; 



254 On the Cause of Chemical Proportions. [April, 



oxygen the oxymuriatic gas disengaged from muriate of rhodium 



contained. Consequently, by linding the composition of tlie 



muriate, we find Hkewise that of the oxide. Muriate of rhodium 

 is composed of 



Muriatic acid 17*5544 



Oxide of rhodium S2-445G 



. 100-0000 - 



And the oxide of rhodium is composed of 



Rhodium 93712 . .-.•.lOO'OO 



Oxygen 6-2S8 .... G'71 



100-000 



We have it now in our power to determine the composition of 

 the oxide, formed by combustion in contact with potash and salt- 

 petre. The 143-3 of muriate of rhodium contain 1 16-804 of 

 oxide of rhodium, in which there are 7'344 of oxygen (for 

 127 : 97 :•• 143-3 : 109-46). The 37 parts of muriate of potash 

 contain 23-56 of potash, and if we add 23-56 to 116-o04, we ob- 

 tain 140-364. But the oxide employed in the analysis weighed 148 

 parts. Therefore, 7 '6'36 are wanting. This loss (abstracting the 

 inevitable loss in such an analysis) must be tlie oxygen carried off 

 by the muriatic acid. But the oxygen lost is equal to tlie quantity 

 found in tiie oxide of the muriate. Hence it follows that the 

 oxide, comliincd with the potash, must contain twice as much 

 oxj'gcn as that in tlie muriate. Tlie oxygen of the potash com- 

 bined with the oxide of rhodium is 3*99, and 3-99 x 2 = '/•dS. 

 Tiiat is to say, that the peroxide of rhodium contains 4 times as 

 mucli oxygen as the potash with which it is combined. The sur- 

 ]>Ius of oxygen, which we find in this result, appears to draw its 

 origin fi'om the triple muriate with which the muriate of potash 

 was impregnated. The peroxide of rhodium may be separated 

 from the potash by acids ; but it cannot combine with them with- 

 out losing a portion of its oxygen. 



Dr. WoUaston has made us acquainted with rliodium in a state 

 of combination to which the metal cannot be brought either by 

 nitromuriatic acid or oxydation by means of heat, and which 

 would certainly have remained long unknown, if rhodium had not 

 been discovered in combination with platinum. This form of com- 

 bination is the soda-muriate of rhodium, from the colour of which 

 Dr. Wollaston derived the name of t!ie metal. I precipitated a 

 solution of this muriate, prepared by Dr. Wollaston, by adding a 

 small excess of caustic potash. An orange coloured precipitate 

 fell, wliich after some time divided into tv,o layere. I'he under- 

 most was thin, very heavy, and yellowish; the uppermost was more 

 bulky, light, and of a reddish colour, like tlic hydrate of iron. I 

 collected as much of it as I could, without mi.King it with the 



'? 



