94- Mr. R. Phillips's Experiments on Platina. 



to be exactly as indicated by the undulatory theory : if the re- 

 sults were not widely different from this, he would undoubt- 

 edly refer the difference to error of experiment. We see that 

 the experiment with the prism draws a clear line of distinc- 

 tion ; but from what I have observed, I believe the velocity 

 will not eventually be found extensively different from that 

 according to the said theory. The slightest difference is, how- 

 ever, of fatal consequence ; for the ratio ought, according to 

 common consent, to depend rigorously on the refractive index, 

 which is one of the fundamental principles of the theory. 



XVII. Experiments on Platina. By Richard Phillips, 



F.B.S. L. # E. $c. 

 HPHE third volume of the Quarterly Journal of Science 

 -*- contains a paper, by Mr. J. T. Cooper, On some Com- 

 binations of Platinum. In this communication the author 

 states, that when a neutral solution of tartrate of soda is heated 

 with one of muriate of platina, a blackish powder is precipi- 

 tated: this substance after being washed, was dried on a sand- 

 bath at 300°, in order to free it from uncombined water; it 

 lost afterwards 2*8 per cent, by exposure to a red heat ; and 

 as nothing could be procured from the black powder but 

 platina and water, Mr. Cooper considers it to be a hydrate of 

 the metal, composed of 44-328 == 2 atoms of platina -f 1*125 

 = 1 atom of water: these proportions agree tolerably well 

 with the results of the experiment. 



It is singular that Mr. Cooper does not particularly advert 

 to the interesting fact which he announces; for this is, I be- 

 lieve, the first instance on record of the combination of water 

 with a metal, not previously converted into an oxide; and it 

 is almost as remarkable, that of the numerous authors whom 

 I have consulted on the subject, no one mentions this com- 

 pound. 



Although, with some particular views, I have repeatedly form- 

 ed this black powder, it is only lately that I have investigated 

 its properties. Having dissolved some platina and precipitated 

 it in the manner described, I duly washed the powder and 

 dried it at 212°; after this I gradually heated it to redness, 

 and found that it diminished 1*41 per cent, in weight. This 

 experiment, slightly varied, was repeated with a difference of 

 only 0*14 per cent, in the weight lost. It will be observed 

 that although Mr. Cooper dried the precipitate at 300°, while 

 I subjected it only to 212° before heating it to redness, yet 

 I found the diminution of weight, caused by the subsequent 

 and higher temperature, to be but little more than half of that 

 which occurred in his experiment. 



