254 M. Andre del Rio*s Analyns of [Oct. 



gravity, according to Citizen Mendez, was 15. I suppose its 

 specific gravity was diminished by the three-eightlis of a grain 

 of silver which it contained ; but it is, at all events, clearly 

 demonstrated that rhodium easily amalgamates with mercury, 

 by the intervention of gold, although it will not do so alone. 1 

 must confess I was much deceived as to my principal object of 

 knowing if this alloy be obtained at the Parting House from the 

 fused silver ingots, or from the amalgamated silver, which 

 would not a little have assisted us in ascertaining its local situa^ 

 lions, and the ores from which it is derived, cittjumstances 

 which at present we are ignorant of. 



b'4. Having found by experiment that neither protosulphate of 

 iron, nor oxalic acid, precipitate rhodium, I dissolved the button 

 weighing 66*13 grains (whose specific gravity according to 

 Citizen Mendez was 15*48) in aqua regia. The button when 

 beat out under the hammer, for want of a flatting mill, presented 

 tin-white spots on the yellow ground, showing that the alloy 

 was not uniform ; the chloride of silver which precipitated from 

 the solution, contained half a grain of silver, which gives more 

 than three quarters of a grain per cent. This clearly shows 

 how necessary it is to use sulphuric acid to extract all the silver 

 at the Parting House. I meant to take only one half of this 

 solution, but for want of graduated tubes I took more, and pre- 

 cipitated it with protosulphate of iron ; the reduced button 

 weighed 30*7 grains, and its specific gravity was 19*07. On 

 addmg the protosulphate to the solution, it became as black as 

 ink, and red by refraction in the sun, with much eiFervescence 

 and disengagement of deutoxide of azote ; but as soon as that 

 ceased it resumed its former transparence. Having distilled it 

 to dryness, to expel the nitric and muriatic acids, and added 

 water, a large quantity of subsulphate of iron remained undis- 

 solved ; by the addition of a little sulphuric acid and boiling 

 the liquid, the whole dissolved, and the solution assumed a pale 

 bright flesh colour ; I then immersed in it a plate of iron, which 

 became copper red, but by washing in distilled water, the 

 coloured coating appeared very slight, and a very fetid odour 

 was exhaled, which I know not how to describe. I have per- 

 ceived the same odour on adding water to the alloy fused with 

 potash. After filtering and washing, sliglitly flexible pelHcles 

 remained, which, when dry, had the colour of tombac, and 

 weighed 10*6 grains. On attempting to reduce them entirely 

 with borax (for, according to Thomson's Chemistry, even the 

 protoxide may be reduced), I obtained merely a green glass. 

 Thus, considering them as metallic (for if they were not abso- 

 lutely, they >vere very nearly so) we shall have 25*4 per cent, of 

 rhodium in the alloy, without reckoning what still remained 

 alloyed with the gold. I had taken for that the lower half of 

 the solution which had been left at rest for a long time. Could 



