^fi On some Comlinations 6f Ptat'ma* 



way, I have not been able to combine platina with mortf 

 than about 6 per cent, of chlorine, though the metal was 

 in a very minute state of division, and successively heated 

 in the gas. The circumstances unlavourable to perfect 

 combination in the experiment, are the extreme density of 

 the particles of the metal, the small surface exposed, and 

 the facility with which the partial compound is again de- 

 composed by the agency of heat*. Probably the true 

 compound might be formed in this way, by employing ex- 

 tremely fine platina leaf. 



The best mode 1 have found of procuring platinana, 13 

 to boil pure platina in test muriatic acid, and to add occa- 

 sionally a little nitric acid; the solution, after being evapo- 

 rated to dryness, is treated with a small quantity of muriatic 

 acid, which is again expelled. The dry mass is then cau- 

 tiously heated nearly to redness, and afterwards boiled with 

 a considerable quantity of distilled water, to separate any 

 platinane that may be present : after being washed and dried 

 it is the substance in questiouj and exhibits the following 

 properties. 



Phyidcal and Chemical Properties. 



Its colour is dull olive brown or green. It is obtained 

 in small lumps, which are easily reduced to fine powder. 

 It has rather a harsh feel. It has no smell or taste. It is, 

 ififusible. It is not apparently affected by the atmosphere;" 

 at least no difference could be perceived in its weight or 

 other sensible properties, when 10 grains had been thus 

 exposed for about four days. It is nearly insoluble in vi'ater. 

 When it is kept in contact with this fluid, a minute portion 

 appears to be dissolved or decomposed, and nitrate of silver 

 occasions a slight precipitate : the effect is increased when it' 

 is boiled in water. When a little of it is kept for several 

 days in water, a slight pellicle forms on the surface, having 

 the metallic lustre: it is probal)lv the platina revived. This 

 effect seems to be connected with the agency of light, for 

 I found that it did not take place under similar circum-' 

 stances in darkness. The direct solar rays effected no 

 change on platinana rubbed on paper, after an exposure of 

 several hours. When healed on a thin slip of platina it 

 assumes a dark-brown colour ; at a red heat the chlorine is 



* It is perhaps worthy of notice, that several of the combinations ot 

 platina in their relations to temperature, seem to exhibit remarkable pecu- 

 liarities. 'I hus the c<'mpi>und of |n>tash and oxi'le of platina, platinana, &c. 

 are only formed a. cer ain te.npcrauires; at lower dcjirees of heat the com-' 

 pounds arc not forrncd, and at higher they are d'ecbmposed. 



expelled. 



