8 ELECTROCHEMICAL INVESTIGATION OF LIQUID AMALGAMS 



PREPARATION OF THE AMALGAMS. 



The thallous sulphate used in preparing the thallium amalgams was a 

 sample which had been many times recrystallized, both as acid sulphate 

 and as sulphate. The original preparation had been of a high grade of 

 purity. The indium amalgams were prepared from a sample of very pure 

 indium, which, through the kindness of Professor L. M. Dennis, of Cornell 

 University, was available for this work. 23 The sample in question had 

 been carefully purified for use in the determinations of the atomic weight 

 of indium, although it was not the purest specimen used for this purpose, 

 and was finally fused in a current of hydrogen. It contained no impurity, 

 except a trace of iron. Metallic tin was obtained by the electrolysis of an 

 acid solution of pure stannous chloride, using a pure carbon anode. The 

 fine needles of tin were washed with distilled water and alcohol and dried 

 in a desiccator over sulphuric acid. 



Pure mercury was obtained as follows : Crude mercury was shaken 

 first with sulphuric acid to remove the major part of the metallic impuri- 

 ties and then for some time with dilute nitric acid and mercurous nitrate. 

 The sample was now wholly free from contamination with the more 

 electropositive metals. It was then distilled under a pressure of 20 mm. 

 of hydrogen in an apparatus somewhat similar to that described by 

 Hulett. 24 The hydrogen was passed through three towers, containing 

 solid potash, in order to purify and dry it. The entire apparatus, as far 

 as the connection to the pump, was wholly fused together in order to avoid 

 rubber connections or glass joints. The pipettes in which the mercury 

 was kept were themselves used as the receivers of this still, and the 

 mercury was sealed in them without for an instant coming in contact with 

 the air. The stopcock, regulating the supply of gas bubbling through the 

 mercury, was lubricated with sirupy phosphoric acid. The mercury thus 

 obtained must have been very pure. Distillation in air, recommended by 

 Hulett, affords an excellent means of oxidizing other metals present; but 

 our experience leads us to fear that the product contains a trace of 

 dissolved oxygen. Accordingly, we used hydrogen instead of air. 



The water used in making up the solutions was distilled twice, first 

 from an alkaline permanganate solution, and then from very dilute 

 sulphuric acid. 



Since amalgams of all the metals studied are very susceptible to oxida- 

 tion, they were made and introduced into the measuring apparatus wholly 

 out of contact with the atmosphere, and the mercury from which they 

 were made was never allowed to come into contact with the air after its 

 distillation in rarified hydrogen. 



23 For details of purification of this indium see Jour. Amer. Chem. Soc., 29 (1907). 



24 Zeit. phys. Chem., 33, 611 (1900). 



