1890.] The Liquation of Gold and Platinum Alloys. 185 



A. Composed of about 880 gold to 050 platina. 



B. Composed of abont 700 gold to 120 platina. 



In the one case the maximum difference between the gold per- 

 centage is a variation of 032, viz., 887 on the outside against 883*8 

 at the centre of the alloy, and in the platinum 047*5 on the outside 

 against 052 '5 at the centre, an extreme variation of 005 is shown. 



In the other case the maximum difference between the gold per- 

 centage is a variation of 041, viz., 732*4 on the outside, against 694*1 

 at the centre of the alloy, and in the platinum 122 on the outside 

 against 166 at the centre, an extreme variation of 044. 



Thus showing indisputably that the platinum in cooling liquates 

 from the gold and becomes concentrated towards the centre of the alloy. 



In support of these experimental results I give the actual figures 

 obtained from six platinum-gold ingots, taken at different times and 

 of different qualities, as they occurred in the course of refining com- 

 mercially. Each of these bars, after melting and assaying, was 

 separately heated with a view to extract the amount of gold con- 

 tained. It will be at once seen that the higher percentage of gold 

 indicated by the assay of a portion cut from one end of the ingot is 

 not borne out by the actual amount of fine gold obtained by refining, 

 which, of course, truly represents the proportion of gold existing in 

 each bar. 



dumber. 



"Weight in 

 troy ounces. 



Platinum 

 by assay. 



Gold by 

 assay. 



Percentage of 

 gold by the 

 fine gold 

 actually 

 obtained. 



42 



728-5 



o-iii 



0-825 



0-812 



67 



355 -0 



0-120 



0-660 



0-630 



109 



589-5 



0-120 



0-800 



0-780 



126 



435-0 



0-045 



0-850 



0-845 



149 



480-5 



086 



0-842 



0-830 



188 



473-0 



o-iio 



0-830 



0*821 



These results prove that the percentage of gold in the outer portion 

 of ingots of platinum-gold alloy does not represent the true per- 

 centage of gold in the alloy, and that liquation does take place to an 

 extent which, independently of its scientific and metallurgical in- 

 terest, has, I believe, been by many overlooked up to the present 

 time in commercial transactions with such metal. 



The results given were observed in platinum-gold alloyed with 

 silver, with copper, and with both silver and copper ; but, in order to 

 prove whether or not such alloy had any tendency to carry the 



