i Milligramme 



Equivalents. 



11-593 



In Milligrammes, 

 absolute weight. 

 1088-0 



11-455 



252-0 



0-019 



2-2 



HYDRATES AND CARBONATES OF THE ALKALI-METALS, ETC. 467 



Rubidia, R 2 0, 

 Carbonic acid, . 

 Oxide of platinum, 



Total, . 1342-2 

 Which is 4 mgrm. more than the substance analysed, . 1338*2 



From the quotients it would appear that the substance contained 0*138 eqq. of rubidia 

 not carbonate in 11*593 eqq. of total rubidia; yet the chloride of barium test showed no 

 free alkali at all. 



It is rather remarkable that fused carbonate of rubidia at a red heat attacks platinum, 

 even in an atmosphere of hydrogen, nitrogen, or carbonic acid. Id the case of hydrogen 

 an appreciable quantity of caustic rubidia is formed independently of the action of the 

 platinum ; but whether a similar assertion holds in the case of nitrogen or carbonic acid, 

 my analyses are not sufficiently exact to show. I hope, one day, to repeat these experi- 

 ments in gold vessels, and to thus settle the question. 



SUMMARY. 



I. Regarding the Hydrates. 



The hydrates of barium and lithium, if kept at a red heat in an atmosphere of 

 hydrogen, quickly lose their water, and become pure monoxides, obviously a plain case 

 of dissociation in which the hydrogen plays no chemical part. The result, no doubt, 

 would be the same in an atmosphere of nitrogen, or in a vacuum. The behaviour of the 

 hydrates of the alkali-metals, properly so called, still remains to be ascertained. 



II. In regard to the Carbonates. 



1. Carbonate of baryta, if kept at a red heat in hydrogen, gradually loses its carbonic 

 acid, and at last leaves a residue of pure oxide. In an atmosphere of nitrogen no 

 decomposition takes place. 



2. Carbonate of litliia, at a red heat in hydrogen, loses its carbonic acid very slowly, 

 but at last completely, and is reduced to Li 2 0. 



In an atmosphere of nitrogen, the same reduction takes place, but it proceeds still 

 more slowly. A residue obtained after ten hours' heating had, approximately, the 

 composition Li 2 + Li 2 C0 3 , indicating the existence of a relatively stable basic carbonate. 



In an atmosphere of carbonic acid, of any pressure from 30 to 60 inches of 

 mercury, normal carbonate remains. The composition of this carbonate shows that the 

 atomic weight of lithium is less than 7*00, the value demanded by my analyses being 

 6*98±0*01. 



3. Carbonates of Soda and Potash. — These carbonates, if kept at a red heat in an 

 atmosphere of carbonic acid, remain unchanged ; in an atmosphere of nitrogen or 



