476 GOLD, PLATINUM, PALLADIUM, & c . 



Now, as 4-5 is equivalent to an atom of chlorine, 

 Atom of 3.75 mu st represent the atomic weight of iri- 



iridium. 



dium. 



I repeated this experiment twice, employing 

 each time 8*25 'grains of chloride .of iridium ; 

 because my stock of salt had been too much ex- 

 hausted by the preceding trials to allow me to 

 employ a greater quantity. These two experi- 

 ments did not quite agree with each other ; the 

 first leaving a greater quantity of iridium than 

 3*75 grains, and the second a smaller quantity : 

 the mean of the two made the quantity of iridi- 

 um amount to 3*88 grains. This approaches as 

 near to 3*75, the atomic weight deduced from 

 the first experiment, as could be expected, when 

 we take into view the very small scale on which 

 the experiments were made. For when we em- 

 ploy in our trials very small quantities of matter, 

 exact results are not to be looked for ; because 

 the unavoidable inaccuracies arising from weigh- 

 ing, or from want of absolute correctness in the 

 weights which we employ, bear too great a pro- 

 portion to the whole quantity used. But the 

 first experiment, which was made with great care 

 upon a quantity sufficiently great for accuracy, 

 gives us, I conceive, the true atomic weight of 

 iridium. 



I believe the crystals usually called muriate of 

 iridium should be called chloride of iridium; 

 for the loss of weight being only -625 per cent., 



