceedingly fine capillary and the glass was wiped with a clean cotton cloth 



32 Ostwald-Luther, Hand- und Hiilfsbuch, p. 131 (Leipzig, 1902). 



33 de Koninck and Prost, Zeitschr. f. Angew. Chem., 1896, 460, 564. 

 "Ostwald-Luther, Hand- und Hiilfsbuch, p. 142. 



