J. W. Mallet on the Atomic Weight of Lithium. 351 



in contact with muriatic acid in a gas cylinder rilled with mer- 

 cury, and the carbonic acid evolved was measured. It was 

 found in one experiment =60*98, and in another =61*00 per cent 

 of the carbonate of lithia. Hermann also dissolved this carbon- 

 ate in sulphuric acid, evaporated to crystallization, and dried the 

 crystals of sulphate of lithia over a spirit-lamp. 100 parts of 

 the dry salt gave an amount of sulphate of baryta correspond- 

 ing to 74 parts of sulphuric acid. 



In 1831 Berzelius* repeated the experiments of Hermann, 

 and with the following results. 4*4545 grm. of fused carbonate 

 of lithia dissolved in sulphuric acid gave 6*653 grm. of sulphate 

 of lithia ; and 1*874 grm. of this anhydrous sulphate gave 3*9985 

 grm. of sulphate of baryta. 



In 1839 Hagenf reexamined with accuracy some of the min- 

 erals containing lithia, and discovered that this alkali occurred 

 in them, not pure, as it had been previously supposed, but ac- 

 companied by soda ; and as in the preparation of lithia salts for 

 analysis most of the earlier chemists had taken no steps for the 

 separation of the soda, it became obvious that most of the de- 

 terminations which had been made of the equivalent of lithium 

 were necessarily quite erroneous ; and that the results of Ber- 

 zelius and Hermann alone deserved any confidence, the salts 

 analyzed by them having been prepared from precipitated car- 

 bonate of lithia. % 



Hagen himself found that 1*002 grm. of pure sulphate of 

 lithia in crystals left on being strongly heated *852 grm. of the 

 anhydrous sulphate, and being redissolved and precipitated with 

 a salt of baryta gave 1*8195 grm. of sulphate of baryta. 



The above are the results of the experiments which have been 

 made up to the present time. I have not given along with each 

 the equivalent number deduced by the analyst himself, but have 

 preferred to make the calculation in each case, using the most 

 recently determined equivalents for the other substances involved 

 in the several processes,! and I here present the results in tabu- 

 lar form — 



* Pogg. Ann. xvii, 379. Berz. Jahresb. x, 96. 

 f Pogg. Ann. xlviii. 361. 



\ It is true that Arfwedson prepared his sulphate of lithia by dissolving the car- 

 bonate in sulphuric acid ; but this carbonate seems to have been obtained by precipi- 

 tating the sulphate of lithia (containing soda) with acetate of baryta, filtering, 

 evaporating the filtrate, and igniting — a process which of course would not remove 

 the soda. 



§ The equivalents used are — 



Oxygen, - - - 100- 



Chlorine, - 443*28 (Marignac). 



Sulphur, - - - 200- 



Carbon, - - - -75- 



Silver, - - - 1349-66 (Marignac). 



Barium, .... 857*32 (Marignac). 



