354 J". W. Mallet on the Atomic Weight of Lithium. 



was fused in a covered platinum crucible, poured out upon a 

 sheet of platinum, and the fused mass broken np while warm, 

 and quickly enclosed in a bottle with a well ground stopper. 



This anhydrous chlorid of lithium was beautifully clear arid 

 colorless, and a portion of it taken for careful qualitative exam- 

 ination appeared to be perfectly pure — it was at least completely 

 free from any traces of the earths or heavy metallic oxyds, and 

 might be fairly supposed to have been also freed from all chlo- 

 rid of sodium or potassium by the repeated treatment with ether 

 and absolute alcohol. 



On fusion in an uncovered vessel for some time the salt loses 

 a little chlorine, and takes up oxygen, so that when redissolved 

 in water it reacts alkaline to test-paper ; but it was found that 

 this change could be completely avoided by mixing a little pure 

 sal-ammoniac with the chlorid of lithium before evaporation to 

 dryness, and fusing the dry mass in a covered crucible. The 

 heat applied must not be too great until the sal-ammoniac has 

 been driven off, — as in a first experiment, in which the quantity 

 of NH4CI was considerable and the heat rapidly applied, the 

 greater part 'of the chlorid of lithium was volatilized and lost, 

 although the platinum crucible was covered and was not raised 

 to more than a low red heat. 



Having got then pure fused chlorid of lithium, it remained 

 to determine its composition or the per-centage of chlorine which 

 it contains. The salt is a deliquescent one, and it seemed doubt- 

 ful at first whether the absorption of moisture could be pre- 

 vented during weighing, but it was found that in a platinum 

 crucible provided with a tightly fitted cover, the portion taken 

 for analysis, consisting of but three or four fragments of the 

 fused cake, could be weighed with ease and certainty ; the weight 

 remaining constant for more than five minutes in the hot dry 

 atmosphere of a summer day. The balance used was an excel- 

 lent one of Berlin make, permitting of accurate weighing to the 

 one-tenth of a milligramme. Both it and the weights used were 

 subjected to a careful examination as to adjustment beforehand. 



Three or four pieces of the fused chlorid of lithium were 

 placed in the platinum crucible used for weighing, the cover was 

 put on, and then the vessel was heated for some time to a tem- 

 perature not much below the fusing point of the salt. The cru- 

 cible was cooled over oil of vitriol, weighed, reheated, again 

 cooled, and a second time placed upon the balance, so as to ob- 

 serve perfect correspondence between the two weighings. The 

 fragments of chlorid of lithium were then placed in a beaker 

 of convenient size, and dissolved in water, while the crucible 

 was once more heated, cooled, and weighed; its weight now 

 being subtracted from the former weighing gave the amount of 

 Li CI used. The solution of Li 01 was precipitated by a slight 



