56 ELECTROCHEMICAL INVESTIGATION OF LIQUID AMALGAMS 



cases solid amalgams could be seen floating on the liquid amalgam in the 

 pipettes. Hence it was evident that the solubility of lithium in mercury is 

 about 0.036 per cent. This agrees well with the observation of Kerp and 

 Bottger," who obtained a solid amalgam containing 0.69 per cent to 0.72 

 per cent (having approximately the formula LiHg 5 ) from a mother-liquor 

 containing 0.04 per cent of lithium. In view of these facts it is evident 

 that Cady was much in error in his supposition that his amalgam contained 

 1.8 per cent of lithium far more than corresponds even to the solid 

 amalgam. In answer to our personal enquiry, Professor Cady states that 

 the cause of this error was a defective method of analysis, which multiplied 

 by 50 the absolute amount of lithium in each amalgam, but did not affect 

 the ratio of the two concentrations. 



The saturated liquid amalgam, whose preparation is described above, 

 we diluted to form two less concentrated amalgams, and these were driven 

 into the pipettes under hydrogen in the usual manner. Analysis showed 

 them to contain 0.0255 per cent and 0.0144 per cent of lithium respectively. 

 With these amalgams a cell was set up, two cups being filled with each. 

 No constant readings could be obtained, but the value 0.0169 w ^ tn a P os ~ 

 sible error of 0.0002 volt was indicated. The electromotive force deduced 

 from the simple concentration law equation is 0.0159; hence it appears 

 that, as had been expected, lithium ranks with lead, thallium, and indium 

 rather than with zinc and tin. It is pleasant to note that this result agrees 

 qualitatively with the outcome of Cady's experiments, in spite of their 

 inconsistency of detail. 



The cell on standing rapidly changed in potential, and in a few hours a 

 number of small crystals were observed in the electrolyte, which itself 

 had assumed a dark -brown color. Hoping to establish a constant con- 

 dition in a fresh portion of the electrolyte, in order to obtain better results 

 upon refilling the cell, we allowed the solution of the chloride in pyridine 

 to stand over metallic lithium. In a few days the pyridine had become of 

 a dark -blue hue, which upon opening the bottle disappeared in a very few 

 moments. In a similar bottle containing pyridine and lithium, but no 

 lithium chloride, no blue color was formed, but nevertheless the lithium 

 attacked the solvent in another way, and a brown powder was deposited. 

 It thus appears that dry lithium attacks dry pyridine, and the hope of 

 obtaining really satisfactory results in this way was dispelled. 



Several other series of potential measurements were tried, in some of 

 which lithium sulphate took the place of the chloride in the electrolyte; 

 but the series recorded above was the most satisfactory. More dilute 

 amalgams gave more erratic potentials. In some cases a potential of over 

 one volt was observed for several minutes, in the case of a cell where 

 about 0.02 volt was the value which theoretical considerations would give. 



"Zeit. anorg. Chem., 25, i (1900). 



