146 THE ATOMIC WEIGHTS. 



ZINC. 



The several determinations of the atomic weij^ht of zinc are by no 

 means closely concordant. The results obtained by Gay-Lussac* and 

 Berzelius f were undoubtedly too low, and may be disregarded here. 

 We need consider only the work done by later investigators. 



In 1842 Jacquelain published the results of his investigations upon 

 this important constant. | In two experiments a weighed quantity of 

 zinc was converted into nitrate, and that b^ngnition in a, platinum cruci- 

 ble was reduced to oxide. In two other experiments sulphuric acid 

 took the place of nitric. As the zinc contained small quantities of lead 

 and iron, these were estimated, and the necessary corrections applied. 

 From the weights of metal and oxide given by Jacquelain the percent- 

 ages have been calculated : 



Nitric Series. 



9.917 grm. Zn gave 12.3138 grm. ZnO. 80.536 per cent. Zn. 



9.809 " 12.1800 " S0.534 " 



Sulphuric Series. 



2.398 grm. Zn gave 2.978 grm. ZnO. 80.524 " 



3.197 " 3.968 " 80.570 



Mean of all four, So. 541, ± .007 



Hence Zn = 65.723.' 



The method adopted by Axel Erdmann § is essentially the same as 

 that of Jacquelain, but varies from the latter in certain important details. 

 First, pure zinc oxide was prepared, ignited in a covered crucible with 

 sugar, and then, to complete the reduction-, ignited in a porcelain tube 

 in a current of hydrogen. The pure zinc thus obtained was converted 

 into oxide by means of treatment with nitric acid and subsequent igni- 

 tion in a porcelain crucible. Erdmann's figures give us the following 

 percentages of metal in the oxide : 



80.247 

 80.257 

 80.263 

 80.274 



Mean, 80.260, ± .0037 



Hence Zn = 64.562. 



* Memoire d' Arceuil, 2, 174. 



tGilb. Annal., 37, 460. 



t Compt. Rend., 14, 636. 



g Poggend. Annal., 62, 611. Berz. Lehrb., 3, 1219. 



