IRiDIUM. 473 



SECT. V. 



OF THE ATOMIC WEIGHT OF IRIDIUM. 



I PREPARED a quantity of muriate of indium 

 from the black matter which remains when 

 crude platina is dissolved in nitro-muriatic acj$. 

 The process which I followed was nearly that 

 pointed out by Vauquelin in his paper on os- 

 mium and iridium. This black matter was 

 found to contain a very considerable proportion 

 of iron and some titanium ; the quantity of in- 

 dium which it yielded was much less than I had 

 anticipated. 



1. Muriate of iridium crystallizes in tetrahe- Properties 

 drons ; it has a great deal of lustre, and a brown 

 colour so deep that the salt appears black. Its 

 taste is intensely bitter and astringent ; its solu- 

 tion in water has a red colour, so deep that the 

 liquid continues opaque even after it has been a 

 good deal diluted with water. When so much 

 diluted as to be transparent, the colour appears 

 yellow. 



The aqueous solution of muriate of iridium is 

 rendered colourless by the addition of a few 

 drops of any of the following bodies : 



Gallic acid, 

 Prussiate of potash, 



