20 



CHEMISTRY. 



SECT. V. OfPaHadinm. 



~ This metal was lately discovered by Dr Wollaiton, 

 in crude plat ma. Mr Chenevix announced soon af- 

 ter that he had succeeded in forming this metal arti- 

 ficially, by combining together platinum and mer- 

 cury ; but as nobody has been able to repeat his 

 experiment with success, we must suppose him mis- 

 taken. 



To obtain palladium, dissolve a sufficient quantity 

 of crude platina in nitro-muriatic acid, and pour a so- 

 lution of the salt called ]>rn*r-ili- at iiirrciiri/ into the 

 liquid. A yellowish white powder falls When this 

 powder is washed and dried, and exposed to a red 

 heat, it leaves a white matter, which is jxilladium. 

 When strongly heated with sulphur and borax, it may 

 be melted into a button. 



Properties. J. Palladium thus obtained is a white metal, very 

 like platinum in its appearance. Its specific gravity, 

 when hammered, is 11.871. It is as malleable as 

 platinum, breaks with a fibrous fracture, and appears 

 of a crystallized texture. It is not altered by ex- 

 posure to the air, and a very violent heat is necessary 

 to fuse it. 



'_'. When kept strongly heated, its surface acquires 

 a blue colour. This is supposed a commencement of 

 oxydizement. A more violent heat maki-s it resume 

 the original metallic appearance. Sulphuric, nitric, 

 and muriatic acids dissolve a portion of it when as- 

 sisted by heat, and assume each a red colour. Nitro- 

 muriatic acid iu the best solvent of it. 



3. Neither hydrogen nor carbon combine with this 

 metal. But when brought into contact with sul- 

 phur while red hot, it melts immediately, and the sul- 

 phuret formed continues in fusion till only obscurely 

 red. It is rather paler than the pure metal, and very 

 brittle. 



4. The simple incombtistibles do not combine with 

 palladium ; but it unites with the metals, and forms 

 alloys, wh'ch have been examined and described by 

 Mr Chenevix. 



SECT. VI. Of ntioditim. 



This metal exists also in crude platina, and was 

 l " n ' discovered by Dr Wollaston still more recently than 



the last. 



How pro- The process followed by Dr Wollaston for obtain- 

 cured. ing it, is somewhat complicated. Crude platina is 

 dissolved in nitro muriatic acid, and the platinum 

 precipitated by sal ammoniac. A piece of clean zinc 

 is immersed into the residuary solution, which throws 

 down a black powder. This black powder is digest- 

 ed with dilute nitric acid in a very gentle heat, to dis- 

 solve some copper and lead with which it is frequently 

 contaminated. It is then disoolved into nitro-muriatic 

 acid, common salt is added to the solution, and the 

 wholi- is gently evaporated to dryness. The residuum 

 is washed repeatedly with small quantities of alcohol, 

 which dissolves two salts, consisting of the oxides of 

 platinum and palladium in combination with common 

 salt. There remains behind a deep red-coloured nub- 

 (lance, consisting of the oxide of rhodium united to 

 common salt. By solution in water, and gradual 



evaporation, rhomboidal crystals of a deep red CO- Elemcou 

 lour are obtained. These crystals being dissolved ' 

 in water, and a plate of ?iric immersed into the solu- 

 tion, a black powder precipitates, which being strong- 

 ly heated with borax, becomes white, and assumes a 

 metallic lustre. In this state it is rhodium. 



1. Rhodium thus obtained, is white. Its specific Propcrtisit 

 gravity exceeds 11. No degree of heat hitherto ap- 

 plied is sufficient to melt it. Of course its malle- 

 ability and other similar properties are unknown. 



2. It is not oxidized by exposure to heat and air. 

 Neither is it much acted on by acids. The only 

 oxide of rhodium known is of a yellow colour. It 

 may be obtained by disolving the red crystals men- 

 tioned above, and precipitating by mean* t pta*h. 

 This oxide, when dissolved in nitric or muriatic acid, 

 does not crystallize. 



S. It unites readily with sulphur, and by that 

 means is easily melted. When the sulphur is driven 

 off by heat, the metallic button obtained is not mal- 

 leable. The action of the other simple combustibles 

 is not known. 



4. It does not combine with the simple incombus- 

 tibles. It forms alloys with all the metals tried by 

 Dr Wollaston, except mercury, with which it does 

 not combine. It does not, like platinum and palla- 

 dium, destroy the colour of gold when alloyed with 

 it. 



SECT. VII. Of Indium. 



This metal was discovered by Mr Smithson Ten- indium, 

 nant, in 1803. Attempts were made by DescosuU, H 

 and by Fourcroy and Vauquelin soon after, to obtain curc d. 

 the rame metal, but they succeeded but imperfectly. 



When crude platina is dissolved in nitro-nuiriatic 

 acid, a black powder remains, which preceding che- 

 mists considered as plumbago, but which Mr Tmnant 

 ascertained to be a compound of two new metals. 

 When kept for some time in a red heat, mixed with 

 its own weight of potash in a platinum crucible, water 

 poured on the mixture forms a deep orange-coloured 

 solution. Muriatic acid being digested on the pow- 

 der which remains, becomes first blue, then green, 

 and at last deep red. By repeated fusions with pot- 

 ash, and digestions in muriatic acid, the whole ot the 

 black powder is decomposed and dissolved. The 

 potash solution contains the metal called omnium ; the 

 muriatic acid solution the metal called iriniiiiH. 



A piece of zinc being put into this la.-t solution, 

 precipitates' a black powder; when heated it becomes 

 white, and U indium. 



1. It has the appearance of platinum, and seems Propeitiei. 

 as difficult of fusion as that metal. It resists the 



action of acids, even the nitro muriatic, almost com- 

 pletely. 



2. Its affinity for oxygen seems weak ; but, like 

 other metallic bodies, it unites with that principle. 

 The change of colour which its solution in muriatic 

 acid assumes, teems to prove that it is capable of 

 combining with different dozes of oxygen. When 

 the colour is /////<, the metal seems oxidized to a 

 minimum; when nil, it seems oxidized to a maxi- 

 mum. 



3. The simple combustibles do not eeem to com- 



