ATOMIC WEIGHTS 269 



GALLIUM. 



Gallium has been so recently discovered, and obtained in such small 

 quantities, that its atomic weight has not as yet been determined with 

 much precision. The following data were fixed by the discoverer, Lecoq 

 de Boisbaudran : ' 



S.lO-ii grammes gallium ammonium alum, upon ignition, left .5885 

 grm. GaoOg. 



Hence Ga = 70.12. 



.4481 gramme gallium, converted into nitrate and ignited, gave .6024 

 grm. Ga^Og. 



Hence Ga = 69.70. 



These values, assigned equal weight, give in mean Ga = 69.91, with 

 an uncertainty of perhaps half a unit. 



IXDIUM. 



Eeieh and Eichter, the discoverers of indium, were also the first to 

 determine its atomic weight." They dissolved weighed quantities of the 

 metal in nitric acid, precipitated the solution with ammonia, ignited the 

 precipitate, and ascertained its weight. Two experiments were made, 



as follows: 



.5135 grm. indium gave .6243 grm. In^Os. 

 .699 " .8515 



Hence, in mean. In = 110.61; a value known now to be too low. 

 An unweighed quantity of fresh, moist indium sulphide was also dis- 

 solved in nitric acid, yielding, on precipitation, 



.2105 grm. IiuO, and .542 grm. BaSO^ 



Hence, with Ba,S04 = 233.43, In = 111.99; also too low. 



Soon after the publication of Eeieh and Eichters paper the subject 

 was taken up by Winkler." He dissolved indium in nitric acid, evap- 

 orated to dryness, ignited the residue, and weighed the oxide thus 

 obtained. 



>Journ. Chem. Soc, 1878, p. 646. 



2jouri,_ prakt. Chem., 92, 484. 



3 Journ. prakt. Chem., 94, 8. 

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